Plankton multiproxy analyses in the Northern Patagonian Shelf, Argentina: community structure, phycotoxins and characterization of toxic Alexandrium strains.

GUINDER V. A.; TILLMANN U; KROCK B; DELGADO AL; KROHN T; JOHN E. GARZÓN CARDONA; METFIES K; LÓPEZ ABBATE M. C.; SILVA R; RUBÉN LARA

Frontiers in Marine Sicences

Frontiers

Año: 2018

2296-7745

The extensive Argentinecontinental shelf supports high plankton productivity and fish catches. Inparticular, El Rincón coastal area and the adjacent shelf fronts (38.5?42º S,58.5?62º W) comprise diverse habitats and hold species of economic andecological value. So far, studies of the microbial community at the base of thefood web remain scarce. Here we describe the late winter plankton (5-200 µm) structurein terms of abundance, biomass, species composition, functional groups and phycotoxinprofiles in surface waters of El Rincón in September 2015. Diatoms were the mostabundant and the largest contributors to carbon biomass at most stations. They dominatedin the coastal, inner-shelf (depths <50 m), while dinoflagellates and smallflagellates (<15 µm) dominated offshore at middle-shelf waters (depth ~100m). Likewise, large (>20 µm) heterotrophicprotists, such as various ciliates and dinoflagellates species were moreabundant offshore. Scanning of phycotoxins disclosed that paralytic shellfishpoisoning (PSP) toxins were dominated by gonyautoxins-1/4 (GTX1/4). Lipophilictoxins were detected in low abundance, e.g.domoic acid (DA), although a bloom of Pseudo-nitzschiaspp. (up to 3.6 x 105 cells L-1) was detected at inner-shelfstations. Pectenotoxin-2 (PTX-2) and 13-desmethyl spirolide C (SPX-1) were themost abundant in the field. PTX-2 co-occurred 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) wereisolated. 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, 5 novel spirolides. Phylogenetic analyses of these newly isolatedstrains from the South Atlantic revealed a new ribotype group suggesting a biogeographicaldistinction of the population. The plankton survey presented here contributeswith baseline knowledge to evaluate potential ecosystem changes and to track theglobal distribution of toxigenic species.