Chapter 6: Oceans on the edge

Marine ecosystem- the web of organisms that live in the ocean
Mangrove swamps
1. what are they?
  1. swampy forest
    1. Adapted to daily flooding + salty conditions
      1. twisty roots anchor and trap mud providing great habitat for marine life e.g lobster, prawn
2. located along shorelines in tropical and subtropical zones
  1. in highly populated areas e.g central america, west africa + south asia
    1. over past 50 years, 50% of magroves destroyed
3. problems with revoval of mangroves:
  1. less protection for tsunamis
    1. loss of shelter + breeding areas for fish so fishing affected
      1. fewer tourists - habitats for marine and other wildlife will die
        stored CO2 released form soil
        local people not benefitting from prawn farms
4. prawn farming
  1. Prawn farming - used to be sustainable
    1. more intensely harvested in ponds
      1. because of commercial pressures, unsustainable exploitation now takes place, removal for aquaculture
        e.g. vietnam's Mekong Delta
  2. problems
    1. coastal erosion
      1. loss of tsunami defence
        pollution from antibiotics and pesticides used
Food web
1. interconnections between different organisms that rely upon one another as their source of food
  1. energy is lost in each step up the chain - more organisms at bottom
2. the number of top predators e.g. shark reletively low compared with the fish they feed on e.g. tuna
  1. use a lot of energy chasing prey so need a lot of prey to survive
3. nutrient cycle
  1. re-use of important substances e.g. nitrogen within an ecosystem
    1. fish take in nitrates when they eat plants/algae
      1. fish waste converted to bacteria + ammonia - eventually into nitrates
        absorbed by algae - restoring original balance
4. disruption
  1. overfishing - more fishing than is sustainable
    1. interferes with the equilibrium of ocean animal populations
      1. e.g. overfishing of tuna - decrease in shark numbers - increase in mackerel
        some species fished to extinction e.g Baiji white dolphin
  2. eutrophication
    1. run-off of e.g. nitrate fertilisers from land to sea - causes overfeeding and agal bloom - uses up oxygen and other species suffocate
    2. e.g. Gulf of Mexico
  3. Siltation
    1. plants near coast get buried in silt from soil which has been washed into sea
      1. can't reach sunlight + die
    2. common in south east Asia
Climate change
1. Warmer water
  1. tropical seas could face famine
    1. Microscopic plankton - become stressed and less productive in warmer waters
      1. becuase warmed-up surface doesn't mix well with colder nutrient rich water below
        less plankton grow - food shortages - reduction at every level
  2. species migration to cooler areas
2. More acidic water and bleaching
  1. oceans absorb some of extra CO2 in atmosphere - dissolves in water - carbonic acid
    1. small rises in acidity damage coral reefs - appear bleached after losing vibrant colour
      1. Australia's great barrier reef may lose 95% of living coral by 2050
3. Higer sea levels
  1. caused by melting ice sheets on land masses
    1. Coastal marine ecosystems e.g mangrove swamps + uk salt marshes - permenently submerged
      1. marititme communities disappear - 10cm rise
        collpase of Larsden B ice shelf, Antarctica 2002
Firth of Clyde
1. Pressures
  1. Overfishing
    1. active and passive methods
      1. important source of local income + kelp harvesting
        fish and crustacean populations high - warm ocean current (Gulf stream)
        completely overfished e.g Lamlash Bay - scallops
  2. Tourism
    1. falling income from farming + fishing has led locals to start tourism
      1. Yachting, kayaking, diving are popular - such activities disturb wildlife
  3. Sewage disposal
    1. tougher laws have stopped disposal of sewage from homes straight into the sea
  4. Military testing
    1. last ice age left deeply eroded seafloor valleys - used for testing royal navy's nuclear submarines
      1. serious accident - devastate ecosystem
2. Lamlash Bay
  1. Scallops (an expensive restaurant delicacy) used to thrive here
    1. live on the sea floor - havested using heavy dredging machinery - scours sea bed
      1. this destroys maerl (coral) - habitat for fish species - decline
        concerned locals + divers set up COAST (community of Arran Seabed Trust)
        campaigning for no-take zones in a sustainabilty plan - Aims
        - improve marine environment, reverse maerl + fish decline
        sustain livelihood of tourism + fishing
        increase popularity for diving + tourism
        2008 - scottish government makes no-take zone
  2. conflict
    1. 'no-take' zone policy
      1. + increased fish, seals and porpoises, good for tourism
        - fishermen lost jobs
    2. Increase tourism
      1. + boosts local economy
        - disrupts local wildlife
    3. Oil + gas exploration
      1. + Provides jobs
        - Increases pollution and spoils landscape
  3. Future plans
    1. may soon be designated a Coastal and Marine Park (CMP)
      1. aim to ensure activities are sustainable - long-term economic benefits to people + protecting environment
    2. Scottish Marine Act - new laws to manage future conflicts in scottish waters
      1. wants 31% renewable electricity - major tidal + offshore wind resources
        could interfere ship navigation
        ruin landscape
      2. species e.g. dolphins + marine mammals need protecting from pollution
3. 60km stretch of sea water along Scotland's west coast - waters home of the clyde home to 40,000 animal + microbe species
  1. seals, porpises, large basking sharks, leatherback turtles and killer whales

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Chapter 6: Oceans on the edge

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