Several kilometers of green tides (GT) formed by seaweed and seagrass were recently observed in intertidal, swash, and shallow subtidal zones of Palk Bay and Gulf of Mannar regions, southeast coast of Tamil Nadu, India. On a finer scale (few hundreds of Kgs), GT of Ulva rigida observed in the Palk Bay region during November 2018 was due to eutrophication and heavy currents and waves. While finer scale to massive (several tons) GT of seagrass mixed with seaweeds observed during May 2019 in Gulf of Mannar (GoM) region was recurrent due to heavy wind-driven rough waves and strong current drift but not due to eutrophication as seagrasses do not bloom like seaweeds. GTs of seaweeds and seagrasses appeared in both study regions were due to strong wind and current patterns observed in respective periods. GTs that occurred in both GoM, and Palk Bay regions were appearing to be seasonal but not annual. The present study infers that GTs of free-floating and stranding seagrass and seaweeds could alter the reproduction of benthic and coastal flora and fauna communities. Thus, further studies need to be conducted to understand the negative impact of GTs. Alternatively, these seaweed and seagrass sources can be exploited for commercial and biomedical research purposes.

 Green tides, Ulva rigida, seagrass, currents, Tamil Nadu