Sea Surface (pelagic)

Sea Surface (pelagic) - The Open Ocean The Epipelagic The...

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The Open Ocean
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The Epipelagic The EPIPELAGIC zone extends from the surface to approximately 200m deep It is similar to the PHOTIC zone – the zone which receives enough sunlight to allow organisms to photosynthesize The epipelagic can be divided into: NERITIC (coastal) and OCEANIC
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Although the epipelagic zone accounts for less than 10% of the ocean’s volume the majority of pelagic marine species are found in this zone The Epipelagic
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The Epipelagic Unlike shallow waters where there may be benthic primary production (e.g. seaweeds, seagrasses) all primary production in the epi pelagic occurs within this zone The neritic system may receive nutrients from land- based sources, or from organic materials washed into the coast (drifting seaweeds, stranded carcasses) But the oceanic system receives almost no external input of organic matter nutrients The epipelagic does supply food to other systems - e.g. dead organisms drop to the mesopelagic and below - e.g. currents wash epipelagic plankton into coastal waters where they are consumed by sessile, benthic filter feeders.
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The Epipelagic Because there is no bottom where organic sediments and nutrients can accumulate there are no epipelagic deposit feeders But floating suspension/filter feeders are common Large pelagic predators are also found and are the peak of the epipelagic trophic pyramid Phytoplankton (autotrophic) are the main producers in the epipelagic system (although there may be floating planktonic seaweeds – Sargassum ) Zooplankton (heterotrophic) are also important in the epipelagic system
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Sargassum sp.
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Plankton is often categorized according to size…
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Table 15.01
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Phytoplankton 95% of the oceans productivity is the result of phytoplankton It also accounts for half of the world’s primary production (land and marine) and produces half of the world’s oxygen supply As noted before cyanobacteria are important phytoplankton (accounting for half of oceanic primary production) and they dominate the PICOPLANKTON NANOPLANKTON includes coccolithophores, silicoflagelates and other protists (e.g. crypotphytes) Diatoms and dinoflagellates are common members of MICROPLANKTON
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Zooplankton Zooplankton are the most important herbivores in the epipelagic zone But few are strict herbivores and may also eat other zooplankton Zooplankton are represented by more than 5000 species of permanent plankton = HOLOPLANKTON (including all three protozoan phyla, cnidarians, ctenophores, chaetognaths, crustaceans, and invertebrate chordates) and temporary plankton = MEROPLANKTON (e.g. larval stages of invertebrates and fishes)
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There are a number of protozoa in zooplankton (see invertebrate lecture) the most important include: Forimaniferans Radiolarians Ciliates These may graze on pico, nano or micro plankton. Some can switch between being grazers and
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This note was uploaded on 01/23/2012 for the course BIOL/EVPP 449 at George Mason.

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Sea Surface (pelagic) - The Open Ocean The Epipelagic The...

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