Red tide of Noctiluca miliaris off south of Thiruvananthapuram subsequent to the ‘stench event’ at the southern Kerala coast

Abstract

'Red tides' refer to the discoloration of the ocean surface caused by the blooming of some planktonic organisms. A few species of dinoflagellates (a group of protists) periodically form red tides along the west coast of India and Noctiluca miliaris is the most frequent one. Noctiluca red tide observed on 29 September 2004, seems to be significant since the phenomenon has occurred within a fortnight of the stench event that had created panic among people living along the southern Kerala coast. Mass fish kill was noticed on 17 September 2004 along the Trivandrum coast, with foul smell coming from the sea. Many people, especially children, who got exposed the stench, were hospitalized due to vomiting and nausea. Initial reports indicated that the causative organisms for the stench and fish kill were Cochlodinium sp. and Gonyaulax diegensis. Later, detailed study on samples collected from all along the southern Malabar Coast reported it was due a holococolithophore bloom. In the present communication, the favourable environmental conditions that prevailed in the region of the Noctiluca red tide are described.