Chapter 6: Oceans on the edge

Chapter 6: Oceans on the edge

1. Marine ecosystem- the web of organisms that live in the ocean

2. Mangrove swamps

   • what are they?
     • swampy forest
       • Adapted to daily flooding + salty conditions
         • twisty roots anchor and trap mud providing great habitat for marine life e.g lobster, prawn
   • located along shorelines in tropical and subtropical zones
     • in highly populated areas e.g central america, west africa + south asia
       • over past 50 years, 50% of magroves destroyed
   • problems with revoval of mangroves:
     • less protection for tsunamis
       • loss of shelter + breeding areas for fish so fishing affected
         • fewer tourists - habitats for marine and other wildlife will die
           • stored CO2 released form soil
             • local people not benefitting from prawn farms
   • prawn farming
     • Prawn farming - used to be sustainable
       • more intensely harvested in ponds
         • because of commercial pressures, unsustainable exploitation now takes place, removal for aquaculture
           • e.g. vietnam's Mekong Delta
     • problems
       • coastal erosion
         • loss of tsunami defence
           • pollution from antibiotics and pesticides used

3. Food web

   • interconnections between different organisms that rely upon one another as their source of food
     • energy is lost in each step up the chain - more organisms at bottom
   • the number of top predators e.g. shark reletively low compared with the fish they feed on e.g. tuna
     • use a lot of energy chasing prey so need a lot of prey to survive
   • nutrient cycle
     • re-use of important substances e.g. nitrogen within an ecosystem
       • fish take in nitrates when they eat plants/algae
         • fish waste converted to bacteria + ammonia - eventually into nitrates
           • absorbed by algae - restoring original balance
   • disruption
     • overfishing - more fishing than is sustainable
       • interferes with the equilibrium of ocean animal populations
         • e.g. overfishing of tuna - decrease in shark numbers - increase in mackerel
           • some species fished to extinction e.g Baiji white dolphin
     • eutrophication
       • run-off of e.g. nitrate fertilisers from land to sea - causes overfeeding and agal bloom - uses up oxygen and other species suffocate
       • e.g. Gulf of Mexico
     • Siltation
       • plants near coast get buried in silt from soil which has been washed into sea
         • can't reach sunlight + die
       • common in south east Asia

4. Climate change

   • Warmer water
     • tropical seas could face famine
       • Microscopic plankton - become stressed and less productive in warmer waters
         • becuase warmed-up surface doesn't mix well with colder nutrient rich water below
           • less plankton grow - food shortages - reduction at every level
     • species migration to cooler areas
   • More acidic water and bleaching
     • oceans absorb some of extra CO2 in atmosphere - dissolves in water - carbonic acid
       • small rises in acidity damage coral reefs - appear bleached after losing vibrant colour
         • Australia's great barrier reef may lose 95% of living coral by 2050
   • Higer sea levels
     • caused by melting ice sheets on land masses
       • Coastal marine ecosystems e.g mangrove swamps + uk salt marshes - permenently submerged
         • marititme communities disappear - 10cm rise
           • collpase of Larsden B ice shelf, Antarctica 2002

5. Firth of Clyde

   • Pressures
     • Overfishing
       • active and passive methods
         • important source of local income + kelp harvesting
           • fish and crustacean populations high - warm ocean current (Gulf stream)
             • completely overfished e.g Lamlash Bay - scallops
     • Tourism
       • falling income from farming + fishing has led locals to start tourism
         • Yachting, kayaking, diving are popular - such activities disturb wildlife
     • Sewage disposal
       • tougher laws have stopped disposal of sewage from homes straight into the sea
     • Military testing
       • last ice age left deeply eroded seafloor valleys - used for testing royal navy's nuclear submarines
         • serious accident - devastate ecosystem
   • Lamlash Bay
     • Scallops (an expensive restaurant delicacy) used to thrive here
       • live on the sea floor - havested using heavy dredging machinery - scours sea bed
         • 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
     • conflict
       • 'no-take' zone policy
         • + increased fish, seals and porpoises, good for tourism
           • - fishermen lost jobs
       • Increase tourism
         • + boosts local economy
           • - disrupts local wildlife
       • Oil + gas exploration
         • + Provides jobs
           • - Increases pollution and spoils landscape
     • Future plans
       • may soon be designated a Coastal and Marine Park (CMP)
         • aim to ensure activities are sustainable - long-term economic benefits to people + protecting environment
       • Scottish Marine Act - new laws to manage future conflicts in scottish waters
         • wants 31% renewable electricity - major tidal + offshore wind resources
           • could interfere ship navigation
             • ruin landscape
         • species e.g. dolphins + marine mammals need protecting from pollution
   • 60km stretch of sea water along Scotland's west coast - waters home of the clyde home to 40,000 animal + microbe species
     • seals, porpises, large basking sharks, leatherback turtles and killer whales