subtopic 4.4: water pollution

Pictureimage from www.renewedlivinginc.com
Over two thirds of Earth's surface is covered by water; less than a third is taken up by land. As Earth's population continues to grow, people are putting ever-increasing pressure on the planet's water resources. In a sense, our oceans, rivers, and other inland waters are being "squeezed" by human activities—not so they take up less room, but so their quality is reduced. Poorer water quality means water pollution.

This unit is a minimum of 4 SL hours.




Guiding Questions:
  • How does pollution affect the sustainability of environmental systems?
  • How do different perspectives affect how pollution is managed?
Understandings:

water pollution

4.4.1 Water pollution has multiple sources and has major impacts on marine and freshwater systems.
  • ​Identify different sources of freshwater and marine pollution.
Substances causing water pollution can be chemical or microbial. Bot degrade the quality of water. Water pollution is the contamination of bodies of water by pollutants, either directly or indirectly.
Water pollution occurs when harmful substances contaminate water bodies such as rivers, lakes, and oceans, disrupting ecosystems and posing risks to human health. These pollutants can enter water in different ways, typically classified into point source and nonpoint source pollution. Understanding the distinction between these two types is essential for addressing water quality issues and implementing effective management strategies. While point source pollution can be traced to a specific, identifiable location, nonpoint source pollution comes from a wide area, making it more challenging to control. Both types of pollution contribute to the degradation of water ecosystems and require targeted solutions to mitigate their impact.
Pollutants, categorized by type, pollutant name, example, and effects:
Pictureimage frompostconflict.unep.ch
Industrial waste:
  • Industries produce large amounts of waste that contain toxic chemicals and pollutants harmful to the environment and human health.
  • Common industrial pollutants include lead, mercury, sulphur, asbestos, and nitrates, among others.
  • Inadequate waste management systems in many industries result in waste being dumped into freshwater sources, contaminating rivers, canals, and eventually seas.
  • Toxic chemicals from industrial waste can:
    • Change the color of water
    • Increase the amount of minerals, leading to eutrophication (excessive nutrients in water)
    • Alter water temperature
    • Pose a serious hazard to aquatic organisms.
​Sewage and wastewater
  • Sewage and wastewater from households are chemically treated and released into water bodies.
  • This wastewater often contains harmful bacteria and chemicals that pose serious health risks.
  • Pathogens are a common water pollutant and are abundant in urban sewer systems, contributing to the spread of diseases.
  • Microorganisms in water can cause deadly diseases and provide breeding grounds for disease carriers.
  • Carriers (such as mosquitoes) spread these diseases through various forms of contact, with malaria being a common example.
Mining activities:
  • Mining involves crushing rocks to extract coal and other minerals from underground.
  • The extracted raw materials often contain harmful chemicals that, when mixed with water, can increase the level of toxic elements, causing potential health issues.
  • Mining activities release metal waste and sulphides from rocks, which are harmful to water quality.
Marine dumping:
  • ​​Household garbage (paper, aluminum, rubber, glass, plastic, food) is sometimes deposited into the sea in certain countries.
  • These materials take 2 weeks to 200 years to decompose.
  • When these items enter the sea, they cause water pollution and harm marine animals.
\Oil leakage:
  • ​​Oil spills are a major concern as large amounts of oil enter the sea and do not dissolve in water.
  • Oil spills pose serious threats to marine wildlife, including fish, birds, and sea otters.
  • Example: A ship carrying oil may spill its contents in an accident, causing varying levels of damage depending on the quantity of oil spilled, the size of the ocean, and the toxicity of the pollutant.
Burning of fossil fuels:
  • ​​Burning fossil fuels releases harmful chemicals such as sulphur dioxide and nitrogen oxides into the atmosphere.
  • These pollutants can combine with water vapor to form acid rain, which contaminates water bodies.
  • Acid rain lowers the pH of water, harming aquatic life and disrupting ecosystems.
  • Fossil fuel combustion also contributes to air pollution, which can indirectly lead to water pollution through atmospheric deposition.
Chemical fertilizers and pesticides:
  • ​​Chemical fertilizers and pesticides are used by farmers to protect crops and promote growth.
  • When these chemicals mix with water, they become harmful to both plants and animals.
  • During rainfall, these chemicals run off into rivers and canals, causing serious damage to aquatic animals and ecosystems.
​Leakage from sewer lines:
  • Small leaks in sewer lines can contaminate underground water, making it unsafe for drinking.
  • If not repaired promptly, leaking water can surface and become a breeding ground for insects and mosquitoes, increasing health risks.
Radioactive waste:
  • ​​Nuclear energy is generated through nuclear fission or fusion, using uranium, a highly toxic chemical.
  • The nuclear waste produced is radioactive and requires careful disposal to prevent accidents.
  • Improper disposal of nuclear waste can cause serious environmental hazards.
  • Major nuclear accidents have occurred in Russia and Japan, highlighting the risks.
Noise Pollution:
  • Underwater noise pollution is a growing threat to marine ecosystems.
  • Major sources include shipping, seismic surveys, military sonar, and offshore drilling.
  • The noise disrupts communication, migration, and feeding patterns of marine species, particularly whales and dolphins.
Picture
image fromwww.aadnc-aandc.gc.ca
Case Study: The Deepwater Horizon Oil Spill Location: Gulf of Mexico, United States
Source of Pollution: Oil spill from the BP-operated Deepwater Horizon drilling rig
Date: April 20, 2010
The Deepwater Horizon Oil Spill is one of the most infamous examples of water pollution, causing catastrophic environmental damage. The spill resulted from a blowout at the Macondo oil well, leading to the release of approximately 4.9 million barrels of crude oil into the Gulf of Mexico over a period of 87 days. The oil spread across vast areas of the ocean, affecting coastlines from Texas to Florida.

Impacts on the Environment:
  • Marine Life: The oil slick contaminated critical marine habitats, killing thousands of fish, birds, marine mammals, and invertebrates. Sea turtles, dolphins, and bird species were particularly affected by the toxic exposure to oil and the resulting lack of oxygen in water.
  • Ecosystems: Coral reefs, seagrass beds, and coastal wetlands suffered extensive damage. The oil reduced sunlight penetration, disrupting photosynthesis in marine plants and impacting entire food webs. The heavy oiling of coastal wetlands also led to the erosion of vital buffer zones that protect against storms.
  • Human Impact: The spill had severe economic consequences for local fishing and tourism industries. Fish stocks were contaminated, and commercial fishing operations were halted in many parts of the Gulf.
Management Strategies:
  • Containment and Cleanup: Multiple response strategies were employed, including the use of containment booms, dispersants, and skimmers to remove oil from the water's surface. Despite these efforts, much of the oil reached shorelines and marine sediments.
  • Restoration Projects: The U.S. government initiated long-term restoration projects aimed at rehabilitating damaged ecosystems. Coastal marshlands were restored, mangrove planting was promoted, and artificial reefs were constructed to help regenerate fish populations.
  • Regulation and Policy: The disaster prompted significant changes in U.S. offshore drilling policies, including stricter safety regulations, more rigorous inspections, and improved response strategies for future oil spills. BP was also held financially accountable for the environmental damage and clean-up costs through the Oil Pollution Act.
Activity: Research a specific example of water pollution that is not listed here.
  • identifying the location
  • source of pollution
  • the impacts on the environment
  • management strategies attempting to address it

plastic pollution

4.4.2 Plastic debris is accumulating in marine environments. Management is needed to remove plastics from the supply chain and to clear up existing pollution.
  • Outline two harmful effects of plastic pollution on marine ecosystems.
  • Explain the role of oceanic gyres in the accumulation of plastic debris in the ocean
Pictureimage fromwaterpollutiononline.weebly.com
​Plastic pollution is one of the most pervasive environmental challenges facing marine ecosystems today. Every year, millions of tonnes of plastic waste end up in oceans, harming wildlife, disrupting ecosystems, and contributing to environmental degradation. The accumulation of plastics in marine environments, particularly in oceanic gyres, has led to the formation of vast "garbage patches." Management strategies are crucial to reducing plastic input into the ocean, cleaning up existing debris, and addressing the long-term effects of microplastics in marine food chains.
Oceanic Gyres and Plastic Aggregation
Ocean currents play a significant role in the distribution of plastic debris. These currents form large circular systems, called gyres, which trap and concentrate plastic waste. The five major oceanic gyres—located in the North and South Pacific, North and South Atlantic, and Indian Oceans—are particularly notorious for accumulating plastics. The most well-known of these is the Great Pacific Garbage Patch, a massive accumulation of plastics located between Hawaii and California.

How plastics accumulate in gyres:
  • Ocean currents: Plastics, especially lightweight materials, are carried by surface currents. As these currents converge in gyres, they trap debris in a rotating vortex.
  • Buoyancy of plastics: Most plastics are buoyant, allowing them to float on the ocean's surface. However, over time, sunlight and wave action break larger plastics into smaller particles, which remain suspended in the water column or sink to the seafloor.
Picture
https://populationeducation.org/8-facts-about-the-garbage-gyres-in-our-oceans/
Picturehttps://www.recyclingtoday.com/news/cleanhub-report-analyzes-sources-of-ocean-plastic-pollution/
The Harm from Oceanic Plastic Pollution
Plastic pollution in marine environments has severe consequences for biodiversity, ecosystems, and human health. Key harmful effects include:
  • Threat to Marine Life:
    • Ingestion: Marine animals, including fish, seabirds, and marine mammals, often mistake plastics for food. Ingesting plastic can lead to internal blockages, malnutrition, and even death. Affected species include sea turtles, which confuse plastic bags with jellyfish, and seabirds, whose stomachs may fill with plastic debris.
    • Entanglement: Animals can become entangled in plastic debris, such as fishing nets, ropes, and six-pack rings. This can lead to drowning, injury, and impaired mobility, affecting species like seals and dolphins.
  • Habitat Destruction:
    • Plastics smother coral reefs and seagrass beds, which are critical habitats for marine biodiversity. As plastics accumulate, they can prevent light from reaching these ecosystems, stunting growth and reducing biodiversity.
  • Introduction of Invasive Species:
    • Floating plastic debris can serve as "rafts" for invasive species, allowing them to travel across oceans and colonize new areas. This can disrupt local ecosystems by introducing species that compete with native organisms for resources.
Microplastics:

