2-12 - 2/12/08 ; 2/14/08 Chapter 4 The Deep Sea 1. The...

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2/12/08 ; 2/14/08 Chapter 4 – The Deep Sea 1. The Deep-Sea a. Definition i. Includes water and seabed beneath the edge of the continental shelf (>200m) b. What is the deep sea? i. Zones: 1. Mesopelagic (0.2-1k) a. Features i. Plains 2. Bathyal (1-4k) a. Features: i. Seamounts 3. Abyssal (4-6k) a. Features: i. Ridges 4. Hadal (>6k( a. Features: i. Trenches – know the least about ii. Hydrothermal vents iii. Seamounts c. How do we sample the deep sea? i. Only about 500m 2 of the sea floor has been quantitatively sampled ii. Sampling methods 1. Epibenthic sled 2. Box cores 3. Mid water trawl 4. Submersibles a. Great depths but can only handle a small number of people iii. Sampling the deep sea 1. Bathysnaps a. Motion sensitive cameras 2. Bathysnacks a. Baited cameras d. The deep sea environment i. Light in the deep sea 1. Aphotic
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a. Absolutely no light available from the service b. Can affect predator prey interactions 2. Dysphotic a. Some light penetrating from the surface. But below the level that primary production can occur. Enough for vision. 3. Bioluminescence 4. Darkness affects organismal interactions ii. 1. T = -1 ° C to 4 ° C, average 2 ° C 2. Salinity 34.8 ± 0.3 iii. Pressure changes a lot w/ depth 1. +1 atm for each 10m 2. Pressure range 20-1000 atm 3. Pressure affects proteins, lipids, calcification a. Functions tend to be sluggish; b. Organisms in the deep sea have c. Formation of calcium carbonate shells, more soluble at higher pressures and higher pressures i. Shells tend to be thin 4. Greatest affect of how the districution of organisms in the deep sea iv. O 2 is plentiful in the deep sea 1. What processes contribute to the changes in O 2 with depth? a. Deep water formation v. Constant water movement 1. Bottom currents: a. Refresh oxygen b. Provide food flux c. Transport larvae, etc. 2. Sources of bottom currents: a. Tidal currents b. Oceanic conveyor i. Primary componet ii. Keeps the water constantly moving in the deep sea c. Coriolis current vi. Deep sea sediments 1. Vast majority is soft sediment – mud a. Usually from particulate matter from above 2. Two main classes of sediment
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a. Clay – inorganic sediments b. Biogenic oozes (>20% biogenic skeletal material) Siliceous oozes (diatoms & radiolarians) Calcareous oozes e. Food in the Deep Sea i. Vast amount of food is from particulate organic matter coming down from above. 1. Zooplankton fecal pellets 2. Marine snow a. Various sizes 3. Blooms 4. Chitinous skeleton of the zooplankton a. Shells are shed and form a fraction of the organic matter in the deep sea ii. Sources/types of POM 1. a. Can measure sediments at different depths 2. Fecal pellets 3. Moults 4. Aggregates 5. Large falls iii. POM flux to the deep sea 1. Less than 1 in 10 molecules makes it to the sea floor 2. Only ~1/3 of that can be characterized a. Nutritional quality of the POM decreases as it gets deeper 3. Sinking rates ~100 m/d
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2-12 - 2/12/08 ; 2/14/08 Chapter 4 The Deep Sea 1. The...

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