Estuaries help the world in many ways. The Ohio State University states that they are areas of breeding for animals that live in deeper waters; they provide homes and feeding grounds for a variety of animals; they are an area where the basic needs of life are available for the wildlife; they are buffers for pollution and, due to their calm waters and proximities to oceans or lakes, developments such as marinas, homes and tourists sites build in the areas, making them endangered.
Estuaries are highly productive ecosystems. Nutrients travel down rivers and streams and drain into estuaries. These nutrients are used by plants to help create food. Some of the plants grown here are phytoplankton, marsh grasses and mangroves. As the plants die they turn to detritus which are used by microbes, such as bacteria and fungi. As the detritus becomes smaller they become food for thousands of organisms. Smaller animals feed on the detritus and larger animals feed on the tiny particles. Some of the wildlife that rely on the estuaries are snook, trout, mullet, grouper, silver perch, catfish, spiny lobster, shrimp, crabs, oysters and clams. Estuaries are also used by other animals for breeding and nesting, such the endangered brown pelican. If area of this food chain is changed or broken, it changes or ends lives for the rest of the chain.
As humans invade the areas of the estuaries, many different aspects are affected. Estuaries are excellent at filtering pollutants from the water, but as the pollutants become more plentiful, these ecosystems become overwhelmed. Then when pollutants include heavy metals, pesticides and petroleum chemicals, the filtering process breaks down. The pollutants become trapped by the saline layers, and are not washed into the ocean. They are then carried to the bottom of the estuary by salt wedges. These pollutants are then dispersed across the water layers where organisms consume and store them in their bodies. These organisms, when consumed by others, pass the pollutants up the food chain. Eventually they end up in fish, and then humans.
Where estuaries meet major inland waterways, pollution is extremely bad. These ecosystems suffer from pathogen contamination and introduction of invasive species which jeopardize the lives of native fish and wildlife. When the inflow of freshwater is changed, the nutrient dispersal and overload from agricultural sources lead to lower levels of dissolved oxygen. This affects the estuary plants that make up the bottom of the food chain.
There have been many species of animals and plantl ife that have been listed as endangered which once called estuaries their home. These include: West Indian Manatees, Southern Resident Orcas, the Light-footed Clapper Rail, Chinook Salmon, Green Sturgeon, Largetooth Sawfish, Johnson’s Seagrass, and Mangrove Rivulus.
As an estuary’s health deteriorates, the water quality deteriorates also. This leads to lower diversity and density of plants and animals. Since this then leads to a lower quality of life for the ecosystem, as the animals and plants become endangered, so does the estuary.