Capturas de peces con diferentes artes de pesca asociadas a variables limnológicas de la laguna Gómez (Junín)

En este trabajo se presentan los resultados de un año de muestreos de peces con red de arrastre costero y trampa para peces y se relacionan sus capturas con variables limnológicas. La CPUE fue mayor con la trampa (255,34) que con los arrastres costeros (151,08) en cambio se capturaron menor cantidad de especies (12 y 15 respectivamente). La especie más abundante para los dos artes de pesca fue el porteño, 41,34% con el arrastre y 83,34% con la trampa. La composición de especies varió estacionalmente, y la riqueza y abundancia de peces aumentó significativamente con la temperatura del agua (r=0,66 y r=0,57 respectivamente; ambos p<0,05). Este patrón o tendencia estacional se observó con los arrastres pero no con la trampa.Facultad de Ciencias Naturales y Muse

Protist taxonomic and functional diversity in soil, freshwater and marine ecosystems

Protists dominate eukaryotic diversity and play key functional roles in all ecosystems, particularly by catalyzing carbon and nutrient cycling. To date, however, a comparative analysis of their taxonomic and functional diversity that compares the major ecosystems on Earth (soil, freshwater and marine systems) is missing. Here, we present a comparison of protist diversity based on standardized high throughput 18S rRNA gene sequencing of soil, freshwater and marine environmental DNA. Soil and freshwater protist communities were more similar to each other than to marine protist communities, with virtually no overlap of Operational Taxonomic Units (OTUs) between terrestrial and marine habitats. Soil protists showed higher γ diversity than aquatic samples. Differences in taxonomic composition of the communities led to changes in a functional diversity among ecosystems, as expressed in relative abundance of consumers, phototrophs and parasites. Phototrophs (eukaryotic algae) dominated freshwater systems (49% of the sequences) and consumers soil and marine ecosystems (59% and 48%, respectively). The individual functional groups were composed of ecosystem- specific taxonomic groups. Parasites were equally common in all ecosystems, yet, terrestrial systems hosted more OTUs assigned to parasites of macro-organisms while aquatic systems contained mostly microbial parasitoids. Together, we show biogeographic patterns of protist diversity across major ecosystems on Earth, preparing the way for more focused studies that will help understanding the multiple roles of protists in the biosphere

Picoplankton abundance and cytometric group diversity along a trophic and latitudinal lake gradient

20 pages, 8 figures, 1 tableThe picoplankton (PP) is responsible for major ecosystem functions in most aquatic environments. However, not much is known about the factors that regulate its total abundance and community structure. Using flow cytometry (FC) to detect particles based on their pigments and nucleic-acid content, we described and quantified the photosynthetic picoplankton (PPP) and the heterotrophic bacterioplankton (HB) populations (or groups) composing PP in 32 water bodies located along a trophic and latitudinal gradient in the Argentinean Patagonia to determine flow-cytometrically defined community structures. We set out to identify the environmental variables regulating total PP abundance, group structure and cytometric diversity. We identified a total of 28 different cytometric populations within the HB, 14 of phycoerythrin (PE)-rich picocyanobacteria (Pcy), 8 of phycocyanin (PC)-rich Pcy, and 41 of picoeukaryotes (Peuk) in the different water bodies, with average 3.9 HB and 4.6 PPP groups per water body. We found a strong influence of environmental factors and a less marked effect of latitude on PP structure. HB and PPP abundances decreased towards higher latitudes but their cytometric diversity did not, whereas HB, PC-rich Pcy and Peuk abundances together with PPP diversities increased with higher values of chlorophyll a (chl a). The relative contribution of PE-rich Pcy to total Pcy decreased with chl a, whereas the relative contribution of PC-rich Pcy and the number of PC-rich cytometric populations increased with chl a values. Peuk prevailed over Pcy with increasing trophic status and light attenuation, whereas HB prevailed over PPP with increasing trophic statusThis work was funded by a grant of the Argentinean Funds for Technical and scientific Investigation (FONCYT, PICT 32732) and the Program ‘Luis Santaló’ of the National Research Council of Spain and the National Council of Scientific and Technical Research of Argentina (CSIC-CONICET, PROBA 2007AR0018). We thank Dr. Guillermo Tell, Dr. Rodrigo Sinistro, Dr. M. Laura Sánchez and Mr. Adrián Rua for their collaboration during the field campaigns, and Dr. Ramon Massana (ICM) for general supportPeer reviewe

