Killary Survey unlocks key to early warnings for Harmful Algal Blooms

The processes whereby algal blooms move into sensitive seafood production sites on the west coast of Ireland are now far better understood thanks to a recent survey by the Marine Institute and NUI Galway using cutting-edge scientific equipment.

The survey was part of the BOHAB project, a study of the biological oceanography of algal blooms on the west coast. BOHAB is a three-year Marine Institute / NUIG project funded under the NDP.  Its aim is to provide advance warning of algal blooms and toxic periods to shellfish and finfish farmers in order to enable producers to make risk management decisions on the threat of harmful algal events. 

Killary Harbour was chosen as the focal area for the  BOHAB project over the last eighteen months because of the persistent algal bloom problems experienced by mussel farmers along the south shore over the last 10 years.

This latest two-week survey aimed to find out how algal blooms move into Killary Harbour. It took place between 19th – 30th July, on two boats chartered by the BOHAB project; the M.V Lughnasa and the R.V. Conamara. They carried a French team led by Dr. Patrick Gentien, IFREMER and an American team lead by Dr. Percy Donaghay, University of Rhode Island. A Spanish scientist, Dr. Beatriz Reguera was also present to carry out research on the presence and life cycles of the Dinophysis group of toxin producing phytoplankton.

During the survey thin layers of phytoplankton were observed in Killary and presented a good opportunity to study the mechanisms for the linkage between the coastal and inshore populations. The association between the occurrence of phytoplankton and the density of the seawater was studied. In the summer, warmer, less salty water appears near the surface and cooler, more salty water occurs near the seabed. A sharp density gradient may occur between these water masses and thin layers of phytoplankton may develop here. 

The survey was successful in finding out more about the mechanisms of water movement within Killary Harbour and it’s adjacent coastal areas. Preliminary observations suggest that phytoplankton may come into the inner fjord in thin layers at depth rather than as a visible surface bloom. This has significant implications for shellfish and finfish industry as it provides us with more accurate information on how best to monitor algal blooms and how to target sub-surface sampling.

“These preliminary results are very encouraging” according to Joe Silke of the Marine Institute, “With this information we can begin to develop monitoring methods to identify potentially toxic and fish killing algal events by targeted sampling before it arrives into a production area.” “Ultimately we would aim to use the results of these surveys to be able provide notice to shellfish and finfish producers, anything from a week up to a month in advance of a toxic event” added Mr. Silke. This would allow producers to make informed management decisions on harvesting, market planning, and put systems in place to minimise the impact of the HAB event such as precautionary steps such as appropriate aeration systems on salmon farms.

Dr. Caroline Cusack is the BOHAB Project Manager. The project is lead by Joe Silke, Marine Institute and Dr Robin Raine in NUI Galway.

Further information on the BOHAB project may be had from Dr Caroline Cusack, BOHAB Project Manager, Martin Ryan Institute (MRI), National University of Ireland, Galway (NUIG), Galway, Ireland.