Characteristics of marine aggregates during the phytoplankton spring bloom in a temperate tidal basin

Abstract

High abundance of aggregates has often been related to high primary production and phytoplankton blooms. Especially in shallow and turbid coastal regions the formation of aggregates and their sinking velocities also depends on the interaction between primary produced organic matter and lithogenic particles. Nine roller tank experiments were conducted during spring 2012 in the Northern Wadden Sea (Germany) to determine temporal dynamics of formation, composition, and sinking velocity of aggregates, in relation to the wax and wane of the phytoplankton bloom. Highest sinking velocities (June-July) did not coincide with highest SPM concentrations (January-March). After the diatom bloom almost 80% of SPM was rapidly settling in aggregates but only 10% rapidly settled during the subsequent Phaeocystis bloom. The results suggest interactive effects of particle size, specific density and the availability of organic and inorganic particulate matter. Our study underlines the importance of marine aggregates as carrier of organic matter and of lithogenic particles as ballasting material for sedimentation in tidal basins