In situ prey selection of mixotrophic and heterotrophic flagellates in Antarctic oligotrophic lakes: an analysis of the digestive vacuole content

12 pages, 4 figures, 3 tablesWe investigated the selective predation of mixotrophic and heterotrophic flagellates (MF and HF) on different heterotrophic prokaryote phylotypes (HPP; Bacteria + Archaea) living in natural assemblages from oligotrophic Antarctic lakes. In situ prey preference was analyzed for the first time on different mixotrophic taxa (Pseudopedinella sp., Ochromonas-like cells, Chrysophyceae >5 µm). The relative abundances of seven different HPP hybridized by CARD-FISH (catalyzed reporter deposition-fluorescent in situ hybridization) in natural community were compared with the proportions of hybridized cells inside digestive vacuoles. Our results showed some general trends to selectivity over some HPP. Alphaproteobacteria and Betaproteobacteria were the most abundant groups, and strikingly, a negative selection trend was detected in most samples by all bacterivorous protists. In contrast, for Actinobacteria a positive selection trend was observed in most samples, whereas Bacteroidetes seemed to be randomly preyed upon. Interestingly, similar prey preferences were observed in all bacterivorous flagellates. Our results suggest that phylogenetic affiliation determines part of the process of prey selection by protists in these lakes. Nevertheless, other features, such as cell size, morphology and the presence of the S-layer, might also significantly contribute to prey selectivity on the HPPThis study was financed by the Consejo Superior de Investigaciones Cientı´ficas – Consejo Nacional de Investigaciones Cientı´ficas y Te´cnicas (CSIC-CONICET) (Spain-Argentina) Project PROBA (2007 AR0018, CSIC), the Spanish Project MIXANTAR (REN 2002-11396-E/ANT) and the Argentinean projects CONICET-PIP 01301, FONCYT PICT 32732 and UNComahue 04/ B166. Marina Gerea and M. Romina Schiaffino were supported by CONICET fellowships. Irina Izaguirre, Claudia Queimalin˜os and Fernando Unrein are CONICET researchersPeer reviewe

Influence of geographic distance and local environmental factors in shaping small eukaryote community structure along a latitudinal gradient of lakes

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainSmall eukaryotes of pico and nanoplanktonic size (0.2-5 µm, hereafter named picoeukaryotes, Peuk) are responsible for numerous ecosystem functions and processes in most aquatic ecosystems. However, despite their recognized importance, the factors governing their community structure and biogeographical patterns are still poorly understood. We studied the latitudinal variation of Peuk in 40 freshwater bodies from Argentinean Patagonia (45°S) to Maritime Antarctica (63°S), to find out factors that influence Peuk community composition (PeukCC). PeukCC was assessed by a 18S rRNA gene fingerprinting approach (denaturing gradient gel electrophoresis, DGGE). Diversity was also assessed for some of the water bodies with next-generation sequencing (HiSeq Illumina). The abundance of Peuk (both autotrophic and heterotrophic) decreased significantly towards higher latitudes and increased significantly with nutrient content. The number of dominant operational taxonomic units (OTUs) increased significantly with increasing trophic gradient. The regional dominant OTU number decreased faster than the local one toward higher latitudes. The partial canonical ordination analysis showed that not only local environmental factors, but also geographic distance exerted influence on PeukCC. Significant differences were found in PeukCC between Antarctic and Patagonian water bodiesPeer Reviewe

First freshwater member ever reported for the family Bathycoccaceae (Chlorophyta; Archaeplastida) from Argentinean Patagonia revealed by environmental DNA survey

We characterized molecularly the first freshwater member ever reported for the family Bathycoccaceae in Lake Musters (Argentinean Patagonia). Members of this family are extremely numerous and play a key ecological role in marine systems as primary producers. We cloned a fragment comprising the SSU rRNA gene + ITS region from environmental DNA using specific mamiellophyte primers. The unique SSU rRNA gene sequence obtained clustered robustly with Bathycoccus prasinos. Analysis of the two-dimensional structure of the ITS region showed the presence of a typical supplementary helix in the ITS-2 region, a synapomorphy of Bathycoccaceae, which confirmed further its phylogenetic placement. We finally discuss the possible causes for the presence of this organism in Lake Musters

