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

Abstract

Alexandrium is detected throughout Scottish coastal waters on a near annual basis, and corresponding paralytic shellfish poisoning (PSP) toxins are found in Scottish shellfish. Previous studies at selected Scottish sites have shown diversity within the genus Alexandrium. In order to examine the distribution, diversity and toxicity of Alexandrium populations around the Scottish coast, historic cyst and cell data were compiled and cultures established from sediment and water samples. Historic data showed high cell densities of Alexandrium in Shetland, Orkney, the Western Isles and mainland east coast. Low abundances of Alexandrium cysts were observed along the west coast. Four species of Alexandrium (A. tamarense, A. ostenfeldii, A. minutum and A. tamutum) were established in laboratory culture and identified using morphological criteria. Sequencing of LSU rDNA from isolates of A. ostenfeldii, A. minutum and A. tamutum confirmed their identification and showed them to be similar to other European strains. Alexandrium tamarense, identified by morphological criteria, was observed to have a widespread distribution around the coast. Both toxin-and non toxin-producing strains of this species were isolated, suggesting the presence of A. tamarense Groups I and III. Alexandrium ostenfeldii was isolated from the east coast and Shetland Isles and was observed to produce both spirolide and PSP toxins. Alexandrium tamutum was identified from cultures isolated from Shetland and Orkney, the most northerly observation of this species to date. PSP toxins were not detected in isolates of A. minutum from the east coast and Orkney or of A. tamutum under the culture conditions used. This study has highlighted the diversity of Alexandrium in Scottish waters and reveals the requirement for temporal and regional studies on a species level in order to understand the variation in cell densities and PSP toxicity that is observed on an annual and decadal scale.

Molecular discrimination of toxic and non-toxicAlexandriumspecies (Dinophyta) in natural phytoplankton assemblages from the Scottish coast of the North Sea

“…Thus, while cells of additional Alexandrium species in the diverse plankton assemblage would have been counted by the Utermo¨hl method applied at the generic level, they would not have been included in the summed Alexandrium estimate by qPCR. A study by Brown et al (2010) reports on the occurrence of potentially PSP-toxigenic A. ostenfeldii in the region covered by our study and this species was also found along the Scottish east coast, albeit in low abundance, in an earlier field application of FISH probes (John et al, 2003a). If present in sufficient numbers, A. ostenfeldii could conceivably bias the fit between qPCR and toxin data.…”

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

“…Cork Harbour is one of several estuaries located along the Atlantic coastline of Europe that harbours PSP toxin-producing populations of Alexandrium sp. (Probert 1999, Hansen et al 2003, Franco et al 1994, Nascimento et al 2005, Touzet et al 2008b, Brown et al 2011. A. ostenfeldii concentrations were highest in the North Channel, similar to concentrations of A. minutum and A. tamarense, which co-occur annually in Cork Harbour (Touzet et al 2008b).…”

Bioactive compounds of marine dinoflagellate isolates from western Greenland and their phylogenetic association within the genus Alexandrium

“…These findings are surprising in the sense that the Alexandrium tamarense species complex typically produces high molar relative amounts of the N-sulfocarbamoyl B-and C-toxins in natural populations and cultured isolates from many regions of the world (Cembella, 1998), including the south Atlantic (Montoya et al, 2010), north Atlantic and North Sea (Brown et al, 2010), south Pacific (Contreras et al, 2012), and the northeastern (Gu et al, 2013a) and northwestern (Cembella et al, 1987) Pacific. This general pattern is also consistent within A. tamarense Group I ribotype strains from the western Arctic (Chukchi Sea), where the N-sulfocarbamoyl toxin C2 dominated, followed by STX and GTX2/ 3, with lesser amounts of GTX1/4 and NEO in decreasing relative molar ratios (Gu et al, 2013b).…”