Influence of nutrient status on algal bloom and flocculation

Abstract

Phytoplankton such as diatom and dinoflagellate in seawater secrete microbial extracellular polymers (ECP). These materials allow phytoplankton cells to align and form large flocs. The resultant algal aggregates enhance the vertical transport of biomass in the ocean. Therefore, algal flocculation may regulate the termination of algal blooms as well as the circulation of organic materials in the natural environment. However, information from previous research about the role of ECP in algal flocculation is limited and often contradictory. The main purpose of this study is to investigate the effects of nutrient status on the bioflocculation and sedimentation of phytoplankton blooms with an emphasis on the role of ECP. The preliminary results indicate that blooms of phytoplankton can be produced under laboratory conditions. ECP production is shown to be positively correlated to the nitrate consumption. Results also demonstrated to various extents that ECP production affects the flocculation of diatom and dinoflagellate population.