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Benthos - Introduction to Oceanography - Lecture Slides, Slides of Oceanography

Gujarat UniversityOceanography

These are the lecture slides of Oceanography. Key important points are: Ocean Convergence, Earth Structure and Plate Tectonics, Ocean Convergence, Benthos, Drifting Plankton, Benthic Organisms, Benthic Habitat, Benthic Organisms, Benthic Environment, Immobile

Typology: Slides

2012/2013

Uploaded on 01/24/2013

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amrusha 🇮🇳

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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

  • 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

Benthos

  • Of the 250,000 known species that inhabit the marine environment, >98% 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!

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

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

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 Docsity.com

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

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

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

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

Salt Marshes are Vital Habitats!

http://en.wikipedia.org/wiki/File:Bride-Brook-Salt-Marsh-s.jpg

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?t=417951Docsity.com

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

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

Coral Bleaching

www.cgrer.uiowa.edu/peoplecarmichael/atmos_course/ATMOS_PROJ_99/jlmichfin/main.html Docsity.com