Download Benthos

Benthos
• Intertidal Zone
• Muddy bottom and sandy bottom
communities
• Salt marshes and seagrass beds
• Coral reefs
• Deep ocean benthos
Zonation is a vertical banding of the
organisms living on the rocky
coastline.
These distinct bands occur in part
from many complex physical and
biological factors that effect marine
organisms.
Tidal Zones on a Rocky Ocean Shore
Splash Fringe Level
High Tide Level
Mid Tide Level
Low Tide Level
Low Fringe Level
Spray or Splash Zone
Mostly
shelled
orgs
High Tide Zone
Middle Tide Zone
Low Tide Zone
Many
soft
bodied
orgs and
algae
periwinkles
ulva
opihi
Mussels & starfish
Biotic factors affecting organisms
living in the intertidal zone:
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•
•
•
•
Competition for space and food
Predation
Reproduction
Substrate settlement preference
Osmoregulation
Abiotic factors affecting organisms living
in the intertidal zone:
• Salinity
• Temperature
• Air and light exposure
• Tidal flow
• Waves and current action
• Substrate
• Wind direction and strength
• Dissolved O2
• Storms
• Natural Disasters
Infauna:
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•
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live within the sediment, mostly soft bottom;
mostly clams and worms (polychaetes)
burrow tubes for food scavenging and oxygen supply
Orgs that live in the interstices of the sand
32,000 polychaetes in sand/m2
vs
50-500 earth worms in soil/m2
Ecological Role:
• clean sediments
• aerate soil
• Found from the Arctic to Southern
Australia
• Salt marshes grow in muds and sands
that are sheltered by barrier islands.
• Flood and ebb currents transport
saltwater, nutrients, plankton and
sediments in and out of the marsh.
Species composition and zonation governed by:
• Salinity gradient: river runoff, tides
• Intertidal exposure
Low species diversity
Ribbed
mussel
Fiddler
crab
Salicornia
Fundulus heteroclitus
Distichles spicata
Hawaiian Stilt
Hawaiian Coot
Found on all the main
islands except Lanai
Found on all the
main islands
Waikiki & Diamond Head
1934
Ecological Importance:
Act as a giant sponge:
• The salt marsh absorbs large
volumes of water, thus minimizing
the impacts of flooding and erosion
and recharging groundwater.
• Salt marsh plants help purify water by
absorbing toxins and in some cases
metabolizing them into harmless
substances.
• Most productive food factories on earth.
Of the original 215 million acres of
wetlands in the U.S. (excluding
Alaska and Hawaii) , about 106
million acres remain.
distribution of wetlands
in the U.S. in the 1780s
distribution of wetlands
in the U.S. in the 1900s
Current distribution of wetlands and deepwater habitats
Major Causes of Wetlands Loss and Degradation
Human Actions
• Drainage
• Dredging and stream channelization
• Deposition of fill material
• Diking and damming
• Tilling for crop production
• Levees
• Logging
• Mining
• Construction
• Runoff
• Air and water pollutants
• Changing nutrient levels
• Releasing toxic chemicals
• Introducing non-native species to the ecosystem
• Grazing by domestic animals
Natural Threats
• Erosion
• Subsidence
• Sea level rise
• Droughts
• Hurricanes and other
storms
Seagrass beds
Classification
Five kingdom system:
Monera
Protista
Angiosperms
Plantae
Fungi
Gymnosperms
Animalia
• True marine angiosperm
• Evolved from shoreline Lillie-like plants~100
mya
• Vascular plants reinvaded the seas 3 different
times (algae is nonvascular; i.e., no need for
roots to transport water and nutrients)
• Can grow and reproduce while completely
submerged under water
Distribution: 12 genera of seagrasses (5
in the high latitude and 7 in the low latitude)
Halophila hawaiiana- only form of seagrass in Hawaii
Develop in:
• intertidal and shallow subtidal
areas on sands and muds
• marine inlets and bays
• lagoons and channels, which are
sheltered from significant wave
action
1. Help stabilize the sediment
2. Prevents resuspension of sediments in
water (water is clearer)
3. Binds substratum, reduces turbidity,
and reduces erosion
4. Sediment accumulation slows velocity
of incoming water
5. Food for many organisms
6. Refuge for many organisms
Threats to Seagrass Beds
Seagrass productivity is highly
dependent on a number of factors:
• salinity
• water temperature
• turbidity
This ecosystem is particularly sensitive
to degradation due to:
• agricultural pollution-run-off of
herbicides
• industrial pollution
• domestic pollution
Coral Reef Communities
Hermatypic corals:
• possess zooxanthellae
• are reef builders
Light: Clear water
Warm temperature: 18-32oC
Low nutrients
Low productivity in water
Ahermatypic corals:
• no zooxanthellae
• rely on tentacular feeding
• can live in aphotic zone
0m
High light levels
Moderate wave energy
6m
Moderate light levels
Occasional storm wave energy
13 m
Cauliflower coral
(Pocillopora meaandrina)
Lobe coral
(Porites lobata)
Low light levels
Low wave energy
Finger coral
(Porites compressa)
25 m
Very low light,
Primarily downwelling
No wave energy
Plate coral
(Porites rus)