oceanography 35
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- Life in the intertidal
- • Escape from physical pounding by burrowing in sediments • Problems: – Sand shifts: impermanent – Chemical env: oxygen is depleted in sediments high concentration of sulfides, ammonia
- Feeding Strategies
- ⬢ Deposit feeders are organisms that extract food from sediment ⬢ Suspension feeders extract food from the water column ⬢ Carnivorous feeders feed directly on other animals
- Coral Reefs
- ⬢ Greatest known animal diversity of any marine community; about 25 % of all marine species ⬢ Typically found where temperatures average over 18°C ⬢ Reef growth requires relatively normal salinity and clear water
- Symbiosis
- • Two or more species living in intimate association. • Frequently the association is mutualistic – the partners all benefit. • Frequently found in extreme environments
- Reef Building
- ⬢ Reef⬐building corals have symbiotic dinoflagellate algae in the genus Symbiodinium living inside their tissues. ⬢ Coral polyps also use their tentacles and nematocysts to feed on particles, but Symbiodinium symbionts produces most food. ⬢ Reef⬐building corals are confined to shallow⬐water by a need for light. ⬢ Warm water causes coral to release algae. ⬢ Coastal pollution decreases light penetration and kills coral reefs. ⬢ Global warming and rising sea levels, as well as pollution may be the death of coral reefs. ⬢ Other corals, octocorals, and anemones may inhabit much cooler and deeper waters but do not produce reefs.
- Deep Sea Environment
- ⬢ Temperature range of about ⬐2 to 3°C ⬢ Pressures of 200 to over 1000 atmospheres ⬢ Hydrothermal vents and cold seep communities
- Hydrothermal Vents
- ⬢ Ocean water percolates down through fractures in recently formed ocean floor ⬢ Reacts with anoxic rock to form sulfides, which take with it when water returns to surface.
- Hot Vents
- ⬢ Vents are usually clustered in fields, underwater versions of Yellowstone's geyser basins. ⬢ Individual vent openings range from less than a half inch to more than six feet in diameter. ⬢ Such fields normally deeper than a mile. ⬢ Most discovered along the crest of the Mid⬐Oceanic Ridge, a 46,000⬐ mile⬐long chain of mountains that wraps around Earth like the seams on a baseball. ⬢ A few vents have also been found at seamounts, underwater volcanoes that are not located at the intersection of crustal plates. ⬢ Animals use bacterial symbionts to harvest this energy.
- Vestimentiferan Worms
- ⬢ Vent animals do not feed directly from the external medium. ⬢ The Vestimentifera have no obvious gut. They have a specialized organ, the trophosome, which contain sulfide⬐oxidizing bacteria. ⬢ Animal supplies oxygen and sulfide to the bacteria. ⬢ The animal, in turn, can digest the bacteria and derive nutrition.
- Tubeworm Symbiosis
- ⬢ Gases (hydrogen sulfide, carbon dioxide, oxygen) used by bacteria are transported in the blood of the tubeworm.
- Mussel Symbiosis
- ⬢ Methane rich water flows across the gills. Bacteria in the gills use the methane as a carbon and energy source.
- Cold Seeps
- ⬢ Areas where energy rich fluids (e.g., oil) are seeping out of the ocean floor owing to the geology of the underlying sediments
- Oil and Gas Seeps
- ⬢ Hydrocarbon seeps are places where gas and oil flow naturally out of the seafloor. Rather than harming the marine fauna, they support dense biological communities.
- Food Sources in cold seeps
- ⬢ primary producers are chemotrophic bacteria ⬢ Oxidize methane, sulfides released from sediments. ⬢ Symbionts with mussels, worms
- Gas Hydrates
- ⬢ Gas hydrates are ice⬐like minerals that form at the low temperatures and high pressures in the deep sea. ⬢ contain gases, such as hydrocarbons, that form crystals with water ⬢ Known as hydrate crystals. ⬢ Require particular temperature and pressure