Nutrient pollution from agricultural runoff, particularly rich in nitrogen and phosphorus from fertilisers, can lead to eutrophication. This process involves the excessive growth of algae and aquatic plants due to an abundance of nutrients. As these organisms die and decompose, they consume a significant amount of dissolved oxygen in the water, leading to hypoxic or anoxic conditions. Aquatic animals, especially fish, suffer or die from the lack of oxygen. Eutrophication also leads to the disruption of food chains, loss of biodiversity, and the deterioration of water quality, impacting both ecosystems and human communities.

Invasive species introduced through biological pollution can have devastating effects on native aquatic ecosystems. These non-native species often lack natural predators in their new environments, allowing them to proliferate uncontrollably. They can outcompete native species for resources, leading to a decline or extinction of indigenous aquatic life. For example, the introduction of the zebra mussel in various water bodies around the world has led to significant ecological and economic impacts. These mussels multiply rapidly, disrupt food chains, alter habitats, and block water intake pipes, showcasing the multifaceted challenges invasive species pose to aquatic ecosystems.

Waterborne pathogens due to biological pollution can lead to a range of health issues. These pathogens, including bacteria, viruses, and parasites, often enter water bodies through untreated sewage or animal waste. Illnesses such as cholera, typhoid, and dysentery are common outcomes. For example, E. coli bacteria can cause severe gastrointestinal problems, kidney failure, and even death in vulnerable populations. Cryptosporidium, another waterborne pathogen, leads to respiratory and gastrointestinal illness. These health issues underscore the critical need for effective water treatment and sanitation practices to mitigate biological pollution.

Urban runoff is a significant source of chemical pollution in water bodies. It occurs when rainwater flows over urban areas, collecting a variety of pollutants like oil, heavy metals, and chemicals from streets, rooftops, and industrial areas. This mixture then enters water bodies without undergoing treatment. For instance, runoff can carry motor oil and heavy metals from roads, pesticides from gardens, and chemicals from industrial sites into rivers and lakes. This not only deteriorates the water quality but also poses severe risks to aquatic life and human health, leading to a complex set of environmental and health challenges.

Thermal pollution exacerbates the effects of chemical pollution by increasing the toxicity of certain chemicals. When the temperature of water bodies rises due to the discharge of heated water from industrial processes, it can increase the solubility and reaction rates of chemicals. For instance, elevated temperatures can enhance the toxicity of heavy metals like lead and mercury, leading to more severe impacts on aquatic life. Additionally, warmer waters can reduce the amount of dissolved oxygen available, stressing aquatic organisms and making them more susceptible to the harmful effects of chemical pollutants.