bio 207 chapter 13: life on the continental shelf

continental shelf

the submerged edges of a continental plate that extends from the low tide line, biologically richest part of the ocean

shelf break

the end of the continental shelf where the slope steeply increases

estuaries

well developed in areas where shelf has gradual slope and is very wide, east coast and Gulf of US

depth at shelf break

average of 490 feet

width of shelf

ranges from 0.6 to 470 miles, average of 48

United Nations

1950s, said countries have control over marine resources out to 200 nautical miles (1.15 land miles) off their coast

shelf importance

majority of fisheries global catch, area for larvae, juveniles and adults, wide variety of organisms

temperature

varies more than the deep sea, less than an estuary, fluctuates because water is shallower and due to waves and currents circulating water

water turbulence

created by waves and currents, keep the water column well mixed, affects temperature and available nutrients

“rain down”

term when nutrients fall to the bottom, lost in the deep sea

neritic zone

the pelagic environment above the shelf

water clarity

less due to nutrients and suspended sediment

nutrient sources

autotrophs, detritus, from estuaries and terrestrial ecosystems via rivers

soft-bottom subtidal communities

unvegetated soft-bottom communities, seagrass beds

unvegetated soft-bottom communities

dominant bottom type of the shelf, benthos of infauna, epifauna and meiofauna, sessile species are rare, patchy distrubution, deposit and filter feeders

larvae

attracted to areas where adults reside, thought to be result of chemical cues in the water

unvegetated soft-bottom infauna

snails, clams, urchins, annelids

unvegetated soft-bottom epifauna

crustaceans and brittle stars, tube-builders to assist with stability of habitat

unvegetated soft-bottom meiofauna

protozoan cnidarians, crustaceans, nematodes, annelids, have appendages and attachment structures to lock themselves to sediment grains, found nowhere else

bioturbators

organisms that disturb bottom sediments by churning the bottom to oxygenate benthic soils, worms, mollusks, fish, sperm whales, skates, rays

seagrass beds

developed in sheltered, shallow waters with good water clarity, tolerance of temperature, water clarity, nutrient availability, home to sessile animals and epiphytic algae, cool or sub/tropical waters, found with algae

Zostera

eelgrass, prefers cooler temperate waters, Pacific and North Atlantic, consumed by herbivores, important to food chain after decaying

Thalassia

turtle grass, sub/tropics, consumed and “farmed” by sea turtles, bite the tops off and are more tender and easier to digest when they grow back

seagrass bed food web

producers: seagrasses
carnivores: sea stars, fishes, seabirds

rocky bottom subtidal communities

less common, results from submerged rocky shoreline with lots of hiding places, rock formations attract sessile organisms and those who cannot survive in soft bottomed communities

different types of hard-bottomed communities

oyster reefs, tube worms, calcareous algae

rocky bottom food web

producers: plankton and seaweeds
carnivores: sea stars, fishes, lobsters, nudibranchs, sea otters

kelp communities

brown algae found in cold waters, very nutrient-needy and can grow up to 20 inches a day, sea urchins are largest consumer, thousands of organisms depend on forests for habitat or tropic needs

Laminaria

common in North Atlantic, North Pacific and Asiatic coast of the Pacific, smaller kelp species with maximum heights of about 10 feet, provides enormous amount of primary production

Macrocystis

largest species of kelp that can grow up to 100 feet, Pacific and coasts of North and South America, form thick kelp forests

sea urchins

largest consumer of kelp, prey to sea otters

sea otters

feed on sea urchins, keep kelp forests healthy