dead zones, climate change and ocean acidification fish 323
TRANSCRIPT
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Dead zones, climate change and ocean acidification
Fish 323
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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
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Primary causes
• Agricultural run off
• Oregon: zones thought to be natural
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The Black Sea
• Extensive dead zones in the 1980s• Fertilizer use declined dramatically with collapse of
Soviet Union• By 1996 no dead zone found
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The Louisiana dead-zone
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Ecosystem consequences
• Shifting distributions of mobile animals
• Killing of less mobile species
• Level of concern is subject to considerable debate
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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.
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Climate change
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Temperature Scenarios
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Key impacts
• Warmer (mostly)
• Change in rainfall wetter some places, drier others
• Sea level increase
• Increased variability and storms
• Increased CO2 in ocean
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Projected changes in temperature
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Rainfall and runoff
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Sea level rise
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Tuvalu and Pacific Islands
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Tuvalu will disappear
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Impacts on fisheries
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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
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Ocean acidification
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Consequences of acidification
• coccolithophores, corals, foraminifera, echinoderms, crustaceans and molluscs cannot form calcarious structures
• Decreased survival and reproduction of other animals
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Coccolithophore
• are single-celled algae, protists and phytoplankton belonging to the division haptophytes. They are distinguished by special calcium carbonate plates
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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?
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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