A TEAM of researchers have plumbed to the depths of Lough Hyne to solve the mystery of disappearing marine sponges in the unique West Cork Lough.
The team, led by Professor of Marine Biology James Bell from Te Herenga Waka Victoria University of Wellington in New Zealand and Professor Rob McAllen from UCC, has been studying the loss of possibly thousands of sponges from the underwater cliffs inside Lough Hyne.
The team secured funding from the National Parks and Wildlife Service of the Department of Housing, Local Government and Heritage to study the unusual event.
Professor Bell has spent a large part of his academic career working in Lough Hyne and his PhD at UCC investigated these unusual sponge communities in the semi-enclosed saltwater lough near Skibbereen.
In a paper published in Science of the Total Environment this week, Professor Bell and co-authors discussed the possible reasons for the drop in numbers and the implications for life in other temperate mesophotic ecosystems (TMEs).
While it remains unclear why so many of the sponges experienced such a strong decline in numbers between about 2010 and 2015, in the past couple of years, there have been signs of a potential natural recovery of the affected species.
There were several possible causes, including outbreaks of disease, increases in nutrients or heatwaves and research is still ongoing into the cause.
However, changes in water chemistry remain one highly likely cause.
Professor Bell said that long-term sponge abundance reconstruction showed the number of sponges on the cliffs had been relatively stable for at least 20 years until 2010.
“The innermost sites were affected the most, suggesting the change originated inside the lough or that its sheltered conditions exaggerated an effect starting from the surrounding coast.”
Professor Bell added that the sudden, unexpected decline of the sponges shows the importance of monitoring these temperate mesophotic ecosystems around the world.
The Lough Hyne Marine Nature Reserve is the only one of its kind in Ireland.
A magnet for marine biologists, it hosts many rare species and contains a high number of habitats within a small area of about 0.5 square kilometres.