How chemicals affect animals in aquatic environments
Water is the force of life for all living beings. While some animals live in aquatic environments, all animals, whether they are land or water-based, need water for survival. When rivers, streams, lakes, or oceans are contaminated, it not only harms the animals, but also wrecks havoc on the entire ecosystem. Additionally, when one body of water becomes contaminated, other water sources subsequently can become polluted when they are connected. In order to protect this invaluable and limited resource and the creatures that depend on it, it will be necessary for individuals, organizations, and governments around the world to take action.
There are a wide variety of animals that live in water ecosystems, whether they are freshwater or marine environments. For example, more than 40% of the world’s fish can be found in freshwater environments. This is concerning considering there are no longer any natural surface water communities that have been unaffected by human-made chemicals. Additionally, these toxic substances have been discovered in fish and mammals thousands of miles from their original known use. The United Nations Department of Economic and Social Affairs has stated that “the biodiversity of freshwater ecosystems have been degraded more than any other ecosystem” (OneGreenPlanet, 2017). According to the U.S. Environmental Protection Agency (EPA), 46% of rivers and streams are in poor condition and have difficulty supporting aquatic life.
The number of chemicals in use today that affects an animal’s natural environment, and consequently ours, is astounding. It is estimated that there are over two million known chemical compounds, and another couple hundred thousand produced annually. In the United States and Canada, there are approximately 30,000 chemicals used commercially. The types of chemicals and their uses vary widely, from pesticides and fertilizers to caffeine and birth control pills to stain repellents and sunscreens. For example, there are approximately 22 million tons of fertilizers and chemicals used annually and the use of pesticides and fertilizers on farms has increased by 26-fold over the past 50 years. Another example is perfluorinated compounds, also known as PFCs, which are used to make stain repellent and nonstick coating for a variety of products. Polycyclic aromatic hydrocarbons (PAHs) originate from oil spills and urban runoff and remained in Pacific waters after the Exxon Valdez oil spill. All of these chemical compounds are made to be sturdy and resilient but the resulting consequence is that they are also resistant to decomposing in the environment and therefore can pollute water systems and harm wildlife. Furthermore, these chemicals may not be fatal individually, but the combinations of certain chemicals together in the environment can be even more toxic. For example, pesticides are regulated separately from each other but the mixture of multiple pesticides together can be even more problematic. Unfortunately, these chemicals are entering the natural surface waters in varying ways all over the world.
One way that chemicals enter the water system is through industrial factories and building systems around the world. A 2012 report found that U.S. industrial facilities were responsible for dumping 226 million pounds of chemicals into more than 1,400 waterways in one year. Furthermore, this is a problem in other parts of the world as well. Worldwide, it is estimated that over 180 million tons of chemicals from industrial and mining practices are dumped into lakes, rivers, and oceans every single year. Abandoned mines create acidic water that is high in metal consequently affecting the pH levels of that ecosystem. In developing countries, 70 percent of industrial waste is dumped into aquatic habitats, without being treated first.
Fertilizers and pesticides also enter the water system when they are washed away by rainwater. They enter rivers and streams and eventually end up in the oceans. For example, the Mississippi River starts in Minnesota and passes through large agricultural areas before finally reaching the Gulf of Mexico where toxins collected along the way have created dead zones. These dead zones then affect marine life, birds and land animals. The reasoning behind this is that fertilizers and pesticides contribute to excessive amounts of nitrogen and phosphorous in the water which stimulates the growth of plants, or algae blooms. These plants then deprive the aquatic life of necessary oxygen. This occurs in freshwater ecosystems as well, such as rivers, lakes, and bays, consequently killing freshwater fish and other aquatic life in this oxygen starved environment. Fertilizer and pesticide runoff is both a residential issue as well as agricultural, however the EPA states that agriculture is the nation’s leading cause of poor water quality.
Beyond human-made chemicals and toxins, biological waste from animals and humans negatively affects aquatic systems also. Factory farms contribute to water pollution when the lagoons containing animal wastewater overflow or leak, or when runoff from the farms travel to nearby waterways. Animal waste can act similarly to pesticides and fertilizers by creating algae blooms. Additionally, animal waste may typically contain hormones that can cause reproductive issues in fish.
There are numerous research studies that confirm the destructive outcomes of toxic chemicals in aquatic environments. Furthermore, the adverse impacts of these substances are both broad and diverse. For example, PAHs have been found to cause heart defects in herring and pink salmon embryos and when zebrafish absorbed PAHs through their skin, their hearts were severely malformed. Turtles experience signs of liver damage and are immunocompromised when found with high concentrations of PFCs. Concentrations of pesticides can modify the physiology, behavior, learning, and ability of fish to escape predators. Similarly, small amounts of metals such as mercury and zinc reduce the swimming rate of crab and fish larvae. Phthalate esters, PCBs, and pesticides have been found to have detrimental effects on the survival, growth, behavior, and reproduction of marine fish and shellfish.
Given that it is now known that these chemicals have harmful consequences for both freshwater and marine animals, some studies have questioned whether small doses would be less damaging. The results show that even in low doses, there can be biological effects. Furthermore, the effects can be indirect as well as direct. When toxic chemicals are present in the environment, organisms can absorb them through their skin or ingest them. The toxins then travel up the food chain, via consumption and the food web, and as a result, larger animals such as fish, birds, and mammals accumulate the toxins in higher concentrations.
With all of this knowledge, information, and research, the problem then becomes how we can fix this issue. As individuals, there are actions that can be taken to help lessen the negative impacts of toxic chemicals on aquatic life. Individuals can practice eco-friendly landscaping and gardening methods by eliminating the use of fertilizers and pesticides. Waste, such as paint and oil, can be disposed of properly at a public waste facility. People can choose organic food and products which helps to support the position of less pesticide use by farmers and other producers. Rain gardens also help to prevent soil erosion and chemical runoff by filtering pollutants. At the municipal level, treatment plants can work to remove more of the chemicals in wastewater before they enter the environment, given that many of these substances are ending up in aquatic habitats due to insufficient filtering at the plant. At the governmental level, incentives could be initiated for a variety of improvements. Farming businesses could receive incentives to reduce the use of pesticides and fertilizers. Manufacturers could receive incentives for better chemical containment or research to develop and employ less harmful chemicals. Lastly, research can be done preemptively on chemical substances to determine their effects on aquatic environments prior to their production and use. Unfortunately, a significant amount of damage has already occurred. In order to reverse or at least minimize the negative impacts of chemicals on freshwater and marine wildlife, effective and consistent actions must be taken by individuals, organizations and governments worldwide.
Sources: American Fisheries Society, National Geographic, National Public Radio, One Green Planet, Popular Science, Science Daily, World Wildlife Fund