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Phytoplankton Abundance and Contributions to Suspended Particulate Matter in the Ohio, Upper Mississippi and Missouri Rivers.
Citation:
BUKAVECKAS, P. A., A. MACDONALD, A. AUFDENKAMPE, J. CHICK, J. E. HAVEL, R. SCHULTZ, T. R. ANGRADI, D. W. BOLGRIEN, T. M. JICHA, AND D. L. TAYLOR. Phytoplankton Abundance and Contributions to Suspended Particulate Matter in the Ohio, Upper Mississippi and Missouri Rivers. ECOSYSTEMS. Springer, New York, NY, 73(3):419-436, (2011).
Impact/Purpose:
To document research results.
Description:
A survey of the Ohio, Missouri and Upper Mississippi Rivers revealed large (five-fold) differences in summer average chlorophyll a (CHLa). Average concentrations were highest in the Mississippi (32.3 + 1.8 µg L-1) with lower values in the Missouri (19.7 + 1.1 µg L-1) and Ohio (6.8 + 0.5 µg L-1). Inter-annual variation was low suggesting that basin- specific factors exert greater control over river-wide CHLa than regional-scale processes influencing climate and discharge. The large majority of sites were characterized by low light availability (< 4 E m-2 d-1) and elevated nutrient concentrations (TP > 25 µg L-1; DIN > 150 µg L-1). Regression analyses revealed that TP was the best predictor of inter- and intra- river variation in CHLa and that light utilization efficiency was also influenced by TP. Light and TP were inversely related suggesting that shifts in resource availability may result in co-limitation. Microzooplankton (principally rotifers) were the dominant grazers accounting for >80% of benthic and pelagic filtration. Estimation of CHLa loss rates due to grazing and sedimentation yielded required doubling times on the order of 1-2 d to sustain CHLa downriver. CHLa and POC were positively correlated in all three rivers suggesting that phytoplankton were an important component of suspended organic matter. Their contribution to POC in rivers (41%) was similar to that of lakes (39%) but lower relative to reservoirs (61%).