Water Pollution's Impact On Temperature: A Complex Relationship

Water temperature is a critical factor in determining water quality. It influences the types and diversity of aquatic life, the maximum dissolved oxygen concentration, and the rate of chemical and biological reactions. Human activities such as industrial cooling, power plant operations, and urban runoff can cause thermal pollution, leading to abrupt changes in water temperature. These changes can have detrimental effects on aquatic ecosystems, including reduced biodiversity, altered food chains, and decreased oxygen levels. Understanding and managing water temperature is crucial for maintaining the health and balance of aquatic environments.

Thermal pollution

Causes of Thermal Pollution

In addition to power plants, other industrial sources of thermal pollution include petroleum refineries, pulp and paper mills, chemical plants, and steel mills. These facilities also use water to cool machinery and discharge water at elevated temperatures.

The process of sucking in water from a natural source and releasing heated water back is called once-through cooling and has been known to adversely affect aquatic environments. Deforestation and human land-use changes can also cause thermal pollution by exposing rivers and streams to more sunlight, leading to water warming.

Impacts of Thermal Pollution

Mitigation of Thermal Pollution

Oxygen levels

Natural Factors Influencing Oxygen Levels

• Elevation: Streams get much of their oxygen from the atmosphere, so streams at higher elevations will generally have less oxygen.
• Salinity: Salty water holds less oxygen than fresh water.
• Temperature: Cold water can hold more dissolved oxygen than warm water. As water temperatures increase, dissolved oxygen levels decrease.
• Turbulence: More turbulence creates more opportunities for oxygen to enter streams.
• Aquatic Vegetation: Aquatic vegetation and algae directly release oxygen into the water during photosynthesis (during the day). At night, plants use oxygen for their metabolism.
• Riparian Vegetation: Plants along the stream shade the water, decreasing temperatures, and as temperature decreases, dissolved oxygen increases.

Human Factors Influencing Oxygen Levels

• Clearing Land: Construction and logging may send excess organic matter into streams. Microorganisms decompose this matter, using up oxygen in the process.
• Point Source Pollution: Sewage effluent and factory discharge into waterways can be decomposed by bacteria, leading to areas of low oxygen downstream.
• Nutrient Pollution: Nutrient pollution can cause excess plant and algae growth. The bacteria that eat dead plant material consume oxygen from the water.
• Destruction of Riparian Areas: Development or overgrazing decreases the amount of shade and increases water temperature. Warmer water holds less dissolved oxygen than colder water.

Effects of Low Oxygen Levels

Low oxygen levels can have a significant impact on aquatic life. Fish and other aquatic organisms may struggle to survive in stagnant water with high levels of rotting organic material, especially during the summer when dissolved oxygen levels are typically at a seasonal low.

Low oxygen levels can also lead to eutrophic conditions, an oxygen-deficient situation that can cause a water body to "die". This can result in the loss of many fish, as seen in summertime fish kills in local lakes.

Additionally, low oxygen levels can contribute to the formation of "dead zones", such as the one in the Gulf of Mexico, where subsurface waters become depleted of oxygen and cannot support most life.

Biochemical effects

Water pollution has a range of biochemical effects on the environment and human health.

Water pollution can cause eutrophication, which is the depletion of dissolved oxygen in the affected water body. This occurs when large quantities of nutrients are introduced into a water body. This can kill fish and other aquatic organisms. Eutrophication can be caused by the increase in temperature in water bodies, which decreases the solubility of oxygen in the water. The increase in water temperature also increases the metabolic rate of aquatic organisms, further reducing the amount of dissolved oxygen available. This can cause the death of fish and other aquatic organisms, alter food chain composition, reduce species biodiversity, and foster the invasion of new thermophilic species.

Water pollution can also increase the levels of pathogens, nutrients, and invasive species in water bodies. It can increase the concentrations of some pollutants such as ammonia and pentachlorophenol due to their chemical response to warmer temperatures. Warmer temperatures can also increase the incidence of algal blooms, which can further reduce oxygen levels in the water.

Water pollution can also affect the survival and breeding of aquatic species, with some species unable to tolerate changes in water temperature. This can lead to a loss of aquatic species and changes in the abundance and spatial distribution of coastal and marine species.

