METABARCODING AND MICROSCOPY CHARACTERIZATION OF PLANKTONIC PROTIST ASSEMBLAGES FROM FRONTAL AREAS OF THE ARGENTINE SEA

ALMANDOZ, GASTÓN O.; SPRONG, P.; FABRO, E.; BARRERA, F.; MASCIONI, MARTINA; ANTONI, J.; FERRARIO, MARTHA E.; METFIES, K.

Jornada; XXXVIII JORNADAS ARGENTINAS DE BOTÁNICA; 2021

SAB

The Argentine Sea is worldwide recognized as ahighly productive area, with large phytoplanktonblooms occurring in spring-summer. Despite thewell-known importance of frontal areas for biomassaccumulation, phytoplankton diversity remain almostunexplored. Here we studied protist compositionduring January 2016 by 18S metabarcodingand microscopy in three tidal fronts located fromv43 to 55° S. Protist composition varied along latitudinaland inshore-offshore gradients. An assemblagelargely dominated by an OTU assigned to theprasinophyte species Pycnococcus provasolii wasobserved at Valdés front, where microscopy revealeda bloom of 11.6×106 cells L-1. A second assemblagemainly represented by OTUs assignedto picoplanktonic prasinophytes (Clade VIII) andPicochlorum sp. (Trebouxiophyceae), the diatomMinidiscus trioculatus and the dinoflagellate Gyrodiniumfusiforme was observed at Blanco Capefront, with increasing dinoflagellate abundance towardsstratified waters. Diatoms notably increasedat de los Estados Island front, mainly representedby an OTU assigned to Chaetoceros contortus,coinciding with an abundance of 2.0×105 cells L-1of Chaetoceros spp. Moreover, the presence ofcold-water species, such as Phaeocystis antarctica,Chaetoceros atlanticus, and Fragilariopsis kerguelensis,was detected off-shore. Our results suggesta strong influence of water masses and local hydrographicconditions on protist distribution.