Microplastics, defined as plastic particles less than 5 mm in size, are a significant concern due to their widespread presence in marine environments. These tiny particles are either produced intentionally (such as microbeads in cosmetics) or result from the breakdown of larger plastic items. Microplastics are particularly harmful because they can easily enter the marine food chain.
  • Bioaccumulation: Microplastics are ingested by small marine organisms, such as plankton, at the base of the food chain. As larger animals consume these smaller organisms, the microplastics accumulate in their bodies. Over time, these plastics bioaccumulate in higher concentrations as they move up the food chain, reaching larger predators like fish, marine mammals, and even humans.
  • Biomagnification: As microplastics move through trophic levels, they not only accumulate in individual organisms but also increase in concentration. This process, known as biomagnification, means that top predators, including humans, are exposed to higher concentrations of plastics and the toxins they carry.
  • Transport of Surface Toxins:
    • Adsorption of toxins: Plastics have a high affinity for hydrophobic chemicals, meaning they attract and hold on to toxins present in the marine environment, such as polychlorinated biphenyls (PCBs), dioxins, and persistent organic pollutants (POPs). These chemicals adhere to the surface of plastic particles and are then ingested by marine organisms.
  • Toxic effects: When ingested, these microplastics act as carriers for the adsorbed toxins, which can then be released inside the organisms. These toxins are harmful, leading to reproductive issues, developmental abnormalities, and immune system impairments in marine animals. As humans consume seafood contaminated with microplastics and toxins, there are potential long-term health risks.
Picture
https://www.grida.no/resources/6915
Management Strategies to Address Plastic Pollution
  • Reducing Plastics in the Supply Chain:
    • Banning Single-Use Plastics: Many countries have started banning single-use plastics, such as straws, plastic bags, and cutlery, to reduce plastic waste. Policies like the European Union’s Single-Use Plastics Directive are examples of efforts to curb the entry of plastics into marine environments.
    • Extended Producer Responsibility (EPR): Governments can enforce regulations that require manufacturers to take responsibility for the entire lifecycle of plastic products, encouraging them to design more sustainable alternatives and improve recycling systems.
    • Circular Economy Approaches: Transitioning to a circular economy, where plastic products are designed to be reused, recycled, or composted, can drastically reduce the amount of plastic waste generated
  • International Cooperation:
    • Global Plastic Agreements: International treaties and agreements, such as the UN Environment Assembly's global agreement on plastic pollution, aim to unite countries in reducing plastic production, improving waste management, and addressing marine plastic pollution.
    • Marine Protected Areas (MPAs): Establishing MPAs can help protect critical marine habitats from the harmful effects of plastic pollution. By limiting human activities, MPAs provide a buffer against the continued accumulation of debris in ecologically sensitive regions
  • Cleaning Up Existing Plastic Pollution:
    • Ocean Cleanup Projects: Technologies such as the Ocean Cleanup Project are being developed to remove plastics from gyres. These systems use large, floating barriers to collect plastic debris from the ocean's surface, which is then transported back to land for recycling or disposal.
    • Beach Cleanups: Coastal communities and environmental organizations often organize beach cleanups to prevent plastic waste from entering the ocean. These efforts also raise awareness about the importance of reducing plastic consumption.
    • Biodegradable Plastics: Research into biodegradable plastics is ongoing, with the goal of developing materials that break down more quickly in marine environments. However, concerns remain about the potential environmental impact of these alternatives, including whether they degrade completely in real-world conditions.
Activity: Analyse the graphs below

The graph below shows ​latest research suggests that smaller rivers play a much larger role than previously thought. In the chart we see the comparison of the latest research (in red) with the two earlier studies which mapped global riverine inputs. This chart shows how many of the top-emitting rivers (on the x-axis) make up a given percentage of plastic inputs (y-axis).
​Most of the world’s largest emitting rivers are in Asia, with some also in East Africa and the Caribbean.
  • What do you see in the two graphs?
  • What do you think is happening?
  • Which river contributes the most, and how does its contribution compare to others in the list?
  • Discuss the significance of rivers from the Philippines in contributing to ocean plastic pollution based on the graph. What percentage of total pollution do these rivers contribute collectively?
  • Compare the contributions of rivers from India (Ulhas, Ganges) and the Philippines. What conclusions can you draw about regional differences in plastic pollution sources?
  • Compare the regional focus of the rivers in Graph 2 with the global perspective provided in Graph 1. Discuss the implications of regional hotspots for plastic pollution in terms of international efforts to reduce ocean plastic waste.

measuring water quality

4.4.3 Water quality is the measurement of chemical, physical and biological characteristics of water. Water quality is variable and is often measured using a water quality index. Monitoring water quality can inform management strategies for reducing water pollution.
  • Outline two chemical characteristics that are commonly monitored to assess water quality.
  • Distinguish between direct and indirect parameters used to determine water quality
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Water quality refers to the condition of water based on a set of chemical, physical, and biological parameters. It is essential to monitor water quality in aquatic systems to ensure that it remains suitable for human consumption, aquatic life, and ecosystem services. Water quality can vary widely due to factors such as pollution, temperature changes, and natural processes. It is often assessed using a Water Quality Index (WQI), a numerical scale that simplifies complex water data into a single number, making it easier to evaluate the overall health of a water body. Monitoring water quality enables governments and environmental organizations to develop effective management strategies to reduce pollution and protect aquatic ecosystems.


Water quality in aquatic systems is assessed by measuring several important parameters, each of which provides insights into the health of the water body. 
  • Direct parameters are measurements that assess the physical, chemical, or biological properties of water itself, providing immediate and specific information about the water’s condition. These parameters directly reflect the quality of the water and its suitability for supporting life or for human use.
  • Indirect parameters are measurements that do not directly measure the water’s quality but instead infer it by assessing factors that can influence or result from water quality issues. These parameters often involve assessing the impact of water quality on the environment or organisms, giving indirect indications of water quality conditions.

Direct Measurements
pH:
  • Definition: A measure of how acidic or basic the water is on a scale of 0-14, with 7 being neutral.
  • Importance: Most aquatic organisms thrive in water with a pH between 6.5 and 8.5. Extreme pH levels can be toxic to aquatic life and can affect the solubility of metals and nutrients.
  • Sources of Variation: Acid rain, industrial discharge, and natural processes like volcanic activity can alter pH levels.

Temperature:
  • Definition: The warmth or coldness of water.
  • Importance: Temperature affects the metabolic rates of aquatic organisms, the solubility of oxygen, and the sensitivity of aquatic species to pollution. Sudden temperature changes (thermal pollution) can stress or kill aquatic organisms.
  • Sources of Variation: Thermal pollution from industrial processes, climate change, and seasonal changes can affect water temperature​​
Dissolved Oxygen (DO):
  • Definition: The amount of oxygen available in water for aquatic organisms to breathe.
  • Importance: Dissolved oxygen is crucial for the survival of fish, invertebrates, and other aquatic life. Low DO levels can lead to hypoxia, which can cause large die-offs in aquatic species.
  • Sources of Variation: Factors such as temperature, organic pollution, and algal blooms can reduce DO levels.
Picturehttps://limnoloan.org/water-quality-parameters/secchi-disk/
Turbidity:
  • Definition: A measure of water clarity or how much light can penetrate through the water. Turbidity can be measured with Secchi disks
  • Importance: High turbidity can reduce light penetration, affecting photosynthesis in aquatic plants and decreasing oxygen production. It can also clog the gills of fish and smother aquatic habitats.
  • Sources of Variation: Turbidity increases due to sediment runoff, erosion, algae growth, or wastewater discharge.
​​Nitrate Concentrations:
  • Definition: The amount of nitrogen in the form of nitrates (NO3) in the water.
  • Importance: Nitrates are essential nutrients for plant growth but can lead to eutrophication when present in excess. This process can cause harmful algal blooms, which reduce dissolved oxygen levels and harm aquatic life.
  • Sources of Variation: Agricultural runoff, sewage, and industrial effluents are common sources of nitrates.

Phosphate Concentrations:
  • Definition: The amount of phosphorus in the form of phosphates (PO4) in the water.
  • Importance: Like nitrates, phosphates are nutrients that contribute to eutrophication. Excess phosphates can trigger algal blooms, leading to oxygen depletion and poor water quality.
  • Sources of Variation: Fertilizers, detergents, and sewage discharge are significant sources of phosphates.

Concentrations of Specific Metals:
  • Definition: The presence of metals such as lead, mercury, cadmium, and arsenic in water.
  • Importance: Metals can be toxic to aquatic life and humans. They bioaccumulate in the food chain, causing health problems in top predators and human consumers.
  • Sources of Variation: Industrial discharge, mining activities, and leaching from contaminated soils can introduce metals into aquatic systems.
Indirect Measurements

  • Biochemical Oxygen Demand (BOD): 
    • Definition: BOD measures the amount of oxygen required by microorganisms to break down organic matter in a water sample over a specified period (typically five days). It provides an indication of the organic pollution present in the water.
    • Importance: High BOD levels suggest a large amount of organic matter in the water, which can lead to oxygen depletion, stressing aquatic life. A high BOD indicates poor water quality and potential for eutrophication.
    • Source: BOD levels increase due to organic pollutants such as sewage, agricultural runoff, and industrial waste entering the water system.

  • ​Total Suspended Solids (TSS):
    • Definition: The total amount of suspended particles, including sediments, organic matter, and pollutants, in the water.
    • Importance: High levels of suspended solids reduce water clarity and can smother aquatic habitats, leading to reduced biodiversity.
    • Sources of Variation: Erosion, construction activities, urban runoff, and stormwater contribute to increased TSS levels.
Application of skills: Use methods for measuring key abiotic factors in aquatic systems, for example, dissolved oxygen, pH, temperature, turbidity, and concentrations of nitrates, phosphates and total suspended solids. Possible methods may include the use of oxygen and pH probes, a thermometer, a Secchi disc, nitrate/phosphate tests.
4.4.4 Biochemical oxygen demand (BOD) is a measure of the amount of dissolved oxygen required by microorganisms to decompose organic material in water.
  • Define BOD
  • Describe how BOD is used to determine water quality
  • State how BOD is measured
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Biochemical Oxygen Demand (BOD) is a crucial parameter for assessing water quality in both freshwater and marine environments. It measures the amount of dissolved oxygen required by aerobic microorganisms to break down organic matter present in a water sample. BOD is typically expressed in milligrams of oxygen consumed per litre of water over a five-day period at a temperature of 20°C. This process of decomposition consumes oxygen, and high BOD values indicate a large presence of organic pollutants, which can negatively affect water quality and aquatic life.

How BOD Works
​Microorganisms, such as bacteria, naturally occur in aquatic ecosystems and play a vital role in breaking down organic materials like plant debris, sewage, and waste from agricultural and industrial sources. During this breakdown process, these microorganisms consume oxygen. The more organic matter present, the more oxygen is required for its decomposition.
  • High BOD: Indicates a high concentration of organic material, which requires a significant amount of oxygen to decompose. High BOD levels are typically associated with polluted water that contains large amounts of sewage, agricultural runoff, or industrial effluents.
  • Low BOD: Suggests that the water contains little organic matter, and therefore less oxygen is needed for decomposition. Low BOD levels are usually found in clean, unpolluted water.
Picture
https://blog.iceslicer.com/how-do-deicers-affect-biochemical-oxygen-demand
The Standard BOD Test
The standard method for measuring BOD involves taking a water sample and placing it in an airtight container, which is then incubated at 20°C for five days. The difference in the amount of dissolved oxygen (DO) before and after incubation provides the BOD val e. The test reflects how much oxygen is used by microorganisms to break down the organic matter in the water.

Steps of the BOD Test:
  1. Initial DO Measurement: A sample of water is collected, and the initial dissolved oxygen level is measured.
  2. Incubation: The sample is stored in a dark container at 20°C for five days to prevent additional oxygen from entering the system and to allow microorganisms to decompose the organic material.
  3. Final DO Measurement: After five days, the dissolved oxygen level is measured again.
  4. BOD Calculation: The BOD is calculated by subtracting the final DO from the initial DO and expressing the result in mg/L of oxygen consumed.

Significance of BOD as an Indirect Measure of Organic Matter
​BOD is an indirect measure of the amount of organic matter in a water sample. Instead of measuring the organic matter directly, BOD indicates how much oxygen is consumed during its decomposition, providing insight into the levels of pollution present. High BOD values are often associated with water bodies that have been contaminated by organic waste, such as:
  • Untreated sewage: Contains large amounts of organic matter, leading to high BOD levels.
  • Agricultural runoff: Nutrient-rich water that promotes the growth of algae and other organisms, which increases organic material and therefore BOD.
  • Industrial effluents: Factories and industries often discharge organic waste, contributing to elevated BOD in nearby water bodies.

