Chemical conditions in the boundary layer surrounding phytoplankton cells: implications for trace metal bioavailability
Phytoplankton play a key role in the carbon cycle in both freshwater and marine ecosystems, and growth of phytoplankton is influenced by trace metals in fresh and ocean waters. Over the last 40 years, a general consensus has developed that the best predictor of the biological uptake of waterborne trace metals by these micro-organisms is the concentration (or activity) of the free metal ion in the ambient water. However, an important but untested assumption of the established paradigm is that equilibrium is established between metal species in the bulk solution and those in the boundary layer surrounding the phytoplankton cells. My laboratory results suggest that key chemical factors (redox, pH and complexation) near cell surfaces are influenced by algal metabolites; trace metal uptake can be markedly influenced by this boundary layer effect. The observation of the boundary layer effect should be of great interest to researchers in the fields of Environmental Sciences, Aquatic Sciences and Biological Oceanography who seek to predict the effects of climate change and ocean acidification on planktonic primary production.