Estuaries

IntroductionIntroduction

• We’ve already seen what it’s like near the edge!We’ve already seen what it’s like near the edge!

• Ocean life is rough. Adaptation is the key to long term Ocean life is rough. Adaptation is the key to long term survival.survival.

• What about in environements which appear to be less What about in environements which appear to be less disturbed? Does chaos still rule in a world of “living disturbed? Does chaos still rule in a world of “living on the edge,” such as estuaries? on the edge,” such as estuaries?

• Let’s find ouch, shall we?Let’s find ouch, shall we?

EstuariesEstuaries

• Estuaries are old structures.Estuaries are old structures.

• Invading seas to land masses form Invading seas to land masses form drowned river drowned river valleysvalleys or or coastal plain estuariescoastal plain estuaries..

• Others are known asOthers are known as bar-built estuaries, where bar-built estuaries, where sediment accumulation restricts sea/fresh water sediment accumulation restricts sea/fresh water interaction.interaction.

• Glaciers can also create estuaries by cutting off sea Glaciers can also create estuaries by cutting off sea water access to inland lakes (water access to inland lakes (fjordsfjords). ).

Salty sources: Cape Hatteras is a perfect example of a Salty sources: Cape Hatteras is a perfect example of a man-made estuary. (High exchange, high productivity)man-made estuary. (High exchange, high productivity)

Milford Sound, NZ. Little exchange (low D.O.)Milford Sound, NZ. Little exchange (low D.O.)

Good example of a fjord system.Good example of a fjord system.

Salt wedges Salt wedges

Tidal Action:Tidal Action:

Animals in some Animals in some estuaries are subjectedestuaries are subjectedto two cycles of to two cycles of varying salinity.varying salinity.

Animals in theseAnimals in theseharsh environments harsh environments enjoy benefits of enjoy benefits of highly productive highly productive grounds at the expense of grounds at the expense of difficult living conditions.difficult living conditions.

How well do you tolerate change?How well do you tolerate change?

Some animals are just better than others…Some animals are just better than others…

Plants play an importantPlants play an importantrole in estuary “stability.”role in estuary “stability.”

Cordgrass (Cordgrass (SpartinaSpartina) ) is an example of a grassis an example of a grasswhich promotes bank which promotes bank stability while providing stability while providing shelter for many small shelter for many small animals.animals.

Like mangroves, they excreteLike mangroves, they excreteexcess salt from their blades.excess salt from their blades.

Other plants store water in Other plants store water in succulentsucculent “leaves.” “leaves.”

This form of water storage This form of water storage dilutesdilutes salts taken up salts taken up by the plant during photosynthesis.by the plant during photosynthesis.

Mudflats and marsh creeks serve as spawning Mudflats and marsh creeks serve as spawning grounds for many species of fish. grounds for many species of fish.

Catadromous: Sea to freshCatadromous: Sea to fresh Anadromous: Fresh to seaAnadromous: Fresh to sea

Primary productivity:Primary productivity:very high in esturary very high in esturary mudmudflatsflats..

Especially for these Especially for these horn snailshorn snailsCerithidea californicaCerithidea californicawhich are excellent which are excellent deposit feedersdeposit feeders..

And the list goes on…And the list goes on…

Birds have also evolved to take advantage of Birds have also evolved to take advantage of abundant food sources on mudflats.abundant food sources on mudflats.

Feast or famine?Feast or famine?

When the tide is in…When the tide is in…

food is scarce.food is scarce.

When the tide drops…When the tide drops…

animals feast while they animals feast while they can…can…

Biofiltration: Estuary’s most important role?Biofiltration: Estuary’s most important role?

This salt marsh is dominated by grasses and benthic bacteria.This salt marsh is dominated by grasses and benthic bacteria.

Figure 12.18Figure 12.18

Figure 12.19Figure 12.19

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