Summer dynamics of Alexandrium ostenfeldii (Dinophyceae) and spirolide toxins in Cork Harbour, Ireland

Abstract

Proliferations of toxic Alexandrium spp. have adversely affected the shellfish aquaculture industry worldwide. A. ostenfeldii can produce several biotoxins, including the recently characterised fast-acting toxins spirolides (SPX). A dual labelling fluorescent in situ hybridisation (FISH) assay was developed for discriminating simultaneously between the closely related taxa A. ostenfeldii and A. peruvianum. Surveys were undertaken throughout the summers of 2006, 2007 and 2008 in Cork Harbour, Ireland, where a mixed community of Alexandrium spp. develops annually. A. peruvianum was not detected but the presence of A. ostenfeldii was confirmed by FISH and morphological analysis. The species never reached high concentrations (max. ~200 cells l -1 ) and contributed on average to only 0.4% of the Alexandrium community, usually dominated by A. minutum and A. tamarense (Group III). Although cell concentrations were several orders of magnitude lower, the dynamics of A. ostenfeldii were similar to those of other Alexandrium spp. during the 3 consecutive summers, suggesting a common response to environmental forcing. Analytical chemistry performed on extracts from passive solid-phase adsorption samplers identified lipophilic toxins dominated by okadaic acid, but also 13-desmethyl SPX C and 20-methyl SPX G, with dynamics generally congruent with those of A. ostenfeldii. The passive samplers enabled the quantification of background toxin levels at very low A. ostenfeldii concentrations, showing potential for forecasting of toxic events. The ability to quantify toxic A. ostenfeldii cells within high density microalgal populations of morphologically similar species makes the dual FISH assay valuable for phytoplankton monitoring programs and future biogeographical and population dynamics studies.KEY WORDS: Harmful algal bloom · HAB · Alexandrium · Solid-phase adsorption toxin tracking · SPATT · Spirolides · Fluorescent in situ hybridisation · FISH · Cork Harbour Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 425: [21][22][23][24][25][26][27][28][29][30][31][32][33] 2011 specific geographic areas (Balech 1995). Members of the A. tamarense species complex and the A. minutum clade have frequently been involved in shellfish contamination with levels of neurotoxins unsafe for human consumption (FAO 2004). The corresponding human intoxication syndrome, known as paralytic shellfish poisoning (PSP), is caused by structural derivatives of the alkaloid compound saxitoxin. Spirolides (SPXs) are lipophilic marine biotoxins that were discovered more recently. These macrocyclic imines were first characterised from A. ostenfeldii cells following monitoring of shellfish in Canada (Cembella et al. 2000). SPXs are potent fastacting toxins that interact with muscarinic receptors in nerve cells and cause acute neurotoxic activity in mice (40 and 1000 µg kg -1 for intra-peritoneal injection and oral administration, respectively) (Richard et al. 2001). SPX-producing strains of A. ostenf...

Phylogenetic relationships, morphological variation, and toxin patterns in theAlexandrium ostenfeldii(Dinophyceae) complex: implications for species boundaries and identities

“…Balech (1995) similarly reported a mix of straight and curved margins in material from North America; however, he considered this an exception. The s.a. plate, which has commonly been considered the most important feature for the delineation of A. peruvianum from A. ostenfeldii (Balech 1995, Touzet et al 2011, was also found to be problematic. Most of the A. peruvianum isolates contained significant amounts (20%-30%) of the doorlatch shaped s.a. plates typical for A. ostenfeldii.…”

“…Consistent assignment has furthermore been complicated by the lack of consensus regarding the weight of the different diagnostic features: while some investigators have given priority to the s.a. shape , others considered the anterior 1′ margin most important (MacKenzie et al 1996, Kremp et al 2009). In addition to these inconsistencies, morphogenetic identification is not simple either, despite the availability of extensive sequence data and recognition of specific genetic signatures (Touzet et al 2011). GenBank contains numerous identical sequences from isolates assigned to A. ostenfeldii and A. peruvianum.…”

“…Both A. ostenfeldii and A. peruvianum are now regularly encountered in field surveys and monitoring programs worldwide (MacKenzie et al 2004, Gribble et al 2005, Nagai et al 2010, Brown et al 2010, Touzet et al 2011. Dense blooms associated with toxins have been reported from Peru (Sanchez et al 2004), the estuaries of the U.S. east coast (Borkman et al 2012) and the Baltic Sea (Witek 2004).…”

An evaluation of the applicability of microarrays for monitoring toxic algae in Irish coastal waters

“…However although it is known to occur in Cork Harbour, it appears to exist in much lower numbers then either A. minutum or A. tamarense (WE) (Touzet et al, 2011). A.…”

Molecular Techniques to Estimate Biodiversity with Case Studies from the Marine Phytoplankton

“…Probes are available for detecting toxic species of the marine pennate diatom genus Pseudo-nitzschia that are associated with domoic acid in natural samples (e.g., Scholin et al, 1996Scholin et al, & 1997 as well as for toxic species in the important bloom forming microalgae, Chrysochromulina (Simon et al, 2000) and Prymnesium (Simon et al, 2000;Töbe et al, 2006) from marine and brackish environments. Probes targeting the different species of the toxigenic paralytic shellfish toxin (PSP) producing dinoflagellate genus Alexandrium include those detecting the North American Alexandrium tamarense ribotype (Miller and Scholin 1998;John et al, 2003), the toxic Temperate Asian ribotype (Hosoi-Tanabe and Sako 2005), the non-toxic Western European ribotype (John et al, 2005, Touzet et al 2008, the non-toxic Mediterranean species complex (John et al, 2005), A. minutum, the non-toxic co-occurring morphologically similar species A. andersoni in Irish coastal waters (Touzet and Raine 2007;Touzet et al 2008) and A. peruvianum (Touzet et al, 2011) and the spirolide producing taxa A. ostenfeldii (John et al, 2003, Touzet et al, 2011 All of these probes have been applied in field studies (John et al, 2005;Anderson et al, 2005). A set of FISH probes are also developed (John et al, in prep.…”