Stomata And Nutrient Pollution: A Complex Relationship

Storms can increase nutrient pollution, which is a form of water pollution caused by excessive inputs of nutrients, usually nitrogen and phosphorus, which act as fertilizers and cause excessive growth of algae. During storms, water from rain or snow, known as stormwater, flows over streets, parking lots, and roofs, collecting excess nutrients and pollutants before entering storm drains or bodies of water. This stormwater runoff can carry fertilizers, pet and yard waste, and other pollutants, directly into water bodies without being filtered by soil, plants, or water treatment facilities. Urban and suburban areas, with their high amounts of paved and hard surfaces, produce significantly more stormwater runoff, contributing to nutrient pollution. Additionally, heavy rainfall or snowmelt can cause wastewater systems to overflow, leading to the discharge of untreated sewage into nearby water bodies, further exacerbating nutrient pollution.

Stormwater runoff from urban areas

The impact of stormwater runoff is more pronounced in urban and suburban areas due to the high proportion of paved and hard surfaces. This leads to increased volumes of stormwater runoff, which can overwhelm wastewater systems and result in combined sewer overflows, where untreated sewage is discharged directly into nearby streams, rivers, or other water bodies.

Atmospheric deposition, vehicular transportation, and metallic building materials are identified as major sources of stormwater pollution. The transportation sector, including vehicles and road infrastructure, contributes significantly to this issue.

Nutrient pollution from stormwater runoff has severe ecological and environmental consequences. Nitrogen and phosphorus, in particular, play a crucial role in the eutrophication of water bodies, leading to harmful algal blooms, fish kills, and biodiversity loss. The excess growth of algae caused by nutrient pollution blocks light necessary for the growth of plants like seagrasses. When the algae and seagrass die and decay, they deplete the oxygen levels in the water, creating an environment that can kill fish, crabs, oysters, and other aquatic life.

To address stormwater runoff and its associated nutrient pollution, green infrastructure solutions can be employed. These techniques slow down and disperse stormwater, allowing it to infiltrate the ground and be naturally filtered by plants. Examples of green infrastructure include rain gardens, pervious pavement, rain barrels, and green roofs.

Increased rainfall and snowmelt

Nutrient pollution is caused by an excess of nutrients, mainly nitrogen and phosphorus, which act as fertilisers in bodies of water, leading to excessive algae growth. This process has severe ecological and economic impacts. Ecologically, the excessive algae growth blocks light, hindering the growth of other plants like seagrass. When the algae and seagrass die, they decay, depleting the oxygen levels in the water and endangering aquatic life such as fish, crabs, oysters, and other animals. Economically, the consequences include increased water treatment costs, losses in commercial fishing and shellfish industries, and reduced tourism income.

The impact of increased rainfall on nutrient pollution is evident in the example of the Chesapeake Bay, which received exceptionally heavy rainfall in 2011. The resulting runoff, carrying silt, mud, debris, and other pollutants, made its way into the bay, contributing to nutrient pollution.

Snowmelt also plays a crucial role in nutrient pollution, especially in urban areas. As snow accumulates pollutants during winter, the subsequent snowmelt runoff carries these contaminants into water bodies. Urban snowmelt can include diverse pollutants such as coal and gas combustion products, snow-melting agents, and automotive exhaust. The impact of snowmelt on water quality is further exacerbated by the fragile ecosystem of rivers emerging from freezing, which have a poor self-purification capacity.

The combination of increased rainfall and snowmelt intensifies the problem of nutrient pollution, as seen in the case of the US, where it threatens water quality in over 40% of the contiguous country. This issue is of particular concern during "rain-on-snow" events, which can lead to economically and environmentally devastating floods while also contributing to nutrient pollution.

Nitrogen and phosphorus pollutants

Nutrient pollution is caused by an excess of nutrients, usually nitrogen or phosphorus, in bodies of water. Nitrogen and phosphorus are natural parts of aquatic ecosystems and are essential for the growth of all living organisms. However, when too much of these nutrients enter the environment, they can act as fertilisers, causing the excessive growth of algae. This process is known as eutrophication.

Fertilisers used on lawns and in agriculture are a significant source of nitrogen and phosphorus pollutants. When excess fertiliser is applied to fields, it can run off into nearby waterways, contributing to eutrophication. Animal feedlots are another source of nitrogen and phosphorus pollution, as are sewage treatment plants.

