The resting cyst and toxicity of Alexandrium ostenfeldii (Dinophyceae) in New Zealand

Examination of dinoflagellate cysts in sediments around the New Zealand coast revealed that a previously undescribed resting cyst (hypnozygote) of Alexandrium ostenfeldii (Paulsen) Balech et Tangen was common. In a number of locations these cells were the dominant dinoflagellate cyst type within the seafloor sediments although the motile form was rarely observed within the plankton. On occasion quite high numbers of cysts (9.0 × 103 cysts m−1) were observed within the fine sediments accumulated on mussel culture ropes. Vegetative cell cultures were established by hatching cysts from locations spanning a wide latitudinal range. Examination of the paralytic shellfish poisoning (PSP) toxicity of these cultures using high-performance liquid chromatography (HPLC) showed considerable differences between the toxin profiles of isolates from different locations. One isolate (Wellington Harbour) showed no trace of any PSP toxins. Two isolates from the North Island west coast produced similar profiles composed mainly of the sulpho-carbamate derivatives GTX, and GTX5 and an isolate from the southern South Island east coast (Timaru) produced almost exclusively saxitoxin (STX). Repeated analysis of toxin profilesover an 18-month period showed that these were stable properties of the isolates. The potential for paralytic shellfish poisoning by A. ostenfeldii is therefore widespread throughout New Zealand though significant differences in specific toxicity occur in populations from different geographical areas.