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Estuaries

Partially enclosed coastal areas where freshwater mixes with seawater Aka: Saltmarshes, lagoons, mudflats, sloughs, coastal wetlands Highly productive environments Important role in many marine species life history. Estuaries. Drowned river valleys Coastal plain estuaries

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Estuaries

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  1. Partially enclosed coastal areas where freshwater mixes with seawater Aka: Saltmarshes, lagoons, mudflats, sloughs, coastal wetlands Highly productive environments Important role in many marine species life history Estuaries

  2. Drowned river valleys Coastal plain estuaries Rising sea level (melting of last ice age) encroached lowlands E.g. Chesapeake Bay Bar-built Sedimentation partially blocks sea E.g. Batiquitos Lagoon; San Eligo Lagoon Tectonic Coast lands subside via plate movements E.g. San Francisco Bay Fjords Glacier-carved estuaries Very deep, up to 1000s ft deeper than neighboring sea E.g. parts of Norway, Alaska, New Zealand… 4 basic types:

  3. Broad range of salinity Incoming seawater is more dense than freshwater influx Salt wedge is affected by tides & fluctuates seasonally Low freshwater influx, partial blocking, and high evaporation can increase salinity Negative estuaries Water mixing

  4. Tolerate wide range Euryhaline Narrow range Stenohaline species Brackish adapted Intermediate salinity Osmotic regulation Osmoconformers Internal fluctuations with environment (blue) Osmoregulators Maintain constant internal concentration via active transport (red) Both… Salinity Adaptations

  5. Lots of nutrients Freshwater influx Tidal flushing Carries plankton Sustains lots of consumers Coastal fishes, flatfishes, crustaceans, mollusks, worms… Nurseries Anadromous fishes (spawn in freshwater) Salmon, smelts, shad Catadromous fishes (spawn at sea) Freshwater eels Productivity & protection

  6. Why so productive? ↑ 1o production ↑ nutrients Tides & rivers Recycling Decomposition Breaking down detritus →DOM (dissolved organic matter) Nitrogen fixation Producers can use the organics

  7. Breeding, feeding and nesting grounds Key stopover point on the Pacific Flyway for over 370 species of migratory and native birds E.g. Tijuana River Estuary Most of our local lagoons Diverse species & resources Willet, godwits, dowitchers, plovers, & sandpipers Oyster catchers, herons, egrets Ducks, terns, & gulls Birds and estuaries

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