Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 12

Estuaries

Coller Marine Science Estuaries: where rivers meet the seas

Estuaries: Coastal Wetlands

•  Objectives –  Name and identify the characteristics of estuaries. –  Describe the processes that lead to the formation of different types of

estuaries. –  Identify and describe the types of habitat within wetland ecosystems (e.g.

salt marsh, mudflat) –  Describe and evaluate the significance of wetland ecosystems in terms

of primary production, flood control, water quality, habitat etc. –  Discuss and describe the unique environmental conditions which arise

from the mixing of salt and fresh waters. –  Describe the adaptations of organisms which allow them to thrive in

wetland communities. –  Identify and explain the factors which lead to salt wedges, stratification,

and siltation.

Types of Estuaries http://oceanservice.noaa.gov/education/kits/estuaries/estuaries04_geology.html

•  Drowned River Valleys and Coastal Plains –  Formed by sea level rise. –  More common on passive margins.

•  Bar Built Estuaries, Negative Estuaries (Coastal Saline Lakes) –  Sediment accumulates and forms a sand bar with associated mud flats. –  If rivers flow is low then waters can be isolated in coastal lagoons. –  If in addition evaporation rates are high and isolation from the open ocean is long term

then the salinity of coastal lakes can exceed that of the open ocean, (negative estuary). •  Tectonic Estuaries

–  Formed by subsidence of low lying coastal areas or uplift of shallow inlets. –  More common on active margins.

•  Fjords –  Formed by glacial retreat and rising sea levels. –  Found mainly in polar and sub polar regions. Latitudes higher than 40°N or S. Alaska,

Canada, Scandinavia, New Zealand, Chile.

Bar-Built Estuaries

Bar-Built Estuaries

Bahia Jiquilisco, El Salvador

Negative Estuaries

Fjords

Fjords Saguenay Fjord, Quebec

Norway

Tectonic Estuaries

Drowned River Valleys

Economic and Environmental Function of Estuaries

•  Water purification: Physical and chemical purification. •  Primary Production •  Habitat for numerous migratory birds and a myriad of other animals •  Flood Control •  Prevention of coastal erosion •  Protection from storm surge •  Nursery for many commercially important species of fish. •  Recreation and aesthetic value

Distribution of Water on Earth

U.S.G.S.

Most water on earth is saline

The vast majority of freshwater is in icecaps and ground water.

Salt Wedges

Stenohaline v. Euryhaline •  Stenohaline: Organisms that cannot tolerate large fluctuations in ambient salinity.

Stenohaline is derived from the words: "steno" meaning narrow, and "haline" meaning salt. Freshwater fish such as Goldfish and marine fish such as Haddock cannot tolerate dramatic changes in salinity.

•  Euryhaline: Organisms that can survive large fluctuations in external salinity. Bull

Sharks, Sturgeon and many shore crabs can tolerate broad fluctuations in external salinity.

Stenohaline v. Euryhaline •  Stenohaline: Organisms that

cannot tolerate large fluctuations in ambient salinity. Stenohaline is derived from the words: "steno" meaning narrow, and "haline" meaning salt. Freshwater fish such as Goldfish and marine fish such as Haddock cannot tolerate dramatic changes in salinity.

•  Euryhaline: Organisms that can

survive large fluctuations in external salinity. Bull Sharks, Sturgeon and many shore crabs can tolerate broad fluctuations in external salinity.

Halophytes: Estuarine Plants •  Salt tolerant Plants •  Some secrete salt through salt glands in leaves

(cordgrasses, mangroves) •  Some store large quantities of water to offset

salt absorption (succulents). •  Some sequester salt in special cells.

Spartina sp.

Salicornia sp.