Transcript Benthos
Benthos Benthic organism size classification • Megafauna • Macrofauna • Meiofauna (-flora) >10 mm 10 – 0.1mm Interstitial organisms • Microfauna <0.1mm 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 http://www.microscopy-uk.org.uk 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