Trends in phosphatase activity along a successional gradient of tidal freshwater marshes on the Cooper River South Carolina |
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| Authors: | Xiaoqing?Huang Email author" target="_blank">James?T?MorrisEmail author |
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| Institution: | 1.Department of Biological Sciences,University of South Carolina,Columbia |
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| Abstract: | Phosphatase activity was measured in sediments from tidal freshwater habitats adjacent to the Cooper River in South Carolina
representing different stages of ecological succession. It was found that sediment (0–5 cm) acid phosphatase activity, alkaline
phosphatase activity and phosphodiesterase activity increased with increasing successional stage and phytomass. Acid phosphatase
activity in creased from 7.5±1.2 (±1 SD) in subtidal sediment from a shallow open water habitat without vegetation to 61.2±4.9
μmol g−1 hr−1 (μmol of p-nitrophenol released per gram of dry sediment per hour) in intertidal sediments colonized by emergent macrophytes,
while alkaline phosphatase activity increased from 2.1±0.1 to 19.01±1.5 μmol g−1 hr−1. Phosphodiesterase activity increased from 1.8±0.1 to 20.2±2.0 μmol g−1 hr−1 along the same gradient. Acid phosphatase activity was highly correlated (R2=0.92, P<0.001) with the organic matter content of the sediment. A study of phosphatase kinetics showed that Vmax of all phosphatases also increased along the successional gradient. Trends in phosphatase activity and Vmax correlated positively with plant biomass and negatively with concentrations of soluble reactive phosphorus in porewater,
sediment extractable phosphorus, and total phosphourus. The porewater N∶P atom ratio decreased along the succession gradient
from 25.3 in an early stage, open water community to 13.0 in a community dominated by emergent vegetation. The data also show
that the distribution of the forms of phosphorus changed with successional stage. The change in distribution and the increased
biological demand for phosphorus that paralleled succession were mediated by the activity of phosphatase enzymes. |
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