Benthos

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Benthos
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Benthos

• Intertidal Zone
• Muddy bottom and sandy bottom communities
• Salt marshes and seagrass beds
• Coral reefs
• Deep ocean benthos

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Intertidal Zonation
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.
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Which tidal cycle has the greatest effect on
marine organisms living in the intertidal zone?
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Tidal Zones on a Rocky Ocean Shore
Splash Fringe Level

High Tide Level
Mid Tide Level
Low Tide Level
Low Fringe Level
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Mostly shelled orgs
Spray or Splash Zone
High Tide Zone
Middle Tide Zone
Many soft bodied orgs and algae
Low Tide Zone
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Big Island
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periwinkles
ulva
opihi
Mussels starfish
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What are some stresses that affect the organisms
residing in the intertidal zone?
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• Biotic factors affecting organisms living in the
  intertidal zone
• Competition for space and food
• Predation
• Reproduction
• Substrate settlement preference
• Osmoregulation

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• 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

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What are some adaptations to living in the
intertidal zone?
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Muddy bottom and sandy bottom communities

• Infauna 
• 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
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Muddy bottom and sandy bottom communities

• 32,000 polychaetes in sand/m2
• vs
• 50-500 earth worms in soil/m2
• Ecological Role
• clean sediments
• aerate soil

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Salt marshes
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Salt marshes

• 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.

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Zonation in Salt Marsh

• Species composition and zonation governed by
• Salinity gradient river runoff, tides
• Intertidal exposure
• Low species diversity

Ribbed mussel
Fiddler crab
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Salicornia
Fundulus heteroclitus
Distichles spicata
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Hawaiian Stilt
Hawaiian Coot
Found on all the main islands except Lanai
Found on all the main islands
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Waikiki Diamond Head
1934
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• 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.

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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
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Current distribution of wetlands and deepwater
habitats
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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

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• Natural Threats
• Erosion
• Subsidence
• Sea level rise
• Droughts
• Hurricanes and other storms

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Seagrass beds
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Seagrass- true vascular plants
Classification
Angiosperms
Gymnosperms
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Seagrasses

• True marine angiosperm
• Evolved from shoreline Lillie-like plants100 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)
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Halophila hawaiiana- only form of seagrass in
Hawaii
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Development of Seagrass Beds

• 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

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Ecological roles

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

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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

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Coral Reef Communities
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• 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

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Hawaiian Coral Zonation
0 m
High light levels Moderate wave energy
6 m
Cauliflower coral (Pocillopora meaandrina)
Moderate light levels Occasional storm wave energy
Lobe coral (Porites lobata)
13 m
Low light levels Low wave energy
Finger coral (Porites compressa)
25 m
Very low light, Primarily downwelling No wave
energy
Plate coral (Porites rus)