Bacterial community structure in a latitudinal gradient of lakes: the roles of spatial versus environmental factors

19 pages, 5 figures, 3 tables1. We analysed the latitudinal variation of bacterioplankton in 45 freshwater environments (lakes, shallow lakes and ponds) across a transect of more than 2100 km stretching from Argentinean Patagonia (45°S) to Maritime Antarctica (63°S), to determine the factors that mainly determine bacterioplankton community structure. 2. Bacterioplankton community composition (BCC) was assessed by a fingerprinting method (denaturing gradient gel electrophoresis) followed by band sequencing, whereas the abundances of total bacteria and picocyanobacteria were estimated by epifluorescence microscopy. 3. Bacterioplankton community composition was controlled by a combination of spatial (latitude and longitude) and environmental [e.g. phosphate, light diffuse attenuation coefficient (Kd) and dissolved organic carbon] factors. Total bacterioplankton abundance declined with latitude. A multiple regression analysis showed that phosphate, Kd and latitude had significant effects on total bacterioplankton abundance. 4. Of 76 operational taxonomic units identified in the studied lakes, 45 were shared between Patagonian and Antarctic water bodies, 28 were present only in Patagonian lakes and three were restricted to the Antarctic lakes. Significant differences were found in BCC between Patagonia and Antarctica. Among the sequences, 54% were similar (>97% sequence similarity) to others reported from cold habitats elsewhere on the planet (glaciers, high mountain lakes, Arctic). 5. Our results provide new evidence that supports the hypotheses of biogeographic patterns of bacterial assemblages and suggest that both spatial and environmental factors control bacterioplankton community structureThe Antarctic expeditions were supported by the ‘Instituto Anta´rtico Argentino (DNA)’ in the framework of a cooperative project between this institution, UBA and ICM-CSIC. This work was financed by the Argentinean Funds for Technical and Scientific Investigation (FONCYT, PICT 32732), the Spanish Project MIXANTAR (REN 2002-11396-E ⁄ANT) and the CSICCONICET joint project PROBA (2007AR0018, CSIC)Peer reviewe

Geographical distance and local environmental conditions drive the genetic population structure of a freshwater microalga (Bathycoccaceae; Chlorophyta) in Patagonian lakes

The patterns and mechanisms underlying the genetic structure of microbial populations remain unresolved. Herein we investigated the role played by two non-mutually exclusive models (i.e. isolation by distance and isolation by environment) in shaping the genetic structure of lacustrine populations of a microalga (a freshwater Bathycoccaceae) in the Argentinean Patagonia. To our knowledge, this was the first study to investigate the genetic population structure in a South American microorganism. Population-level analyses based on ITS1–5.8S-ITS2 sequences revealed high levels of nucleotide and haplotype diversity within and among populations. Fixation index and a spatially explicit Bayesian analysis confirmed the occurrence of genetically distinct microalga populations in Patagonia. Isolation by distance and isolation by environment accounted for 38.5% and 17.7% of the genetic structure observed, respectively, whereas together these models accounted for 41% of the genetic differentiation. While our results highlighted isolation by distance and isolation by environment as important mechanisms in driving the genetic population structure of the microalga studied, none of these models (either alone or together) could explain the entire genetic differentiation observed. The unexplained variation in the genetic differentiation observed could be the result of founder events combined with rapid local adaptations, as proposed by the monopolisation hypothesis.This study was partially funded by grants of the FonCyT–Argentina (PICT 32732 and 0794) and CONICET–Argentina (PIP 498). LDF was supported by CONICYT–Chile (doctoral grants N° 21110037 and 78130011); Universidad Bernardo O’Higgins (Proyecto interno VRIP N° 170201); Programa de Doctorado en Sistemática y Biodiversidad y la Dirección de Postgrado de la Universidad de Concepción (mobility grant); and the University of Neuchâtel (mobility grant, IDPOB). EL was supported by Swiss National Fund grant SNF 31003A_163254

