Runoff Pollutants: Aquatic Life Under Threat

Runoff pollutants have a detrimental impact on aquatic life. Water contamination is the result of human activities such as urbanisation, industrialisation, and agricultural activities. The overuse of pesticides and fertilisers, as well as sewage from residential and industrial areas, eventually find their way into the aquatic environment. This results in the degradation of water quality and the spread of infectious diseases.

Runoff from urban and suburban areas carries fertiliser, pesticides, oil, and other pollutants from streets and yards into local rivers and streams. This adversely affects water quality and aquatic life.

Agricultural runoff is a critical environmental concern, resulting from excess fertilisers, pesticides, and other pollutants washing into rivers and lakes, thereby jeopardising aquatic ecosystems and water quality. This phenomenon contributes significantly to the eutrophication of water bodies, leading to oxygen depletion and harm to aquatic life.

The effects of runoff pollution are vast and long-lasting. It erodes streams, kills fish, pollutes both drinking water and swimming areas, floods homes, and causes many other problems.

Eutrophication and hypoxia

Eutrophication, the over-enrichment of water by nutrients such as nitrogen and phosphorus, has emerged as one of the leading causes of water quality impairment. Eutrophication occurs when there is an abundance of nutrients in water bodies, which fuels harmful algal blooms, dead zones, and fish kills. This process is accelerated by human activities, such as agricultural runoff, industrial activities, and sewage disposal.

The two most acute symptoms of eutrophication are hypoxia and harmful algal blooms, which can destroy aquatic life in affected areas. Hypoxia, or oxygen depletion, occurs when a water body has dissolved oxygen concentrations of less than 2-3 mg/L. This is caused by excess nutrients, primarily nitrogen and phosphorus, and waterbody stratification due to saline or temperature gradients. These conditions lead to algal blooms as algae thrive in nutrient-rich environments. When the algae die and decompose, they consume oxygen, creating "dead zones" where most organisms cannot survive due to the lack of oxygen.

The impacts of eutrophication and hypoxia on aquatic ecosystems are significant. Excessive algal growth reduces light penetration, hindering the growth of other plants and the success of predators that rely on light. It can also alter the pH of the water, impairing the chemosensory abilities of organisms that depend on chemical cues for survival. The decomposition of dead algae further depletes oxygen levels, creating hypoxic or anoxic conditions that can lead to ecosystem collapse.

In addition to hypoxia, eutrophication can have other detrimental effects on aquatic life. It can cause a loss of subaquatic vegetation, changes in species composition and biomass, coral reef damage, and the formation of dead zones. These impacts can lead to a reduction in biodiversity and the dominance of certain species, such as jellyfish. Eutrophication also affects the provision of ecosystem services, including tourism, recreation, fisheries, and shellfish for local communities.

Addressing eutrophication and hypoxia requires a comprehensive approach that includes education, outreach, fiscal incentives, ecosystem preservation, and research. By raising awareness, implementing nutrient-reducing practices, and exploiting synergies with other environmental goals, we can mitigate the impacts of eutrophication and hypoxia on aquatic life.

Oil spills

Immediate Impact on Water Ecosystems:

• Direct harm to marine animals: Oil spills can cause direct harm to a variety of marine animals, including fish, shellfish, birds, and mammals. Oil can lead to suffocation, poisoning, and skin irritation in these creatures.
• Disruption of water flow patterns: Oil spills can spread over a large area, disrupting water flow patterns and affecting a wider ecosystem.
• Impact on plankton: Plankton, which plays a vital role in the marine food chain, can be smothered or poisoned by oil pollution.
• Vulnerable surface plants and animals: Plants and animals near the water surface are particularly vulnerable to the harmful effects of oil spills.

Long-Term Effects on Water Quality:

• Continuous monitoring: Long-term exposure to oil spills requires continuous monitoring and remediation efforts to mitigate the impact on aquatic life.
• Lingering oil residues: Even small amounts of oil can linger in water bodies, affecting the long-term health of aquatic organisms.
• Presence of harmful compounds: Different types of oil contain harmful compounds that can persist in trace amounts and accumulate in sediments over time, posing a threat to water quality.
• Disruption of marine life balance: Oil spills can disrupt the delicate balance of marine life, affecting the overall health and biodiversity of the ecosystem.

