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Intertidal, rocky coasts
Mud and sand bottoms
Deep-sea
Hot-spring vents
Greatly varied habitat -- supratidal "splash zone"
to deepest ocean basin.
Environmental demands:
1. Characteristics of seafloor and overlying water
2. Exchange of substances between sediments
3. Conditions established by other members of the community
Sediment bottom is unstable
--> Few large, attached plants
--> Few grazing animals
Organic matter imported from other environments
o Sand beaches -- "clean;" sparse organic matter in
sediments
o Mud flats - - more protected environments
Environmental characteristics:
o Uniform water conditions (cold!)
o Fine-grained sediments
o Limited supply of organic matter
-- Home for less than 1% of life in the sea
Deposit-feeding infauna are dominant:
Food-producing autotrophs are chemosynthetic bacteria (not
plants)
Bacteria support diverse and exotic benthic communities:
Introduction
Intertidal, rocky coasts
Mud and sand bottoms
Coral reefs
Deep-sea
Hot-spring vents
Benthos occupy the interface between sea floor and overlying seawater -- from the supratidal "splash" zone to the deepest ocean basins. The environmental demands that benthic organisms must meet are defined by:
1. Characteristics of seafloor and overlying water
2. Exchange of substances between sediments and overlying water
3. Conditions established by other members of the community
Benthos are the vast majority of animal species in the oceans. The enormous diversity of benthic life is related to the wide range of environmental conditions on the sea floor. These conditions include:
1. Availability of food
2. Variety of seafloor types (substrates)
3. Variations in temperature, salinity, turbulence, exposure
Review of habitat and nutritonal strategies of the benthos
Habitat Nutrition
Epifauna suspension, filter-feeders
motile
sessile
Infauna deposit feeders
Highly variable physical conditions (T, S, waves, tides, exposure)
Diverse and productive communities
Distinct depth zonation (especially for epifauna and plants) reflect
ability to cope with environmental stresses
Typical inhabitants include ...
Tidal pools in the supratidal zone experience large daily and seasonal variation in temperature and salinity. This is the habitat of a highly specialized communities of algae and animals.
Intertidal inhabitants include:
Subtidal inhabitants include:
Because the sediment bottom is unstable, there are few large,
attached plants and therefore few grazing animals. Primary (plant-derived)
organic matter is imported from other environments (e.g., rocky
shores, land) and may accumulate in sediments.
* Sandy sediments and beaches are "clean;" organic matter
is sparse.
* Mud flats are more protected from the turbulence of waves and
currents. Thus, sediment grain-size is is finer, and more organic
matter can accumulate. Anaerobic conditions may exist at depth
in mud flats due to the bacterial reduction of sulfate to H2S.
Animals that utilize degraded plant material in water or in sediment
are dominant -- deposit/detritus feeders are most common, but
suspension feeders and predators are also present. Representative
benthos in fine-grained near-shore sediments include:
The floor of the deep sea is characterized by uniform (and
cold!) water conditions, fine-grained sediments, and a a very
limited supply of organic matter. The deep-sea floor is home to
less than 1 % of the life in the oceans.
* Deposit-feeding infauna are dominant. These include worms, burrowing
crustaceans, and sea cucumbers. Because deposit-feeders process
larger volumes of sediment, the upper layers of deep-sea sediments
are mixed -- the process is called "bioturbation."
* Suspension-feeders and epifaunal scavengers and predators (such
as bottom fish, starfish, and large crustaceans) are common but
less abundant than deposit-feeders.
As noted in several previous lectures, the food-producing autotrophs in these communities are chemosynthetic bacteria (not plants). These bacteria support diverse and exotic benthic communities: crustaceans, clams, molluscs, fish, enormous tube worms with red flesh.
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