Environmental Impacts of High BOD Levels
  • Oxygen Depletion: When large amounts of organic matter are decomposed, oxygen levels in the water decrease. This can lead to hypoxia (low oxygen levels) or anoxia (no oxygen), both of which are detrimental to aquatic life. Fish, invertebrates, and other oxygen-dependent species may die or migrate to areas with higher oxygen levels.
  • Eutrophication: High BOD is often linked to nutrient pollution (such as nitrates and phosphates) that stimulates algal blooms. When algae die, they become organic matter, further increasing BOD. The decomposition of the algae consumes oxygen, exacerbating oxygen depletion and contributing to the degradation of the ecosystem.
  • Disruption of Food Chains: Low oxygen levels can disrupt food chains, as species at the top of the food chain, such as fish and birds, depend on smaller oxygen-dependent organisms for survival. The loss of these organisms can affect the entire aquatic food web.

eutrophication

4.4.5 Eutrophication occurs when lakes, estuaries and coastal waters receive inputs of mineral nutrients, especially nitrates and phosphates, often causing excessive growth of phytoplankton.
  • ​Explain the process of eutrophication and its impacts.
  • Describe positive and negative feedback as applied to eutrophication.
​Eutrophication is a process that occurs when water bodies, such as lakes, estuaries, and coastal regions, receive an excess input of nutrients, primarily nitrates and phosphates. These nutrients stimulate the rapid growth of phytoplankton, small algae, and other aquatic plants, leading to a range of environmental problems. Eutrophication is often a result of human activities, such as the release of agricultural fertilizers, detergents, and untreated sewage into water systems.
Picturehttps://www.unep.org/nowpap/what-we-do/prevent-and-reduce-pollution/eutrophication
Causes of Eutrophication
While eutrophication can occur naturally, it is often accelerated by human activities, a process known as cultural eutrophication. The main sources of nutrient pollution are:
  • Agricultural Runoff:
    • The use of synthetic fertilizers in agriculture is a major source of nitrates and phosphates entering water bodies. Rainwater washes excess fertilizers from fields into nearby rivers, lakes, and coastal waters, contributing to nutrient pollution.
  • Sewage and Wastewater:
    • Untreated or poorly treated sewage is rich in organic matter, nitrates, and phosphates. Domestic sewage from households often contains detergents, which are high in phosphates, especially in areas without adequate wastewater treatment infrastructure.
  • Industrial Effluent:
    • Certain industries, particularly food processing and agriculture-related sectors, release wastewater rich in nutrients into rivers and lakes, exacerbating eutrophication.
  • Detergents:
    • Phosphate-based detergents used in households and industries also contribute to eutrophication. Many regions have regulated the use of phosphate detergents, but in areas where this regulation is lacking, detergents are a significant source of phosphates in water bodies.
The Process of Eutrophication
  • Nutrient Input:
    • The primary drivers of eutrophication are nitrates (NO3−) and phosphates (PO4³−). These nutrients are essential for the growth of phytoplankton and aquatic plants. In natural, balanced ecosystems, the growth of these organisms is limited by the relatively low availability of nutrients.
  • Phytoplankton Growth:
    • When excess nutrients enter a water body, the growth of phytoplankton is no longer limited, resulting in algal blooms—massive, rapid growth of algae. These blooms can turn the water green and block sunlight from reaching deeper layers, disrupting the natural balance of the ecosystem.
  • Decomposition and Oxygen Depletion:
    • As phytoplankton and algae die, they are decomposed by aerobic bacteria. This process consumes large amounts of oxygen from the water, leading to hypoxia (low oxygen levels) or even anoxia (absence of oxygen). The depletion of oxygen causes severe stress on aquatic life, especially fish and other species that rely on oxygen for survival.
Picture
image from www.bbc.co.uk
​Algal Blooms and Their Occurrence
​
Algal blooms occur when the limiting nutrient in a water body (often phosphate or nitrate) is suddenly available in higher concentrations. Under normal circumstances, the growth of phytoplankton and algae is restricted by the availability of these nutrients. However, when large quantities of nutrients are introduced, this restriction is lifted, allowing rapid algal growth.
  • Toxic Algal Blooms: Some algal blooms, known as harmful algal blooms (HABs), produce toxins that are harmful to both aquatic organisms and humans. These toxins can accumulate in the tissues of shellfish and fish, posing health risks to animals and people who consume them.
  • Seasonality of Algal Blooms: Algal blooms are often seasonal, occurring during warm months when sunlight and temperature conditions are favorable for algae growth. These blooms can cover large areas of water bodies and persist for weeks or months.
4.4.6 Eutrophication leads to a sequence of impacts and changes to the aquatic system.
  • Explain the sequence of events that leads to hypoxia in a water body following an algal bloom
Picture
The consequences of marine eutrophication is very simple to explain. The quiet unseen changes of the body of water caused by algae and plants suffocates many of the organisms as we said before. Not only does eutrophication kill other species but the organisms that happen to survive in the water with few oxygen change.

The Sequence of Impacts Caused by Eutrophication
  • Excessive Growth of Phytoplankton:
    • When nutrient levels, particularly nitrates and phosphates, increase in lakes, estuaries, or coastal waters, they fuel the rapid growth of phytoplankton. This excessive growth, also known as an algal bloom, results in dense layers of algae covering the surface of the water.
    • While phytoplankton are important primary producers in aquatic food webs, excessive growth can block sunlight from penetrating deeper into the water, affecting submerged aquatic vegetation. This reduces photosynthesis in these plants, depriving other organisms of food and oxygen.
  • Phytoplankton Death:
    • The lifespan of phytoplankton is relatively short, and once their population booms, they inevitably die off in large numbers. As phytoplankton die, their organic matter sinks to the bottom of the water body, where it undergoes decomposition.
    • The sheer volume of dead organic material leads to a surge in microbial activity, particularly from bacteria that specialize in breaking down organic matter. This decomposition process is where the most severe impacts of eutrophication begin to manifest.
  • High Rates of Decomposition:
    • The decomposition of dead phytoplankton is carried out by aerobic bacteria that use up large amounts of dissolved oxygen from the water. The higher the rate of decomposition, the faster oxygen is depleted.
    • This leads to an increase in Biochemical Oxygen Demand (BOD), which is a measure of how much oxygen is required to break down organic material in water. As the demand for oxygen increases, oxygen levels in the water decrease.
  • Rapid Consumption of Dissolved Oxygen:
    • As bacteria consume oxygen during decomposition, dissolved oxygen (DO) levels in the water drop significantly. This is particularly problematic in warm, stagnant, or slow-moving waters, where the natural replenishment of oxygen through the atmosphere is limited.
    • The depletion of oxygen can lead to hypoxia, where dissolved oxygen levels fall below the level necessary to sustain most aquatic life (typically below 2 mg/L). In extreme cases, anoxia occurs, where there is no oxygen left in the water at all.
  • Hypoxia and Anoxia:
    • Hypoxic and anoxic conditions are deadly to most aquatic organisms that rely on oxygen for survival. Fish, crustaceans, and invertebrates are especially vulnerable, as they suffocate without adequate oxygen.
    • In these low-oxygen environments, only certain bacteria that can survive without oxygen, such as anaerobic bacteria, thrive. These bacteria produce toxic byproducts, such as hydrogen sulfide, which further degrades the water quality.
  • Death of Aquatic Life:
    • As oxygen levels plummet, mass fish kills and the death of other aquatic organisms occur. Species such as fish, mollusks, and zooplankton, which are highly sensitive to changes in oxygen levels, either migrate out of the affected area (if they can) or perish.
    • The lack of oxygen and the toxic byproducts of anaerobic decomposition make it impossible for most organisms to survive, leading to a sharp decline in biodiversity. The result is a "dead zone"—an area of water where oxygen levels are too low to support most marine life.
  • Formation of Dead Zones:
    • Dead zones are large areas of water that are devoid of life due to oxygen depletion. These zones are often found in coastal areas or enclosed water bodies where nutrient pollution is prevalent. One of the most well-known examples is the Gulf of Mexico dead zone, which forms annually due to nutrient runoff from the Mississippi River Basin.
    • The formation of dead zones disrupts ecosystems, destroys fisheries, and has severe economic consequences for regions dependent on aquatic resources.
4.4.7 Eutrophication can substantially impact ecosystem services.
  • Describe how eutrophication can affect fisheries and the provisioning of food from aquatic ecosystems.
  • Outline two ways in which eutrophication reduces the aesthetic value of water bodies
Ecosystem services are the benefits that humans derive from natural ecosystems. These services are divided into four main categories: provisioning services (such as food and water), regulating services (such as water purification and climate regulation), cultural services (such as recreation and aesthetics), and supporting services (such as nutrient cycling and soil formation). Eutrophication, the excessive input of nutrients like nitrates and phosphates into water bodies, can drastically reduce the capacity of ecosystems to provide these services, leading to significant environmental, economic, and social impacts.

Impacts of Eutrophication on Ecosystem Services
  • Fisheries (Provisioning Services):
    • Impact: Eutrophication can lead to severe declines in fish populations and aquatic biodiversity, which are vital components of provisioning services. The oxygen depletion (hypoxia or anoxia) caused by excessive algal blooms and the subsequent decomposition process can create "dead zones", where oxygen levels are too low to support fish and other marine life.
    • Consequences:
      • Fish Kills: The reduction in dissolved oxygen can lead to mass fish die-offs, affecting both wild fisheries and aquaculture. This has direct economic impacts on communities that rely on fishing for their livelihoods.
      • Loss of Biodiversity: As oxygen levels decrease, sensitive species such as certain fish and invertebrates are unable to survive, leading to a loss of biodiversity and the collapse of local food webs.
      • Economic Losses: Fisheries experience a decline in productivity, leading to reduced catches and income for fishermen and coastal communities. The economic losses can be particularly severe in regions where fishing is a primary source of income.
  • Recreation (Cultural Services):
    • Impact: Eutrophication severely affects the recreational value of water bodies by degrading water quality, limiting access to clean water, and creating aesthetically unpleasant conditions. Recreational activities like swimming, boating, and fishing are often hindered by the presence of toxic algal blooms and the accompanying foul odors and water discoloration.
    • Consequences:
      • Water Contamination: Harmful algal blooms (HABs) can produce toxins that pose health risks to humans and animals. Contact with or ingestion of contaminated water can lead to illnesses such as skin rashes, gastrointestinal issues, and respiratory problems, making it unsafe for recreational activities.
      • Restricted Access: When eutrophic conditions develop, beaches and lakes may be closed to prevent public exposure to harmful algal blooms, limiting recreational use. This reduces opportunities for water sports, camping, and tourism.
      • Economic Impact on Tourism: Regions that rely on tourism for their economies can suffer greatly when eutrophication reduces the aesthetic and recreational appeal of their water bodies. Hotels, restaurants, and other businesses that depend on tourists visiting lakes, rivers, and coastal areas may experience significant financial losses.
  • Aesthetics (Cultural Services):
    • Impact: Eutrophication negatively impacts the aesthetic value of water bodies, affecting people's enjoyment of natural environments. Water that is clear and visually appealing becomes cloudy, green, and malodorous due to excessive algal growth and decomposition.
    • Consequences:
      • Algal Blooms: The proliferation of algae creates unsightly, thick green mats or scums on the surface of water bodies. This affects the beauty of lakes, rivers, and coastal areas, which are often valued for their scenic qualities.
      • Odors: As algae decompose, they release gases such as hydrogen sulfide, which produces a foul odor. This reduces the attractiveness of water bodies for both local residents and visitors, further diminishing their aesthetic and cultural value.
  • Health (Regulating and Cultural Services):
    • Impact: Eutrophication can pose serious health risks, especially when toxic algal blooms occur. These harmful algal blooms produce toxins that can contaminate drinking water sources and negatively affect human and animal health.
    • Consequences:
      • Toxic Algal Blooms (HABs): Certain species of algae, such as cyanobacteria, produce toxins that are harmful to both humans and wildlife. Exposure to these toxins through contaminated water can lead to health problems, including liver damage, neurological disorders, and respiratory issues.
      • Drinking Water Contamination: Water supplies contaminated with algal toxins may become unsafe for human consumption. Treating eutrophic water for drinking purposes is costly, and some toxins produced by harmful algae are resistant to conventional water treatment methods.
      • Shellfish Poisoning: Shellfish that filter water can accumulate toxins produced by harmful algae. When humans consume contaminated shellfish, they can suffer from conditions such as paralytic shellfish poisoning (PSP), which can be life-threatening.

