Highlights
- Submarine groundwater discharge impacts on tropical coastal waters were studied.
- Nutrient sourced SGD input stimulate the growth of diatoms in the coastal waters.
- Acidification may alter the balance between plankton communities.
- Long term monitoring studies of interactive effects of potential drivers needed.
Abstract
Submarine groundwater discharge (SGD) is a significant contributor to effect phytoplankton community shift and marine ecosystem changes, yet little information is available about its influence in the Indian coastal waters. This microcosm study assessed the impact of groundwater input on carbonate chemistry changes, plankton community structuring and marine ecosystem dynamics in coastal waters off Kochi, southeastern Arabian Sea (SEAS), southwest India. The relatively high nutrient content (nitrate and silicate) and low nitrate to silicate ratio (N/Si < 1) in the groundwater favoured the growth and fast abundance of diatom species (Thalassiosira sp.). The increased growth rate of diatoms in coastal groundwater additions shifts the community composition towards higher microphytoplankton relative to picoplankton proportion. Increased heterotrophic thecate dinoflagellates such as Protoperidinium species with SGD might become the significant consumers of bloom forming diatoms in the coastal waters. The SGD driven acidification with increased nutrient supply may alter the balance between autotrophic and heterotrophic plankton communities, which becomes intense with the effective increase in atmospheric aerosols and anthropogenic inputs, amplifying the scope of coastal ocean acidification.
Cheriyan E., Rao D. B., Elangovan S. S., Kumar B. S. K. & Gupta G. V. M., 2025. Submarine groundwater discharge impacts on coastal waters of southeastern Arabian Sea: changes to carbonate chemistry and plankton communities. Estuarine, Coastal and Shelf Science 314: 109150. doi: 10.1016/j.ecss.2025.109150. Article (subscription required).
