First record of a fish-killing Gymnodinium sp. bloom in Kuwait Bay, Arabian Sea: Chronology and potential causes

Abstract

Significant natural and aquaculture fish deaths in Kuwait Bay occurred from September to October of 1999 and were attributed to a bloom of the dinoflagellate Gymnodinium sp. A chronology of the bloom event suggests that a period of low winds and stable water-column structure preceded the bloom. Maximum cell concentrations of Gymnodinium sp. (> 6 × 106 cells l-1) were also immediately preceded by a more than 20-fold increase in mean inorganic nitrogen concentrations (up to 60 μM) and elevated inorganic phosphate concentrations. This, combined with elevated inorganic and organic nutrient concentrations within the bloom, suggests that coastal nutrient eutrophication was likely to have contributed significantly to bloom development and support. Termination of the Gymnodinium sp. bloom coincided with a bloom of the non-toxic ciliate Mesodinium rubrum, which appeared as large red patches in Kuwait Bay. While no adverse human health effects were associated with the bloom, closure of shellfish and selected finfish (largely mullet Liza macrolepis) markets resulted in significant economic losses to the region. The occurrence of this toxic algal bloom event, the first within the Arabian Sea, highlights the need for monitoring and research programs in the Arabian Sea and Kuwait Bay that focus on nutrients and eutrophication, in addition to oil related pollution issues.