STUDIES OF INTERACTION BETWEEN DISSOLVED METALS AND THEIR SPECIATION AND PHYTOPLANKTON IN A CONTINUOUS FLOW PHOTOBIOREACTOR

Abstract : Half of the world primary productivity is due to marine phytoplankton. Factors that affect the physiology of these organisms are therefore very important to understand plankton dynamics in the global ocean coastal and pelagic settings. Depending on local conditions, metallic micronutrients can be limiting (e.g., Fe in HNLC areas) and affect plankton population structure. While iron is a pivotal micronutrient that impacts global primary productivity, interactions of other metals with phytoplankton have also gained attention. Among these interactions are the potential effects of increased trace metals on plankton dynamics and vice versa. In order to examine the impact of other trace metals upon selected phytoplankton species, we furthered the development of an already existing continuous flow photobioreactor to make it compatible with trace-metal-clean conditions and neutral with respect reduced sulfur gases which were examined. The effect on reduced sulfur dynamics has global relevance because a fraction of this pool (dimethylsulfide) is gaseous and after fluxing into the atmosphere, it is active in Earth's solar radiation balance. Experimenting with mono-specific continuous cultures, we examined the effects of environmentally relevant, dissolved Ag and Cd concentration and speciation on the growth of Isochrysis isogalbana and Phaeodactylum tricornutum. Results acquired so far suggest that while increased Ag and Cd levels have little effect on the growth of these phytoplankton species, they have one reduced sulfur release. Effects of pCO2 on culture growth and metal speciation were also investigated. Preliminary results of the photobioreactor and this suite of experiments will be presented.