Chapter 7, Estuaries, in: Introduction to the Biology of Marine Life (9th Edition)

The Chesapeake Bay, San Francisco Bay, Great South Bay, Tampa Bay, Puget Sound, and the Mississippi River Delta, the Hudson River Bay, Columbia River and Willapa Bay in Oregon, are among 100 bodies of water designated as estuaries in the US. Over 1/3 of the US population lives within the drainage basins of these estuaries.

Types of estuaries:
a. Coastal plan estuaries;
b. Bar built estuaries;
c. Coastal lagoons;
d. Deltas;
e. Tectonic estuaries;
f. Fjords.

Because of the patterns of freshwater and seawater mixing, there is an inward flow of nutrient rich seawater along the bottom of th estuary and a net outward flow at the surface, creating an estuarine upwelling. The time necessary for the total volume of water in an estuary to be replaced is called the flushing time.

The body fluids of osmotic conformers fluctuate to remain isotonic with the water. Most estuarine animals are stenohaline, tolerating exposure only to limited salinity ranges. A few species are euryhaline, capable of withstanding a wide range of salinity. Continue reading →