The effects of environmental variation on the sinking rates of marine phytoplankton with an emphasis on light intensity

The effects of light intensity on the sinking rates of phytoplankton were investigated using cultures of Chaetoceros gracilis and C. flexuosum in laboratory experiments and assemblages from the open ocean and marginal ice zone of the Greenland Sea in field experiments. A homogeneous sample method (SETCOL) was used to determine sinking rates of chlorophyll, biogenic silica, phaeophytin, particulate carbon and particulate nitrogen. For the experiments with diatom cultures, the light intensity under which the culture was grown was positively correlated with sinking rates as measured by chlorophyll and silica as well as with growth rates. Experiments conducted in the field indicated that variation in sinking may be associated with changes in water temperature, density, and nutrient concentrations. Environmental factors explaining variation in sinking rates support the hypothesis that buoyancy regulation is affected by physiological processes. Particulate matter sinking rates in the field were characteristic of passively sinking cells and were somewhat lower than rates previously reported for temperate, sub-polar, and polar regions.