Benthic organisms

98% of species that inhabit the marine environment live on or in the ocean floor

This ranges from the rocky, sandy and muddy intertidal zone to the muddy deposits of ocean trenches

Vast majority of ocean species live on the continental shelf

Rocky Shores

Organisms that live on the surface of the ocean floor are called epifauna

Either permanently attached to the bottom or they move over it

Typical rocky shore can be divided into a spray zone which is above the spring high tide zone and is underwater only during storms

Intertidal zone- lies between high and low tide extremes

Intertidal zone can be separated into subzones

High tide zone- covered only by the highest tides

Middle tide zone- alternately covered by high tides and exposed by low tides

Low tide zone- usually wet uncovered by very low tides

Spray zone

also known as the supralittoral zone

many animals have shells to avoid drying out

few species of algae

rock lice are common -scavengers

limpets also common

High tide zone

again most animals have shells

algae called rock weeds conspicuous

Middle tide zone

more types of algae and soft-bodied animals

total biomass much greater than high tide zone

organisms include barnacles, mussels carnivorous snails and sea stars

anemones are common also hermit crabs and sea urchins

Low tide zone

almost always submerged

variety of algae and surf grass

shore crabs

Sediment-covered shores

includes beaches, salt marshes and mud flats

intertidal zonation

sublittoral

low tide zone

middle tide zone

high tide zone

supralittoral

Life in the sediment

burrowing is the most successful adaptation for life in sediment covered shores

much more stable environment

no fluctuations in temperature or salinity

no danger of drying out

Feeding mechanisms

Suspension feeding-organisms use specially designed structures to filter plankton from seawater

some bivalves have siphons that they extend to the surface to feed

deposit feeding

Sandy Beaches

most animals burrow into the sand and are hidden from view

Bivalve molluscs- bivalve-an animal having two hinged shells. Mollusk- member of the phylum Mollusca characterized by a soft body and hard shell

Other animals

Annelid worms- segmented worms, tend to live in burrows and move to surface to feed

Crustaceans- crabs, lobsters, shrimp, sand crabs

Echinoderms- includes heart urchins, sand stars

Mud flats

Eelgrass and turtle grass are widespread

large populations of bivalve mollusks and other invertebrates

fiddler crabs have burrows that can exceed 1 meter

male fiddlers have one oversized claw and one small claw

Shallow Offshore

mainly sediment covered extends from spring low tide to the seaward edge of the continental shelf

rocky exposures occur near the shore

moderate to low species diversity

the giant kelp bed associated with rocky bottoms is a specialized community with higher diversity

Rocky Bottoms

within the shallow sublittoral zone these are usually covered with algae

Along the Pacific coast the giant brown bladder kelp attaches to rocks as deep as 100 feet

pneumatocysts- gas filled floats

allow the algae to grow upwards for 100 feet to get good exposure to sunlight

Lobsters

common on rocky bottoms

large antennae serve as feelers

Caribbean species sometimes migrate single-file across the sea floor in lines that are several miles long

scavengers

Oysters

thick shelled, sessile mollusks

grow best where there is a steady flow of clean water

food for sea stars fishes crabs and snails

oyster beds are composed of many empty shells

produce planktonic larvae

Corals

individual corals are called polyps

small benthic marine animals that feed with stinging tentacles and are related to jellyfish

most species are about the size of an ant

they live in large colonies

construct hard calcium carbonate structures for protection

Coral Reefs

coral accumulations that are classified as coral reefs are restricted to shallow warmer-water regions

corals are very temperature sensitive

need water where the average monthly temperature exceeds 64F

if water exceeds 86F many corals will die

Environmental conditions

strong sunlight- needed for the symbiotic photosynthetic microscopic algae called zooxanthellate that lives within their tissues

strong wave or current action

lack of turbidity

salt water

hard substrate for attachment

Coral reefs

well-developed vertical and horizontal zonation of the reef slope

zones can be identified by the types of corals and assemblages of other organisms

Symbiosis

algae, mollusks and foraminifers contribute to the reef structure

individual reef building corals are hermatypic because they have a mutualistic relationship with the zooxanthellae

the algae provide a continual supply of food to the coral and the coral provides nutrients to the algae

corals receive 90% of their nutrition this way

Commensalism- symbiotic relationship in which one party benfits and the other is unaffected

Corals

the greatest depths to which corals can grow is 500 feet

relatively delicate plant corals can grow at these depths

low nutrient levels- hermatypic corals thrive

moderate nutrient levels- favor flashy benthic plants and suspension feeders

high nutrient levels- phytoplankton mass exceeds benthic algal biomass

Coral Bleaching

loss of color in reef organisms

zooxanthellae die or are expelled

coral loses its food supply and dies

can be caused by increased water temperatures

The Deep Ocean Floor

environment is quite stable homogeneous

temperatures range from 28.8F-37F

oxygen content is relatively high

pressures exceed 2940lbs per square inch

thin layer of sediment covers much of the ocean floor

except for hydrothermal vent communities all benthic organisms receive their food the surface waters

Hydrothermal Vent Communities

Have 100 times more biomass than the rest of the deep ocean floor

most important members of these communities are the archaea which are bacteria-like forms

via chemosynthesis they manufacture carbohydrates from CO2 and water

form the base of the food web for vent organisms

many animals rely on a symbiotic relationship with archaea and tube worms and giant clams have them living in their tissues

vents can become inactive and the organisms die

Low Temperature Seeps

three additional submarine seep environments have been found to support chemosynthetic communities

Hypersaline seeps found at the base of the Florida Escarpment in the Gulf of Mexico

Hydrocarbon seeps-associated with oil and gas seeps in the Gulf of Mexico

Subduction zone seeps - water slightly warmer and contains methane