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07 Deep Sea Habitat

07 Deep Sea Habitat - The Deep Sea Vast and stable...

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The Deep Sea Vast and stable environments with diverse and bizarre fish faunas that include ~ 11% of known fishes Most extensive environments, but ‘stable’ is oversimplification Temperature ranges from -1.8 0 C at poles to +13 0 C in Mediterranean, 2 0 C is typical Pressure influences biochemistry and gas exchange The Deep Sea ... Light is extinguished rapidly with depth 99% extinct at 40 m in Gulf of Maine 140 m in Sargasso Sea decreasing solar light and increasing significance of biological light Surface light still influences the lives of organisms long after it has ceased to support photosynthesis Fishes visually competent down to a depth of 1200-1300 m (man to 950 m) The Deep Sea ... Salinity relatively constant as far as organisms are concerned, but fractions of 1% are significant oceanographically in driving currents that affect the boundaries of species distributions, reproductive patterns, and food availability Oxygen can be critical Deepsea environments Below the well-lighted, well-mixed epipelagic zone, conditions change rapidly Photosynthetic algae disappear Below 200 m (Mesopelagic Zone) light fades to extinction at about 1000m Temperature falls through a more or less permanent thermocline to 4 to 8 0 C Nutrients, [DO], and circulation decline Pressure increases Deepsea environments ... Below 1000 m (Bathypelagic Zone) conditions are uniform or nearly so down to bottom (Deepwater Benthic zone) Mesopelagic, bathypelagic and deepwater benthic habitats are the most extensive on earth Mean ocean depth 4000 m 98% of volume below 100 m 75% below 1000 m Deepsea environments ... Probably the most numerous fishes in existence are small pelagic forms, particularly bristlemouths, genus Cyclothone Deep scattering layer = millions of swimbladders Diversity and abundance is indicated by midwater trawling 12 km 2 off Bermuda, 1500 trawl hauls 115,000 individuals, 46 families, 220 spp
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