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Dead zones, climate change and ocean acidification

Dead zones, climate change and ocean acidification. Fish 323. Dead zones. Regions of very low oxygen also called hypoxic zones Few forms of marine life can survive In 2008 405 dead zones were identified world-wide Are often ephemeral – they come and go

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Dead zones, climate change and ocean acidification

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  1. Dead zones, climate change and ocean acidification Fish 323

  2. Dead zones • Regions of very low oxygen also called hypoxic zones • Few forms of marine life can survive • In 2008 405 dead zones were identified world-wide • Are often ephemeral – they come and go • Causes: settlement of plankton to bottom where decay consumes most oxygen

  3. Primary causes • Agricultural run off • Oregon: zones thought to be natural

  4. The Black Sea • Extensive dead zones in the 1980s • Fertilizer use declined dramatically with collapse of Soviet Union • By 1996 no dead zone found

  5. The Louisiana dead-zone

  6. Ecosystem consequences • Shifting distributions of mobile animals • Killing of less mobile species • Level of concern is subject to considerable debate

  7. The “good” side of Dead Zones • Hypoxic zones have been with us for a long time – are the source of scale records used in paleo-ecological studies • Oil, gas and coal resources are the result of anoxia • Can be a potential site of carbon sequestration.

  8. Climate change

  9. Temperature Scenarios

  10. Key impacts • Warmer (mostly) • Change in rainfall wetter some places, drier others • Sea level increase • Increased variability and storms • Increased CO2 in ocean

  11. Projected changes in temperature

  12. Rainfall and runoff

  13. Sea level rise

  14. Tuvalu and Pacific Islands

  15. Tuvalu will disappear

  16. Impacts on fisheries

  17. The debate • What can be done • Reduction in CO2 emissions • Carbon sequestration • Ocean fertilization • Mediation – atmospheric shielding • The role of adaptation • How rapidly can plants and animals adapt • How rapidly can human society adapt

  18. Ocean acidification

  19. Consequences of acidification • coccolithophores, corals, foraminifera, echinoderms, crustaceans and molluscs cannot form calcarious structures • Decreased survival and reproduction of other animals

  20. Coccolithophore • are single-celled algae, protists and phytoplankton belonging to the division haptophytes. They are distinguished by special calcium carbonate plates

  21. The projections • Corals, etc will disappear leading to dramatic changes in marine food webs • But cocolithophores have become more abundant and heavier as oceans have warmed • How rapidly can species adapt to changing ocean acidity?

  22. Summary re climate change • The major long term challenge in aquatic resource management • While there is much debate about magnitude of impacts it is safe to assume that things will change • There will be winners and losers

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