Trace metal effects on the production of biotoxins by microalgae

Mass production of bioactive compounds was enhanced by the addition of particular trace metals to specific microalgae. An increase in domoic acid isomer-C production by Pseudo-nitzschia australis was achieved by adding copper (Cu) or Zinc (0.1-0.2 mu mol l(-1)) to standard growth media. The combined addition of selenium (Se) and Magnesium (0.1 mu mol l(-1) and 3.6 mu mol l(-1) respectively) elicited a 58% increase in gymnodimine production by Karenia selliformis. Addition of Cu (0.16 mu mol l(-1)) resulted in a 100% increase in the production of palytoxin-related compounds by Ostreopsis siamensis and a 50% increase in okadaic acid diol esters produced by Prorocentrum lima. Yessotoxin production by Protoceratium reticulatum was increased by adding Se (0.1 mu mol l(-1)). Enhanced toxin production in culture is important for the isolation of novel bioactive compounds, for the preparation of certified toxin standards and for toxicological studies. The effects of trace metals on biotoxin production are of concern given the substantial inputs into coastal waters from road and land run-off. Subsequent increases in algal bloom toxicity could impact on shellfish aquaculture.