Sandy Bottom Ecosystems

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Sandy Bottom Ecosystems

• November 6, 2007

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Soft-Bottom Communities

• Dominated by infaunal organisms
• Sediment not firm enough for seaweeds to attach
• Grain size determined by water flow
• A 3-D benthic ecosystem

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Sediment Grain Size

• What are the things grain size affect?
• What are the different grain sizes, and how do we
  measure them?

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Flow

• With sandy habitats with slow flow, we get
  sediment deposition
• With sandy habitats with fast flow, there is more
  turbulence, and thus more sediment resuspension
• How are flow and sediment grain size related?

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Sediment Organic Matter

• What is sediment organic matter?
• Sediment organic matter affects the biology and
  chemistry of the sediments
• Which areas would we expect to have high organic
  matter, and which areas would we expect to have
  low organic matter in the sediments?

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Subtidal Zone

• From the bottom of the intertidal zone to the
  continental shelf break
• Physical Characteristics
• Temperature
• Tidal Currents
• Stratification
• Nutrients
• Sediment

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Soft-Bottom Subtidal Communities

• Vegetated or Unvegetated

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Feeding Modes

• Suspension Feeders
• Deposit Feeders
• Scavengers
• How does sediment grain size affect feeding modes
  in soft sediment ecosystems?

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Organism Adaptations

• Color

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Organism Adaptations

• Shape

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Organism Adaptations

• Size
• Abundance of Meiofauna

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How do Animals Change the Habitat?

• Animals can destabilize the sediments by digging
  and loosening them
• Animals can stabilize sediments by anchoring them
• Animals can affect the surface roughness of the
  sediments
• Creating tubes
• Fecal matter
• Burrows
• Mounds

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How do Animals Change the Habitat?

• Bioturbation particle mixing by organisms can
  result from
• Burrowing (small particle movement)
• Excavating (digging deep and depositing grains on
  sediment surface)
• Feeding and defecation (particles are repackaged
  and put on surface)

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Disturbance in Soft-Bottom Communities