The oceans occupy >70% of the EarthThe oceans occupy >70% of the Earth’’s surface with a s surface with a volume of 1.5 x 10volume of 1.5 x 109kmkm3 3 (4 x 1020gallons)• In the open ocean, the concentration of inorganic nutrients and organic carbon is low.• Surface waters contain significant concentrations of prokaryotic cells: 105to 106cells mL-1.• Light penetrates the top 300 m of the ocean, referred to as the photic zone.• The number of prokaryotes in the open ocean decreases with depth.• Until recently, Archaeawere thought to exist only in “extreme” environments.•Archaeaare estimated to make up to half of the prokaryotic cells in the ocean.• Microbes in deep ocean water (>1000 m) must endure low temperature and high pressure.• 90% of total ocean volume is <4oC.Profile from the North Pacific Ocean
• Much of the primary productivity in the ocean is due to microbial photosynthetic activity.• Chlorophyll, an estimate of photosynthetic biomass, can be quantified by satellite (left). • Inputs from terrestrial systems and bottom sediments result in higher concentrations of organic matter and nutrients in coastal regions.• Higher photosynthetic activity supports higher densities of chemotrophic bacteria and aquatic animals.• Marine bays and inlets receiving sewage or agricultural waste runoff have very high phytoplankton and bacterial populations. Inshore ocean areas are more nutritionally rich than open Inshore ocean areas are more nutritionally rich than open ocean waters and support denser populations of ocean waters and support denser populations of phototrophsphototrophsAreas rich in chlorophyll appear in red; blue and purple areas have low chlorophyll concentrations. Dotted line = coastline.
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