THE EFFECTS OF THE DIARRHETIC SHELLFISH POISONING TOXINS, OKADAIC ACID AND DINOPHYSISTOXIN-1, ON THE GROWTH OF MICROALGAE

The diarrhetic shellfish poisoning toxins okadaic acid (OA) and dinoph ysistoxin-1 (DTX-1) are potent phosphatase inhibitors produced by cert ain species of marine dinoflagellates. OA can cause hyperphosphorylati on of a broad range of animal and higher-plant proteins, but little is known regarding the effects of the DSP toxins on marine organisms or their biological function, A variety of microalgae, including a clone of Prorocentrum lima known to produce both OA and DTX-1, were incubate d with solutions of OA and in one case DTX-1 or a combination of OA an d DTX-1. OA inhibited the growth of all non-DSP-producing test species at micromolar concentrations, but P. lima was not affected even at mu ch higher levels, This differential activity of OA suggests that the D SP toxins may play an allelopathic role and raises questions regarding the strategies adopted by DSP-producing dinoflagellates such as P. li ma to avoid autotoxicity. The effects of DTX-1 on microalgal growth we re found to be equivalent to those of OA, and the effects of both toxi ns in combination were simply additive.