The Marine Institute has today confirmed that the orange discolouration in the seawater along the Dublin and east coast shorelines is due to naturally occurring algal blooms. The Marine Institute Phytoplankton Monitoring Programme monitors coastal waters around Ireland for phytoplankton and algal blooms on a year round basis.
Speaking about the occurrence Joe Silke, Marine Institute said, “We have confirmed from samples today the presence of a phytoplankton species called Noctiluca scintillans. These blooms have been reported along the east coast of Ireland for the past few weeks and are typical for this time of the year. Last year there were extensive blooms of the species in the south west of the country and we typically see them every year.”
These algal blooms are a natural part of the phytoplankton life-cycle and species like Noctiluca scintillans are mostly harmless. The orange discolouration of the water is due to the presence of the Noctiluca scintillans phytoplankton bloom, and is sometimes called a red tide.
“This species is well known as a summer member of the coastal phytoplankton and can discolour the water to an orange or brown colour as the cell counts increase when it blooms or accumulates against the shoreline. Noctiluca scintillans is harmless to humans and fish just tend to avoid the accumulation where the water is discoloured. When the bloom decays or at night time there can be some deoxygenation of the water, leading to localised smells similar to other decaying algae such as seaweed,” Joe Silke said.
Noctiluca scintillans is also bioluminescence, and at night blue light is emitted when disturbed by waves on the shore or in the wave of a boat.
The Marine Institute monitors phytoplankton under a national programme which has been in place since the 1980s. During this period, phytoplankton scientists have developed an understanding of phytoplankton populations and dynamics around the Irish coastline. The Marine Institute’s Phytoplankton Monitoring Programme is one of the few worldwide to carry ISO 17025 Quality accreditation.