Cadmium Exposure and Phosphorus Limitation Increases Metal Content in the Freshwater Alga Chlamydomonas reinhardtii

The characteristics of metal accumulation in freshwater microalgae are important to elucidate for a full understanding of metal cycling and toxicity in a freshwater system. This study has utilized an elemental profiling approach to investigate the impacts of Cd exposure and phosphorus (P) availability on metal accumulation after 7 days in batch culture-grown Chlamydomonas reinhardtii. Multivariate statistical analysis of the elemental data demonstrated distinct responses between both stresses. Sublethal concentrations of Cd (up to 15 mu M) caused increased accumulation of Co. Cu, Fe, and Zn content also increased in response to enhanced Cd concentrations but only when P availability was low. While Cd exposure effected the accumulation of a few specific metals, P limitation increased the accumulation of all essential trace metals and macronutrients analyzed including Co, Fe, K, Na, and Zn but not Mn. The accumulation of Cd also markedly increased in response to P limitation. The impact of P availability on essential metal accumulation was the same when either inorganic P or an organic P source (glycerophosphate) was used. These results highlight the potential risks of metal toxicity for freshwater microalgae and aquatic food chains when P availability is limiting and which can be exacerbated by Cd pollution.