Economic and Social Consequences
  • Economic Costs: Eutrophication has significant economic costs due to its impacts on fisheries, tourism, recreation, and water treatment. The loss of income from fisheries and tourism, combined with the costs of treating contaminated water and cleaning up affected areas, can place a financial burden on governments, businesses, and local communities.
  • Social Costs: Communities that depend on ecosystem services for their livelihoods and well-being, such as fishing or tourism-based economies, are particularly vulnerable to the impacts of eutrophication. Reduced access to clean water for drinking, recreation, and cultural use can also diminish quality of life.
4.4.8 Eutrophication can be addressed at three different levels of management.
  • Explain how alternatives to fertilizers and detergents can reduce the human activities that cause eutrophication.
  • Describe how constructed wetlands and riparian buffer zones help reduce the release of pollution into water bodies.
  • Outline how dredging of eutrophic lakes can help remove pollutants from the environment and restore ecosystems.
​Eutrophication, caused by the excessive input of nutrients such as nitrates and phosphates into water bodies, can lead to severe ecological consequences like algal blooms, hypoxia, and the degradation of aquatic ecosystems. To mitigate these impacts, management strategies can be implemented at three key levels: reducing human activities that produce pollutants, reducing the release of pollutants into the environment, and removing pollutants from the environment while restoring ecosystems. These approaches not only apply to eutrophication but also serve as general strategies for addressing other types of pollution
Reducing Human Activities that Produce Pollutants
​The first level of management focuses on preventing the generation of pollutants at the source by changing human activities that contribute to eutrophication. This strategy targets the root causes of nutrient pollution and seeks to minimize the introduction of nitrates, phosphates, and other pollutants into the environment.
Reducing the Release of Pollutants
The second level of management involves reducing the amount of pollutants that are released into the environment, particularly focusing on wastewater treatment and runoff management. This approach aims to capture and remove pollutants before they can enter water bodies and contribute to eutrophication.
Removing Pollutants from the Environment and Restoring Ecosystems
​When prevention and reduction measures are insufficient or after pollution has occurred, the third level of management focuses on the removal of pollutants from the environment and the restoration of affected ecosystems. This process involves rehabilitating water bodies that have already been impacted by eutrophication and reversing the damage caused by excess nutrients
​Application of skills: Create a systems model to show the impacts and changes eutrophication produces in an aquatic system. This model should include examples of positive feedback (for example, increase in
nutrients>increase in death of organisms>increase in decomposition>increase in nutrients).

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algia Blooms

​4.4.9 There is a wide range of pollutants that can be found in water.
  • Explain how persistent organic pollutants (POPs) such as PCBs become biomagnified in aquatic food chains.
  • Describe how tributyltin (TBT) as an endocrine disruptor affects aquatic organisms and ecosystems.
  • Outline how thermal pollution from industrial processes can lead to changes in aquatic ecosystems.
Water pollution is a significant global environmental issue that affects freshwater and marine ecosystems, human health, and economic activities. Pollutants enter water systems from various sources and can take multiple forms, including organic matter, dissolved substances, persistent chemicals, plastics, and thermal pollution. Each type of pollutant impacts ecosystems differently, from disrupting hormonal functions in aquatic life to causing long-term health risks in humans through biomagnification. Understanding the diversity of water pollutants is critical to developing effective management strategies and safeguarding ecosystem services.

Types of Water Pollutants
  • Organic Matter (e.g., Sewage)
    • Definition: Organic matter refers to biodegradable substances such as human waste, animal waste, and food waste. When these substances enter water bodies, they are decomposed by microorganisms, leading to oxygen depletion.
    • Impact:
      • High levels of organic matter lead to increased biochemical oxygen demand (BOD), which can cause hypoxia (low oxygen) or anoxia (no oxygen), killing fish and other aquatic organisms.
      • Organic matter may also introduce pathogens (e.g., bacteria, viruses, and parasites) into the water, posing health risks to both humans and animals.
    • Example: Untreated or inadequately treated sewage discharged into rivers and lakes leads to eutrophication and the formation of dead zones due to oxygen depletion.

  • Dissolved Substances (e.g., Tributyltin, an Endocrine-Disrupting Chemical)
    • Definition: Dissolved substances include chemicals that dissolve in water, such as heavy metals, pesticides, and industrial chemicals. Tributyltin (TBT) is an example of a dissolved chemical used as an antifouling agent on ships. It is a known endocrine disruptor, meaning it interferes with the hormone systems of organisms.
    • Impact:
      • Endocrine-disrupting chemicals (EDCs) can cause reproductive and developmental problems in aquatic species, such as feminization of male fish, abnormal development, and decreased fertility.
      • TBT, specifically, has been linked to imposex in snails, a condition where female snails develop male characteristics, reducing their ability to reproduce.
    • Example: Tributyltin (TBT) has been banned in many countries, but its long-lasting effects persist in marine environments where it was historically used.

  • Persistent Chemicals that Become Biomagnified (e.g., PCBs)
    • Definition: Persistent organic pollutants (POPs) are chemicals that resist degradation and remain in the environment for extended periods. Polychlorinated biphenyls (PCBs) are a group of synthetic chemicals once widely used in electrical equipment. POPs accumulate in the tissues of organisms and become increasingly concentrated at higher trophic levels, a process known as biomagnification.
    • Impact:
      • PCBs and other POPs accumulate in the fatty tissues of organisms and are passed up the food chain, leading to higher concentrations in top predators, including humans.
      • Health effects in humans and wildlife include cancer, immune system damage, and reproductive disorders. Long-lived species like seals, whales, and birds of prey are particularly vulnerable to biomagnification.
    • Example: PCBs, despite being banned in many countries, continue to affect ecosystems because of their persistence in the environment. Fish and marine mammals often have high concentrations of PCBs in their tissues.

  • Plastics
    • Definition: Plastics are synthetic materials that are non-biodegradable and highly persistent in the environment. They enter water bodies through runoff, littering, and improper waste disposal. Plastics in the environment break down into smaller particles called microplastics (less than 5 mm in size).
    • Impact:
      • Large plastic debris can entangle marine animals such as turtles, birds, and fish, leading to injury or death. Many animals mistake plastics for food, causing blockages in their digestive systems.
      • Microplastics are ingested by a wide range of organisms, from zooplankton to fish, and can transfer toxins up the food chain. Plastics also attract and absorb toxic chemicals like persistent organic pollutants (POPs), further increasing their harmful effects when ingested.
    • Example: The Great Pacific Garbage Patch is a massive accumulation of plastic debris in the Pacific Ocean, where microplastics are found in high concentrations, affecting marine ecosystems and food chains
​.
  • Heat Energy (Thermal Pollution)
    • Definition: Thermal pollution occurs when industries, power plants, or factories discharge heated water into natural water bodies, raising the overall temperature of the water. This often occurs in cooling processes where water is used to cool machinery or reactors and is then returned to the environment at a higher temperature.
    • Impact:
      • Increased water temperature reduces the solubility of oxygen, leading to lower dissolved oxygen levels, which can stress or kill aquatic life.
      • Some species are sensitive to temperature changes and may experience shifts in metabolic rates, reduced reproduction, and migration to cooler areas, which can disrupt ecosystems.
    • Example: Power plants that use water for cooling can significantly increase the temperature of nearby rivers or lakes, leading to localized ecosystem disruptions.

Impacts of Water Pollutants on Ecosystems and Human Health
  • Ecosystem Impacts:
    • Biodiversity Loss: Pollutants such as organic matter, plastics, and persistent chemicals disrupt food chains, reduce biodiversity, and create dead zones where most aquatic life cannot survive.
    • Disruption of Food Webs: Persistent chemicals like PCBs accumulate in the tissues of top predators, which can lead to reproductive failure and the collapse of certain species populations.
    • Habitat Degradation: Plastic debris can damage coral reefs, seagrass beds, and other critical habitats, reducing their ability to support marine life.
  • Human Health Impacts:
    • Waterborne Diseases: Organic matter from sewage introduces pathogens into water, increasing the risk of waterborne diseases such as cholera, dysentery, and gastrointestinal infections.
    • Toxic Exposure: Persistent chemicals and endocrine disruptors like PCBs and TBT can have long-term health effects on humans, including cancer, immune system suppression, and reproductive issues.
    • Microplastic Ingestion: Humans can ingest microplastics through contaminated seafood, with potential long-term health risks, including exposure to the toxic chemicals absorbed by plastics.
4.4.10 Algal blooms may produce toxins that threaten the health of humans and other animals.
  • Explain how cyanotoxins from freshwater algal blooms pose a threat to human health
  • Describe the ecological impact of dinoflagellate blooms (red tides) in marine environments.
  • Explain how toxins produced by harmful algal blooms (HABs) can affect both aquatic life and human health
Picturehttps://www.sdcoastkeeper.org/blog/harmful-algal-blooms-san-diego-county/
Harmful algal blooms (HABs) occur when certain types of algae or microorganisms grow excessively in water bodies, producing toxins that can harm humans, animals, and the environment. These blooms are often triggered by an excess of nutrients, such as nitrates and phosphates, entering the water through agricultural runoff, sewage, or industrial pollution. HABs can occur in both freshwater and marine environments and are a growing concern worldwide.
Not all algal blooms are harmful, but some species of algae and microorganisms produce toxins that can have severe health impacts. These toxic blooms can affect ecosystems, local economies (especially fisheries and tourism), and human health. HABs also disrupt aquatic food webs, kill fish and marine organisms, and degrade water quality.