Heavy metals

There are several methods for removing heavy metals from water, including physicochemical and biological methods. Physicochemical methods, such as reverse osmosis, chemical precipitation, and membrane filtration, are widely used but are costly and generate large amounts of secondary pollutants. Biological methods, such as biosorption, bioaccumulation, and phytoremediation, are considered more cost-effective and eco-friendly.

Biosorption is a metabolically independent process that uses dead biomass, such as plant biomass, agricultural waste, and microbial biomass, to remove heavy metals from water. Metabolically dependent methods, on the other hand, use living organisms, such as bacteria, fungi, and algae, to remove heavy metals. These organisms can either accumulate heavy metals in their cells or reduce them to less toxic forms.

Some of the commonly used biosorbents include rice husk, wheat husk, banana peels, and microbial biomass. Bacteria, such as Pseudomonas alcaliphila, Microbacterium paraoxydans, and Desulfovibrio vulgaris, have been found to be effective in removing heavy metals from water.

Plastic pollution

One of the primary ways plastic pollution harms aquatic life is through ingestion. Marine animals, such as seabirds, sea turtles, fish, and marine mammals, often mistake plastic waste for food. This ingestion can lead to internal blockages, starvation, and suffocation. For example, sea turtles may feel full after ingesting plastic bags, leading to starvation. Additionally, microplastics, which are smaller plastic particles, can be consumed by smaller organisms and accumulate in the food chain, eventually reaching apex predators such as sharks and orcas. These microplastics can adsorb toxins, transferring them to the fatty tissues of the organisms that ingest them.

The presence of plastic waste in aquatic ecosystems can further contribute to the destruction of habitats. Certain chemicals in plastic can promote the growth of fungi, bacteria, and algae, which can overtake and impede the growth of naturally occurring plants that marine life depends on. Additionally, large mats of algae or moss can block sunlight and nutrients from reaching deeper into the water, disrupting the delicate balance of the ecosystem.

Furthermore, plastic pollution can have indirect effects on aquatic life by attracting other contaminants. As plastic breaks down into smaller particles, it can adsorb toxins from the surrounding environment. When animals ingest these contaminated plastics, they are exposed to harmful chemicals, which can have long-term health consequences.

The impacts of plastic pollution on aquatic life are widespread and severe, affecting a diverse range of species. It is crucial to address this issue through global efforts to reduce plastic production, improve waste management, and promote sustainable alternatives to single-use plastics.

Sewage

Sources of Sewage

Effects of Sewage on Aquatic Life

The impacts of sewage on aquatic life are far-reaching. Sewage can transport pathogens, such as bacteria, viruses, and parasites, which can cause diseases in both humans and marine organisms. For example, pathogens can lead to infections and diseases such as typhoid fever, salmonella, cholera, and cryptosporidium.

Additionally, sewage often contains excess nutrients, particularly nitrogen and phosphorus, which can cause eutrophication in aquatic ecosystems. This leads to excessive growth of algae, reducing light transmission in the water and decreasing oxygen levels. The resulting oxygen-depleted "dead zones" can suffocate fish and other aquatic organisms.

Furthermore, sewage can alter ocean temperature, pH, salinity, and oxygen levels, disrupting the biological processes and physical environments essential for marine life to thrive.

Preventing and Mitigating Sewage Pollution

To address the negative impacts of sewage on aquatic life, it is crucial to implement effective wastewater treatment processes. This includes primary, secondary, and tertiary treatment phases to remove solid waste, biological material, and remaining contaminants. Additionally, regular monitoring and controlling of pollutant discharge into aquatic environments are necessary to maintain ecological balance.

On a personal level, individuals can contribute by properly disposing of waste, reducing the use of pesticides and fertilizers, and supporting initiatives that promote sustainable practices and regulate pollution.

Frequently asked questions