As an Erasmus student, you earned a Joint Master’s from the Universities of Southampton, Bordeaux, and the Basque Country, conducting investigations on microplastics in fish through collaboration with the National Oceanography Centre in Southampton. What drew you to this area of research?

As a child, I grew up watching golden sunsets on the white sandy beaches of the beautiful island of Sri Lanka. I knew since then that I always had this hidden passion to dive into the waters of that horizon. Every little aspect connected with the ocean and marine life never failed to fascinate me.

After completing my undergraduate studies with first-class honours in Fisheries and Marine Sciences at the University of Ruhuna, having also received recognition for several other achievements throughout my time in the programme, I earned a phenomenal opportunity to pursue the Erasmus Mundus Joint Master’s Degree. This changed my entire life trajectory. Truly, it was an amazing two years.

Throughout the Erasmus Mundus programme, I was able to learn from some of the best lecturers and pioneers in various disciplines of oceanography and marine biology. Alongside that, these two years allowed me to experience different cultures, work with diverse ethnic backgrounds, and most significantly, create a broad network among early career ocean professionals from different countries all over the world. Marine plastic pollution has been a growing concern in the recent past, and according to the European Commission, considerable measures have been implemented to control microplastic pollution in the marine realm by 2030. This triggered my focus on microplastic contamination in marine organisms during my Master’s thesis. I was privileged to work actively with the microplastics team at the National Oceanography Centre, Southampton, under the European Union’s Horizon 2020 research and innovation programme (LABPLAS project). This was under the brilliant supervision of Professor Richard Lampitt and Dr Alice Horton, and it enabled me to witness first-hand their cutting-edge research.

You are now completing a PhD at University of Galway and are part of iCRAG, with your poster and presentation on ‘Connecting past and present knowledge to assess the future of our mesopelagic fish resources and ecosystem functioning’ receiving accolades last March at the Irish Geological Research Meeting (IGRM). Could you share some key highlights of this research?

Upon completing my Master’s degree, I encountered my current – and very interesting – PhD opportunity in deep-sea fish migration and carbon cycling, funded by iCRAG. Following a successful interview, the Department of Earth and Ocean Science at University of Galway enrolled me in this four-year structured PhD programme. As for key highlights of this research project, I focus primarily on acoustic data collected during journeys to the Northeast Atlantic Ocean, where echo sounders were used across multiple frequencies. I also use hydrography data and environmental DNA analysis to better distinguish acoustic signals. One of the most fascinating components of this study was the opportunity to join multiple research cruises over the last two years. These included the ROV Survey in the Whittard Canyon in RV Celtic Explorer, conducted under the brilliant guidance of Professor Louise Allcock; the Ocean Climate Section Survey, conducted under the supervision of Dr Caroline Cusack in RV Tom Crean; and the International Blue Whiting Survey in RV Celtic Explorer, conducted under Mr Michael O’Malley as chief scientist. All these excursions allowed me to gain invaluable hands-on experience using acoustic data acquisition, working with environmental DNA, hydrography data collection, remotely operated vehicle (ROV) Operations, and marine mammal observation.

As for other highlights, it is always a pleasure to present our research findings. At last year’s IGRM, I was able to present some of the key findings from the ROV Survey, which received honorary mentions. Additionally, I presented scientific posters at the Challenger Society conference in Oban, Scotland, and the International Council for the Exploration of the Sea (ICES) conference in Newcastle, England, which brought more national and international exposure and collaboration to this current research project.

A major association in research into mesopelagic fish is their impact on carbon. Can you give us a brief overview of why it is so important to investigate this relationship, especially in the context of climate change?

Mesopelagic fish account for the majority of world fish biomass, with current estimates indicating it at ≈2 to 16 Gt, which is approximately 67–94% of total fish biomass.

As a result of this updated estimate, which is two to ten times greater than formerly accepted micronekton net sampling, mesopelagic fish have gained particular attention as potentially a significant element of the ocean carbon cycle. They play an important role in carbon export due to their substantial diel vertical migrations. This is when a large proportion of these fish consume organic carbon by feeding at night in the epipelagic zone (< 200 metres from the ocean surface), hiding from predators in the mesopelagic zone (200–1,000 metres) during the day.

They transport carbon from the epipelagic zone to the mesopelagic zone through the egestion of faecal matter and carbonates, respiration of carbon dioxide, and mortality through predation or deadfall. Current research maintains that the scale of fish carbon movement is largely uncertain, and its contribution to climate-relevant carbon sequestration is not well documented. (

Understanding the biogeochemical role of mesopelagic fish in the Northeast Atlantic Ocean is therefore crucial, as their harvesting could significantly alter biogeochemical dynamics – not only because of reduced mesopelagic fish biomass but also through a series of cascading changes in the food web dynamics.

Microplastics is a word that is appearing more frequently in headlines these days. Can you speak to its association with the world of marine environments?

Microplastics (MPs), or plastic particles less than 5mm in size, have emerged as a major environmental concern in marine ecosystems across the world. Land-based sources have been estimated to release four times as much plastic into the ocean as marine-based sources. Beyond this, rivers play a substantial role in transporting land-derived material to the ocean, accounting for 2.8–18.6% of total coastal plastic emissions. While river-dominated beaches make up 0.87% of global coastlines, they receive approximately 52% of plastic pollution brought by rivers. Population density, degree of urbanisation, industrialisation within catchment areas, rainfall rates, and external barriers may contribute to the amount and timing of plastic litter carried by rivers. Ingestion of MPs acts as ecotoxicological risks to marine organisms, including damage to their gastrointestinal (GI) tracts and stomachs. MPs have been proven, in neurotoxicology and behavioural modification studies, to cause nematodes, mussels, and fish to exhibit a reduction in locomotion and dietary behaviours under excessive overload conditions. Addressing specific sources of marine litter, such as fishing gear, microplastics from wastewater treatment plants, and atmosphere fallout, is critical for comprehensive understanding and successful mitigation. The Marine Strategy Framework Directive (MSFD) and numerous regional conventions serve as important platforms for assessing and addressing these concerns.

You are currently working under the supervision of Dr Martin White and Professor David Reid. How has their guidance assisted your research efforts to date?

Dr Martin White is my principal supervisor and one of the most amazing mentors I’ve had in my academic career. His extensive knowledge and long-term proficiency in physical oceanography contributed significantly to my research endeavours. Dr White’s advice has been extremely beneficial to my development, providing essential insights into understanding oceanographic data and efficiently relating past environmental records to contemporary hydrography conditions. He was able to consistently offer solutions and answers when I had questions or ran into challenging research problems, and it is always a pleasure to work with him. I genuinely couldn’t have asked for a better principal supervisor.

Professor David Reid, my co-supervisor, is currently working as chairperson of the Science Committee in the International Council for the Exploration of the Sea (ICES) and was a Principal Investigator in Ecosystem-Based Fishery Management at the Marine Institute in Ireland. I was privileged to work closely with him, an experience which complemented my research journey perfectly due to his profound expertise in fisheries biology, particularly fisheries management and mesopelagic ecosystems. His significant contributions to scientific discourse have greatly enriched my understanding of sustainable ecosystem-based fisheries management, and his guidance has allowed me to study historical acoustic data with contemporary ecological knowledge. He emphasises using environmental DNA approaches, a method which enhanced my analytical capabilities and fostered my own innovative approaches to assessing the future of mesopelagic fish resources.

The culmination of the guidance afforded to me has in no small way successfully assisted my navigation through this multidisciplinary PhD project.