Picture
https://www.epa.gov/habs/what-are-effects-habs
Freshwater Example: Cyanotoxins
Cyanobacteria, commonly found in freshwater environments such as lakes, ponds, and reservoirs, are notorious for producing cyanotoxins. These toxins can cause a range of health effects in humans and animals, from mild skin irritation to severe liver damage and neurological effects.
  • Common Cyanotoxins:
    • Microcystins: The most common group of cyanotoxins, microcystins are hepatotoxins, meaning they primarily affect the liver. They are produced by several species of cyanobacteria, including Microcystis.
    • Cylindrospermopsin: Another potent cyanotoxin that affects the liver and kidneys.
    • Anatoxin-a: A neurotoxin that can cause paralysis, respiratory failure, and death.
  • Health Impacts:
    • Humans: Ingestion of water contaminated with cyanotoxins can lead to nausea, vomiting, diarrhea, liver damage, and in severe cases, death. Contact with contaminated water can also cause skin irritation and respiratory issues.
    • Animals: Livestock, pets, and wildlife that drink contaminated water are at risk of poisoning. Cyanotoxins have caused mass die-offs of fish, birds, and mammals in some regions.
  • Example:
    • Lake Erie (USA/Canada) has experienced severe cyanobacterial blooms in recent years, largely due to agricultural runoff containing high levels of phosphorus. In 2014, a cyanobacterial bloom in Lake Erie caused the city of Toledo, Ohio, to issue a "Do Not Drink" advisory due to the presence of microcystins in the city's drinking water supply. This event highlighted the serious risks posed by freshwater HABs to public health and water security.
Marine Example: Dinoflagellate ToxinsIn marine environments, dinoflagellates are often the primary culprits of HABs. One of the most well-known harmful algal blooms in marine ecosystems is the red tide, caused by certain species of dinoflagellates, including Karenia brevis.
  • Common Dinoflagellate Toxins:
    • Brevetoxins: Produced by Karenia brevis, brevetoxins are potent neurotoxins that can cause neurotoxic shellfish poisoning (NSP) in humans when contaminated shellfish are consumed. NSP symptoms include nausea, vomiting, diarrhea, and neurological effects such as tingling, muscle weakness, and in rare cases, respiratory failure.
    • Saxitoxins: Produced by various species of dinoflagellates, saxitoxins cause paralytic shellfish poisoning (PSP), a potentially fatal condition that affects the nervous system. Symptoms include tingling, numbness, paralysis, and respiratory failure.
  • Health Impacts:
    • Humans: Consumption of shellfish contaminated with brevetoxins or saxitoxins can lead to neurotoxic or paralytic shellfish poisoning. Inhalation of aerosolized brevetoxins (produced when waves break onshore during red tides) can also cause respiratory problems in humans.
    • Marine Animals: Fish, marine mammals, and seabirds are particularly vulnerable to the toxins produced during marine HABs. Fish kills are common during red tides, and marine mammals such as dolphins and manatees have been known to die from brevetoxin exposure.
  • Example:
    • Red Tide in the Gulf of Mexico (USA): The Gulf of Mexico frequently experiences red tides caused by Karenia brevis. These blooms produce brevetoxins, which contaminate shellfish and cause large-scale fish kills. The 2018 red tide was one of the most severe in recent history, affecting Florida's Gulf Coast. Beaches were closed, tourism suffered, and thousands of dead fish, dolphins, and sea turtles washed ashore due to brevetoxin exposure.
Organisms Involved in Harmful Algal Blooms
  • Cyanobacteria (Freshwater):
    • Also known as blue-green algae, cyanobacteria are one of the primary organisms responsible for HABs in freshwater systems. These bacteria are capable of producing a group of toxins known as cyanotoxins, which can be harmful or even fatal to humans, pets, and wildlife.
  • Dinoflagellates (Marine):
    • In marine ecosystems, dinoflagellates are one of the most common organisms involved in HABs. Some species of dinoflagellates produce potent toxins, including neurotoxins, which can contaminate shellfish and lead to serious health issues in humans and other animals. These marine HABs may also be referred to as "red tides" due to the red or brown discoloration of the water caused by the high concentration of dinoflagellates.
  • Protists and Other Algae:
    • Other types of algae and microorganisms, such as protists, can also contribute to harmful algal blooms. While not all species produce toxins, some can still cause significant environmental damage by depleting oxygen levels in the water, leading to fish kills and dead zones.
Environmental and Economic Impacts of HABs
  • Ecosystem Disruption: HABs can cause large-scale fish kills, disrupt food webs, and create dead zones where oxygen levels are too low to support life. This affects not only aquatic organisms but also the species that depend on them, including humans.
  • Economic Losses: HABs impact fisheries, tourism, and coastal economies. Fish kills reduce the availability of fish and shellfish, harming commercial and recreational fishing industries. Beach closures and contaminated water discourage tourism and recreation, leading to significant economic losses in affected regions.
  • Water Contamination: HABs can contaminate drinking water supplies, posing a serious public health risk. The cost of treating contaminated water is high, and in some cases, water supplies may become temporarily unsafe for human consumption.
Solutions to Red Tides
  • Nutrient Trading:
    • Establish nutrient trading programs to reduce excess nitrogen and phosphorus runoff.
    • Farmers and industries can trade pollution credits to encourage lower nutrient emissions into water bodies.
  • Red Tide Forecasts:
    • Use satellite data and water quality monitoring to forecast red tide events.
    • Early warnings help coastal communities and industries prepare and mitigate the impact on fisheries and tourism.
  • Reducing Runoff:
    • Implement better agricultural practices (e.g., buffer zones, controlled fertilizer use) to reduce nutrient runoff into waterways.
  • Public Awareness and Regulations:
    • Increase public awareness of red tide causes and impacts.
    • Enforce stricter regulations on wastewater and agricultural runoff to limit nutrient inputs.
  • Water Treatment Technologies:
    • Invest in advanced water treatment to reduce nutrient levels before they enter the ocean.
​4.4.11 The frequency of anoxic/hypoxic waters is likely to increase due to the combined effects on global warming, freshwater stratification, sewage disposal and eutrophication.
  • Define hypoxic and anoxic waters and explain how global warming contributes to the increase in these conditions.
  • Describe two ways in which freshwater stratification can contribute to the development of anoxic or hypoxic conditions in lakes and rivers
Hypoxia refers to low oxygen levels in water, typically below 2 mg/L, while anoxia refers to a complete absence of oxygen. These conditions can severely impact aquatic ecosystems by creating dead zones—areas where most marine or freshwater life cannot survive. Dead zones are becoming more common in both freshwater and marine environments, driven by a combination of environmental and human-induced factors.
The increasing frequency of hypoxia and anoxia in water bodies is linked to multiple causes, including global warming, stratification of freshwater, sewage disposal, and eutrophication. These factors can combine to exacerbate the decline of oxygen levels, creating conditions where aquatic life cannot thrive. Understanding the causes of hypoxia and anoxia is essential to mitigating their effects and protecting aquatic ecosystems.

Factors Contributing to Hypoxia and Anoxia
  • Global Warming:
    • Global warming is increasing the temperature of both marine and freshwater systems, which has significant effects on dissolved oxygen levels. As water warms, it loses its ability to hold oxygen, leading to lower dissolved oxygen concentrations.
    • Warmer temperatures also increase the metabolic rates of aquatic organisms, leading to higher oxygen demand. Combined with reduced oxygen solubility, this creates a perfect storm for the development of hypoxic or anoxic conditions.
    • Global warming is also leading to more extreme weather events, such as heavy rainfall, which can increase nutrient runoff from agriculture, further contributing to eutrophication and oxygen depletion.
  • Freshwater Stratification:
    • Stratification occurs when water bodies develop distinct layers based on temperature, salinity, or density. In freshwater systems, this often happens during the warmer months when the top layer (epilimnion) becomes warmer and less dense than the cooler, deeper layer (hypolimnion). The lack of mixing between these layers prevents the circulation of oxygen to deeper waters, leading to hypoxic or anoxic conditions in the bottom layers.
    • Stratification can be intensified by climate change, as warmer surface waters become more resistant to mixing. In lakes and reservoirs, this leads to seasonal dead zones where oxygen-depleted deep waters cannot support life.
  • Sewage Disposal:
    • The release of untreated or inadequately treated sewage into water bodies contributes significant amounts of organic matter and nutrients, particularly nitrates and phosphates. The organic matter is broken down by bacteria, a process that consumes large amounts of oxygen.
    • As oxygen is used up during decomposition, hypoxic or anoxic conditions can develop, particularly in enclosed or poorly circulating water bodies such as lakes, estuaries, and coastal zones. Sewage disposal is a major driver of oxygen depletion in many urban and developing regions.
  • Eutrophication:
    • Eutrophication, the over-enrichment of water bodies with nutrients (especially nitrates and phosphates), leads to excessive growth of algae and other aquatic plants. When these plants and algae die, they sink to the bottom, where they are decomposed by aerobic bacteria that consume oxygen.
    • This decomposition process is one of the leading causes of hypoxia and anoxia in water bodies, particularly in coastal areas that receive nutrient runoff from agriculture, wastewater, and urban sources. The resulting oxygen depletion can create large-scale dead zones, where oxygen levels are too low to support most marine life.
Picturehttps://climateandcapitalism.com/2020/08/12/dead-zones-industrial-agriculture-versus-ocean-life/
The Formation of Dead Zones
​
​Dead zones are areas in oceans, estuaries, and lakes where oxygen levels are too low to support most forms of life. These zones are typically caused by the combined effects of nutrient pollution, stratification, and climate change. Dead zones are expanding globally, particularly in coastal areas where nutrient pollution is high.

​
  • How Dead Zones Form:
    1. Nutrient Loading: Nutrients such as nitrates and phosphates enter water bodies from sources like agricultural runoff, sewage, and industrial discharge.
    2. Algal Blooms: The excess nutrients trigger the rapid growth of algae and phytoplankton, creating dense algal blooms.
    3. Decomposition: As the algae die, they sink to the bottom of the water body and are decomposed by bacteria. This decomposition process consumes large amounts of oxygen.
    4. Oxygen Depletion: Over time, oxygen levels drop significantly, creating hypoxic or anoxic conditions in the deeper layers of water.
    5. Dead Zones: Without sufficient oxygen, most aquatic organisms, such as fish and invertebrates, cannot survive, leading to the formation of dead zones.
  • Consequences of Dead Zones:
    • Biodiversity Loss: Dead zones lead to mass die-offs of fish, crustaceans, and other oxygen-dependent species. This loss of biodiversity can disrupt food chains and degrade ecosystem health.
    • Disruption of Fisheries: Commercial and recreational fisheries are often impacted by dead zones, as fish stocks decline in oxygen-depleted areas. This can lead to economic losses for fishing communities.
    • Ecosystem Imbalance: Dead zones often favor anaerobic bacteria, which can produce toxic byproducts such as hydrogen sulfide. These byproducts can further degrade water quality and harm remaining aquatic life.
Picture
https://www.vims.edu/research/topics/dead_zones/formation/
Examples of Dead Zones
  • The Gulf of Mexico Dead Zone (USA):
    • One of the largest and most well-known dead zones occurs annually in the Gulf of Mexico. This dead zone is primarily caused by nutrient runoff from the Mississippi River, which drains agricultural and urban areas in the Midwest. The excessive nutrients fuel algal blooms, and the subsequent decomposition process depletes oxygen in the Gulf’s waters.
    • The Gulf of Mexico dead zone can reach up to 22,000 square kilometers in size, affecting marine life, commercial fisheries, and local economies. The zone typically forms in the summer months, when nutrient runoff is highest and water temperatures are warm.
  • The Baltic Sea Dead Zone (Europe):
    • The Baltic Sea is home to one of the world’s largest hypoxic areas. This dead zone is largely caused by nutrient pollution from agriculture, sewage, and industrial sources in the countries surrounding the Baltic Sea.
    • Stratification in the Baltic Sea further exacerbates the oxygen depletion, as the denser saltwater at the bottom prevents mixing with the oxygen-rich surface waters. The dead zone has been expanding for decades and poses a significant threat to the Baltic’s marine ecosystems and fisheries.


