Sedimentation of phytoplankton: Role of ambient conditions and life strategies of algae

Pigment content in particles accumulated in sediment traps are often not directly correlated with phytoplankton abundance, but are rather indicative of transformations phytoplankton underwent on its downward move and following resuspension. We argue that the variability in temporal and spatial sedimentation patterns of different phytoplankton groups is not only an outcome of pigment persistence, but is also associated with dissimilarity in life strategies and dependent on the physical conditions of the water column. Pigment concentrations were measured on weekly-biweekly basis in the water column and in five sets of traps positioned in Lake Kinneret, Israel. Highly degradable peridinin and chlorophyll c reached the deep traps in minute quantities indicating that dinoflagellates mostly recycled in the epilimnion; these migrating algae dominated plankton community under low turbulence and high light. When fast-sinking diatoms persisted in the water column during holomixis they could reach the bottom intact, and fucoxanthin was found in equal proportions in water and traps, chlorophytes rarely dominated phytoplankton, but lutein and chlorophyll b harbored by this group were often the most abundant signature pigments in traps, reflecting the effect of high accumulation rates of these stable compounds in resuspensed particles from the bottom.