Grazing rates of protists in wetlands under contrasting light conditions due to floating plants

12 pages, 3 figures, 2 tablesWe examined the effect of light attenuation, due to floating plants, on the community structure of the main phagotrophic protists and their grazing rates in a wetland in the Lower Paraná Basin. Ingestion experiments (winter and summer) were conducted at 2 sites in the same shallow lake that had contrasting light scenarios: open waters (light) and under profuse macrophyte coverage (dark: light attenuation ~97%). We compared the rates at which protists ingested 3 types of tracer prey: fluorescently labelled heterotrophic bacteria (FLB), picocyanobacteria (FLC) and picoeukaryotic algae (FLA). Light influenced both the structure of the microbial communities and the protistan grazing rates. Heterotrophic flagellates (HF) were more abundant under the macrophytes, whereas mixotrophic algae (cryptophytes) and autotrophic and heterotrophic picoplankton populations attained higher abundances in open waters. Specific grazing rates (SGRs) of mixotrophs on heterotrophic bacteria (HB) were higher in the light (7.9 to 15.5 prey cells grazer−1 h−1), than in darkness (0.1 to 5.1 prey cells grazer−1 h−1); the same trend was observed on picocyanobacteria (Pcy) (1.1 and 0.2 prey cells grazer−1 h−1, light and dark). SGRs of HF were 1.0 to 7.3 cells grazer−1 h−1 (on HB) and 0.01 to 1.8 prey cells grazer−1 h−1 (on Pcy), with highest values in summer and no pattern in relation to light. SGRs of ciliates were higher in summer and in darkness. Clearance rates (CR) on Pcy were higher than on HB, for both HF and mixotrophic algae. In winter, cryptophytes contributed up to 93% of the microbial grazing in the light, whereas HF were more important in darkness; in summer, bacterivory was dominated by heterotrophs in both light scenarios. Our experimental results highlight the importance of light conditions in structuring bacterial grazing by protistsThis study was supported by the joint Project PROBA CSIC-CONICET (2007 AR0018, CSIC—Santaló Res. 1606/08 CONICET), and by a grant from the Agencia Nacional de Promoción Científica y Tecnológica (PICT 2006/536)Peer reviewe

Comparative analysis of bacterioplankton assemblages from maritime Antarctic freshwater lakes with contrasting trophic status

14 pages, 5 tablesThe bacterioplankton assemblages of eight maritime Antarctic lakes with a wide range of trophic status and geographic span (six lakes from Hope Bay, Antarctic Peninsula and two from Potter Peninsula, King George Island) were described using denaturing gradient gel electrophoresis and band sequencing during two consecutive austral summers (2003–2004). Analyses of the gels identi- Wed a total of 230 bands spread across 57 diVerent positions. Among those bands, 14 were shared between lakes from Hope Bay and Potter Peninsula, 17 were observed only in particular lakes, and 17 were registered both years in the same lake. We successfully reampliWed and sequenced 43 bands located in 36 diVerent positions belonging to Bacteroidetes, Actinobacteria, Betaproteobacteria and Cyanobacteria. The closest matches for 63% of the sequenced bands were from Antarctic or from other cold environment clones and sequences already in the databases, suggesting the widespread dominance of microbial communities adapted to cold habitats. The results of the multivariate analyses (Cluster Analysis and CCA) indicated that the nutrient status of the lake inXuences the bacterioplankton assemblagesThe Antarctic expeditions were supported by the “Instituto Antártico Argentino (DNA)”, in the framework of a cooperative project between this institution, UBA and ICM-CSIC. This work was Wnanced by grants of the Argentinean Funds for Technical and ScientiWc Investigation (FONCYT, PICT 04440 and PICT 32732), and by the Spanish projects MIXANTAR (REN2002-11396 E/ANT) and MICRODIFF (DGICYT REN2001-2120/MAR) grant SB2001-0166 from the Spanish MECyD. We wish to thank the members of the Esperanza Station for the logistic support, P. Rodriguez and E. Moreno-Díaz for their assistance with the Weld work, and Dr. Ramon Massana for general support. We also thank the reviewers for their valuable suggestions on the manuscriptPeer reviewe