Benthos

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Benthos

• Unlike the drifting plankton and swimming nekton,
  benthic organisms commonly referred to as
  benthos live on or near the ocean bottom
• A benthic habitat may be shallow or deep
• Most benthic organisms are sessile (immobile) and
  anchored to the benthic environment others crawl
  or swim over the ocean bottom

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Benthos

• Of the 250,000 known species that inhabit the
  marine environment, gt98 are benthos!
• The majority of benthic organisms live on the
  continental shelf sunlit areas of relatively
  high primary productivity
• Benthos include animals,
  protists (algae) and even
  plants!

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Intertidal Zones

• Rocky shorelines team with organisms that live on
  the ocean floor (epifauna)
• Typical rocky shores are divided into distinct
  zones, characterized by the height of the water
  (which is itself determined by the tides)
• So called intertidal zones are among the most
  densely-populated areas on Earth hundreds of
  species crowd this junction of land and sea

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Life in the intertidal zone is harsh!

• Adverse conditions require special adaptations of
  organisms to live both underwater (some of the
  time) and exposed to air (the rest of the time)!
• Strong wave activity, desiccation (drying out),
  limited space, rapid changes in temperature,
  salinity, pH, and oxygen content, and predation
  are just some of the challenges found here

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Spray zone region above the spring high tide
line covered by water only during storms
Intertidal zone region between the high and low
tidal extremes
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Intertidal Zone
Mostly shelled organisms

• High tide zone relatively dry
• Middle tide zone alternatively wet and dry
• Low tide zone usually wet, but exposed during
  low tides

Mostly soft-bodied organisms and algae
http//www.humboldt.edu/intertid/zones.html
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Life in the intertidal High tide zone

• Most animals living in the high tide zone have
  protective coverings to prevent desiccation
• Seaweeds living in the high tide zone have thick
  cell walls to reduce water loss during low tides
• Many organisms in the high tide zone are sessile,
  and remain attached to bottom, competing with
  others for limited space

www.armofthesea.info/flora_faunaff_speciespp/moll.
htm
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Life in the Intertidal Middle tide zone

• Seawater constantly bathes the middle tide zone,
  so a greater variety of seaweeds and soft-bodied
  organisms live here
• Greater biomass in middle tide zone, and so
  greater competition for space!
• Mussels and barnacles are common here
  hard-bodied, filter-feeding organisms which
  require seawater to feed and to
  support planktonic larval stages

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Crying cockles and mussels, alive, alive-O!

• The middle tide zone is also home to carnivorous
  snails and sea stars
• You, too, can be a sea sleuth.
• Sea stars pry open clams and mussels with
  hundreds of tube feet Predatory snails bore
  holes with scraping tongues and suck out prey
• Hermit crabs, sea urchins, and sea anemones are
  also found here

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Life in the Intertidal Low tide zone

• The low tide zone is almost always submerged, so
  an abundance of algae (seaweed) is typically
  present
• Seaweeds are multi-cellular algae (protists)
• Seaweeds attach themselves with a structure known
  as a holdfast and use gas bladders to reach
  upward to sunlit surface water photosynthetic
  important source of habitat

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Life in the Intertidal Low tide zone

• Numerous crabs and shellfish live in the low tide
  zone
• Benthic fish swim through the low tide zone,
  along with larval nektonic forms which seek
  shelter and habitat in this protected area

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Salt marshes are sediment-covered shores

• Salt marshes and estuaries (regions where
  freshwater and saltwater meet) are highly
  productive benthic habitats
• Much of this productivity comes from sea grasses,
  mangroves and other vascular plants
• Salt marshes form in estuaries and are
  characterized by specialized plants capable of
  surviving in (and then out of) salt water

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Salt marshes Home Sweet Home

• Salt marshes via their specialized plants
  form protective barriers against erosion, and
  promote new land formation as plant roots trap
  sediments on each tidal cycle, and filter out
  excess nutrients and pollutants
• Salt marshes also provide protective habitat for
  larval fish species, and provide food and shelter
  for migratory waterfowl marsh plants also form
  the base of the food web via decay

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Salt Marshes are Vital Habitats!
http//en.wikipedia.org/wiki/FileBride-Brook-Salt
-Marsh-s.jpg
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Sand and Cobble Beach Communities

• Not all intertidal areas are rocky or muddy some
  are sandy or consist of gravel or cobbles
• As benign and peaceful as sandy beaches look,
  they are among the most hostile environments for
  small organisms
• Sand grains are abrasive and many organisms must
  have protective coatings and/or be able to burrow
  below the surface for protection

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Sand and Cobble Beach Communities

• In fact, very few organisms survive in wave-swept
  sandy beaches
• Some larger crabs can outrun the crashing waves
  and locate food within sand grains
• Coquina shells and mole crabs are common along
  Long Island sandy beaches

www.stripersonline.com/surftalkshowthread.php?t41
7951
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Coral Reef Communities

• Corals are animals (Cnidarians) related to
  anemones and jellyfish
• Most corals secrete hard skeletons of calcium
  carbonate and produce coral reefs
• An individual coral known as a polyp feeds by
  capturing and eating plankton that drift within
  reach of their tentacles
• Corals produce sexually and asexually

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Coral Reef Communities

• Corals form symbiotic relationships with
  dinoflagellates, known as zooxanthellae
• Zooxanthellae receive nutrients and shelter from
  the coral, and photosynthesize, providing the
  coral with organic compounds
• Zooxanthellae provide corals
  (otherwise translucent)
  with their brilliant colors

www2.watertown.k12.wi.us/pagesfifth_grade_websites
.cfm
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Tropical coral reefs support large numbers of
species

• Reef-building corals provide substrate for other
  organisms to attach and hide
• Corals also provide a source of food in otherwise
  weakly-productive regions
• Coral bleaching (the loss of the symbiotic
  zooxanthellae in response to environmental
  stress) may kill the coral, and have devastating
  impacts on the coral reef community

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Coral Bleaching
www.cgrer.uiowa.edu/peoplecarmichael/atmos_course/
ATMOS_PROJ_99/jlmichfin/main.html
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Corals are stressed by environmental change

• A water temperature change of only 1C above the
  normal summer high temperature for a few weeks
  leads to coral bleaching
• Coral expels zooxanthellae or zooxanthellae
  expels itself
• El Niño events can drive coral bleaching
• May be reversible corals can re-aquire new
  zooxanthellae if the stress is not too severe

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Want to learn more?

• Take our Marine Biology and/or Marine Habitat
  Ecology courses!

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Until then, so long and thanks for all the fish!