C-13 LABEL IDENTIFIES EELGRASS (ZOSTERA-MARINA) CARBON IN AN ALASKAN ESTUARINE FOOD WEB

The food web of Izembek Lagoon, Alaska draws most of its carbon from eelgrass (Zostera marina) and phytoplankton. The13C:12C ratios of these primary producers are sufficiently different to enable their contributions to consumers to be estimated from consumer13C:12C ratios. Although the technique is conceptually simple, carbon inputs from other sources and isotope fractionations occurring in the food web limit its precision. Isotopic data nevertheless helps to establish the major carbon fluxes through the community and to assess the importance of eelgrass carbon to individual animals. It is particularly useful when dealing with detritus food chains, where direct observations of animal feeding habits are difficult to make. The Izembek community draws much of its carbon from eelgrass. Detritus food chains provide the major pathway for assimilation of eelgrass carbon by the community, but grazers are also important. Eelgrass carbon is more important to benthic animals than to the eelgrass epibiota and the fishes, which depend mainly on phytoplankton carbon. © 1979 Springer-Verlag.