Man-made structures are perfect spot for seabirds to dine, QUB study reveals
Man-made structures in tidal streams can help seabirds find food, according to new research led by Queen's University.
It carried out the research along with the University of Plymouth and Bangor University in a tidal channel linking Strangford Lough with the Irish Sea.
Strong currents passing through hard structures, such as boulders, piers or floating buoys, can cause turbulent wakes which can make prey more available to foraging seabirds, such as the terns in the study.
The research found that terns found more food at the SeaGen turbine than they did at a rock island and a whirlpool. SeaGen, in a tidal channel linking Strangford Lough with the Irish Sea, also experienced the highest currents.
SeaGen, the world's first commercial-scale tidal turbine, did not have its turbines as it was in the process of being removed, and the wake was created by its tower. It was built by Belfast's Harland & Wolff, commissioned in 2008 and supplied energy to the UK power grid.
"We found that SeaGen's wake has the power to mix up the entire water column, making potential prey items more accessible to foraging terns, similar to a prey conveyor belt," said Dr Lilian Liber, Bryden Centre Research Fellow from the School of Chemistry and Chemical Engineering at Queen's, who led the research.
"We used a combination of vantage point counts, drone flights, hydrodynamic modelling and hydroacoustics (using sound to measure underwater characteristics) and found that SeaGen's wake generated the most intense foraging hotspot for terns, coupled to the flood tide," she added.
Co-investigator Dr Alex Nimmo-Smith, an oceanographer and UAV pilot at the University of Plymouth, said: "The drone provided an eye in the sky, allowing us to track the highly localised foraging behaviour of the terns over SeaGen's turbulent wake structure."
The researchers could not determine if this had an overall positive impact on local seabirds, but said that it highlights the impact that offshore structures have on the environment.
SeaGen's removal means that researchers will be able to study how flow patterns change once the structure is fully decommissioned.
The Bryden Centre at QUB is an £8.4m cross-border research centre for renewable energy projects which opened last year.
The research has been published in the nature research journal Communications Biology.