Occurrence and distribution of Karenia brevisulcata (Dinophyceae) during the 1998 summer toxic outbreaks on the central east coast of New Zealand

Abstract

Massive mortality of marine life and algal blooms around central New Zealand during January and March 1998 have been attributed to the toxic dinoflagellate, Karenia brevisulcata (= Gymnodinium brevisulcatum). Phytoplankton surveys in January and February 1998 showed the presence of K. brevisulcata both offshore, in the relatively warm, southwards-directed East Auckland and East Cape Currents, and inshore, in the relatively cold, northwards-directed Wairarapa Coastal Current, along the entire east coast of the North Island. Small numbers of this species (200 cells 1⁻¹) were also recorded on the southwest coast of North Island. A bloom of K. brevisulcata occurred in Wellington Harbour during February–March 1998. Reports of human respiratory distress progressed northwards along the Wairarapa Coast at about the same speed (0.23 m s⁻¹) as observed for the Wairarapa Coastal Current, suggesting the passage of a bloom along the coast. We relate the timing of these events to local oceanographic conditions.