Chapter 15 Animals of the Benthic Environment

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Chapter 15 Animals of the Benthic Environment

• Essentials of Oceanography
• 7th Edition

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Benthic organisms

• Benthic organisms are those that live in or on
  the ocean floor
• More than 98 of known marine species are benthic
• The vast majority of benthic species live within
  the shallow continental shelf

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Benthic biomass closely matches surface
productivity
Surface productivity
Figure 13-6
Figure 15-1
Benthic biomass
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Rocky shores

• Most organisms live on the surface (epifauna)
• Zonation of rocky shores
• Spray zone (rarely covered by water)
• High tide zone
• Middle tide zone
• Low tide zone (rarely exposed)
• Upper zones have mostly shelled organisms
• Lower zones have many soft-bodied organisms and
  algae

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Rocky shores Intertidal zonation and organisms
Figure 15-2a
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Sea anemone

• A vicious predator cleverly disguised as a
  harmless flower but armed with stinging cells

Figure 15-4
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Sediment-covered shores

• Most organisms burrow into the sediment (infauna)
• Sediment-covered shores include
• Beaches
• Salt marshes
• Mud flats

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Sediment-covered shores Intertidal zonation and
organisms
Figure 15-8
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Sediment-covered shores Modes of feeding
Figure 15-9
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How a clam burrows
Figure 15-10
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Shallow offshore ocean floor

• Extends from the spring low-tide shoreline to the
  edge of the continental shelf
• Mostly sediment-covered but contains rocky
  exposures
• Includes
• Kelp forests
• Coral reefs

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Kelp forests

• Kelp forests are found on rocky bottoms and
  provide habitat for many organisms
• Gant brown bladder kelp Macrocystis has a strong
  holdfast and gas-filled floats
• Macrocystis can grow up to 0.6 meter (2 feet) per
  day

Figure 15-15a
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Coral reefs

• Coral reefs are hard, wave-resistant structures
  composed of individual coral animals (polyps)
• Individual coral polyps
• Are about the size of an ant
• Are related to jellyfish
• Feed with stinging tentacles
• Live attached to the sea floor in large colonies
• Construct hard calcium carbonate structures for
  protection
• Contain symbiotic photosynthetic zooxanthellae
  algae

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Coral reefs Environmental conditions

• Coral reefs need
• Warm water 18-30C (64-86F)
• Strong sunlight (for symbiotic algae)
• Strong wave/current action
• Lack of turbidity
• Salt water
• Hard substrate for attachment
• Coral reefs found in shallow, tropical waters

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Coral reef distribution and diversity
Figure 15-18
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Coral reef zonation
Figure 15-19
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Stages of coral reef development
Figure 2-30
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Coral bleaching

• Coral bleaching occurs when symbiotic
  zoothanthellae algae is removed or expelled
• Associated with high water temperatures

Figure 15B
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The deep-ocean floor

• Characteristics of the deep ocean
• Absence of sunlight
• Temperatures around freezing
• Average salinity
• High dissolved oxygen
• Extremely high pressure
• Slow bottom currents (except abyssal storms)
• Low food supply

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Food sources for deep-sea organisms
Figure 15-22
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Deep-sea hydrothermal vent biocommunities

• Found in deep water near black smokers along the
  mid-ocean ridge
• Do not rely on food from sunlit surface waters
• Organisms include
• Tube worms
• Clams
• Mussels
• Crabs
• Microbial mats

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Alvin approaches a hydrothermal vent biocommunity
Figure 15-23
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Locations of deep-sea biocommunities
Figure 15-24
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Deep-sea vent biocommunity food source
Chemosynthesis

• Deep-sea vent biocommunities rely on bacteria and
  archaeon that chemosynthesize

Figure 15-25
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Other deep-sea biocommunities

• Low-temperature seep biocommunities are
  associated with
• Hypersaline seeps
• Hydrocarbon seeps
• Subduction zone seeps

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End of Chapter 15

• Essentials of Oceanography
• 7th Edition