Seasonal dynamics and environmental drivers of productivity in the Cochin Estuarine System: Insights from estuarine turbidity maxima
Date
2025Author
Adarsh, V. B.
Muraleedharan, K. R.
Azeez, A.
Gireeshkumar, T. R.
Nair, R. C.
Shivaprasad, A.
Sudheesh, P.
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The Cochin estuarine system, characterised by its Estuarine Turbidity Maximum (ETM) zones, undergoes significant seasonal variations influenced by riverine input and tidal forces. This study examined the seasonal shifts of ETM zones from June 2008 to May 2009, utilising in-situ data to explore turbidity, salinity, light availability, and chlorophyll-a production throughout the year. During the monsoon season, intense river discharge resulted in elevated turbidity, confining the ETM zone to the inlets. In contrast, the post-monsoon and pre-monsoon periods showed a notable upstream shift in the ETM zones, with maximum turbidity moving up to 12�km towards the southern arm by the end of the post-monsoon and up to 25�km by the end of the pre-monsoon period. Chlorophyll-a production is mainly influenced by light availability, turbidity, and nutrient levels. To better understand these dynamics, we categorised ten stations into four groups and normalised the data across key variables: light availability depth, fluorescence, turbidity, and nutrients. Despite lower light availability and higher turbidity during the pre-monsoon months, chlorophyll-a production showed peaks due to longer residence times and a stable hydrographic environment for sustained nutrient availability. Our findings underscore the importance of seasonal dynamics and particle residence times in determining estuarine productivity, highlighting the complex interplay between environmental conditions and biological processes in shaping the system's production potential.
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