MEA 200 Lecture 19: L19. Living on the Ocean Floor & Benthic Communities
30 Mar 2017
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Document Summary
Living on the ocean floor & benthic communities. More than 98% of 250,000 known marine species live in or on ocean floor benthic organisms live mainly on continental shelves. Their distribution is affected by surface ocean currents. Move over sea floor (e. g. , crabs, snails) Less risk of temperature extremes and drying out. The physical and biological conditions cause horizontal bands of organisms to form in the intertidal waters. Physical conditions determine the organisms found in the upper bands. Biological conditions determine the organisms found in the lower bands. Middle tide zone covered by all high tides/ exposed by all low tides. Animals have shells to avoid drying out. Marine algae rock weeds with thick cell walls. Many animals hidden by seaweed and sea grass. Attaches to rocky bottoms with strong holdfast. Kelp forests beds of giant brown bladder kelp and bull kelp. Reefs shallow water communities restricted to tropics. Sunlight for zooxanthellae symbiotic photosynthetic microscopic algae in coral tissues.
