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Lecture 21-posted - Trophic cascades are an example of top-down regulation of community composition and plant biomass Bottom up control Phosphate

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Trophic cascades are an example of “top-down ” regulation of community composition and plant biomass: Bottom up ____________________________________ _____________________________________________) control Phosphate addition
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Both removing top predators and adding nutrients can alter plant biomass… for EXAMPLE: Piscivore(large fish) Herbivore (planktonic crustacean) Planktivore(small fish) Phytoplankton (algae) nutrients What is the effect of harvesting top predators vs. adding nutrients on phytoplankton?
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Each could increase the amount of plant biomass… isn’t this a good thing? Fish populations need around 5 ppm dissolved oxygen Below 2 ppm, anything that can leave, leaves. Below 1 ppm the sea floor sediment-dwellers suffocate. grazers Dead organic matter algae Hypoxic zone Gulf of MX
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What is the relative importance of “top down vs. bottom up forces in structuring communities? y care? Two of the major impacts humans have on the environment are: _______________________  and a ) decompressor Mean trophic level of fish catch (2) _________________
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A combined top down and bottom up approach will likely be successful in restoring the Chesapeake; in others it may be more one or the other Nutrients from farms increase algae… “Greening” of Chesapeake Bay Oyster but oysters (used to) remove algae
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Global patterns of plant productivity are largely caused by “bottom up” forces Net primary production on sea and land roughly equal (48 vs. 56 x 10 15 g/y) Major differences in pattern of peak production with latitude… why? Annual net primary productivity on land and in the ocean (g C m -2 y -1 )
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Consequences of nutrient addition: control Phosphate addition Experiments like this in lakes are why your detergents don’t have phosphates anymore QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. But in the ocean, its more the additon of nitrogen that causes algal blooms
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Why is P limiting in freshwater and N in marine and terrestrial? # of observations
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This note was uploaded on 11/29/2010 for the course BIOLOGY 1211 taught by Professor Patricelli during the Spring '10 term at UC Davis.

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Lecture 21-posted - Trophic cascades are an example of top-down regulation of community composition and plant biomass Bottom up control Phosphate

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