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STABLE ISOTOPIC INDICATORS FOR THE BIOGEOCHEMICAL CYCLING OF ORGANIC MATTER IN A TEMPERATE NORTH PACIFIC ESTUARY, OREGON, USA
Citation:
Sigleo, A C. STABLE ISOTOPIC INDICATORS FOR THE BIOGEOCHEMICAL CYCLING OF ORGANIC MATTER IN A TEMPERATE NORTH PACIFIC ESTUARY, OREGON, USA. Presented at 2002 American Geophysical Union Ocean Sciences Meeting, Honolulu, HI, February 11-15, 2002.
Description:
The distributions of 13C and 15N in suspended particles were examined monthly over a two year period at ten stations along a 60 km transect in the euphotic zone (0.5m) of the Yaquina River and Estuary, Oregon. Organic material in estuaries is a mixture of land-derived and oceanic carbon and nitrogen. In addition, in situ biological processes both produce and consume organic components. The stable isotopes of carbon and nitrogen reflect the isotopic composition of their sources, and thus provide a means of identifying those sources. In the Yaquina estuary both 13C and 15N in planktonic material increased from the freshwater terrestrial region of the river downstream to the Pacific Ocean. Isotopic carbon increased from --27.7 ? 1.4 to -22.1 ? 1.5 per mil 13C between the freshwater terrestrial region of the river to the Pacific Ocean. Particulate nitrogen increased from 2.6 ? 1.0 per mil 15N in the freshwater region to 7.2 ? 1.4 per mil 15N at the ocean. Relative to salinity, the isotopic increases were non-linear, indicating that processes in addition to simple mixing of the two end members were occurring. Isotopic data suggest that river outflow provided a source of nutrients in the freshwater portion of the estuary, whereas heterotrophic remineralization and nutrient recycling were important in the intertidal regions of the estuary.