Stream Traits: Lake Pollution Vulnerabilities

Lakes and streams are vulnerable to water pollution from a variety of sources. Physical pollutants include particles of soil that are eroded from the landscape or washed from paved areas by flowing water, as well as heat discharged from industrial sources or hot surfaces in warm weather. Chemical pollutants, such as nitrogen and phosphorus, can be adsorbed (bound) to particles and incorporated into sediments, where they may be permanently buried or carried by water currents to other locations. An overabundance of algae or other plants can also contribute to water pollution by providing more decaying material and reducing oxygen levels as the material decomposes. Human activities, such as the introduction of non-native species and the over-clearing of shade trees along shorelines, can further alter the ecology of lakes and streams, making them more susceptible to pollution.

The overclearing of shade trees along the shoreline of a lake or stream can allow sunlight to warm waters above the normal temperature range

The overclearing of trees can also cause an overabundance of algae or other plants, which provide more decaying material and a greater reduction in oxygen as the material decomposes. This can be exacerbated by nutrient pollution, which builds up in lakes, ponds, and streams. Nitrogen and phosphorus pollution can impact ecosystem health, and slow-moving or stagnant waters increase the chances of harmful pollution and algal growth.

The large volume of stormwater that rapidly enters streams from paved surfaces can produce flooding that erodes streambanks and destroys natural habitats. This can also contribute to the problem of physical pollutants, as particles of soil are washed from paved areas into lakes and streams.

Particles of soil that are eroded from the landscape or washed from paved areas by flowing water can settle at the bottom of lakes and streams

Nutrient pollution, such as nitrogen and phosphorus, can also build up in lakes and streams. When river or stream currents are slow, or when waters are stagnant, nutrients, sediment, and particles accumulate, increasing the chances of harmful pollution and algal growth.

An overabundance of algae or other plants can provide more decaying material, and hence a greater reduction in oxygen as the material decomposes

An overabundance of algae or other plants can cause a greater reduction in oxygen in lakes and streams. As the plants and algae die, they decompose, which uses up oxygen in the water. This process is made worse by the presence of extra nutrients, such as nitrogen and phosphorus, which cause algal blooms. These blooms can be caused by slow-moving or stagnant water, which allows nutrients, sediment, and particles to accumulate.

In addition to this, human activities can introduce non-native plants and animals, which can change the basic ecology of a lake or stream. This can include the overclearing of shade trees along the shoreline, which allows sunlight to warm the waters above their normal temperature range.

Another type of physical pollutant is heat, which may be discharged from an industrial source or runoff from hot surfaces in warm weather. This can also contribute to the warming of waters.

Furthermore, the large volume of stormwater that rapidly enters streams from paved surfaces can produce flooding that erodes streambanks and destroys natural habitats. This can also contribute to the problem of sediment and particles entering the water, which can carry chemical pollutants that are harmful to the ecosystem.

The large volume of stormwater that rapidly enters streams from paved surfaces can produce flooding that erodes streambanks and destroys natural habitats

Stormwater runoff is a significant contributor to water pollution in lakes and streams. When large volumes of stormwater rapidly enter streams from paved surfaces, it can lead to flooding, which in turn erodes streambanks and destroys natural habitats. This process is known as "urban stream syndrome". The paved surfaces, such as roads and parking lots, are unable to absorb the water, leading to increased surface runoff. As the water flows over these surfaces, it picks up pollutants such as oil, grease, and chemicals, carrying them into nearby streams and lakes. This can have detrimental effects on aquatic life and the surrounding ecosystem.

The impact of stormwater runoff is further exacerbated by the presence of impervious surfaces in urban areas. These surfaces, such as concrete and asphalt, prevent water infiltration, leading to higher volumes of runoff. The rapid flow of stormwater can also cause streambank erosion, as the force of the water scours the banks, carrying away sediment and further degrading the stream habitat.

In addition to the direct impacts on streambanks and habitats, the pollutants carried by stormwater can have far-reaching consequences. Chemical pollutants, such as nutrients, heavy metals, and toxins, can contaminate the water, affecting aquatic life and disrupting the natural balance of the ecosystem. These pollutants can accumulate in the sediment, posing long-term risks to the health of the stream and its surrounding environment.

Furthermore, the increased volume and velocity of stormwater can alter the natural flow patterns of streams. This can lead to changes in water temperature, sediment transport, and habitat availability for aquatic organisms. The altered flow patterns can also impact the stream's ability to dilute and assimilate pollutants, making it more vulnerable to contamination.

To mitigate the impacts of stormwater runoff, it is essential to implement effective stormwater management practices. This includes the use of permeable surfaces, rainwater harvesting, and the creation of natural buffers along streambanks to filter and slow down the flow of stormwater. By addressing the issue of stormwater runoff, we can help protect the health and integrity of our lakes and streams, ensuring their resilience against pollution and preserving their vital role in our ecosystems.

Nutrient pollution builds up in lakes, ponds, and streams

Nutrient pollution is a significant issue for lakes, ponds, and streams. The EPA's 2010 National Lakes Assessment found that almost 20% of the 50,000 lakes surveyed had been impacted by nitrogen and phosphorus pollution. This type of pollution can have severe consequences for the health of aquatic ecosystems, doubling the likelihood of poor ecosystem health. Slow-moving or stagnant waters are particularly vulnerable to nutrient pollution, as nutrients, sediment, and particles accumulate, creating an environment conducive to harmful algal growth.

Nutrient pollution in lakes, ponds, and streams is often a result of human activities. Sources of nutrient pollution include lawn and garden fertilizers, yard debris, sediment and materials from construction sites, sewage discharge, and animal waste. These pollutants typically enter water bodies via stormwater runoff, as rain washes pollutants from impervious surfaces like roads and sidewalks into nearby ponds and lakes.

The impact of nutrient pollution extends beyond the immediate water body. Excess nutrients can travel downstream, affecting larger water bodies like rivers and bays. In the United States, more than 100,000 miles of rivers and streams and close to 2.5 million acres of lakes, reservoirs, and ponds suffer from poor water quality due to nitrogen and phosphorus pollution.

Nutrient pollution also contributes to eutrophication, the aging of aquatic ecosystems. This process can lead to a reduction in oxygen levels as excess plant growth, such as algae, decomposes. Additionally, non-native plants and animals introduced through human activities can further alter the basic ecology of lakes and streams.

To address nutrient pollution in lakes, ponds, and streams, it is essential to focus on reducing the input of nutrients into these water bodies. This can be achieved through proper waste management, controlling stormwater runoff, and promoting sustainable practices in agriculture and urban areas. By mitigating nutrient pollution, we can help restore and maintain the health of aquatic ecosystems and ensure the long-term sustainability of our water resources.

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