Introduction • We’ve already seen what it’s like near the edge! • Ocean life is rough. Adaptation is the key to long term survival. • What about in environements which appear to be less disturbed? Does chaos still rule in a world of “living on the edge,” such as estuaries? • Let’s find ouch, shall we?
Estuaries • Estuaries are old structures. • Invading seas to land masses form drowned river valleys or coastal plain estuaries. • Others are known as bar-built estuaries, where sediment accumulation restricts sea/fresh water interaction. • Glaciers can also create estuaries by cutting off sea water access to inland lakes (fjords).
Salty sources: Cape Hatteras is a perfect example of a man-made estuary. (High exchange, high productivity)
Milford Sound, NZ. Little exchange (low D.O.) Good example of a fjord system.
Tidal Action:Animals in some estuaries are subjectedto two cycles of varying salinity.Animals in theseharsh environments enjoy benefits of highly productive grounds at the expense of difficult living conditions.
Plants play an importantrole in estuary “stability.”Cordgrass (Spartina) is an example of a grasswhich promotes bank stability while providing shelter for many small animals.Like mangroves, they excreteexcess salt from their blades.
Other plants store water in succulent “leaves.”This form of water storage dilutes salts taken up by the plant during photosynthesis.
Mudflats and marsh creeks serve as spawning grounds for many species of fish. Catadromous: Sea to fresh Anadromous: Fresh to sea
Primary productivity:very high in esturary mudflats.Especially for these horn snailsCerithidea californicawhich are excellent deposit feeders.
Birds have also evolved to take advantage of abundant food sources on mudflats.
Feast or famine?When the tide is in…food is scarce.When the tide drops…animals feast while they can…
Biofiltration: Estuary’s most important role? This salt marsh is dominated by grasses and benthic bacteria.