Estuaries, in simplest terms, form in the region where river water enters a sea or an ocean. They are the regions of transition from fresh water to salt water and are extremely rich in nutrients. Due to their nutrient richness, estuaries are home to a large number of species of interest, including fishes, mammals, birds, etc. Estuaries are used for commercial fishing and it has been estimated by EPA that almost two-third of US's commercial fishes and shellfish use estuaries as nursing grounds.
The pollution of estuaries is a matter of grave concern. Estuaries receive pollution from industrial discharges, agricultural runoff, sewage treatment plant discharges, etc. These waste streams contain contaminants such as mercury, pesticides, etc. These contaminants enter the food web through estuarine species, including fishes. We are at a risk of contamination by the ingestion of fishes caught in contaminated estuaries. Unfortunately, many of these contaminated (including mercury, pesticides, lead, etc.) are extremely harmful to us and hence their transmission through the food web should be avoided.
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