Browsing Marine Environment & Food Safety Services by Subject "Algal bloom"
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Harmful and nuisance algal blooms in Irish coastal waters 1990 - 1993Algal blooms occur naturally around our coast. These high concentrations of planktonic algae are associated with favourable conditions of light and nutrients, and often occur at stratification/ mixing fronts. Many blooms are completely harmless, and form the diet of shellfish and zooplankton. Some colour the water red or brown. A few species are toxic and can cause fish kills or make shellfish unsafe to eat. The Fisheries Research Centre monitors phytoplankton in order to detect any toxic or potentially harmful blooms. The harmful and nuisance algal events from 1990 to 1993 are described.
Harmful phytoplankton events caused by variability in the Irish Coastal Current along the west of IrelandFrequent sampling in summer along the western and northwestern coasts of Ireland showed the rapid onshore development of blooms of potentially harmful phytoplankton species. In both 1998 and 1999, concentrations of Gyrodinium cf. aureolum rose by four orders of magnitude to over one million cells per litre in Donegal Bay(northwestern Ireland) in less than 10days. The rapid development of these populations was linked to advection resulting from unfavourable wind-forcing of the Irish Coastal Current (ICG) which runs northwards along the western Irish coast. Current measurements showed that after a particular sequence of changes in wind direction phytoplankton populations could be rapidly advected from areas of slack circulation on the shelf via the ICC into aquaculturally sensitive coastal zones such as Donegal Bay. The model presented is similar to one already demonstrated for the occurrence of toxic events in the bays of southwestern Ireland. Other historical harmful events along the west and northwest coasts relating to substantial losses in both finfish and shellfish culture could also be explained using the model. These include the G. aureolum bloom of 1992, the Prorocentrum balticum bloom in 1997.
Molecular methods for monitoring harmful algal bloom speciesShellfish production can be adversely affected by the presence of harmful microalgae (HABs). Toxins produced by Dinophysis, Alexandrium and Pseudo-nitzschia species can accumulate in shellfish and have the potential to cause serious human illness. In order to satisfy EU legislative requirements pertaining to the production and export of shellfish (EC Hygiene Regulations 2004, No. 853/2004 and No. 854/2004, which replaced the EU Shellfish Hygiene Directive 91/492/EEC in January 2006), monitoring the presence of harmful algal species and biotoxins in coastal waters is performed by EU member states. Routine microscopic monitoring methods are unable to identify certain toxic species, in particular, Alexandrium and Pseudo-nitzschia spp. Electron microscopy is required for species identification and this technique cannot be integrated into a routine monitoring programme. Molecular techniques utilise unique sequence signatures within microorganism genomes for species specific identification. Molecular methods applied for the identification and quantification of HAB species include Fluorescent in-situ hybridisation (FISH) and in-vitro amplification based methods, in particular, real-time PCR.
Report on the incidence and implications of phytoplankton blooms on the East Coast and particularly Wexford Harbour, Summer 1984The Fisheries Research Centre had a number of reports of discoloured water between Brittas Bay Co. Wicklow and Wexford Harbour and south to Kilmore Quay. Samples of water received from Dr. David Jeffrey, Department of Botany TCD, collected from Penny-come-quick beach, co. Wicklow on June 17th and examined by Tom Dunne in the Laboratory contained dense colonies of Phaeocystis pouchetii - a microscopic algae. Subsequent samples collected by Miss Ann Kiley, Wexford County Council, traced the extent of the bloom as far south as Neamstown near Kilmore Quay. A sample taken at Cullenstown west of Kilmore Quay was clear. Also associated with this bloom were large numbers of needlelike diatoms (Nitzschia spp. More seriously, blooms of another microscopic alga (Prorocentrum minimum) began to develop in early July during the later phase of the Phaeocystis bloom.