By: Chris Moss Block 3

Where are they? Places of transition from land to sea, and from fresh to salt water. In the U.S, estuaries make up more than 80% of the coastline along the Atlantic Ocean and Gulf of Mexico, and more than 10% of the Pacific coast. The most well known estuaries in the U.S are Rookery Bay, and the Chesapeake Bay

Precipitation The average rainfall in U.S estuaries is 42 inches per year or about 3.5 inches a month.

Temperature The average annual temperature in an estuary is 51 degrees Fahrenheit. Estuaries are not restricted to a certain climate region, however they are found in both temperate and tropical regions. Since estuaries are shallow and semi-enclosed, temperatures can be slightly higher than in open areas. Cold temperatures can negatively affect fish by slowing down hatching and growth of the young.

Amount of Light Many estuaries are very shallow, with very little plant coverage, so plenty of sunlight reaches the bottom to power photosynthesis. Most reach a depth of less than 20 meters.

Salinity The mixture of seawater and fresh water in estuaries is called brackish water, and its salinity can range from 0.5 to 35 parts per thousand. Salinity of the water increases as you get closer to the seashore. The salinity of estuarine water varies from estuary to estuary, and can change from one day to the next depending on the tides and weather patterns.

Nutrient Levels The inflow of both seawater and freshwater provide high levels of nutrients, making estuaries one of the most productive natural habitats in the world. Of all the essential nutrients for life in an estuary, nitrogen and phosphorus are the two that most often limit the growth of primary producers. Excess nutrients may come from septic tanks, wastewater treatment plants, discharges from sewage and industry, exhaust from car emissions, fertilizers from lawns, golf courses, and farms and animal waste.

Common Species Sea Trout Eels Black tailed Godwit Great Blue Herons Sea Horses Oysters Striped Bass Sea grass Eel grass Loblolly Pine Water Chestnuts Bulrush Cattail

Endangered Species Blueback Herring Gulf Sturgeon Large tooth Sawfish Pacific Herring Saltmarsh Topminnow Rainbow Smelt Sandplain Gerardia Golden Sedge Beach Jacquemontia Key Tree Cactus

Our Influence on Estuaries Estuaries are very susceptible to pollutants that are washed in from the ocean and rivers. Organic and heavy-metal pollutants typically have a long residence time in estuaries and tend to build up in large amounts over time. Fishing is outlawed in many estuaries due to the toxins which have been accumulated in seafood. Once pollutants are introduced into an estuary, they are very difficult to remove. High amounts of biological waste from land runoff arouse phytoplankton production which increases the rate of organic matter entering the estuary. Over time, this creates low dissolved oxygen concentrations in the water, which leads to large fish and shellfish kills due to very low oxygen concentrations for aerobic respiration.

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