Connection between trace metals, chelators and red tide blooms in the Laholm Bay, SE kattegat—an experimental approach

Abstract

The influence of the trace metals, copper, aluminum and iron, and of the strong complexing agents, EDTA and NTA, on phytoplankton growth in water from a brackish water bay was investigated through bioassay experiments. A diatom ( Skeletonema costatum (Grev.) Cleve) and a dinoflagellate ( Prorocentrum minimum (Pav.) J. Schiller) were used as test organisms. The growth of both phytoplankton species was strongly inhibited by copper. This inhibition was generally eliminated by EDTA and NTA. Both phytoplankton species were considerably less inhibited by aluminum than by copper at the same total metal concentration. While S. costatum responded to copper and chelator additions in the same way in sea water samples from different seasons, the growth of P. minimum exhibited pronounced seasonal variation. Other parameters than the values of pCu must be considered in order to account for the experimental results. This work supports the theory that alterations in contents of trace metals and natural chelators in sea water are important factors behind shifts in phytoplankton species composition.