Increasing Frequency of Hypoxic and Anoxic WatersThe frequency and severity of hypoxic and anoxic waters are expected to increase due to several converging factors:
  • Global Warming: Rising temperatures are reducing the ability of water to hold dissolved oxygen, increasing the likelihood of hypoxic events. Warmer waters also stratify more easily, further reducing oxygen mixing between layers.
  • Increased Nutrient Pollution: As agricultural practices intensify and urban populations grow, nutrient pollution is expected to rise. This will increase the frequency of eutrophication events, which are closely linked to the formation of hypoxic and anoxic waters.
  • Coastal Development: Coastal areas are particularly vulnerable to hypoxia due to the concentration of human activities such as agriculture, industry, and urbanization. As coastal populations grow, so does the pressure on marine ecosystems from nutrient runoff and sewage disposal.

Sewage treatment

​4.4.12 Sewage is treated to allow safe release of effluent by primary, secondary and tertiary water treatment stages.
  • Explain how global warming contributes to the formation of hypoxic conditions in aquatic ecosystems.
  • Describe the role of sewage disposal in creating hypoxic or anoxic conditions in water bodies
  • Explain how freshwater stratification can lead to hypoxia in lakes and reservoirs.
​Sewage treatment is a multi-stage process designed to remove contaminants from wastewater to make it safe for release into the environment. This process is crucial for preventing water pollution, protecting ecosystems, and ensuring public health. Treatment typically involves three stages: primary, secondary, and tertiary treatment. Each stage addresses different types of pollutants using biological, chemical, and physical processes. However, challenges remain in implementing equitable sewage treatment systems across different societies, especially in developing countries.
Picture
https://www.meridianmicrotechnology.com/post/how-does-a-sewage-treatment-plant-stp-work
Sewage Treatment Stages

Primary Treatment:
  • Objective: Remove large solid particles and settleable organic material.
  • Process:
    • In this stage, mechanical processes such as screening and sedimentation are used to remove large debris, sand, grit, and organic solids from wastewater.
    • Wastewater flows through screens to remove large objects such as sticks, plastics, and other debris.
    • Sedimentation tanks allow heavier solids (known as sludge) to settle at the bottom, while lighter materials (like grease) float to the surface and are removed.
  • Key Outcome: Primary treatment removes about 30-50% of suspended solids and reduces the biological oxygen demand (BOD) by 20-30%, but it does not remove dissolved substances or pathogens.

Secondary Treatment:
  • Objective: Remove dissolved organic matter and further reduce BOD using biological processes.
  • Process:
    • Secondary treatment relies on biological processes involving microorganisms (such as bacteria) to decompose organic matter in the wastewater.
    • The two main methods are activated sludge systems and trickling filters.
      • Activated sludge systems: Wastewater is aerated to stimulate microbial growth. The microbes consume organic matter and convert it into carbon dioxide, water, and biomass.
      • Trickling filters: Wastewater is distributed over a bed of stones or plastic media where biofilms of microorganisms grow and break down organic material as the water trickles through.
    • After the biological treatment, the wastewater goes through a secondary clarifier to allow the sludge (biomass and residual solids) to settle. The sludge can be recycled back into the system or processed further.
  • Key Outcome: Secondary treatment removes 85-90% of organic material and BOD, and significantly reduces pathogens.

​Tertiary Treatment:
  • Objective: Remove remaining nutrients, pathogens, and fine particles to produce water that is safe for release or reuse.
  • Process:
    • Tertiary treatment often involves a combination of chemical, physical, and biological processes to remove remaining contaminants, such as nitrates, phosphates, heavy metals, and pathogens.
    • Chemical coagulation and flocculation: Chemicals (e.g., alum) are added to clump together small particles into larger aggregates, which can then be removed through sedimentation or filtration.
    • Nutrient removal: Phosphates and nitrates, which contribute to eutrophication, are removed through processes such as biological nutrient removal (BNR) or chemical precipitation.
    • Disinfection: This step kills harmful pathogens (bacteria, viruses, and parasites) to prevent the spread of waterborne diseases. Common disinfection methods include chlorination, ozonation, and UV radiation.
    • Filtration: Fine filters (e.g., sand filters) or membrane filtration are used to remove any remaining suspended solids.
  • Key Outcome: Tertiary treatment produces water that is safe for discharge into sensitive environments (e.g., lakes, rivers) or for reuse in irrigation, industrial processes, or even drinking (with additional treatment). It removes 99% of contaminants.
Challenges of Implementing Sewage Treatment Equitably
  • Access to Infrastructure:
    • Developing countries often lack the financial resources and infrastructure to build and maintain comprehensive sewage treatment facilities. In rural or impoverished areas, untreated or poorly treated sewage is often released directly into rivers, lakes, or the ocean, leading to water pollution and public health risks.
    • Urban areas in developing countries may also face challenges in expanding their sewage treatment capacity to keep up with rapid population growth and urbanization, leading to untreated wastewater being released into the environment.
  • Cost and Technological Barriers:
    • Tertiary treatment is costly and technologically complex, which limits its implementation in many parts of the world. The chemicals, equipment, and expertise required to carry out advanced processes like nutrient removal and disinfection may not be available in low-income regions.
    • Even in wealthier nations, upgrading outdated sewage treatment plants to include tertiary processes can be expensive and politically challenging.
  • Regulatory and Policy Issues:
    • In some countries, there are inadequate regulations or enforcement around wastewater treatment, allowing untreated or inadequately treated sewage to be discharged into water bodies. This contributes to widespread pollution, especially in countries with weak environmental policies.
    • The lack of political will or corruption may delay investment in sewage treatment infrastructure, further compounding the issue.
  • Health and Environmental Impacts:
    • Inequitable access to sewage treatment contributes to widespread waterborne diseases in regions where untreated sewage contaminates drinking water sources. Diseases such as cholera, typhoid, and dysentery are common in areas without proper sewage treatment, leading to high mortality and morbidity rates.
    • Environmental degradation occurs when untreated sewage leads to nutrient pollution (eutrophication), oxygen depletion, and ecosystem collapse in rivers, lakes, and coastal areas. The resulting dead zones harm biodiversity and impact fisheries and tourism.
  • Cultural and Social Factors:
    • In some regions, cultural or social factors may hinder the development of sewage treatment facilities. For instance, inadequate public awareness about the importance of sewage treatment may lead to opposition to sewage treatment plants or wastewater reuse programs.
    • In informal settlements and densely populated urban areas, installing sewage infrastructure can be logistically difficult due to the lack of space, complex land ownership issues, or resistance from local communities.

water quality

4.4.13 Some species are sensitive to pollutants or are adapted to polluted waters, so these can be
used as indicator species.
  • Discuss the role of using biotic indices to determine the quality of aquatic ecosystems.
  • Explain the difference between pollution-tolerant and pollution-intolerant indicator species.
Indicator species are organisms that provide information about the environmental conditions of a particular habitat. Their presence, absence, or abundance can indicate the quality of the ecosystem, particularly in relation to pollution levels. Some species are tolerant of pollution and thrive in degraded environments, while others are intolerant and only survive in clean, unpolluted environments. By monitoring these species, scientists can assess the health of aquatic ecosystems and detect the effects of pollution..
There are two main types of indicator species:
  • Tolerant species: Can thrive in polluted environments and are often used to signal that a habitat is experiencing environmental stress.
  • Intolerant species: Require high water quality and clean environments, and their presence usually indicates a healthy, unpolluted ecosystem.
​Tolerant Species (Pollution-Resistant Indicators)

Tolerant species can survive in polluted or degraded environments where many other organisms cannot. These species are adapted to tolerate poor water quality, low oxygen levels, or the presence of toxic substances. The presence of these species often indicates that an ecosystem is under stress due to pollution.
  • Tubifex Worms (Tubifex spp.):
    • Habitat: Found in freshwater environments, particularly in the sediment of lakes, rivers, and streams.
    • Pollution Tolerance: Tubifex worms are highly tolerant of low oxygen levels and thrive in environments with high levels of organic pollution. They are often found in areas with sewage contamination or heavy nutrient loads.
    • Indicator Role: Their presence in large numbers is an indication of poor water quality, high levels of organic pollution, and low dissolved oxygen. These worms are often used as indicators in benthic (bottom-dwelling) assessments of water pollution.
    • Importance: Tubifex worms can survive in hypoxic (low-oxygen) conditions by breathing through their skin. When these worms dominate a water body, it suggests that the ecosystem is highly polluted and not suitable for more sensitive species.
  • Leeches (Class Hirudinea): Leeches can survive in polluted or low-oxygen waters. Their presence in large numbers often indicates poor water quality.
  • Mosquito Larvae (Family Culicidae): Mosquito larvae thrive in stagnant, polluted waters where other species may struggle to survive. They are often found in areas with high organic pollution, such as sewage-contaminated water bodies.

​Intolerant Species (Pollution-Sensitive Indicators)

Intolerant species are highly sensitive to pollution and environmental changes. These species can only survive in clean, well-oxygenated waters. Their presence in an ecosystem is usually a sign that the water is of high quality, with low pollution levels. If these species are absent or in decline, it may indicate that pollution levels are rising.
  • Mayfly Nymphs (Order Ephemeroptera):
    • Habitat: Found in clean, well-oxygenated freshwater habitats such as streams, rivers, and lakes.
    • Pollution Intolerance: Mayfly nymphs are very sensitive to pollution, particularly low oxygen levels, heavy metals, and chemical pollutants such as pesticides or industrial waste. They require high levels of dissolved oxygen to survive.
    • Indicator Role: The presence of mayfly nymphs in a water body indicates good water quality and a healthy ecosystem. The absence or decline of these nymphs suggests that the water is becoming polluted or that dissolved oxygen levels are too low.
    • Importance: Mayfly nymphs are an important part of freshwater ecosystems, serving as a food source for fish and other aquatic organisms. Their sensitivity to pollution makes them a valuable bioindicator for monitoring water quality.
  • Stonefly Nymphs (Order Plecoptera): Like mayfly nymphs, stonefly nymphs are highly sensitive to pollution and require clean, fast-flowing, well-oxygenated water. Their presence indicates excellent water quality.
  • Caddisfly Larvae (Order Trichoptera): Caddisfly larvae are found in clean freshwater habitats and are sensitive to changes in water chemistry. They are often used as indicators of unpolluted streams and rivers.
Picture
image from www.biomagazine.gr
4.4.14 A biotic index can provide an indirect measure of water quality based on the tolerance to pollution, relative abundance and diversity of species in the community.
  • Explain how a biotic index provides an indirect measure of water quality.
  • Outline the main factors that are considered when calculating a biotic index for a river ecosystem.
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A biotic index is a tool used to assess water quality by examining the types and abundance of living organisms present in a water body. It provides an indirect measure of water quality, as different species have varying levels of tolerance to pollution. By evaluating the presence and diversity of organisms, particularly indicator species, scientists can determine whether a water body is clean, moderately polluted, or heavily polluted.
​
Biotic index is a scale 1-10 that gives a measure of the quality of an ecosystem by the presence and abundance of the species living in it. The Trent Biotic Index is based on the fact that certain species tend to disappear and the species diversity decreases as the organic pollution in a water course increases. The scale corresponds to the four basic water quality (Excellent, Good, Fair or Poor). 

Using this index and indicator species is another indirect method of measuring pollution. The pollutant are not measured directly but their effect on biodiversity is measured. 
  • Aquatic macroinvertebrates are often used as an indicator species. They have some general characteristics that make them very useful to assess stream health. 
  • abundant and found in water bodies throughout the world
  • not extremely mobile.
  • carry out part or all of their life cycle within the stream or river.

