|
Read Full Article (file size: 876697 bytes) Cited by
JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
G03003,
doi:10.1029/2005JG000079,
2006
Phosphate oxygen isotope ratios as a tracer for sources and cycling of phosphate in North San Francisco Bay, California
Karen McLaughlin
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
Carol Kendall
United States Geological Survey, Menlo Park, California, USA
Steven R. Silva
United States Geological Survey, Menlo Park, California, USA
Megan Young
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
Adina Paytan
Department of Geological and Environmental Sciences, Stanford University, Stanford, California, USA
Abstract
A seasonal analysis assesing variations in the oxygen isotopic composition of dissolved inorganic phosphate (DIP) was conducted
in the San Francisco Bay estuarine system, California. Isotopic fractionation of oxygen in DIP (exchange of oxygen between
phosphate and environmental water) at surface water temperatures occurs only as a result of enzyme-mediated, biological reactions.
Accordingly, if phospate demand is low relative to input and phosphate is not heavily cycled in the ecosystem, the oxygen
isotopic composition of DIP (δ18Op) will reflect the isotopic composition of the source of phosphate to the system. Such is the case for the North San Francisco
Bay, an anthropogenically impacted estuary with high surface water phosphate concentrations. Variability in the δ18Op in the bay is primarily controlled by mixing of water masses with different δ18Op signatures. The δ18Op values range from 11.4‰ at the Sacramento River to 20.1‰ at the Golden Gate. Deviations from the two-component mixing model
for the North Bay reflect additional, local sources of phosphate to the estuary that vary seasonally. Most notably, deviations
from the mixing model occur at the confluence of a major river into the bay during periods of high river discharge and near
wastewater treatment outlets. These data suggest that δ18Op can be an effective tool for identifying P point sources and understanding phosphate dynamics in estuarine systems.
Received 28
July
2005;
accepted 21
April
2006;
published 19
July
2006.
Keywords: phosphate oxygen isotopes;
nutrient source;
nutrient cycling;
estuary.
Index Terms: 0470 Biogeosciences: Nutrients and nutrient cycling (4845, 4850); 4870 Oceanography: Biological and Chemical: Stable isotopes (0454, 1041); 4235 Oceanography: General: Estuarine processes (0442); 0414 Biogeosciences: Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912); 0438 Biogeosciences: Diel, seasonal, and annual cycles (4227).
Read Full Article (file size: 876697 bytes) Cited by
Citation: McLaughlin, K., C. Kendall, S. R. Silva, M. Young, and A. Paytan
(2006),
Phosphate oxygen isotope ratios as a tracer for sources and cycling of phosphate in North San Francisco Bay, California,
J. Geophys. Res.,
111,
G03003,
doi:10.1029/2005JG000079.
Copyright 2006 by the American Geophysical Union.
|