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The Marine Institute in Ireland carries out a national phytoplankton monitoring programme which extends back to the late 1980s. This includes a harmful algal blooms (HABs) monitoring service that warns producers and consumers of concentrations of toxic plankton in Irish coastal waters that could contaminate shellfish or cause fish deaths.
Cusack et al. (2001, 2002) summarized the objectives of the monitoring programme. This programme is primarily located along the Atlantic seaboard and Celtic Sea. Scientists working on this monitoring programme have developed an understanding of phytoplankton populations and dynamics around the Irish coastline, especially in relation to those that cause shellfish toxicity. Particular emphasis is put on the detection and enumeration of harmful species; however, the importance of phytoplankton as an indicator of water quality is also studied and is a key component of the European Water Framework.
Since 1990, data have been captured in a systematic manner and logged into an electronic database. Many of the sites were only analysed for toxic and harmful species, because this was the main purpose of the monitoring programme. In addition, however, there were a selected number of sites around the country analysed for total phytoplankton. Over the years, these sentinel sites changed periodically for a number of reasons, mainly the unavailability of persons to take regular samples. Therefore, in order to construct time-series for this report, it was decided to construct regional groups of all of the sentinel sites in the complete database, based on a principal component analysis of the dataset. This resulted in five groups of sentinel sites, which are presented in these maps and graphs as regional locations. Based on the data extracted and amalgamated from these regions, it is deemed to be a good representation of the phytoplankton flora for these regions. The number of sites used to construct each region varies from region to region, and also within each region over time as sites came and went.
Sites were sampled by a variety of methods, either surface samples, discrete Ruttner sampling bottles, or tube samplers. They were preserved on site with neutral Lugols iodine, and returned to the laboratory where 25 ml samples were settled for 24 h in Utermöhl chambers before analysis on an inverted microscope. Species were identified and enumerated and cell counts were expressed in cells l1.
Average sea surface temperatures for western and southern waters of Ireland range from 8 to 10°C in winter to 1417°C in summer (Lee and Ramster, 1981; Elliott, 1991), and temperatures tend to be several degrees higher compared with the eastern waters. This difference is the result of the entry of warm Atlantic water onto the western Irish Shelf. In winter, Irish coastal and shelf waters are vertically well mixed, with little difference in the surface-tobottom distribution of temperature within the water column. As the water column stratifies in summer, a surface-to-bottom temperature difference of up to 6°C is typical of waters along the Atlantic Shelf and Celtic Sea (Cooper, 1967; Raine and McMahon, 1998). Along the coast, turbulent tidal currents are sufficient to prevent establishment of stratification, and the water remains mixed throughout the year. The boundary between mixed and stratified waters in summer is marked by tidal fronts that influence the composition and density of phytoplankton community in these areas.
Further information on the sampling programme and results of individual locations can be accessed at the Marine Institutes HABs website ( target="habwin
Cusack, C., Chamberlain, T., Devilly, L., Clarke, D., and Silke, J. 2001. Summary of phytoplankton monitoring trends in 2001. Proceedings of the 2nd Irish Marine Biotoxin Science Workshop. Marine Institute, Galway, pp. 19-23.
Cusack, C., Chamberlain, T., Devilly, L., Clarke, D., and Silke, J. 2002. Review of phytoplankton and environmental monitoring 2002. Proceedings of the 3rd Irish Marine Biotoxin Science Workshop. Marine Institute, Galway.