Key Components of a Biotic Index
  • Tolerance to Pollution:
    • Species differ in their ability to survive in polluted environments. Some species are highly tolerant of pollution and can thrive in low-oxygen or high-nutrient conditions, while others are intolerant and require clean, well-oxygenated water.
    • Pollution-tolerant species, such as tubifex worms and leeches, often dominate in polluted waters. Their presence indicates lower water quality.
    • Pollution-sensitive species, such as mayfly and stonefly nymphs, are only found in clean waters. Their presence indicates high water quality.
  • Relative Abundance:
    • The number of individuals of each species present in a water body can provide information about pollution levels. A high abundance of tolerant species and a low abundance of sensitive species typically indicates pollution.
    • In contrast, a diverse community with many individuals of pollution-sensitive species suggests good water quality.
  • Species Diversity:
    • The diversity of species in a community is an important indicator of ecosystem health. Clean, healthy water bodies tend to support a greater diversity of species, including both pollution-sensitive and pollution-tolerant organisms.
    • Polluted water bodies, especially those with significant organic pollution, often have low species diversity, dominated by a few tolerant species.

The biotic index works by assigning different levels of tolerance to pollution to the different types of organisms. The types of macroinvertebrates found during sampling are grouped as:
  1. Pollution intolerant: These organisms are highly sensitive to pollution. (e.g., stonefly or alderfly larv
  2.  Semi-Pollution intolerant: These organisms are sensitive to pollution. (e.g.. dragonfly larva or crawfish)
  3. Semi-Pollution tolerant: These organisms will be found in clean and slightly polluted waterways. (e.g., snails or black fly larva)
  4. Pollution tolerant: These organisms will be found in polluted, as well as clean aquatic ecosystems (e.g., leechs, bloodworms)
Application of skills: Apply protocols for assessing biological oxygen demand and a named biotic index.
4.4.15 Overall water quality can be assessed by calculating a water quality index (WQI).
  • Explain how the Water Quality Index (WQI) provides a simplified measure of water quality.
  • Describe two key water quality parameters commonly used in calculating a WQI and explain their importance.
​A Water Quality Index (WQI) is a numerical representation of the overall quality of water in a given sample, providing a simplified and standardized way to assess how suitable the water is for various uses such as drinking, recreation, or ecosystem health. A WQI is a single, weighted average, calculated from the results of multiple individual water quality test parameters. This combined value offers an easy-to-understand metric that reflects the degree of contamination in the water.
Calculating WQI:
  • The WQI is calculated by measuring individual water quality parameters, such as DO, pH, and turbidity. Each parameter is compared to a reference standard (e.g., WHO water quality guidelines).
  • Each parameter is then assigned a sub-index score based on how close its value is to the ideal condition. The weighted average of these sub-indices gives the overall WQI score.
Uses of WQI:
  • WQI helps to communicate water quality status to policymakers, the public, and environmental managers.
  • It simplifies complex data, making it easier to understand the overall condition of a water body and track changes over time.

Using Water Quality Data to Inform Management Strategies
Monitoring water quality provides essential data that can inform various management strategies aimed at reducing pollution and improving water health:
  • Identifying Sources of Pollution:
    • Water quality monitoring helps to pinpoint the sources of pollution, whether from agricultural runoff, industrial effluents, or urban waste. By identifying the sources, governments can implement targeted regulations and cleanup efforts.
  • Developing Regulations:
    • Data from water quality monitoring can guide the development of environmental regulations, such as limits on the discharge of pollutants. For example, regulations on nutrient levels (nitrates and phosphates) in agricultural runoff can help control eutrophication.
  • Restoration Projects:
    • Water quality data can inform restoration projects, such as reforestation of riverbanks to reduce erosion and runoff, or the creation of buffer zones around agricultural fields to limit nutrient leaching into waterways.
  • Public Health Protection:
    • Monitoring water quality ensures that drinking water sources are safe. When pollutants like metals or pathogens are detected, management agencies can issue advisories or take steps to treat the water and protect public health.
  • Adaptive Management:
    • Continuous monitoring allows for adaptive management, where strategies are adjusted based on real-time data. For example, if dissolved oxygen levels drop due to algal blooms, authorities can take immediate action to reduce nutrient inputs.
Importance of the Water Quality Index
The WQI provides a simplified and easy-to-understand measure of water quality that can be used by policymakers, water resource managers, and the public to assess the condition of a water body. It is particularly useful for:
  • Public Communication: The WQI condenses multiple water quality data points into a single value that is easy to interpret. This helps the public understand the general health of water sources without needing technical expertise.
  • Monitoring Changes Over Time: A WQI allows for long-term monitoring of water quality. Changes in the WQI score over time can signal improvements or deterioration in water quality, allowing for timely interventions.
  • Water Management Decisions: The WQI can guide decisions related to water treatment, pollution control, and environmental protection. It helps identify which water bodies need restoration or stricter regulation of pollutants.

Challenges in Using the WQI
  • Parameter Selection:
    • Not all water quality indices use the same set of parameters. Depending on the specific water body or region, certain parameters may be more important than others. For example, thermal pollution might be critical in one area, while nutrient pollution could be more pressing in another.
  • Weighting Factors:
    • The relative importance of each parameter varies based on local environmental conditions and the intended use of the water (e.g., drinking, recreation, or agriculture). Deciding on appropriate weighting factors can be challenging and may require expert knowledge.
  • Local Adaptation:
    • A WQI developed for one region may not be directly applicable to another, as different regions may have unique environmental conditions, pollution sources, and regulatory standards.
  • Missing Factors:
    • The WQI provides a general assessment of water quality but may not detect specific contaminants such as heavy metals, pesticides, or pathogens that could still pose significant risks to human health and the environment.

Comparison to Biotic Indices
​While a biotic index measures water quality indirectly through the presence of certain species, a WQI combines various chemical and physical measurements to produce a more comprehensive view of water quality. Both methods have their strengths:
  • A biotic index reflects the long-term effects of water quality on living organisms and ecosystems.
  • A WQI provides a snapshot of water quality based on a range of parameters, offering a more quantitative analysis of contamination levels.
Example: Vernier’s Water Quality Index (WQI)Vernier’s
WQI is a commonly used example of a water quality index. It uses specific water quality parameters to assess overall water quality and is often employed in environmental education, research, and water management. The parameters used in Vernier’s WQI include dissolved oxygen, pH, turbidity, temperature, nitrates, phosphates, and other factors.
  • Calculation Method:
    • Vernier’s WQI takes readings from each water quality parameter and assigns a sub-index value for each. These sub-index values are based on how the results of each parameter compare to established water quality standards.
    • Each sub-index is then multiplied by a weighting factor, which reflects the relative importance of the parameter to overall water quality.
    • Finally, the weighted sub-indices are summed to produce the overall WQI score.
  • Interpreting the WQI Score:
    • 0-25: Very poor water quality (severe contamination, not suitable for most uses).
    • 26-50: Poor water quality (not suitable for drinking, may require treatment for other uses).
    • 51-70: Moderate water quality (suitable for some uses, but with potential contamination).
    • 71-90: Good water quality (generally safe for most uses, minor contamination).
    • 91-100: Excellent water quality (clean, safe for all uses, minimal or no contamination)
Activity: Consider the role of regulations and standards in environmental impact assessments and international business agreements,
4.4.16 Drinking water quality guidelines have been set by the World Health Organization (WHO), and local governments can set statutory standards.
  • Outline the role of WHO drinking water quality guidelines in protecting public health.
  • Describe two key factors that a private company must consider when adhering to local statutory water standards in a developing country.
The World Health Organization (WHO) provides global guidelines for drinking water quality to ensure that water is safe for human consumption. These guidelines establish minimum standards for various contaminants and parameters, such as microbial, chemical, and physical characteristics of water, to protect public health. Local governments are responsible for translating these guidelines into statutory standards, which are legally binding and enforceable within their jurisdictions. These standards are crucial in protecting communities from waterborne diseases and harmful pollutants.


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WHO Drinking Water Quality Guidelines
​
The WHO’s Guidelines for Drinking-water Quality serve as an international reference for setting drinking water standards. They cover a wide range of potential contaminants and ensure that water is safe for human consumption. Some key components of the guidelines include:
  • Microbiological Quality:
    • Drinking water should be free of pathogenic microorganisms (e.g., bacteria, viruses, protozoa) that can cause waterborne diseases like cholera, dysentery, and typhoid. The presence of Escherichia coli (E. coli) is often used as an indicator of fecal contamination.
  • Chemical Quality:
    • Chemical contaminants such as arsenic, lead, nitrates, and pesticides must be kept below recommended levels to avoid long-term health effects. For example, high nitrate levels can cause conditions such as methemoglobinemia ("blue baby syndrome"), while prolonged exposure to arsenic is linked to cancer.
  • Physical Quality:
    • Parameters like turbidity, color, and taste also play a role in water quality. While these may not always pose direct health risks, they affect the public’s perception of water safety.
Role of Local Governments in Setting Standards
Local governments take the WHO guidelines and adapt them to their specific circumstances, setting statutory standards that take into account the regional context, including the available infrastructure, local sources of pollution, and public health needs. These standards become legally enforceable, requiring water suppliers, municipalities, and private companies to comply with regulations that ensure safe drinking water.
Regulations and Standards in International Business Agreements
When a private company, such as a water bottling company, enters into agreements to operate in a developing country, regulatory standards related to water quality are a key consideration. International business agreements must ensure that companies adhere to both international guidelines (such as the WHO’s) and local statutory standards. This helps ensure that the company’s activities do not compromise the availability or quality of drinking water for local populations. Some important considerations include:
  • Corporate Social Responsibility (CSR):
    • Companies that build water bottling plants or similar facilities in developing countries must often demonstrate that their operations will have positive impacts on local communities. This can include ensuring access to clean water for local populations, reducing their environmental footprint, and engaging in sustainable water management practices.
  • Compliance with Local Laws:
    • Local statutory standards ensure that multinational companies respect the country’s environmental regulations. This may involve adhering to water abstraction limits, water quality monitoring, and effluent discharge standards to prevent environmental degradation and ensure the sustainability of local water resources.
  • International Standards:
    • Many international business agreements will require compliance with international guidelines, such as those set by the International Finance Corporation (IFC) or other development organizations. These guidelines align with WHO recommendations and focus on sustainable business practices, especially when companies operate in developing nations with vulnerable water resources.
Case Study: Nestlé’s Water Bottling Operations in California, USA
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INestlé Waters North America has operated water bottling facilities in California, including extracting water from springs in the San Bernardino National Forest, for decades. The company has been bottling this water and selling it under its various bottled water brands. However, during the extended droughts in California, the company came under scrutiny for continuing its water extraction operations in a water-scarce region







