Plankton Multiproxy Analyses in the Northern Patagonian Shelf, Argentina: Community Structure, Phycotoxins, and Characterization of Toxic Alexandrium Strains

Abstract

The extensive Argentine continental shelf supports high plankton productivity and fish catches. In particular, El Rincón coastal area and the adjacent shelf fronts (38.5-42 • S, 58.5-62 • W) comprise diverse habitats and hold species of economic and ecological value. So far, studies of the microbial community present at the base of the food web remain scarce. Here, we describe the late winter plankton (5-200 µm) structure in terms of abundance, biomass, species composition, functional groups, and phycotoxin profiles in surface waters of El Rincón in September 2015. Diatoms are the most abundant and the largest contributors to carbon biomass at most stations. They dominated the coastal and inner-shelf (depths <50 m), while dinoflagellates and small flagellates (<15 µm) dominated offshore at the middle-shelf waters (depth ∼100 m). In addition, large (>20 µm) heterotrophic protists such as various ciliates and dinoflagellates species were more abundant offshore. Scanning of phycotoxins disclosed that paralytic shellfish poisoning (PSP) toxins were dominated by gonyautoxins-1/4 (GTX1/4), whereas lipophilic toxins were detected in low abundance, for example, domoic acid (DA). However, a bloom of Pseudo-nitzschia spp. (up to 3.6 × 10 5 cells L −1) was detected at inner-shelf stations. Pectenotoxin-2 (PTX-2) and 13-desmethyl spirolide C (SPX-1) were the most abundant in the field. The PTX-2 cooccurred with Dinophysis spp., mainly D. tripos, while SPX-1 dominated at middle-shelf stations, where cells of Alexandrium catenella (1 strain) and A. ostenfeldii (3 strains) were isolated. The quantitative PSP profiles of the Alexandrium strains differed significantly from the in situ profiles. Moreover, the three A. ostenfeldii strains produced PSP and additionally, five novel spirolides. Phylogenetic analyses of these newly isolated strains

Paralytic Toxin Producing Dinoflagellates in Latin America: Ecology and Physiology

“…One of the four isolates was identified as A. catenella/tamarense morphotype, but further morphological and phylogenetic analysis conformed to the description of A. catenella. Toxin profile from this one culture was dominated by C1/2 (72%), GTX1/4 (15%), NEO (9%), GTX2/3 (2%), and STX (2%) (Guinder et al, 2018).…”

“…The three isolates produced six spirolides, being SPX-1 the most abundant (83-93% of the total). The authors reported a novel analog, and named it spirolide M. The other four are still uncharacterized (named "compounds 1-4") (Guinder et al, 2018). The novel spirolides produced by the A. ostenfeldii isolates highlight the richness and structure variability of these toxins, and there are probably more analogs than previously thought, as often seen in toxin-producing plankton.…”

“…Phytoplankton net tows (NT) samples presented PST in low concentrations ranging between 114.4 ng NT −1 and 2593.8 ng NT −1 . Toxin profiles were dominated by GTX1/4; C1/2 and GTX2/3 were also detected (Guinder et al, 2018).…”

“…During the expedition carried out in 2015 by Guinder et al (2018), three of the isolates were identified as A. ostenfeldii. Cells from this species were isolated as mentioned (in 1/10 K medium and transferred to 1/2 K medium flasks and incubated at 15 • C and 50 µmol photons m −2 s −1 on a 16:8 LD photocycle).…”

“…Cells from this species were isolated as mentioned (in 1/10 K medium and transferred to 1/2 K medium flasks and incubated at 15 • C and 50 µmol photons m −2 s −1 on a 16:8 LD photocycle). These cultures were specifically analyzed for spiroimines and also for PSTs (Guinder et al, 2018).…”