Benthic Organisms and their Environment

Benthos

Organisms living in direct association with seafloor.

Epibenthic

Organisms living on seafloor surface.

Burrowers

Organisms living within seafloor sediments.

Infaunal

Organisms completely covered by sediment.

Semi-infaunal

Organisms partly covered, partly in water column.

Borers

Organisms living within hard substrates.

Interstitial

Organisms living within pore spaces of sediments.

Megabenthos

Benthic organisms larger than 1 cm.

Macrobenthos

Benthic organisms between 0.5 mm and 1 cm.

Meiobenthos

Benthic organisms between 0.1 mm and 0.5 mm.

Microbenthos

Benthic organisms smaller than 0.1 mm.

Bioturbation

Reworking of soil by organisms.

Median grain diameter

Measured by sieving and weighing sediment fractions.

Silt-clay fraction

Weight percentage of sediment < 62 µm.

Sorting

Variation in sediment particle size distribution.

Thixotropy

Sediments become less viscous under stress.

Hydromechanical burrowing

Burrowing using fluid-filled body chambers.

Mechanical displacement burrowing

Burrowing using physical movement through sediment.

Suspension feeders

Organisms that gather particles from water.

Deposit feeders

Organisms that ingest sediment and organic matter.

Microbial stripping hypothesis

Deposit feeders digest benthic microbes efficiently.

Passive suspension feeders

Feed by protruding structures into current.

Active suspension feeders

Feed by sucking water into siphon.

Facultative suspension feeders

Switch between active and passive feeding.

Combined suspension feeders

Use both active and passive feeding techniques.

Carnivores

Organisms that primarily eat other animals.

Herbivores

Organisms that primarily consume plant material.

Benthic microorganisms

Microorganisms living in benthic environments.

Redox potential discontinuity (RPD)

Transition between oxic and anoxic sediment layers.

Anoxic sediments

Sediments lacking oxygen, produce 'rotten eggs' smell.

Foraminifera

Amoeboid microorganisms with calcium carbonate tests.

Radiolaria

Amoeboid microorganisms with silica tests.

Ciliates

Microorganisms propelled by cilia, feeding on particles.

Flagellates

Microorganisms propelled by flagella, similar feeding to ciliates.

Phylum Porifera

Sponges with cellular organization and no distinct tissues.

Choanocytes

Flagellated cells in sponges that drive water flow.

Phylum Cnidaria

Includes jellyfish, corals, with radial symmetry.

Hydrozoa

Class of Cnidaria, includes Portuguese man o' war.

Scyphozoa

Class of Cnidaria, includes true jellyfish.

Annelida

Segmented worms with bilateral symmetry and coelom.

Polychaetes

Annelids with many bristles and diverse feeding types.

Oligochaetes

Annelids with few bristles, includes earthworms.

Mollusca

Phylum with bilateral symmetry and a complete gut.

Bivalvia

Mollusks with two valves, used for respiration.

Gastropoda

Mollusks like snails, often with coiled shells.

Cephalopoda

Advanced mollusks like octopus, with complex behavior.

Arthropoda

Segmented animals with jointed appendages and exoskeleton.

Bryozoa

Colonial animals with interconnected zooids.

Brachiopoda

Solitary animals with two calcium carbonate valves.

Echinodermata

Radially symmetrical animals with a water vascular system.

Asteroidea

Class of Echinodermata, includes seastars.

Phylum Chordata

Includes animals with a notochord during development.

Subphylum Tunicata

Includes sea squirts and larvaceans, suspension feeders.

Tadpole larvae

Larval stage with notochord, similar to vertebrates.