Benthos Benthic organism size classification Megafauna Macrofauna Meiofauna
Benthos
Benthic organism size classification • Megafauna • Macrofauna • Meiofauna (-flora) >10 mm 10 – 0. 1 mm Interstitial organisms • Microfauna <0. 1 mm
Abundance and Biomass in sandy sediments
Feeding Mode • Suspension feeders – Tentacles – Water pumping • Deposit feeders – Selective (eat food between grains) – Non- selective (eat sediments)
Grain Size vs Feeding Type Suspension feeders % Deposit feeders Clay Sand
Basic Sediment Transport
Environmental Zones
Grain Size vs Feeding Type • Sandy bottoms – High water flow – Shallow waters Suspension feeders • Muddy (clay-silt) bottoms – Low currents – Deep Ocean Deposit feeders
Sandy beach fauna? Harsh Environment: Abrasion (no algae/plants) Thick shells Adhesion glands
Sediment Stabilizing vs Destabilizing organisms
Intersticial organisms
Intertidal rocky habitats: origin of marine ecology
Intertidal Ecology: Community determinant factors • • Larval Supply / Settlement Physical Forcing Competition Predation
Meroplanktonic Larvae Cypris larva of barnacle
Pelagic history affects benthic population dynamics: larval supply http: //science. whoi. edu/labs/pinedalab/
Intertidal ecology: settlement (importance of behavior)
Intertidal ecology: physical factors (dissecation)
Intertidal ecology: physical factors (wave action)
Intertidal ecology: competition (for space)
Intertidal ecology: predation
Model of Atlantic Northeast coast barnacle population regulation
Pacific Coast Intertidal
Intertidal benthic ecology: Keystone species concept Starfish predation maintains a diverse community Removal of Starfish allows mussels to dominate, and reduces species diversity (from Paine 1966) P. Cury
(Botsford et al. , 1997) A. Bertrand
“Ecosystem engineer species” Overexploiting marine ecosystem engineers: potential consequences for biodiversity (Coleman and Williams 2002) • Ecosystem engineer species: those that substantially modify the physical structure of biotic and abiotic habitat components • These species change directly or indirectly the accessability to natural resources by other species (they are a type of keystone species) • Ecosystem engineers create more complex habitats, commonly resulting in increased biomass and diversity
Coral reef – Acropora corals
Oyster reef restoration
Deep water Coral reefs (Lopphelia spp. )
Manatee Grass Turtle Grass
Ecosystem “engineers species” • Corals, oysters and calcareous polychaete worms for reefs • Marine angiosperm grasses (turtle grass) and large brown macroalgae (kelp) modify current flows, plus act as nursery and refuge habitats • Bivalve mollusks fertilize sediments contributing to benthic plany growth with feces, • Various excavating organisms (fish, crustaceans and worms) • Green turtles and manatees ‘plow’ angiosperm grass fields A. Bertrand
Ecosystem “engineers species” The present overexploitation of "engineering species” should account for ecosystem-wide associated changes, likely a loss of biodiversity in the benthic ecosystem Coleman and Williams 2002 A. Bertrand
Humans as “engineer species” • Trawling disrupts sea bottom…… • Trawling ecosystem effetcs: – – Decrease of spatial complexity Decrease of target and bycatch species Increase of scavenger species Overall loss of biodiversity (macrorganism level)
Trawling
Trawling frequency by german vessels between 1993 & 1996 (Rijnsdorp 1997) P. Cury
No Trawling Area Gulf of Maine
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