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Sediment Microbial Enzyme Activity as an Indicator of Nutrient Limitation in the Great Rivers of the Upper Mississippi River Basin
Citation:
HILL, B. H., C. M. ELONEN, T. M. JICHA, D. W. BOLGRIEN, AND M. F. MOFFETT. Sediment Microbial Enzyme Activity as an Indicator of Nutrient Limitation in the Great Rivers of the Upper Mississippi River Basin . BIOGEOCHEMISTRY. Springer, New York, NY, 97(2-3):195-209, (2010).
Impact/Purpose:
Three conclusions are evident from our comparison of approaches for estimating nutrient limitation in these large floodplain rivers: 1) water chemistry and enzymes indicate that P-limitation is more prevalent than N-limitation; 2) the Ohio River reaches are more extensively P-limited than either the Mississippi or Missouri River reaches; and 3) the N-limitation indicated by sediment chemistry is not reflected in the enzyme activities in the those same sediments, suggesting that the apparent N-limitation is most likely related to excess sediment OC or P concentrations relative to sediment N concentrations.
Description:
Three conclusions are evident from our comparison of approaches for estimating nutrient limitation in these large floodplain rivers: 1) water chemistry and enzymes indicate that P-limitation is more prevalent than N-limitation; 2) the Ohio River reaches are more extensively P-limited than either the Mississippi or Missouri River reaches; and 3) the N-limitation indicated by sediment chemistry is not reflected in the enzyme activities in the those same sediments, suggesting that the apparent N-limitation is most likely related to excess sediment OC or P concentrations relative to sediment N concentrations. The relative activities of the functional classes of enzymes are therefore a measure of nutrient availability that may be used to assess such large-scale phenomena as regional impacts of climate change or anthropogenic disturbances. Our study linking microbial enzyme activities to regional-scale anthropogenic stressors in large river ecosystems suggests that microbial enzyme regulation of carbon and nutrient dynamics may be sensitive indicators of anthropogenic nutrient and carbon loading to these rivers. The activities and ratios of microbial enzymes used in the acquisition of nutrients are inversely related to the overall supply and stoichiometric relations of the corresponding nutrients, especially in river sediments. Since nutrient concentrations in our river waters and sediments were correlated with the extent of agricultural land uses, EEA may also serve as indicators of these nutrient sources on a regional scale.
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Sediment Microbial Enzyme Activity as an Indicator of Nutrient Limitation in the Great Rivers of the Upper Mississippi River Basin