​Key Issues:
  • Water Depletion in a Drought-Stricken Region: Critics argued that Nestlé’s extraction of large amounts of water from a public forest during a severe drought exacerbated water scarcity for local communities, wildlife, and ecosystems.
  • Permitting and Regulations: Nestlé’s water extraction permit from the U.S. Forest Service had expired in 1988, yet they continued operations for years under the expired permit. This raised questions about regulatory oversight and enforcement.
  • Community and Environmental Impact: Environmental groups claimed that water extraction was lowering the water table, reducing stream flows, and damaging the local ecosystem, particularly impacting habitats of endangered species.
Environmental Impact Assessment (EIA):
  • Lack of Rigorous EIA: The outdated permitting system allowed Nestlé to operate without an updated environmental impact assessment that considered the long-term effects of water extraction on the local ecosystem, especially in light of increasing droughts in California.
  • Regulatory Gaps: This case highlighted how regulatory gaps can allow companies to continue operations without re-evaluating their environmental impacts, even in environmentally sensitive areas like national forests.
Regulatory Response:
  • After public pressure and lawsuits from environmental groups, the U.S. Forest Service reviewed Nestlé’s operations. In 2021, the California State Water Resources Control Board ordered Nestlé to cease unauthorized water withdrawals from the San Bernardino National Forest.
  • The company was found to be extracting far more water than was allowed under its outdated permit, leading to stricter enforcement and a reassessment of water rights.
Activity: Research a real-world example of a private company establishing a water bottling plant in a developing country (e.g., Coca-Cola, Nestlé).
  • Identify the regulations (both international and local) that applied to the project, focusing on water usage, waste management, and environmental impact.
  • Review the Environmental Impact Assessment (EIA) process that was followed, and describe the findings related to water resources, pollution, and community impacts.
  • What international water quality standards (e.g., WHO guidelines) were applied to the water bottling plant?
  • What local regulations were enforced to ensure environmental protection and water sustainability?
  • ​What were the main environmental concerns identified in the EIA related to the water bottling plant?
  • How did the company respond to these concerns? Were there any changes made to the project design or operations?
4.4.17 Action by individuals or groups of citizens can help to reduce water pollution.
  • Outline two ways individuals can reduce water pollution through changes in their consumption habits.
  • Describe the role of peaceful protests in reducing water pollution and raising public awareness.
  • Explain how citizen science can contribute to reducing water pollution.
Water pollution poses a significant threat to ecosystems, human health, and biodiversity. While governments and corporations play a large role in managing and mitigating pollution, individuals and citizen groups can also take meaningful action to reduce water pollution through a range of activities. These actions can include changing personal consumption habits, engaging in peaceful protests, conducting research, forming legal teams, and lobbying lawmakers to create stricter regulations on water use and pollution control.

Changes to Consumption and Waste Disposal
​One of the most effective ways individuals can reduce water pollution is by changing their consumption habits and the way they dispose of waste. Some of the key strategies include:
  • Reducing Plastic Use: Plastics are a major source of water pollution, particularly in the form of microplastics. Individuals can minimize plastic pollution by reducing single-use plastic consumption (e.g., bottles, straws, packaging), choosing reusable products, and participating in plastic recycling programs.
  • Proper Disposal of Hazardous Waste: Household chemicals, paints, batteries, and pharmaceuticals can contaminate water sources if they are disposed of improperly. Citizens can reduce pollution by using designated disposal centers for hazardous waste instead of dumping them down the drain or into landfills.
  • Adopting Sustainable Products: Choosing environmentally friendly products, such as biodegradable cleaning products, organic fertilizers, or pesticides, can reduce the amount of harmful chemicals that end up in water bodies through runoff.
  • Conserving Water: Using water more efficiently helps prevent excess runoff from entering sewage systems, reducing the chances of water contamination. Practices such as installing low-flow toilets, fixing leaks, and using greywater systems can help.

Peaceful Citizen Protests and Advocacy
Citizen groups can organize peaceful protests to raise awareness about water pollution issues and put pressure on governments or corporations to take action. Peaceful protests can lead to public awareness campaigns that encourage more people to join the cause. Examples include:
  • Protesting Industrial Pollution: Citizens may gather to protest industries that discharge untreated or poorly treated wastewater into rivers and lakes. These protests often focus on demanding better treatment facilities and stricter enforcement of regulations.
  • Opposing Harmful Infrastructure Projects: Protests can also focus on infrastructure projects that threaten water quality, such as the construction of dams or water bottling plants that may over-extract water and contribute to pollution.
  • Raising Awareness: Large-scale events such as World Water Day or local community initiatives help raise awareness and educate the public about the importance of protecting water resources.

Data Collection and Research by Citizen Scientists
Citizen science allows individuals or groups of non-professional scientists to gather important data on local water bodies. This data can be used to monitor pollution levels, detect harmful substances, and help inform decision-making by governments or environmental agencies. Examples of citizen science initiatives include:
  • Water Quality Monitoring: Individuals or groups can use simple testing kits to measure parameters such as pH, nitrates, phosphates, dissolved oxygen, and turbidity in local rivers, lakes, and streams. This data can be shared with local authorities or environmental NGOs to identify polluted areas that need attention.
  • Tracking Pollutants: Citizens can participate in larger initiatives like tracking plastic waste or monitoring pollution from agricultural runoff. Community-based water monitoring programs often encourage volunteers to help identify the sources of pollution.
  • Crowdsourcing Environmental Data: Platforms like Global Water Watch allow citizen scientists to upload water quality data, contributing to large-scale databases that help track pollution trends over time.

Formation of Legal Teams and Environmental Advocacy Groups
Citizen groups can also form legal teams and work with environmental organizations to take legal action against polluters or advocate for stronger environmental protections. Some key legal strategies include:
  • Filing Lawsuits Against Polluters: Legal teams can sue companies or municipalities that violate water quality regulations by discharging pollutants into water bodies. For example, lawsuits can be filed under local environmental laws or, in some countries, under international environmental agreements.
  • Advocating for Stronger Environmental Laws: Citizen groups can work with legal teams to push for stricter enforcement of existing water quality laws or the development of new policies that better protect water resources. Legal challenges can also aim to hold governments accountable for failing to enforce water pollution regulations.
  • Pursuing Class-Action Lawsuits: In some cases, entire communities affected by water pollution—such as those impacted by toxic spills or industrial waste—can form a collective legal case against the polluting entity. These lawsuits can lead to compensation for affected populations and the implementation of remediation measures.

​Lobbying Lawmakers and Policy Makers
Citizens can influence water policy by lobbying lawmakers and pushing for regulatory changes that promote cleaner water systems. Some actions include:
  • Campaigning for New Water Pollution Laws: Lobbying efforts can focus on passing new legislation to prevent water pollution. For instance, activists may push for laws that ban the use of certain chemicals in agriculture or manufacturing, or stricter regulations for waste management.
  • Strengthening Existing Regulations: Lobbying can also target amendments to existing laws, such as increasing penalties for illegal dumping or industrial violations, or mandating the use of environmentally friendly technologies in wastewater treatment.
  • Engaging with Local and National Governments: Citizen groups can present petitions, hold meetings with government officials, and participate in public hearings to influence water-related decision-making. These efforts can result in stronger water protection policies and improved enforcement of existing laws.
  • International Pressure: Citizen groups can also work with international organizations or non-governmental organizations (NGOs) to apply pressure on governments to meet international environmental standards, such as those set by the World Health Organization (WHO) or United Nations Environment Programme (UNEP).
Key Terms
Water pollution
Plastic debris
Ocean gyres
Microplastics
Eutrophication

​HL ONLY
Biotic index
​Citizen science
Water quality index (WQI)
Wastewater treatment
Persistent organic pollutants (POPs)
Biomagnification
Endocrine disruptors
Tributyltin (TBT)
​Cyanobacteria
Harmful algal blooms (HABs)
​Anoxic dead zones
Hypoxia in oceans
Biodegradable products
Nutrient runoff
Hypoxia
Anoxia
Dissolved oxygen (DO)
Industrial effluents
Agricultural runoff
Biological Oxygen Demand (BOD)
Algal blooms
​Phytoplankton
Hypoxia
​Anoxia
Classroom Material
Subtopic 4.4 Water Pollution Presentation.pptx
File Size: 15326 kb
File Type: pptx
Download File
Subtopic 4.4 Water Pollution Workbook.docx
File Size: 1296 kb
File Type: docx
Download File

Dirty Waters
Water Pollution Guide
Procedure for Measuring BOD
Freshwater Pollution Case Study Activity
Water Pollution Case Study Activity

​Case Studies
  • One example explaining the process and impacts eutrophicat​ion (eg. the eutrophication of the Baltic Sea) 

 Lake Udaisagar in India
Loch Leven in UK
Baltic Sea
Lake Washington
Ganges River
Deep Water Horizons
​Flint Water Crisis
​​Correct use of terminology is a key skill in ESS. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.
Pictureimage from qsr2010.ospar.org
Useful Links

Water Pollution Guide
Environmental Biotechnology - EnviroTech
Measuring Air PollutionAir Pollution Monitoring - EPA
Dissolved Oxygen and Biochemical Oxygen Demand - EPA
Biotic Index - Water Action Volunteers

Chesapeake Bay BioIndex - IAN
Bio-indicators - Knowledge Group​Animation from the Center for Ocean Sciences Education Excellence.
Sources and Impact of Eutrophication
Eutrophication: Policies, Action and Strategies to Address Nutrient Pollution
Facts and Figures about Eutrophication
Planning and Management of Lakes and Reservoirs focusing on Eutrophication (PAMOLARE)
How bad is Eutrophication at Present?
Lake Eutrophication
Planning and Management of Lakes and Reservoirs: An Integrated Approach to Eutrophication - A Student's Guide By the United Nations Environment Programme (UNEP) International Environmental Technology Centre (IETC). © UNEP 2001.
Dead Zones - Save The Seas
Causes of Water Pollution: Nine Significant Contributors
Water Pollution Facts: For the U.S. and Throughout the World
Effects of Water Pollution: 8 Significant Issues
Radioactive Water from Japan’s Nuclear Power Plant - Does It Affect People in the United States
Solutions to Water Pollution - 5 Simple Ways You Can Make a Difference
​In the News
Trying to Save World's Lakes: Controlling Nitrogen Can Actually Worsen  Problem - Science Daily July 24, 2008
Eutrophication on the Baltic Sea - The Baltic Sea Portal
150 Dead Zones Counted In Ocean - NBC News 3/29/2004
Creeping Dead Zones - NASA Science Focus
What Causes Dead Zones - Scientific America Sep 2015
International-mindedness:
  • Countries with limited access to clean water often have higher incidences of waterborne illnesses.
Theory of knowledge:
  • A wide range of parameters are used to test the quality of water and judgments are made about causes and effects of water quality—how can we effectively identify cause–effect relationships, given that we can only ever observe correlation?
​Video Clips
Paul Andersen explains how water quality can be degraded by pollutants. Wastewater is the main source of water pollution and can be measure using the BOD (biochemical oxygen demand). Dead zones, cultural eutrophication, disease, and other pollutants are included. A basic description of sewage treatment, septic systems, and water purification is also included.
Pete McBride takes a photographic and scientific journey along India's sacred waterway, the Ganges, which is revered as a god but struggles with a detrimental pollution problem
Here, Dr.Askwar Hilonga demonstrates how his water filter works.......some sort of marketing and INSPIRATION to his community. Of course it takes time for people to believe that this is TRULY what they have been missing! Hilonga won the Africa Prize for Engineering 2015, sponsored by the Royal Academy of Engineering, UK
Even though 80% of trash starts on land, tons of it ends up in the ocean, swirling around in a massive patch of plastic debris.
TED talk on the Great Pacific Garbage Patch -- an endless floating waste of plastic trash.
Discovering the dirty truth about the future of the Baltic Sea. - See more at: http://www.saveourbalticsea.com/index.php/tv-a-film/dirty-waters#sthash.tNRn2lHl.dpuf
Keeping farm field runoff from reaching the Mississippi River is the focus of a U.S. Department of Agriculture conservation effort in Missouri.