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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

opihi

Mussels & starfish

periwinkles

ulva

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