Ecological Succession And Dredging
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Ecological Succession And Dredging






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Ecological Succession And Dredging Ecological Succession And Dredging Presentation Transcript

  • Ecological Succession and Dredging
    • ecological succession – the replacement of one community with another over time
    • pioneer species – first organisms to come into a new area
        • change ecosystem slightly
        • can then be outcompeted by another species
        • next species replaces pioneer species
    • climax species/community – dominant organisms or community in a mature stable area – outcompete others
  • pioneer species climax species typical ecological succession on land:
    • disturbance - any kind of disruption to community that sends it back to an earlier successional stage
  • disturbances to forest ecosystem: forest fire volcano land slide
  • disturbances to forest ecosystem: farmer plowing field – if the farmer lets the field lie fallow, ecological succession will occur
    • ecological succession also occurs in the ocean
    • usually changes in animal community, not plant community
    • ecological succession affects biodiversity
  • benthic communities include many types of organisms
    • Over time, one community changes the environment slightly and is outcompeted by members of another community.
    • The dominant community has changed – ecological succession is occurring.
    • The community will remain until it is outcompeted or there is a disturbance.
  • example of organisms changing the sediments:
    • some amphipods and worms (deposit feeders) build tubes in sediments
    • tubes stabilize sediments
    • makes it easier for other organisms (suspension feeders) to survive
    • suspension feeders outcompete original deposit feeders
  • example of organisms changing the sediments:
    • some organisms
    • build burrows in
    • anoxic (no oxygen)
    • sediments
    • pump oxygen-rich
    • water through
    • burrows
    • brings oxygen into sediments
    • aerobic bacteria can now survive
    • changes and increases nutrient cycling
    • dredging disturbs benthic habitat
    • - when sediments are dredged up
    • - when dredge spoils are deposited
    Human Disturbance – Dredging: underwater excavation of bottom sediments
  • dredging is often for navigation – sediments settle and build up on bottom > 500 million cubic yards per year in U.S
    • ecological succession may start over after dredging occurs
    • sediment types may change from original
    • therefore species may change from what was originally there
  • Dredge Disposal
    • Dredged material must be disposed somewhere – LIS, ocean, on land?
    • Disposal site depends on level of toxic contamination of sediments
    • Uncontaminated
    • dredged material
    • may be used for
    • beach nourishment,
    • fill, construction,
    • cap landfills
    • dredging may also occur to remove
    • contaminated sediment
    • ecological succession may also occur
    • after dredge spoils are dumped
    • may change sediment grain size
    • can smother existing organisms
    • can impact species that reproduce when dredging is occurring
    • sediments often contain toxic
    • contaminants
    • sediments can harm eggs and larvae
    • sediments can harm coral reefs:
    • clog feeding apparatus
    • block sunlight for photosynthesis
    • make it hard for new larvae to settle and attach
  • Dredge Disposal - OPTIONS
    • Cap disposal sites to prevent leaching of contaminants to water and isolate contaminants from organisms
    • Dredge from inner harbor (more polluted) to outer harbor (less polluted) – less polluted covers more polluted sediments
    • Locate dump sites in deeper water
  • Dredge Disposal - OPTIONS
    • Restrict dredging and disposal to fall and winter (less biological activity)
    • Can use on-land sites or containment islands instead
    • Put dump sites in areas with high natural rate of deposition – less likely to erode