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

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

Congreso; ISME Virtual Microbial Ecology Summit; 2020

Picoplanktonic abundances and diversity were analyzed alonga system of three cascade oligo-mesotrophic reservoirs (Alicura, Piedra delÁguila and Ramos Mexía) of the Limay River, and an affluent (Collon Cura River-CC).Eleven sampling sites were established encompassing lentic and lotic sections.The main limnological variables were measured at each sampling site. The abundanceof autotrophic and heterotrophic picoplankton was obtained using flow cytometry,and bacterioplankton diversity was assessed by Illumina MiSeq. Totalpicoplankton abundance showed an increasing trend downstream in the overallsystem, with local decreases at lotic stretches. In all sites heterotrophic bacteria(HB) abundance exceeded autotrophic picoplankton (APP), and these were dominatedby phycoerithrin-rich picocyanobacteria (PE-rich Pcy). One picoeukaryote (Peuk)and two PE-rich Pcy cytometric populations were mainly observed, although RamosMexía Reservoir displayed an additional Peuk cytometric population. Most sitesshowed dominance of low nucleic acid-containing bacteria (LNA) over highnucleic acid-containing bacteria (HNA). A total of 1319 OTUs were obtained byIllumina MiSeq. Actinobacteria dominated in all sites except in CC, whereBacteroidetes prevailed. OTU richness displayed a spatial pattern, with highervalues at lotic sites and lower ones at lentic sites, whereas equitability showedthe inverse pattern. Canonical Correspondence Analysis (CCA) and Non MetricMulti-Dimensional Scaling were performed based on bacterial OTU diversity; bothrevealed a clear spatial pattern, where samples of each reservoir appearedcloser to each other. CCA showed that the main variables associated to thispattern were turbidity, DOC, Chlorophyll a and conductivity, all increasingdownstream. Despite a slight increase in trophic status at Ramos MexíaReservoir, overall picoplankton community structure was typical of oligotrophicenvironments.