Human Impact: Estuaries And Pollution

Estuaries are highly diverse and dynamic ecosystems that provide a wide range of benefits to humans. From offering nursing sites for many open ocean species to providing jobs for tourism, research, and fishing activities, estuaries are essential to both wildlife and human life. However, human activities and pollution are severely affecting these ecosystems. The two main problems affecting estuaries are sedimentation and pollution from runoff. As more people move to coastal communities, the natural balance of estuaries is being upset, threatening their health. This includes polluting the water and building on the lands surrounding them, which can lead to unsafe drinking water, harmful algae blooms, declines in fisheries, and loss of habitat, among other issues.

Human activities such as boating and industrial development can cause pollution and damage to estuaries

Recreational boating is a popular activity in estuaries, but it also increases the potential for derelict vessels. Abandoned and poorly maintained boats can leak pollutants and damage delicate marsh grasses. This can be extremely harmful to the native plant and animal species in the estuary, as well as to people who may consume contaminated plants and animals.

Industrial development can also have a significant impact on estuaries. Industrial waste and urban runoff can introduce toxic substances such as chemicals, heavy metals, and polycyclic aromatic hydrocarbons (PAHs) into the estuary. These compounds are often identified as carcinogenic, mutagenic, and teratogenic, and they can bioaccumulate in the food web, threatening the health of both the ecosystem and humans who consume plants and animals from the estuary.

In addition to pollution, industrial development can also lead to the destruction and loss of estuarine habitats. Activities such as draining, filling, damming, or dredging can result in the immediate destruction of estuarine habitats. This has been a common practice in the past, with many estuary habitats in North America being converted into agricultural areas or used for shipping ports and urban expansion. This has led to a significant loss of wetlands associated with coastal areas, with 38% of wetlands lost in the United States alone.

The introduction of non-native or invasive species is another human-caused disturbance that can impact estuaries. Invasive species can be accidentally or intentionally introduced into estuaries, outcompeting native species and causing ecological damage. For example, the introduction of the Asian date mussel at Onerahi Beach smothered other marine life on the seafloor.

Overall, human activities such as boating and industrial development can have severe and long-lasting effects on estuaries, threatening the health of these fragile ecosystems and the communities that depend on them.

Draining, filling, damming, and dredging estuaries can result in the immediate destruction and loss of estuarine habitats

Draining, filling, damming, and dredging estuaries can have devastating effects on the environment, leading to the immediate destruction and loss of estuarine habitats. These activities have historically been common in North America, where estuaries have been drained to create agricultural land, filled to expand ports and urban areas, and dammed for flood control or water diversion. The consequences of these actions are severe and often irreversible.

Draining estuaries involves removing the water from these ecosystems, effectively destroying the habitat for numerous species. This process has been prevalent in North America, where 38% of the wetlands associated with coastal areas have been lost to draining, filling, and other human activities. In some regions, the loss of estuarine habitats due to these activities is as high as 60%. This destruction has a profound impact on the biodiversity that relies on estuaries, including commercially important fish and shellfish.

Filling estuaries, often to create shipping ports or expand urban areas, has similar detrimental effects. When estuaries are filled, the unique transition zone between river and sea environments is lost, along with the rich biodiversity it supports. Estuaries are among the most productive natural habitats globally due to the high levels of nutrients provided by the mixing of seawater and freshwater. Filling these areas eliminates this critical habitat, disrupting entire food webs and threatening numerous species.

Damming estuaries for flood control or water diversion can also have significant negative consequences. While this practice may be motivated by a need to manage water flow and prevent flooding, it can alter the natural dynamics of estuaries. Dams can disrupt the natural flow of water, change sedimentation patterns, and impact the movement of species. Additionally, the altered water flow can affect the mixing of seawater and freshwater, reducing the nutrient levels that support the diverse ecosystems found in estuaries.

Dredging, the process of removing sediment and other materials from the bottom of estuaries, is another human activity that can have detrimental effects. While dredging is essential for maintaining navigation channels, it can result in the removal of vital habitats for many organisms. Increased sedimentation can also occur, leading to reduced nutrient flow to wetlands and an unhealthy environment for plant and animal life.

The cumulative impact of draining, filling, damming, and dredging estuaries is the immediate and long-term destruction of vital estuarine habitats. These activities have far-reaching consequences for the numerous species that depend on estuaries, including humans who rely on them for fisheries, recreation, and aesthetic value. It is essential to recognize the importance of estuaries and implement measures to protect and preserve these fragile ecosystems.

Toxic substances, including chemicals and heavy metals, can enter estuaries through industrial discharges, runoff, and sewage

Estuaries are extremely vulnerable to toxic substances, including chemicals and heavy metals, which can enter their ecosystems through various human activities. These toxic substances can have detrimental effects on the environment and human health, and their presence in estuaries is a pressing issue that requires urgent attention and mitigation strategies.

Industrial discharges are a significant source of chemical and heavy metal pollution in estuaries. Many industries release untreated or partially treated waste directly into estuaries, bypassing sewage treatment plants. This waste often contains high levels of chemicals and heavy metals, such as mercury, lead, and zinc, which can have toxic effects on aquatic life and accumulate in the food chain. For example, the Potengi estuary in Brazil is highly impacted by pollution, with almost 60% of domestic sewage being discharged untreated, leading to high concentrations of heavy metals in the soft tissue of oysters.

