Benthic Marine Life

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• Benthic Marine Life
• Lives on (epifaunal) or in (infaunal) sea floor
• Some animals and plants attach to other animals
  (such as barnacles on crabs). These are called
  epibionts.
• Some benthos can move (vagrant) some are attached
  to the sea floor (sessile).
• Includes many single cell animals such as some
  foraminifera, diatoms, etc.
• Benthic life is controlled by
• Salinity
• Oxygen content of water and sediment
• Nutrients and food
• Substrate type (grain size and substrate
  firmness)
• But life also influences oxygen, food, and
  substrate
• These are indirectly tied to water depth.

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• Plants
• Includes algae and sea grasses
• Shallow to deepest water for algae Green
  (usually less than 10 m), brown, red, blue green
• Parts of benthic algae holdfast, stipe, and
  blade (ribbon-like) or thallus (cylinderical or
  club-like)

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• Sponges
• Really just a mass of cells that can move around
  and change form. No tissue.
• Skeleton composed of silica, calcite, or spongin
  (with some silica)
• Natural water pump. Assists in feeding and
  reproduction. Smokers

• How a sponge works
• Sponge has relief off of sea floor, so as water
  current goes over sponge it becomes narrower.
  Velocity increases. As velocity increases,
  pressure decreases. Creates vacuum.
• Notice that incurrent openings in sponge have
  small diameter (water moves fast), but feeding
  chambers are larger (water slows down so sponge
  can feed).
• Notice that excurrent opening at top of sponge is
  slightly constricted. This means that excurrent
  water increases in velocity. Removes waste
  products from sponge.

Feeding chambers
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• Cnidarians
• Benthic ones include anthozoans (corals, sea
  anemones, sea fans, sea pens), and hydra. Polyp
  stages. Remember nematocysts
• Many are colonial
• Two layers of tissue sandwich middle gelatinous
  layer (mesoglea)
• Corals have skeleton composed of calcium
  carbonate.

Sea pens Sea anemones
Corals Sea fan
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• Parts of a reef
• Back reef lagoon (quiet water)
• Reef flat (mostly skeletons with a thin coat of
  sand)
• Reef crest (waves high energy only most massive
  corals live here)
• Reef front most life here. Spur and groove
  structure.
• Fore reef broken material that falls off of reef
  (storms, etc.)

• Coral Reefs
• Ecologic reef skeletal buildup which, at least
  in part is wave resistant. Reefs exert strong
  control over their environments.
• Skeletal framework of modern reefs is mostly
  coral and red algae.
• Need warm, clear, normal salinity water. Most at
  less than 30 degree latitude.
• Reef forming corals are mutually symbiotic (both
  benefit) with dinoflagellates (called
  zooxanthellae algae).

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• Round worms
• Simple body plan
• Feed on detritus (decomposers).
• Release nutrients for other organisms
• Thrive in low oxygen settings

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• Ribbon worms
• Long flat
• Distinct extendible probiscus
• Predators, scavengers
• Chemical tracking of prey or direct contact.
  Follow burrows.
• Stylets and toxins
• Up to 60 long
• Tidal flats and nearshore.

Round worm eating a segmented worm. stylets
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• Segmented worms
• Have spines coming out of segments.
• Include sessile and vagrant forms
• Complex body plan.
• Filter feeders, predators, and deposit feeders
• Predators have strong jaws
• Deposit feeders mix up substrate well

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• Tube worms
• Deep sea vent creatures
• Sessile
• No mouth or digestive system
• Get to be 10 long
• Symbiotic with internal chemosynthetic bacteria

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• Mollusks
• Includes pelecypods (clams, oysters, mussels,
  etc), gastropods (snails, conchs), cephalopods.
• Calcium carbonate shell
• Muscular foot used for locomotion
• All depths, even vents.
• Gastropods
• Trochispiral shell
• Radula for feeding. Conveyer belt with teeth.
  Include herbivores and predators.
• Pelecypods
• Two valves, mirror images
• Mostly filter- and deposit feeders
• Infaunal and epifaunal
• Vagrant and sessile

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Arthropods Jointed legs Horseshoe crabs and
crustaceans Horseshoe crabs lack jaws, pincers
at front of mouth (chelicerae), scavengers,
living fossils, shallow water to mate moult
and mate clusters.
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Crustaceans Ostracodes all depths Isopods look
like pill bugs, grazers and primary
consumers Amphipods similar to ispods but
different leg sizes, hop
Isopod
Crab
Amphipod
Isopod
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• Crustaceans (cont.)
• Barnacles
• Sessile (sea floor and epibionts)
• Skeleton composed of calcareous plates.
• Ontogeny free swimming larvae. Settles
  headfirst onto the sea floor. Cements head to
  sea floor. Secrete plates.
• Filter feeders, common in shallow water settings.

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Echinoderms Spiny skin Pentaradial symmetry
Starfish
Vagrant Predators, all water depths avoid burial
Crinoids (sea lillies)
Holdfast, stem, calyx Sessile Filter feeders
Brittle stars
Loose arms, regenerate new ones Snake-like
arms Scavengers, most in deep sea
Echinoids (sea urchins, sand dollars)
Grazers (algae) and deposit feeders Vagrant.
Uses spines and sucker-like tube feet to move.
Sea cucumbers
Up chuck guts if disturbed All depths (common in
deep sea) Detritovores
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Crinoids