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14 Cards in this Set
- Front
- Back
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compare and contrast the visible ecosystem response to eutrophication with the most serious threat from eutrophication
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The visible ecosystem response is the greening of the water column as the algae and vegetation in coastal areas grow in direct response to nutrient enrichment
the most serious threat is the unseen decrease in dissolved oxygen levels in bottom waters; the greener the water column, the less oxygen is available |
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the worldwide distribution of coastal oxygen depletion is associated with?
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major population centers and watersheds that deliver large quantities of nutrients
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The key to reducing dead zones will be to?
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to keep fertilizers on the land and out of the sea
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Episodic oxygen depletion is the first signal that a system has reached?
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a critical point of eutrophication, which, in combination with physical processes that stratify the water column, tips the system into hypoxia
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What happened in 1976 in the New York Bight?
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a single hypoxic event that covered about 1000 squared km that caused mass mortality of demersal fishes and benthos and blocked the northward migration of bluefish.
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Where is the largest dead zone in the world?
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the Baltic Sea
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What are the four phases of coastal hypoxia?
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first phase enhances the deposition of organic matter
second phase hypoxia occurs transiently, accompanied by mass mortalities of benthic animals third phase hypoxia becomes seasonal or periodic fourth phase hypoxia expands as the concentration of DO continues to fall; anoxia is established and microbially generated H2S is released |
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How does hypoxia impact pelagic species?
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when hypoxia makes deeper cooler water unavailable during the summer, the pelagic species will experience habitat compression
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Explain the statement: "Areas within ecosystems exposed to long periods of hypoxia are missing biomass."
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during long periods of hypoxia, there will be low annual secondary production in these areas and typically no benthic fauna
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When hypoxic conditions prevail, how much potential food energy for fisheries is lost in the Baltic Sea? In Chesapeake Bay? The Gulf of Mexico?
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Baltic Sea = 106,000 MT C
Chesapeake Bay = 6,000 MT C Gulf of Mexico = 17,000 MT C |
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Compare and contrast the area of hypoxia in the northern Gulf of Mexico during years of low river flow vs high river flow. what river are we referring to?
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In the Mississippi River
area of hypoxia during low river flow < 5,000 km2 area of hypoxia during high river flow >15,000 km2 |
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General circulation models predict that climate change alone will deplete oceanic oxygen by?
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increasing stratification and warming as well as by caushing large changes in rainfall patterns, enhancing discharges of fresh water and agricultural nutrients to coastal ecosystems
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Hypoxi and anoxia now rank as major global environmental problems along with what other anthropogenic influences on estuarine and marine environments?
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overfishing, habitat loss, and harmful algal blooms
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The authors suggest that an appropriate management goal would be to?
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reduce nutrient inputs to levels that occurred in the middle of the past century, before eutrophication began to spread dead zones globally
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