ch16 - 16 From the Continental Shelf to the Deep Sea Notes...

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16 From the Continental Shelf to the Deep Sea Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton ©Jeffrey S. Levinton 2001
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Plan for next few lectures • Shelf - Deep Sea gradient trophic approach • Diversity gradient from shelf to deep sea • Special character of deep sea and some deep sea communities • Issue of diversity (number of species) - controls, models, role of history
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Sampling the Subtidal Benthos Dredges , heavy metal frames with cutting edges that dig into sediment Sleds , dredges with ski-like runners that allow only shallow sampling of sediment Grabs , samplers that sample only a defined area at a time Corers , small tubes that are dropped into sediment (useful for microbiota, sediment samples) Types of bottom samplers:
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Sampling the Subtidal Soft-BottomBenthos Sample a large area of bottom Sample a defined area and uniform depth below the sediment-water interface Sample uniformly in differing bottom substrata Have a closing device to prevent washout of specimens as sampler is brought to the surface A good sampler should:
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Sampling the Subtidal Benthos Visual observation is crucial Observations and sampling can be done by submersibles, manned and unmanned
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Alvin from WHOI
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The Shelf-Deep Sea Gradient Supply of nutrient-rich particulates to deep sea is low: Distance from shore Depth and time of travel of material from surface to bottom(decomposition) Low primary production over remote deep sea bottoms
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Input of organic matter from water column declines with depth and distance from shore: continental shelf sediment organic matter = 2-5%, open ocean sediment organic matter = 0.5 - 1.5%, open ocean abyssal bottoms beneath gyre centers < 0.25% Input of organic matter
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Microbial Activity on Seabed 1 Sinking of the Alvin and lunch. Mechanism - not so clear. High pressure effect on decomposition (depth over 1000m) or perhaps low rates of microbial activity in deep sea.
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Microbial Activity on Seabed 2 Deep-sea bottom oxygen consumption 100-fold less than at shelf depths Bacterial substrates such as agar labeled with radioactive carbon are taken up by bacteria at
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ch16 - 16 From the Continental Shelf to the Deep Sea Notes...

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