Runoff from agricultural lands, streets, and yards is another major contributor to the presence of toxic substances in estuaries. Pesticides, automobile fluids, and metals from these sources can wash into estuaries during rainfall or irrigation, posing a significant threat to the health of the estuary. Farmland runoff, in particular, has been the subject of research, as increased fertiliser use can result in higher growth rates in some fish and bivalve species but also a decrease in biodiversity.

Sewage and septic systems are additional sources of chemical and heavy metal pollution in estuaries. Leaky septic systems and inadequate sewage treatment can allow chemicals, heavy metals, and pathogens to enter estuaries, affecting both the environment and human health. Combined sewage overflows (CSOs) are a significant contributor, as they carry residential, industrial, and commercial waste, including metals, oils, grease, and bacteria, which can overwhelm sewage treatment plants during heavy rains.

The introduction of these toxic substances into estuaries has far-reaching consequences. They can cause severe harm to native plant and animal species, as well as people who consume contaminated plants and animals. Additionally, they can have economic impacts on communities that depend on healthy estuaries for recreational and commercial fisheries. It is crucial to address and mitigate the entry of toxic substances into estuaries to protect the delicate balance of these ecosystems and the well-being of the communities that rely on them.

Nutrient pollution, such as eutrophication, can cause explosive algal growth, depleting estuaries of oxygen and affecting water quality

Estuaries are extremely vulnerable to human activities due to their transitional nature between land and sea, and between freshwater and saltwater environments. Nutrient pollution, such as eutrophication, is a major threat to estuaries. Eutrophication is characterised by excessive plant and algal growth due to an increased availability of growth factors like sunlight, carbon dioxide, nitrogen, and phosphorus. This process begins when there is an increased load of nutrients in the water, which leads to an overabundance of algae and plants.

Nitrates and phosphates are essential nutrients that support the growth of plants, but in excessive amounts, they cause eutrophication. This, in turn, stimulates explosive growth in algae, known as algal blooms, which block sunlight and suffocate fish and plant life by depleting the water of oxygen when they die and are consumed by bacteria. Estuarine waters may become hypoxic (oxygen-poor) or even anoxic (completely devoid of oxygen) due to these algal blooms. While hypoxia may stress the animals in estuaries, anoxic conditions can be fatal to them.

Eutrophication can also trigger toxic algal blooms, such as red and brown tides, and the growth of Pfiesteria, a single-celled organism that releases potent toxins. Although consuming fish affected by this toxin is not harmful to humans, exposure to waters where Pfisteria blooms can cause serious health issues. Eutrophication is often devastating to the economies of communities surrounding estuaries, as toxic algal blooms disrupt tourism and adversely affect recreational and commercial fisheries.

Nutrient pollution is the single largest pollution problem affecting the coastal waters of the United States. Most excess nutrients come from sewage treatment plants, septic tanks, and stormwater runoff from over-fertilised areas like lawns, golf courses, and agricultural fields. Over 60% of the coastal rivers and bays in the United States are moderately to severely impacted by nutrient pollution.

Climate change, caused by human activities, can lead to rising sea levels, increased flooding, and changes in water temperature, all of which can have significant impacts on estuarine ecosystems

Estuaries, which are partially enclosed coastal bodies of water where freshwater from rivers and streams mixes with saltwater from the ocean, are extremely vulnerable to human activities and climate change. Climate change, caused by human activities, can lead to rising sea levels, increased flooding, and changes in water temperature, all of which can have detrimental impacts on estuarine ecosystems.

Rising sea levels, a direct consequence of climate change, pose a significant threat to estuaries. As sea levels rise, ocean and estuarine shorelines are displaced, inundating lowlands and altering the tidal range in rivers and bays. This process can lead to the loss of tens of thousands of acres of estuary habitat each year. According to scientific projections, sea levels are expected to rise by at least one foot by 2050 and by two feet before the end of the century. This will result in more frequent and severe coastal flooding, causing water to intrude inland and leading to increased erosion, infrastructure damage, and loss of life and property.

In addition to rising sea levels, increased flooding is another consequence of climate change that affects estuaries. More frequent and intense rainfall can lead to greater stormwater runoff, which carries pollutants, nutrients, and sediments into estuaries. This increase in nutrient runoff can contribute to eutrophication, leading to excessive algae growth and subsequent oxygen depletion in the water, which can be detrimental to estuarine organisms.

Climate change can also cause changes in water temperature in estuaries. As the concentration of carbon dioxide (CO2) in the atmosphere rises, the ocean absorbs more of this gas, leading to increased acidity in marine waters. This, in turn, affects the availability of certain minerals necessary for building and maintaining coral skeletons and supporting other estuarine species, such as shellfish. The combination of ocean acidification and other stressors can lead to coral reef die-off and threaten aquatic life, further degrading estuarine ecosystems.

The impacts of climate change on estuaries are far-reaching. The loss of estuary habitats, disruption of ecosystems, and degradation of water quality can have significant ecological, economic, and social consequences. It is crucial to address these issues through mitigation, adaptation, and conservation efforts to protect and restore the health of estuarine environments and the communities that depend on them.

Frequently asked questions