Spatial patterns in picoplankton communities along a cascade reservoir system (Limay River, Patagonia) in relation to environmental factors

BERNAL CAROLINA; LU LUNHUI; SABIO Y GARCÍA CARMEN ALEJANDRA; SANCHÉZ MARÍA LAURA; VERA MARÍA SOLANGE; SINISTRO RODRIGO; PORCEL SOL; LI ZHE; IZAGUIRRE IRINA

Congreso; ISME VIRTUAL MICROBIAL ECOLOGY SUMMIT; 2020

Picoplanktonic abundances and diversity wereanalyzed along a system of three cascade oligo-mesotrophicreservoirs (Alicura, Piedra del Águilaand Ramos Mexía) of the Limay River, and anaffluent (Collon Cura River-CC). Eleven samplingsites were established encompassing lentic and loticsections. The main limnological variables weremeasured at each sampling site. The abundance ofautotrophic and heterotrophic picoplankton wasobtained using flow cytometry, andbacterioplankton diversity was assessed by IlluminaMiSeq. Total picoplankton abundance showed anincreasing trend downstream in the overall system,with local decreases at lotic stretches. In all sitesheterotrophic bacteria (HB) exceeded autotrophicpicoplankton (APP) in abundance, and the latterwere dominated by phycoerithrin-richpicocyanobacteria (PE-rich Pcy). One picoeukaryote(Peuk) and two PE-rich Pcy cytometric populationswere mainly observed, although Ramos MexíaReservoir displayed an additional Peuk cytometricpopulation. Most sites showed dominance of lownucleic acid-containing bacteria (LNA) over highnucleic acid-containing bacteria (HNA). A total of1319 OTUs were obtained by Illumina MiSeq.Actinobacteria dominated in all sites except in CC,where Bacteroidetes prevailed. OTU richnessdisplayed a spatial pattern, with higher values atlotic sites and lower ones at lentic sites, whereasequitability showed the inverse pattern. CanonicalCorrespondence Analysis (CCA) and Non MetricMulti-Dimensional Scaling were performed basedon bacterial OTU diversity; both revealed a clearspatial pattern, where samples of each reservoirappeared closer to each other. CCA showed that themain variables associated to this pattern wereturbidity, DOC, Chlorophyll a and conductivity, allincreasing downstream. Despite a slight increase introphic status at Ramos Mexía Reservoir, overallpicoplankton community structure was typical ofoligotrophic environments.