Diversity and toxicity of the diatom Pseudo-nitzschia Peragallo in the Gulf of Maine, Northwestern Atlantic Ocean

Abstract

Multiple species in the toxic marine diatom genus Pseudo-nitzschia have been identified in the Northwestern Atlantic region encompassing the Gulf of Maine (GOM), including the Bay of Fundy (BOF). To gain further knowledge of the taxonomic composition and toxicity of species in this region, Pseudo-nitzschia isolates (n=146) were isolated from samples collected during research cruises that provided broad spatial coverage across the GOM and the southern New England shelf, herein referred to as the GOM region, during 2007-2008. Isolates, and cells in field material collected at 38 stations, were identified using electron microscopy (EM). Eight species (P. americana, P. fraudulenta, P. subpacifica, P. heimii, P. pungens, P. seriata, P. delicatissima and P. turgidula), and a novel form, Pseudo-nitzschia sp. GOM, were identified. Species identity was confirmed by sequencing the large subunit of the ribosomal rDNA (28S) and the internal transcribed spacer 2 (ITS2) for six species (36 isolates). Phylogenetic analyses (including neighbor joining, maximum parsimony, and maximum likelihood estimates and ITS2 secondary structure analysis) and morphometric data supported the placement of P. sp. GOM in a novel clade that includes morphologically and genetically similar isolates from Australia and Spain and is genetically most similar to P. pseudodelicatissima and P. cuspidata. Seven species (46 isolates) were grown in nutrient-replete batch culture and aliquots consisting of cells and growth medium were screened by Biosense ASP ELISA to measure total domoic acid (DA) produced (intracellular + extracellular); P. americana and P. heimii were excluded from all toxin analyses as they did not persist in culture long enough for testing. All 46 isolates screened produced DA in culture and total DA varied among species (e.g., 0.04 to 320 ng ml-1 for P. pungens and P. sp. GOM isolates, respectively) and among isolates of the same species (e.g., 0.24 – 320 ng ml-1 for P. sp. GOM). The 15 most toxic isolates corresponded to P. seriata, P. sp. GOM and P. pungens, and fg DA cell-1 was determined for whole cultures (cells and medium) using ELISA and liquid chromatography (LC) with fluorescence detection (FLD); for seven isolates, toxin levels were also estimated using LC - with mass spectrometry and ultraviolet absorbance detection. Pseudo-nitzschia seriata was the most toxic species (up to 3,500 fg cell-1) and was observed in the GOM region during all cruises (i.e., during the months of April, May, June and October). Pseudo-nitzschia sp. GOM, observed only during September and October 2007, was less toxic (19 – 380 fg cell-1) than P. seriata but more toxic than P. pungens var. pungens (0. 4 fg cell-1). Quantitation of DA indicated that concentrations measured by LC and ELISA were positively and significantly correlated; the lower detection limit of the ELISA permitted quantification of toxicity in isolates that were found to be nontoxic with LC methods. The confirmation of at least seven toxic species and the broad spatial and temporal dis...

Pseudo-nitzschia fukuyoi (Bacillariophyceae), a domoic acid-producing species from Nha Phu Bay, Khanh Hoa Province, Vietnam

“…To date, 17 species of Pseudo-nitzschia have been shown to be toxigenic [5,8,19,20]. In this study, LC-MS/ MS analysis confirmed the presence of DA in cultured P. fukuyoi from Vietnamese waters.…”

High diversity of Pseudo‐nitzschia along the northern coast of Sarawak (Malaysian Borneo), with descriptions of P. bipertita sp. nov. and P. limii sp. nov. (Bacillariophyceae)

“…Its transapical axis is narrower (2.6–4.2 μm) compared to P. fraudulenta (Cleve) Hasle and P. subfraudulenta (both >4.1 μm; Moschandreou and Nikolaidis , Fernandes et al. , this study).…”

Molecular characterization of Pseudo-nitzschia community structure and species ecology in a hydrographically complex estuarine system (Puget Sound, Washington, USA)

“…Pseudo-nitzschia australis or P. cuspidata typically dominate toxic Pseudo-nitzschia blooms in Puget Sound and WA coastal waters (Trainer et al 2007), although regional isolates of P. multiseries produce high DA levels in culture (Guannel et al 2011) and P. seriata isolates elsewhere are toxic (Fehling et al 2004, Fernandes et al 2014). Our cruise samples from June 2006 were collected nine months after separate toxic blooms of P. cuspidata and P. australis in Puget Sound resulted in shellfish harvest closures (Trainer et al 2007).…”

“…Interest in Pseudo-nitzschia taxonomy and ecology has increased over the past few decades largely because at least 14 species are capable of producing the neurotoxin, domoic acid (DA). Toxin production among these species varies over ~9 orders of magnitude (Trainer et al 2012, Fernandes et al 2014). DA accumulates in filter feeding shellfish and planktivorous fish and can cause Domoic Acid Poisoning in marine vertebrates that feed on contaminated prey (Lefebvre et al 2010).…”