Streams and Rivers

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Streams and Rivers

• near the source, the water is usually cold, low
  in nutrients, and with a swift current
• consequently silt deposit and phytoplankton
  growth are inhibited
• most organism are supported by algae attached to
  rocks, or by organic debris from land
• trout are often the predominant fishes, locating
  their prey by sight in the clear water

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Streams and Rivers (cont.)

• downstream, the the water is warmer and murkier
  because of sediment and phytoplankton
• waterfowl, frogs, and mudburrowing worms and
  insects are common
• downstream habitat favors species such as catfish
  which located food by scent, rather than sight

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Lakes

• because of sediment buildup phytoplankton and
  rooted plants re limited to shallow waters
• lake floors have numerous microbes which
  decompose debris that sink to the bottom so that
  deep layers are oxygen poor
• seasonal mixing helps restore oxygen to the
  bottom and brings nutrients to the surface
• over time lakes tend to become filled up with
  sediment, turning to bogs and then meadows or
  forest

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Estuaries

• estuarine organisms must be able to tolerate
  powerful currents, turbidity, great changes in
  salinity
• detritus feeders (oysters, clams, lobsters,
  crabs, fish) are common
• estuaries are the nursery grounds for vast
  numbers of marine animals, including most
  continental shelf species

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Oceanic Ecosystems

• water where sufficient light penetrates to allow
  photosynthesis is known as the photic zone
• deeper water are known as the aphotic zone
• the pelagic zone refers to the open sea
• The benthic zone refers to the ocean floor,
  including the littoral (near shore) and abyssal
  (deep) zones

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Intertidal zone
Continental zone
Photiczone
Pelagiczone
Benthiczone(seafloor)
Aphoticzone
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Pelagic Zone

• plankton are free floating organisms with limited
  self mobility, including phytoplankton and
  zooplankton
• most plankton are microscopic (but jellyfish are
  not)
• nekton are the large, motile group of marine
  species fishes, sharks, turtles, seals, whales,
  etc.

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Benthic Zones

• the intertidal (littoral) zone usually has
  relatively few species clams, crustaceans,
  worms, and sea urchins
• the sublittoral zone includes mangroves,
  seagrass, reef, and kelp communities
• the abyssal zone contains specialized creatures
  able to withstand high pressures and food
  deprivation, often with small bodies and large
  mouths

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Figure 17.4
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Coastal Salt Marsh
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Mangroves
Figure 13.18
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Coral Reefs

• coral reefs are among the world's highest
  producers, with great species diversity
• oxygen concentrations are high due to wave motion
  and photosynthesis of symbiotic algae
• reefs are limited to the tropics
• reefs require adequate light, warm temperatures,
  and a hard substrate
• reefs provide a sink for carbon dioxide

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