BenthosBenthos
• 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
High Tide Zone
Middle Tide Zone
Low Tide Zone
Mostly shelled orgs
Many soft bodied orgs and algae
Biotic factors affecting organisms living in the intertidal zone:
• 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
Orgs that live in the interstices of the sand
Infauna: • live within the sediment, mostly soft bottom; • mostly clams and worms (polychaetes) • burrow tubes for food scavenging and oxygen supply
32,000 polychaetes in sand/m2vs
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
Fiddler crab
Ribbed mussel
Salicornia
Distichles spicataFundulus heteroclitus
Found on all the main islands except Lanai
Hawaiian Stilt Hawaiian Coot
Found on all the main islands
Waikiki & Diamond HeadWaikiki & 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
• 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
Major Causes of Wetlands Loss and DegradationHuman Actions
Natural Threats
• Erosion
• Subsidence
• Sea level rise
• Droughts
• Hurricanes and other storms
Seagrass beds
Classification
Five kingdom system:
Monera Protista FungiPlantae Animalia
Angiosperms Gymnosperms
Distribution: 12 genera of seagrasses (5 in the high latitude and 7 in the low latitude)
• 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
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
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
Threats to Seagrass BedsThreats to Seagrass Beds
Coral Reef Communities
Hermatypic corals:• possess zooxanthellae• are reef builders
Light: Clear water Warm temperature: 18-32oCLow nutrientsLow productivity in water
Ahermatypic corals:• no zooxanthellae• rely on tentacular feeding• can live in aphotic zone
Cauliflower coral(Pocillopora meaandrina)
6 m
0 m
25 m
13 m
Lobe coral(Porites lobata)
Finger coral(Porites compressa)
Plate coral(Porites rus)
High light levelsModerate wave energy
Moderate light levelsOccasional storm wave energy
Low light levelsLow wave energy
Very low light, Primarily downwelling No wave energy
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