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THE OCEAN DEPTHS. THE OCEAN DEPTHS. From 100-200 m (600 ft) to the deepest part Mesopelagic (to depth of 3300 ft -1000 m) Twilight THE DEEP - Bathypelagic, Abyssopelagic & Hadopelagic No sunlight at all. THE MESOPELAGIC. From 100-200 m to depth of 3300 ft (1000 m)
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THE OCEAN DEPTHS • From 100-200 m (600 ft) to the deepest part • Mesopelagic (to depth of 3300 ft -1000 m) • Twilight • THE DEEP - Bathypelagic, Abyssopelagic & Hadopelagic • No sunlight at all
THE MESOPELAGIC • From 100-200 m to depth of 3300 ft (1000 m) • Not enough light for photosynthesis, no primary productivity • Enough light to see by – like twilight • Chronically short of food • High pressure
THE MESOPELAGIC - ADAPTATIONS • Small size • Large mouths • Hinged, extendable jaws • Needle-like teeth • Unspecialized diets • Flabby watery flesh – no swim bladder • Large sensitive eyes • Countershading & bioluminescence
THE DEEP • From 1000 m – deepest trenches • No light • Cold • High pressure (up to 1000 atm) • Lack of food • Lack of mates
THE DEEP - ADAPTATIONS • Small size (but larger than mesopelagic) • Black • Small eyes • Sluggish & sedentary • Large mouths (consume prey larger than themselves) • Expandable stomachs • Flabby watery flesh – no swim bladder • Hermaphroditism / Male parasitism / Bioluminescence
Characteristics of the benthic zone: - 90% of the organisms are found on the continental shelf, others are in the abyss - deep sea benthhic fishes dark brown or black - meso- and deep pelagic zone 99% of the organisms are bioluminescent (produce light by chemical reaction) - very stable environment - increases with depth - lack of light is a major limiting factor - reducing food, predation and mating
- oxygen is supplied from cold, saline waters of the poles - biomass decreases with depth - this low population density is directly related to food scarcity NOAA - communities entirely composed of consumers and scavengers - producers are found only in photic zones; decomposers like bacteria are more common in mid-water mesopelagic zone
Hydro-Thermal Vent Communities The exception in benthic communities’ producers are the chemosynthetic bacteria around hydrothermal vent. In 1977, scientists working in the DSV Alvin with project FAMOUS (Robert Ballard), discovered unique hydrothermal vent communities of previously unknown organisms. Since then, vent communities have been found in all oceans at depths varying from 1 to 2 miles down. Bacteria living near the vent use hydrogen sulfide dissolved in seawater to build organic molecules in a process called chemosynthesis. NOAA
Animals clustered near the vents grow to huge sizes; can withstand temperature differences from 36o to 662o. The community also has many suspension-feeders attached to the hard rock bottom which is unusual in the deep sea. Geologist estimate that the vents probably last for 100 years; when supply of H2S is exhausted, the ecosystem dies. NOAA In other areas, called Cold Seeps, also have chemosynthesis. Here methane and sulfide-rich fluids seep into the ocean floor where symbiotic bacteria use sulfur-oxidation for survival. Cold Seeps are home to millions of benthic worms, crabs and mollusks.
OCEAN FLOOR - SEDIMENTS • Continental shelf - terrigenous sediment • derived from eroded continent • Ocean floor – biogenous sediment • Derived from once living organisms (plankton)
