This study describes the spatial and temporal distribution of Dinophysis acuta Ehrenberg and D. acuminata Claparède et Lachmann in Irish waters for the period 1990 to 2004, demonstrating difference between the two species in annual distribution as well as differences in distribution between two localized areas, Bantry Bay on the southwest coast and Killary Harbour on the west coast. Further the relationship between this distribution and shellfish closures for these two important aquaculture areas is described, demonstrating a significant relationship between the occurrence of D. acuta and shellfish toxicity in Bantry Bay.This investigation was built on phytoplankton and toxicity records obtained from the Irish National Monitoring Database, covering the 1990-2004 and 1994-2004 period, respectively.
Furthermore, changes in the environmental parameters, west wind stress (WWS), sea surface temperature (SST) and the NAO winter index were investigated as well as the relationship between the parameters and their influence on the abundance of Dinophysis. Seasonal averages for WWS and SST were constructed from data obtained from the International Comprehensive Ocean Atmosphere Data Set (ICOADS), through the National Centre for Atmospheric Research, US, while seasonal averages for the NAO were constructed from data obtained from the Climatic Research Unit, University of East Anglia, Norwich, UK and Tim Osborn s climate data. An apparent increase in sea surface temperature in the 1990s (1991- 2000) compared to the long term average of the previous three decades is demonstrated, and changes in these parameters linked to the occurrence of D. acuta on the Irish coast investigated. A model describing the occurrence of D. acuta in Irish waters as a function of area, season and the NAO winter index (December March average) could only describe 52 % of the variation in the dataset, and can therefore not be used for predicting future D. acuta occurrences. A relationship between the March sea surface temperature and D. acuta in the southwest of Ireland, however, indicated a predictability of close to 80 %.
Water samples collected from the Oslofjord, Norway, in spring 2004 and 2005 as well as in summer 2005 were used for toxin and genetic analysis. Cells were collected onto filters and single cells were isolated using capillary isolation technique. Okadaic Acid (OA), Pectenotoxins-2 (PTX-2) and Yessotoxins (YTX) were detected in the majority of the analysed filters and correlation analysis demonstrated a stronger relationship between the amount of OA and D. acuminata than between OA and D. norvegica in the samples. D. acuta was not detected in any of the samples. PTX-2 was also detected in isolated cells of D. acuminata (11 pg per cell). Finally, the possibility of distinguishing toxic populations from non toxic using genetic signatures was investigated using single cell PCR (Polymerase chain reaction) and toxin analysis of capillary isolated single cells. Due to few Dinophysis sequences obtained, however, no conclusions could be drawn on this point.