Benthos

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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
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