Impact of monsoon waves on the deposition of chitin tubes of polychaetes along the central-eastern Arabian Sea,
Abstract
The west coast of India is highly productive during the southwest monsoon (SWM; June September), primarily due to coastal upwelling. While the SWM enhances pelagic productivity, it can also induce ecological disturbances in benthic habitats. Here, we report the negative impact of the SWM on the polychaete tube worm Spiochaetopterus sp., which inhabits translucent chitin-based tubes fixed in sandy/muddy subtidal zones. Monthly sampling and fortnightly onshore surveys were carried out along the central west coast of India (Goa) from May 2022 to July 2022. Pre-monsoon conditions in early May were characterized by weak wind, calm sea, and the absence of chitin tube deposition onshore. From late May to early June, increasing wind speed and wave height coincided with the large-scale dislodgement and accumulation of tubes along the shoreline (0.3 499 g/m2; 7 12,197 tubes/m2). In contrast, deposition along estuarine shores (Mandovi and Zuari) was delayed, likely due to weaker waves. Notably, no comparable deposition was observed on the northern (Mumbai) and southern (Kochi) sectors of the west coast. These findings demonstrate that the onset of the SWM triggers hydrodynamic disturbances that dislodge inter-tidal tube-dwelling polychaetes, with potential repercussions for benthic community structure, trophic pathways, and benthic-pelagic coupling. This study provides the first evidence linking SWM-driven hydrodynamics to large-scale dislodgement of chitin tubes along the central west coast of India. Future research should include in-situ time series observations to assess the fate of dislodged tube worms and to evaluate the biochemical properties and economic potential of their tubes for the blue economy.
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