Marine Institute

'Red Tide' Reported on West and North-West Coast

June 28, 2005

Red/brown seawater discoloration and mortalities of marine organisms including pacific oysters, cockles and lugworms have been reported along the west and northwest coast. Samples analysed by the Marine Institute this week have identified an algal bloom (or "red tide") of a microscopic planktonic species called Karenia mikimotoi. This organism has no impact on human health and is not uncommon in Irish coastal waters at this time of the year. The bloom typically starts in offshore waters and is transported into the coastal zone by ocean currents.

Developments of the current bloom are under continuous surveillance and are being updated daily on the Marine Institute website 

Karenia mikimotoi has a widespread distribution and blooms have been recorded in many locations worldwide. The organism was first identified from the east coast of the USA in 1957 and was first recorded in Europe in 1966 when it bloomed in Norwegian coastal waters. It was first recorded in Irish coastal waters in 1976 when it bloomed extensively on the southeast coast. Subsequent blooms were recorded each year between 1978 and 1982 and again each year between 1990 and 1995. The exact geographic location of the blooms has varied from year –to-year but in the main they have been recorded in the southeast, southwest and northwest coasts.

Previous blooms have also been associated with moralities of marine organisms including flatfish (plaice, flounder) and lugworms as well as farmed shellfish and finfish. It is thought that the mortalities are caused by a reaction to mild toxins produced by the plankton and also to low oxygen levels that can occur when the bloom begins to decay.

Algal blooms are naturally occurring and are seen almost every year during the summer months. The Marine Institute routinely analyses water samples from around the coast of Ireland to identify harmful or nuisance phytoplankton, and their impact on shellfish & finfish in particular. The results of the Marine Institute's Phytoplankton Monitoring Programme can be seen on www.marine.ie/habs. These results are also circulated to shellfish and finfish producers, the Department of Communications, Marine and Natural Resources, and the Food Safety Authority of Ireland. 

In addition to routine monitoring and notification of algal blooms, the Marine Institute is carrying out research with NUI Galway, to better understand the development and movements of harmful algal blooms. The aim of the BOHAB (Biological Oceanography of Harmful Algal Blooms) project is to develop the capability to predict the occurrence of harmful algal blooms (HABs) and provide advance warning to finfish and shellfish producers. This will facilitate appropriate management actions, such as harvesting in advance of a HAB event and minimise the impact on seafood production. The three year project, funded by the National Development Plan, has made significant progress to date and will test prediction methods later this year.

ENDS