In addition, water pollution can increase the rates of evapotranspiration from water bodies, leading to the shrinking of lakes and other water bodies. It can also increase the solubility and kinetics of metals in water, leading to an increase in the uptake of heavy metals by aquatic organisms. This can have toxic outcomes for these species and increase the build-up of heavy metals in higher trophic levels in the food chain, increasing human exposure to these metals through dietary ingestion.

Water pollution has also been linked to various human diseases, including diarrhea, skin diseases, malnutrition, and cancer. For example, the presence of enteroviruses in the aquatic environment has been associated with diarrhea, which is a leading cause of illness and death in young children in low-income countries. Exposure to polluted water can also cause skin diseases, with high levels of bacteria in seawater and heavy metals in drinking water being identified as the main pathogenic factors.

Water pollution can also increase the risk of cancer, with arsenic, nitrate, chromium, and trihalomethanes in drinking water being identified as potential carcinogens. Chlorinated by-products from the use of chlorine in water treatment have also been associated with an increased risk of bladder and rectal cancer.

Aquatic life

Water pollution has a devastating impact on aquatic life. The ocean has always been a hostile environment, but it is a mechanism that works without interference. An ecosystem is a complex community of organisms that interact and depend on each other to survive. The issue arises when a third party, such as pollution, is introduced and things are quickly thrown off balance.

Water pollution can cause physical harm to fish and other aquatic organisms. For example, contaminants like heavy metals, oil spills, and pesticides can cause deformities like gill damage, fin and tail rot, reproductive problems, and even death. Oil spills, in particular, have led to the closure of beaches and the death of many fish and birds.

Pollution can also cause a reduction in oxygen levels in the water. Certain pollutants, like nitrogen and phosphorus, often found in agricultural runoff, can promote excessive algae growth. When the algae die and decompose, they consume huge amounts of oxygen, creating 'dead zones' where fish and other life can suffocate.

In addition, some contaminants can promote the growth of fungus, bacteria, and algae, which can overtake and impede the growth of more naturally-occurring plants that marine life depends on to survive. Huge algae or moss mats can also block sunlight and nutrients from reaching plants and fish, disrupting the delicate balance of the ecosystem and reducing its overall resilience.

Plastic is another well-known pollutant. It is made from raw materials like natural gas, plants, and oil, as well as harmful chemical additives that enhance durability and flexibility. When out at sea, other contaminants are attracted to plastic waste, making it even more appealing to marine life. Ingested plastic is extremely harmful to marine animals and has led to the death of at least 100,000 marine animals each year, according to the World Wildlife Fund.

Water pollution also has a knock-on effect on the food chain. Birds, bears, big cats, and wolves that rely on fish as a food source are impacted when their food sources dwindle or are contaminated with chemicals and plastics. Ultimately, the damage ricochets up the food chain and reaches humans as well.

Climate change

The warming oceans have a profound impact on marine ecosystems, particularly sensitive habitats such as coral reefs. The increase in water temperature causes coral bleaching, where corals expel symbiotic algae that normally provide them with energy. This bleaching event can stress and even kill the corals, affecting the critical habitats and food sources they provide for various marine species. Additionally, warming oceans alter ocean circulation patterns, disrupting the transportation of coral larvae and the availability of nutrients, further compounding the stress on coral systems.

The rise in sea surface temperature also influences global climate patterns. The increased temperature leads to a higher amount of atmospheric water vapour, which fuels weather systems that produce heavy precipitation, increasing the risk of intense rain and snow events. Warmer oceans can also contribute to shifts in storm tracks, potentially leading to droughts in certain regions. Moreover, the warming of the oceans is predicted to enhance the intensity of hurricanes and tropical cyclones, making them more frequent and severe.

The expansion of seawater due to higher temperatures contributes to rising sea levels, a significant consequence of climate change. As the oceans heat up, they expand, causing a rise in sea levels. While thermal expansion has contributed to about half of the observed sea-level rise globally, the melting of ice from Greenland, Antarctica, and other glaciers is also a significant factor. These changes in sea levels can have far-reaching impacts on coastal areas, increasing the vulnerability of communities to flooding and other climate-related hazards.

Frequently asked questions