The September 2004 stench off the southern Malabar coast - A consequence of holococcolithophore bloom

Abstract

During the third week of September 2004, particularly on 16th and 17th, an unusual and strong stench was reported from the coast at Kollam and Vizhinjam in Kerala (India). Local dailies reported that over 200 children, mostly below 15 years, complained of nausea, chest pain and short periods of breathlessness because of the stench. Many were hospitalized, but were discharged within a couple of hours. A press report stated that the stench was due to dead fish scattered on the beaches and in the water. The report linked the fish death to oxygen depletion and choking of fish gills. Both were reported to be possibly due to proliferation and eventual putrefaction of a fish-toxic alga Cochlodinium polykreikoides. Information was put up on the web that the bloom was caused by Karenia brevis, a toxic dinoflagellate. It was reported that the stench could be felt up to 5 km inland from the coast. On 20 September 2004, the Government of Kerala requested the National Institute of Oceanography (NIO), Goa to determine the cause of the phenomenon. In response, a team from NIO collected near-shore samples of water on 23 and 26 September off Vizhinjam, Shanghumugham and Kollam. During 3-7 October 2004, RV Sagar Sukti, a coastal research vessel of NIO, was used to collect samples in the waters offshore of Vizhinjam, Veli, Kollam in the depth zones of 20-50 m. The water samples collected on 23 and 26 September from the near-shore spots were analysed for various chemical (dissolved oxygen, hydrogen sulphide, nutrients, and salinity) and biological (microbiological, phytoplankton counting and identification) variables. Data from sea-level records at Cochin Port were also examined to learn about the possible evolution of physical conditions before and after the episode described above. In this preliminary report inferences based on analysis of the data is presented.