Monsoonal variability in abiotic parameters in coastal waters off Trivandrum evokes press and pulse response in biotic variables
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Date
2012Author
Subina, N.S.
Bhosle, S.
Nair, S.
LokaBharathi, P.A.
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Trivandrum Coast experiences coastal upwelling during south west monsoon, which is accompanied by abiotic changes in physio-chemical parameters. The resultant biotic responses could range from an instantaneous pulse to a sustained press reaction. In order to understand the type of biotic responses at primary and bacterial level, temporal variation in physico-chemical and biological parameters were measured at 4 depths off Trivandrum coast during monsoon and compared to non-monsoon seasons. One way ANOVA showed significant variation in environmental parameters with time during monsoon. Principal component analysis of the abiotic variables revealed salinity, nitrite and nitrate to be the three driving attributes of the coastal waters during the upwelling period whereas during the post monsoon period nitrate was the only attribute. Nitrate concentration ranged from 7.5 to 15.3 mu M and 0.7 to 14 mu M in the monsoon and post monsoon seasons respectively. During the monsoon season, chlorophyll a and phaeophytin concentrations were 1.5 plus or minus 1.2 and 1.3 plus or minus 0.9 mg l sup(-1) respectively. These concentrations were 11 and 16 fold higher than the pre monsoon reflecting a pulse response. Canonical correspondence analysis (CCA) showed that the factors responsible for this pulse response were nitrate, nitrite and silicate. However, unlike chlorophyll, bacterial variables showed both short term pulse and long term press reaction off Trivandrum coast.
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