01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-01-0206 |
| Title of Abstract | Subterranean Estuaries: An Overlooked Route for Microplastics to Enter the Oceans |
| Authors | Anish Kumar Warrier*, Gokul Valsan, Anjali Tamrakar, Santhosh Prabhu, Jagath Chand, Vyshnav P. |
| Organisation | Manipal Academy of Higher Education |
| Address | Manipal Institute of Technology, Manipal Udupi, Karnataka, India Pincode: 576104 E-mail: anish.warrier@manipal.edu |
| Country | India |
| Presentation | Oral |
| Abstract | The marine environment is increasingly threatened by microplastics (MPs) derived from riverine inputs, atmospheric transport, and surface runoff. These pathways are well recognised, yet the role of subterranean estuaries⿿zones where freshwater mixes with seawater underground before discharging into the ocean⿿remains largely overlooked. Such systems are important biogeochemical filters, but their capacity to transport MPs to coastal waters is poorly understood. This study investigates the subterranean estuary of Malpe, southwestern India, to assess microplastic flux into the Arabian Sea via submarine groundwater discharge (SGD). Groundwater samples revealed an average MP concentration of 7.56 ± 6.45 particles/L, with microfibers (55.1%) dominating, particularly in the 1000⿿5000 µm size range. Polyethylene was the most abundant polymer (96.8%), reflecting widespread use of fishing nets and gear in the region. Estimated MP flux through SGD was 18.93 ± 10.25 particles/hour, demonstrating a continuous, though often unnoticed, contribution to coastal microplastic pollution. The findings underscore the importance of groundwater as a hidden conduit of MPs to marine ecosystems. Given that fishing and seafood consumption are central to coastal livelihoods in India⿿the world⿿s third-largest fish-producing nation⿿such fluxes raise concerns for ecosystem health, food security, and human well-being. Persistent inputs of fibrous MPs not only threaten marine organisms but also increase the likelihood of trophic transfer into the human diet. To the best of our knowledge, this is the first comprehensive study quantifying microplastic transport via a subterranean estuary. Our results highlight the need to incorporate subterranean estuaries into global assessments of MP pollution sources. Recognising these hidden pathways is vital for developing monitoring frameworks and management strategies that safeguard fisheries, ecosystem services, and the millions of people who depend on the Indian Ocean for sustenance and livelihoods. |
| Are you part of IIOE-2 endorsed project | no |
| Keywords | Subterranean estuary, Submarine groundwater discharge, Microplastic flux, Interstitial water, Pore water |
| For Awards | no |