Algal blooms of Phaeocystis species have occurred several times along the east coast of Ireland, over the summer months, in recent years.
Phaeocystis forms part of the natural cycle of phytoplankton in Irish waters and often occurs after the initial seasonal spring bloom. In the North Sea dense blooms of this species have been associated with nutrient enriched continental coastal waters but this is unlikely to be a factor in the low nutrient waters of the western Irish Sea.
The Phaeocystis species cause water discolouration and foaming along the shore in windy conditions. According to experts in the Marine Institute this species is not harmful to humans either through swimming or from consuming fish that have been exposed to the bloom. The beaches remain safe despite any discolouration of water.
In some cases, oxygen depletion can occur when the bloom decays and this can result in fish and shellfish mortalities, but this has not occurred with previous blooms of Phaeocystis in Irish waters.
Blooms of Phaeocystis species usually dissipate within a few weeks. The progress of any current blooms of Phaeocystis and other potentially harmful algal blooms can be viewed on the Marine Institute’s website here.