Transcript 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: • • • • • 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: • • • 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)