Analysis of phytoplankton composition from southern Malabar Coast during the 2005 monsoon as a follow-up of September 2004 stench event
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One of the main objectives of this study was to follow up and see if holococcolithophore that was predominant in all of over 30 samples from the southern Malabar Coast, Karnataka, India during September-October 2004 was prevalent as well during the monsoon months of 2005. The September 2004 stench event had caused nausea, chest pain and short periods of breathlessness in over 200 children. Results reported in this correspondence are from a follow-up study undertaken to decipher whether such organisms are common among the phytoplankton assemblages in the southern Malabar coastal waters. Sampling was carried out during the monsoon months of June-September 2005 along the same stretch from where stench event was reported. Monthly compositional changes in phytoplankton in particular during nutrient enrichment as a consequence of upwelling were recorded. During September 2004 stench event, the holococcolithophorid accounting for over 95% of total phytoplankton counts. The phyotplankton diversity was minimal with only 23 species of phytoplankton (including those contributing less than 0.005% to total counts) were observed from the entire sampling stretch. While in June-Septemeber 2005 as many as 78 species of plankton were recorded, the holococcolithophorid was almost non-existent during all the four months in the entire 300 Km sampling stretch. Although over 78 species of phytoplankton were identified from the 2005 samples, most of the phytoplankton species were not abundant at all. There were location-wise differences in the phytoplankton assemblages and, no single species was predominant in the whole sampling stretch. Apparently, this is a very significant information to suggest that inter-annual and seasonal differences are natural in phytoplankton assemblages. A continuous monitoring programme for documenting phytoplankton assemblages along the coast at some pre-decided locations is called for. Many issues related to global change, climate considerations and coastal phytoplankton biodiversity changes/patterns can be understood when systematic data is accrued.
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