IDENTIFICATION AND TOXICITY OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE) IN SCOTTISH WATERS¹

Abstract

Contamination of shellfish with paralytic shellfish poisoning (PSP) toxins produced by Alexandrium species poses a potential threat to the sustainability of the Scottish aquaculture industry. Routine LM analysis of water samples from around the Scottish coast has previously identified Alexandrium (Dinophyceae) as a regular part of the spring and summer phytoplankton communities in Scottish coastal waters. In this study, Alexandrium tamarense (M. Lebour) Balech isolated from sediment and water samples was established in laboratory culture. Species identification of these isolates was confirmed using thecal plate dissections and by molecular characterization based on their LSU and, in some cases, ITS rDNA sequence. Molecular characterization and phylogenetic analysis showed the presence of two ribotypes of A. tamarense: Group I (North American ribotype) and Group III (Western European ribotype). Assessment of PSP toxin production using hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) showed that A. tamarense Group I produced a complex array of toxins (∼2,000 fg STX equivalents · cell(-1) ) with the major toxins being C2, neosaxitoxin (NEO), saxitoxin (STX), gonyautoxin-4 (GTX-4), and GTX-3, while A. tamarense Group III did not produce toxins. Historically, it was considered that all Alexandrium species occurring in Scottish waters produce potent PSP toxins. This study has highlighted the presence of both PSP toxin-producing and benign species of A. tamarense and questions the ecological significance of this finding.

Distribution, diversity and toxin composition of the genusAlexandrium(Dinophyceae) in Scottish waters

“…ac.uk and Tees in the north-east of England (Lewis et al, 1995). Previous investigations into species diversity identified A. tamarense (Group I, as defined by Lilly et al, 2007), A. tamutum, A. minutum and A. ostenfeldii in this east coast region (Medlin et al, 1998;Higman et al, 2001;John et al, 2003;Alpermann et al, 2008;Collins et al, 2009). Until recently, little investigation into Alexandrium diversity on the west coast had been undertaken with only A. tamarense (Group I) reported from one site (Higman et al, 2001).…”

Individual-based modelling of the development and transport of a Karenia mikimotoi bloom on the North-west European continental shelf

“…Most research effort in the region has concentrated on biotoxin producing species of Alexandrium (Collins et al, 2009;Touzet et al 2010;Eckford-Soper et al, 2013), Pseudo-nitzschia (Fehling et al, 2004a(Fehling et al, , 2005clusters of organisms. The particles are typically imbued with aspects of the organism's biology (e.g.…”

Identification and quantification of toxic and nontoxic strains of the harmful dinoflagellate Alexandrium tamarense using fluorescence in situ hybridization and flow cytometry

“…The highly toxic Group I A. tamarense ribotype has historically been thought to dominate in Scottish waters (Bresnan et al 2008). More recently, it has been shown that the morphologically identical nontoxin-producing Group III ribotype, which had previously only been identified in more southerly waters, can now co-occur with the toxic strain in Scottish waters (Collins et al 2009;Brown et al 2010;Touzet et al 2010;Töbe et al 2013). This makes it impossible to use A. tamarense abundance as a robust early warning of subsequent shellfish toxicity.…”

“…Cell fixation is required to allow sample transport before analysis. However, some key identification features are obscured by Lugol's solution, which is used in almost all regulatory monitoring (Collins et al 2009), identification, and enumeration of Alexandrium, even to genus level, is therefore a skilled task. Lugol's fixed Alexandrium is often confused with other benign genera including Scrippsiella and manual manipulation of individual cells with a pin is often required to allow their identification.…”

“…Identification of Alexandrium cells to species level using light microscopy is more difficult still (Collins et al 2009). Identification relies on the observation of a number of morphological features, such as cell size, thecal plate, the size and shape of the apical pore plates, sulcal list, posterior sulcal plate and the presence or absence and position of the posterior attachment pores (Hosoi-Tanabe and Sako 2006).…”