Discrimination of the toxigenic dinoflagellatesAlexandrium tamarenseandA. ostenfeldiiin co-occurring natural populations from Scottish coastal waters

Abstract

Blooms of the toxic dinoflagellate Alexandrium tamarense (Lebour) Balech, a known producer of potent neurotoxins associated with paralytic shellfish poisoning (PSP), are common annual events along the Scottish east coast. The cooccurrence of a second Alexandrium species, A. ostenfeldii (Paulsen) Balech & Tangen is reported in this study from waters of the Scottish east coast. The latter species has been suspected to be an alternative source of PSP toxins in northern Europe. Recent identification of toxic macrocyclic imines known as spirolides in A. ostenfeldii indicates a potential new challenge for monitoring toxic Alexandrium species and their respective toxins in natural populations. In mixed phytoplankton assemblages, A/exandrium species are difficult to discriminate accurately by convention~llight microscopy.Species-specific rRNA probes based upon 18S and 28S ribosomal DNA sequences were developed for A. ostenfeldii and tested by dot-blot and fluorescence in situ hybridization (FISH) techniques. Hybridization patterns of A. ostenfeldii probes for cultured A/exandrium isolates, and cells from field populations from the Scottish east coast, were compared with those of rONA probes fOf A. tamarense and a universal dinoflagellate probe. A/exandrium cell numbers in field samples determined by whole-cell in situ hybridization were much lower than those determined by optical microscopy with the Utermohl-~ethod involving sedimentation chambers, but the results were highly correlated (e.g. r 2 =0.94; n =6 for A. tamarense).Determination of spirolides and PSP toxins by instrumental analysis on board ship demonstrated the presence of both toxin groups in plankton assemblages collected from surface waters near the Orkney Islands, and confirmed the association of A. ostenfeldii with spirolides in northern Europe. These results show that rRNA probes for A. tamarense and A. ostenfe/dii are useful, albeit only semi-quantitative, tools to detect and discriminate these species in field studies.

Detection of the bloom-forming cold-water dinoflagellate Biecheleria baltica in the Baltic Sea using LSU rRNA probes

“…John et al (2003) also reported a substantial cell loss after hybridization of field samples. The major reasons for the low detection efficiency are most likely the screening and concentration processes for FISH involving several sieving and washing steps, resulting in considerable cell loss compared to the processing of samples for the Utermöhl method.…”

“…humic substances, might also have influenced the outcome by inhibiting the molecular procedure. In addition to this, cells in natural samples may sometimes be clumped or obscured by detrital particles, making the detection of target cells difficult (Scholin et al 1999, John et al 2003.…”

“…Fluorescence in situ hybridization (FISH) coupled with ribosomal RNA (rRNA) probes is one of the most popular molecular methods utilized to detect dinoflagellates and has been successfully applied in the detection and quantification of several species (Litaker & Tester 2002, John et al 2003, Touzet & Raine 2007. Many studies of harmful algal bloom species have applied FISH analyses (e.g.…”

Characterization of multiple isolates from an Alexandrium ostenfeldii bloom in The Netherlands

“…A. ostenfeldii is historically seen as background bloomer (Cembella et al, 2000;John et al, 2003), however, dense A. ostenfeldii blooms have been reported recently in the Narragansett Bay and the New River Estuary in the U.S. east coast (Borkman et al, 2012;Tomas et al, 2012), the Baltic Sea coast of Finland (Hakanen et al, 2012), along the Adriatic coast of Italy (Ciminiello et al, 2006), and recently in a creek of the Oosterschelde estuary in the Southwest of The Netherlands (Burson et al, 2014). This Oosterschelde estuary is a shallow, macrotidal and mesotrophic estuary with large stocks of mussels, oysters, and cockles ( Fig.…”

A roadmap for hazard monitoring and risk assessment of marine biotoxins on the basis of chemical and biological test systems

“…there is evidence that CIP toxins and their producers also are found in europe, the USA, and North Africa (Aasen et al, 2005a;Bire et al, 2002;Cembella and Krock, 2008;Ciminiello et al, 2006;John et al, 2003;MacKinnon et al, 2006;Marrouchi et al, 2010;Rundberget et al, 2011;touzet et al, 2008;Villar Gonzalez et al, 2006), and their presence, along with PSP to CTX also primarily in predatory fish consumed by humans (snapper, barracuda, amber jack and moray eel), and more investigations should be conducted on the role on Mtx in human intoxication.…”