Chapter 12 Estuaries Where Rivers Meet the Sea

Chapter 12 Estuaries: Where Rivers Meet the Sea

Estuary • Semi-enclosed areas where fresh water and seawater meet and mix • Close interaction between land sea • Among the most productive environments on earth • Among the environments most effected by humans • Many cites are located along them (NY, London, Tokyo)

Importance of Estuaries • Nurseries of the sea – used by many species for nesting and breeding • Most of the fish and shellfish we eat complete part of their lifecycle here (salmon, herring, oyster) • Used for recreation, jobs, and homes • Of the 32 largest cities 22 are located on estuaries

• Filter out sediments and pollutants from rivers and streams before they flow into the ocean providing cleaner water for humans and marine life

• Estuaries are interconnected with the world ocean and with major systems and cycles on Earth. • Estuaries are dynamic ecosystems with tremendous variability within and between them in physical, chemical, and biological components. • Estuaries support an abundance of life, and a diversity of habitat types.

Estuaries – One of the most Threatened ecosystems on earth • • • Coastal development Introduction of invasive species Overfishing Dams Global climate change (sea level rise)

Living in an Estuary

Organisms of the estuary • Most estuarine organisms are marine species that have developed the ability to tolerate low salinities • Euryhaline – organisms that can tolerate a wide range of salinities – most estuarine organisms are • Stenohaline – tolerate a narrow range in salinity

Dealing with Osmosis • Osmoconformers – body fluids change with the salinity • Osmoregulators – keep the salt concentration of their body fluids more or less constant

Types of Estuarine Communities

• Consist of few species • Species present are in large numbers

Open Water – when tide is in • Water is murky – turbid • Lots of food – plankton • Fish move in

Mudflats – at low tide • Organisms – infauna • Problems – predation, desiccation, temperature changes, salinity changes

Salt Marshes • Dominated by grasses • Temperate and subarctic regions

Mangrove Forests • Tropical equivalents of salt marshes • Dominated by Mangroves (trees) • tropical regions