Project Description

One of the biggest uncertainties in phytoplankton ecology remains that associated with conversion from unequivocal estimates of algal biomass, i.e. chlorophyll, to units of greater geochemical significance, i.e. carbon. The conversion factor varies with algal physiological state and recent history, and is therefore not a constant. Nor can phytoplankton carbon be directly measured due to the confounding effects of non-living POC, e.g. detritus. It is not a trivial issue, because often detrital carbon exceeds that of living POC.

Unfortunately, no satisfactory techniques have been developed which permit direct measurement of the carbon content of detritus, so we have adapted 3D visualization techniques to the study of plankton. Concerning detritus, our approach is to selectively label detritus in a plankton sample using a unique combination of fluorescent stains, and then concentrate the detritus on a black filter as described previously for determination of plankton carbon. We then optically slice "blobs" of detritus and calculate their volume, and then convert to carbon using empirically derived regressions.