Air pollution, such as vehicle exhaust and emissions from power plants, also contributes to nitrogen pollution. When excess nitrogen is released into the atmosphere, it can produce pollutants such as ammonia and ozone, which can impair human respiratory function, limit visibility, and alter plant growth.

The impacts of nitrogen and phosphorus pollutants on aquatic ecosystems are significant. Excessive algae growth harms water quality, food resources, and habitats, and decreases the oxygen available for fish and other aquatic life to survive. This can lead to illnesses and even death in fish and other aquatic organisms. Some types of algae are toxic to humans, causing sickness if people come into contact with polluted water, consume tainted fish or shellfish, or drink contaminated water.

Eutrophication of water bodies

Eutrophication is a process that occurs when water bodies, such as streams, rivers, lakes, and estuaries, experience an excessive growth of aquatic plants and algae due to increased nutrients in the water. This process is considered a serious environmental concern as it often leads to the deterioration of water quality and the depletion of dissolved oxygen in these aquatic ecosystems. Eutrophication can be classified into two types: anthropogenic and natural eutrophication.

Anthropogenic Eutrophication

Anthropogenic eutrophication is primarily caused by human activities such as agricultural practices, the use of fertilizers on golf courses and lawns, and industrial waste. When fertilizers are washed away by rain, they find their way into lakes and rivers, providing an abundance of nutrients to algae, plankton, and other simple plant life. This results in the eutrophication of the water body, favouring the growth of simple plant life over more complex species, thereby reducing biodiversity. Overpopulation and industrial expansion contribute to deforestation, leading to increased soil erosion and nutrient-rich deposits in water bodies. Sewage pipes and untreated sewage also play a role in eutrophication by introducing nutrients into the water.

Natural Eutrophication

Natural eutrophication occurs when water bodies become overly enriched with nutrients through natural events like floods. This process is much slower than anthropogenic eutrophication and can be influenced by temperature changes associated with global warming. Natural eutrophication can also occur due to the weathering of rocks and soil in the watershed, as well as the mixing of water currents from the ocean.

Eutrophication has several adverse effects on aquatic ecosystems, including decreased biodiversity, increased water toxicity, and changes in species dominance. The excessive growth of algae and plankton can block light and deplete oxygen levels, leading to the death of fish and other aquatic organisms. Eutrophic waters can eventually become "dead zones" incapable of supporting life.

Climate change impacts

Storms can increase nutrient pollution, which is a form of water pollution caused by an excess of nutrients, usually nitrogen and phosphorus, that stimulate algal growth. Nitrogen and phosphorus are essential for the growth of algae and aquatic plants, which provide food and habitat for aquatic life. However, when too much nitrogen and phosphorus enter the water, it causes algae to grow faster than ecosystems can handle, leading to harmful algal blooms (HABs).

• As winters warm due to climate change, nutrient pollution is being unleashed into lakes, rivers, and streams. Rising winter temperatures and increased rainfall in previously snowy climates are unlocking frozen chemical runoff from farms and fields, putting water quality at risk.
• Climate change is causing an increase in rainfall and snowmelt events, which carry nutrients and soil into streams and rivers. This is particularly problematic during winter when dormant vegetation cannot absorb the excess nutrients, leading to increased nutrient pollution.
• Warmer winters and more frequent rain-on-snow events are affecting over 50% of the contiguous U.S. and putting 50% of U.S. nitrogen and phosphorus pools at risk of export to groundwater and surface water.
• As a result of climate change, snowfall is turning to rain, leading to increased flooding and higher levels of nutrients that cause coastal eutrophication.
• The combustion of fossil fuels by power plants, large industries, and automobiles is a significant source of nitrogen in the atmosphere, contributing to nutrient pollution.
• Climate change is expected to increase the frequency and intensity of storms, which can worsen stormwater runoff and increase the amount of nutrients and pollutants entering water bodies.
• Stormwater runoff is often worsened by human activities, as it can contain nitrogen and phosphorus pollutants from fertilizers, pet waste, and yard waste.
• With more frequent and intense storms, wastewater systems may become overwhelmed, leading to combined sewer overflows where untreated sewage is discharged directly into nearby streams, rivers, or other water bodies.
• Increased stormwater runoff can also result in soil erosion, releasing adsorbed nutrients into waterways and contributing to nutrient pollution.

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