OPTICAL ASSESSMENT OF PHYTOPLANKTON NUTRIENT DEPLETION

The ratio of light absorption at 480 and 665 nm by 90% acetone extracts of marine phytoplankton pigments has been examined as a potential indicator of phytoplankton nutritional status in both laboratory and field studies. The laboratory studies demonstrated a clear relationship between nutritional status (carbon/nitrogen ratio) and the absorption ratio that was independent of light and temperature climate. The absorption ratio for nutrient-replete cells was shown to vary between taxonomic groups. However, the inter-specific variation was less than the differences observed between nutrient-replete and nutrient-depleted cells. The field data suggest that the absorption ratio may be a useful indicator of nutritional status of natural phytoplankton populations, and can be used to augment the interpretation of other data. © 1990 Oxford University Press.