The difference in OA production around North Stradbroke Island is similar to studies conducted around Heron Island, in which presence and toxicity of P. lima have been previously documented ( Morton and Tindall, 1995; Morton, 1998). Morton and Tindall showed that toxin production by P. lima varied significantly at different sites around the island, implying there may be different strains of P. lima within the same area, which could lead to varying levels of OA production.