Estuaries

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Estuaries
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Introduction

• Weve already seen what its 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?
• Lets find ouch, shall we?

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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).

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Salty sources Cape Hatteras is a perfect example
of a man-made estuary. (High exchange, high
productivity)
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Milford Sound, NZ. Little exchange (low D.O.)
Good example of a fjord system.
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Salt wedges
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Tidal ActionAnimals 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.
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How well do you tolerate change?
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Some animals are just better than others
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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.
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Other plants store water in succulent
leaves.This form of water storage
dilutes salts taken up by the plant during
photosynthesis.
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Mudflats and marsh creeks serve as spawning
grounds for many species of fish.
Catadromous Sea to fresh Anadromous Fresh to
sea
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Primary productivityvery high in esturary
mudflats.Especially for these horn
snailsCerithidea californicawhich are excellent
deposit feeders.
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And the list goes on
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Birds have also evolved to take advantage of
abundant food sources on mudflats.
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Feast or famine?When the tide is infood is
scarce.When the tide dropsanimals feast
while they can
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Biofiltration Estuarys most important role?
This salt marsh is dominated by grasses and
benthic bacteria.
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Figure 12.18
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Figure 12.19
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Figure 12.20
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Figure 12.21
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Figure 12.22
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