Water Pollution's Impact: Biodiversity Under Threat

Water pollution is a growing problem in the 21st century, with pure water becoming scarcer. Aquatic environments are particularly susceptible to the effects of pollution, as they are home to a wide variety of life and biodiversity. Human activity is the main cause of water pollution, with six key threats to aquatic biodiversity: climate change, overexploitation, water pollution, habitat degradation, flow modification, and exotic species invasion.

Water pollution can cause drastic responses in aquatic organisms, including death, migration, reduced reproductive capacity, and suppressed enzyme systems. It can also lead to eutrophication, which results in the growth of plants and algae that can harm other aquatic life and disrupt the food chain.

Agricultural runoff, industrial effluents, and municipal sewage are major sources of water pollution, with untreated wastewater being a significant issue. This has severe consequences for human health and can lead to diseases such as dysentery, diarrhea, and jaundice.

Biodiversity maintenance is crucial for retaining ecosystem services, and protecting freshwater biodiversity is a key challenge. Systematic conservation planning provides a strategic framework for this, but it requires a comprehensive understanding of the complex relationships between biodiversity, ecosystem functions, and human well-being.

Water pollution can cause eutrophication, which leads to algal blooms that deplete oxygen levels in the water, causing fish and shrimp mortalities

Water pollution can cause eutrophication, which is a process where nutrients accumulate in bodies of water, leading to an increase in microorganisms and depletion of oxygen levels. This, in turn, results in algal blooms that have detrimental effects on aquatic life. Eutrophication occurs naturally but is accelerated by human activities, such as agricultural runoff, industrial waste, and sewage disposal. The excessive growth of algae blocks sunlight, causing the death of plants and affecting the survival of predators that rely on light to catch prey.

As the algae eventually die off, their decomposition by bacteria further reduces oxygen levels, creating "dead zones" that cannot support most organisms. This has a direct impact on fish and shrimp populations, leading to mortalities and a decline in biodiversity. The oxygen depletion not only affects aquatic life but also restricts access to water for terrestrial animals and impacts human activities such as fishing and tourism.

To address eutrophication, it is crucial to minimize pollution from sewage and agriculture. Implementing nutrient management techniques, reducing nutrient runoff from fields, and creating buffer zones near water bodies can help mitigate the issue. Additionally, introducing bacteria and algae-inhibiting organisms, such as shellfish and seaweed, can aid in controlling the growth of harmful algae.

By taking these measures, we can help prevent eutrophication and protect the delicate balance of aquatic ecosystems, ensuring the survival of various species, including fish and shrimp.

Water pollution can cause physical changes to the aquatic environment, such as changes in temperature and colour

Changes in Temperature

Water temperature is influenced by air temperature, which means that an increase in air temperature will cause water temperatures to increase as well. Warmer water temperatures can have a detrimental effect on aquatic habitats and biodiversity. Warmer water, for instance, holds less dissolved oxygen than cooler water, which is vital for the survival of aquatic life. Some compounds are also more toxic to aquatic life at higher temperatures.

Changes in Colour

The colour of water can change due to a process called eutrophication, which is caused by an increase in the concentration of nutrients in the water, such as nitrogen and phosphorus. This leads to a proliferation of organisms, particularly microscopic algae, which can turn the water green, as seen in the famous example of the green pool at the 2016 Olympic Games in Rio de Janeiro.

Impact on Biodiversity

Water pollution can introduce harmful chemicals and toxins into the water, which can be toxic to aquatic life and humans

Impact on Aquatic Life

The introduction of harmful chemicals and toxins into water bodies can have detrimental effects on aquatic ecosystems. These pollutants can cause neurological changes, behavioural changes, and reproductive issues in aquatic organisms. For instance, studies have shown that mayfly species, which are considered cool water insects and bioindicators of ecologically important features of freshwater ecosystems, struggle to survive in polluted waters with elevated temperatures and reduced dissolved oxygen levels.

Moreover, the presence of certain chemicals in water can be toxic to specific species. For example, zinc and cadmium have a combined toxic effect on fish, while calcium antagonises the effects of lead, zinc, and aluminium. The complex interactions and combined effects of multiple pollutants in water can further exacerbate their impact on aquatic life.

Impact on Humans

Water pollution can also directly affect human health. The ingestion of microplastics, which are small plastic fragments that form when larger plastics break down, has been linked to potential health issues such as oxidative stress, inflammatory reactions, and metabolic disorders. Additionally, consuming water contaminated by sewage can expose individuals to bacteria that cause diseases like diarrhoea, cholera, dysentery, typhoid, hepatitis A, and polio.

Furthermore, drinking water contaminated with chemical waste, such as pesticides, fertilisers, and heavy metals, can lead to serious health problems. These toxins can interfere with brain function, damage immune and reproductive systems, and contribute to cardiovascular and kidney issues.

Water pollution can reduce the availability of clean drinking water, leading to an increased risk of water-borne diseases

Water pollution poses a serious issue as it can cause variations in the environmental conditions to which aquatic organisms are sensitive. In less extreme cases, only the reproductive capacity and metabolism of the aquatic organisms are affected negatively. However, this can have a negative consequence on their population in the long run.

Waterborne diseases are illnesses caused by microscopic organisms, like viruses and bacteria, that are ingested through contaminated water or by coming in contact with feces. Typhoid fever, cholera, giardiasis, dysentery, Escherichia coli (E. coli), hepatitis A, salmonella, and more are all waterborne diseases.

Water pollution can affect the food chain and disrupt the balance of ecosystems, causing a decline in biodiversity

Water pollution is a serious issue for aquatic environments as it can cause variations in the environmental conditions to which aquatic organisms are sensitive. Aquatic organisms respond to drastic changes in their environment by migrating to another suitable habitat or, in extreme cases, dying. In less extreme cases, only the reproductive capacity and metabolism of the aquatic organisms are affected negatively. However, this can have a negative consequence on their population in the long run.

Zooplankton and macrobenthic organisms are important in the trophic dynamics of freshwater ecosystems. They not only modulate the aquatic productivity by occupying the intermediate level in the food chain but also indicate changes in the aquatic environment. Their diversity has raised importance in recent years due to their ability to indicate any deterioration in water quality resulting from pollution and eutrophication.

Any disruption in the food chain due to diversity loss or degradation results in a decrease in fish numbers at the top of the food web. For example, data from two separate studies about the Egyptian Nile waters conducted several years apart showed a significant reduction in fish species, which has been attributed to several pollution sources generated by industrial activities, agricultural sources, and sewage drains.

In addition, pollution can make rivers more susceptible to drastic changes. For instance, researchers investigated the effects of rising water temperature and low oxygen levels brought about by pollution on the common mayfly species. Mayflies are considered cool water insects and are used as bioindicators that help determine ecologically important features of freshwater ecosystems. During warmer seasons, they struggle to thrive in polluted waters due to elevated temperatures and reduced dissolved oxygen.

Biodiversity maintenance is considered one of the leading keys to ecosystem services retention. Therefore, the ultimate challenge nowadays is the protection of freshwater biodiversity.

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