Cullen Fellowship research on estuarine physics and ecology

Sean Kelly, Cullen Fellowship research on estuarine physics and ecologyNUI Galway PhD student, Sean Kelly, is studying for a PhD through the Marine Institute’s Cullen Fellowship Programme and the National University of Ireland, Galway. His research is investigating ‘marine and freshwater influences on estuarine physics and ecology’, focusing on Lough Furnace, Co Mayo.

“Estuaries, where saltwater from the ocean meets freshwater from river runoff, are incredibly dynamic,” explains Sean. “The salinity and water currents can change drastically depending on the state of the tides and how much river flow occurs.”

As estuaries receive nutrients from terrestrial and marine sources, they often have very high biological productivity, providing a nursery ground for juvenile marine fish and forming a crucial part of the journey of migratory fish. Estuaries are also highly sensitive to human impacts, particularly excessive nutrient loading from agricultural runoff and sewage which enhances algal and phytoplankton growth. This amplified biological activity often causes a reduction in the oxygen content of the water.

According to Sean, Lough Furnace has anoxic (zero oxygen) deep water as consequence of the natural physics. “The bottom water is saline and the surface water is fresh and the two layers generally don’t mix. Renewal or oxygenation of the deep salty water depends on new incoming tidal water. However, in Lough Furnace the tidal inflow is usually limited by the outflowing freshwater, which is common for many coastal systems like fjords.”

“By using Lough Furnace as a natural laboratory, we can begin to understand what the implications of oxygen depletion are for biological communities, which is highly important given the increasing global concern over low oxygen in coastal and estuarine zones.”

Sean’s research supports the long-term monitoring of aquatic ecosystems, in this case at Lough Furnace. Long-term time series data allows assessments to be made on the environmental impacts of climate change and a greater understanding of the implications for aquatic life in these dynamic coastal systems.

“My research allows us to understand how climate change may be modifying oxygen dynamics in coastal waters and how oxygen depletion can negatively impact biodiversity. The findings highlight the additional threats imposed on migratory fish species such as salmon and eel that inhabit these coastal systems,” Sean said.

Sean has been based at the Marine Institute’s Catchment Research Facility in Newport and has found working alongside other scientists to be extremely valuable. Davy Sweeney, Marine Institute and Sean Kelly Cullen Fellow Newport

“Collaborating with researchers with expertise in environmental and biological science on a range of overlapping projects has been very beneficial,” Sean said. “Writing and publishing research papers related to the project, as well as presenting research at conferences has been both the most challenging and also rewarding part of the Cullen Fellowship.”

His research has been jointly supervised by Dr Martin White of NUI Galway and Dr Russell Poole of the Marine Institute.

The Cullen Fellowship programme builds marine research capacity and capability by equipping graduates with the skills and expertise in raising awareness about our ocean, as well as Ireland’s rich marine biodiversity and ecosystems. The programme has provided grant aid to the value of €2.06 million supporting 24 PhD and three MSc students over the last five years. The research addresses a number of the 15 research themes identified in the National Marine Research & Innovation Strategy 2017-2021.

This project (Grant-Aid Agreement No. CF/15/06) is carried out with the support of the Marine Institute and funded under the Marine Research Programme by the Irish Government.


National Marine Research & Innovation Strategy 2017-2021: Published in 2017, the National Marine Research and Innovation Strategy 2017-2021 focuses on the broad topics identified in existing Government policies and strategies and provides a framework that recognises the complexity of research funding in the marine domain.