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Santa Fe de la Vera Cruz, Argentina

Frau D.,Instituto Nacional Of Limnologia Inali | Molina F.R.,Instituto Nacional Of Limnologia Inali | Mayora G.,Instituto Nacional Of Limnologia Inali
Limnology | Year: 2016

The aims of this work were to analyse the feeding selectivity of L. fortunei in a natural assemblage of phytoplankton in a short-term microcosm experiment and to assess whether this selectivity is affected by the presence of Rotifera as a secondary, palatable feeding resource. This bivalve preferred Desmidiales, Chlorococcales, Euglenophyceae and Chrysophyceae algae with a maximum linear dimension from 20 to 100 µm. Organisms between 500 and 40 × 103 µm3 belonging to Desmidiales, Chrysophyceae and Euglenophyceae were also positively selected. Volvocales, Cryptophyceae and one group of medium-size Euglenophyceae (Trachelomonas sp.) had a high, negative selectivity index independent of their cell shape or size (Ivlev’s index of feeding selectivity <−0.7). The mussel positively selected Rotifera, and this only had a measurable effect on large Euglenophyceae, which increase their selectivity value in the absence of Rotifera. The non-parametric multiplicative regression showed that selectivity is largely explained by a combination of cell shape, biovolume and the phytoplankton taxa offered (R2 > 0.8). We concluded that the impact on phytoplankton community structure could be severe, considering that the presence of zooplankton does not have an effect on the majority of phytoplankton groups and that the mussel tends to feed on both items to improve its diet. The negative selection of some phytoplankton taxa is possibly related to the morpho-physiological characteristics of their cell shells. © 2015, The Japanese Society of Limnology. Source

Diego F.,Instituto Nacional Of Limnologia Inali | Yamila B.,Instituto Nacional Of Limnologia Inali | Gisela M.,Instituto Nacional Of Limnologia Inali | Patricia M.,Fundacion YUCHAN
Annales de Limnologie | Year: 2015

This study aimed to determine the factors affecting plankton structure along a salinity gradient during the summer in high-altitude endorheic lakes in Catamarca Province (Argentina). During the summer 2013, eight lakes located between 3000 and 4300 meters above sea level were sampled in a 6-day period being analysed plankton, limnological variables and flamingo abundance. Principal Component Analysis explained 80% of the system variability, permitting lakes to be ordered by salinity: subhaline (SH), hypohaline (HH) and mesohaline (MH). A total of 101 phytoplankton taxa were registered, having Bacillariophyceae the highest richness (43 species registered). HH lakes were dominated by Bacillariophyceae (between 65 and 100%), while Chlorophyceae and Euglenophyceae were more abundant in SH and MH lakes. Zooplankton was poorly represented in richness (only 21 species were registered). MH lakes were dominated by Copepoda (>85% of total abundance) and HH lakes by Rotifera (>51% of total abundance). It was not found a clear pattern in SH lakes. The redundancy analysis explained 70.7% of phytoplankton variability and 75.7% of zooplankton variability. Bacillariophyceae presence was associated with availability of dissolved silica (Si), while Euglenophyceae and Chlorophyceae were associated with a higher nitrogen:phosphorus ratio. Cladocera and Copepoda abundance were linked to Euglenophyceae abundance and the area of lakes while Rotifera displayed a positive relation with the concentration of dissolved organic matter. We conclude that both phytoplankton and zooplankton abundance are mainly controlled by Bottom-Up forces including dissolved Si for Bacillariophyceae, and availability of Euglenophyceae for zooplankton while salinity and altitude have an effect on plankton richness distribution. © EDP Sciences, 2015. Source

Wantzen K.M.,CNRS Cities, Territories, Environment and Societies | Blettler M.C.M.,Instituto Nacional Of Limnologia Inali | Marchese M.R.,Instituto Nacional Of Limnologia Inali | Amsler M.L.,Instituto Nacional Of Limnologia Inali | And 3 more authors.
International Journal of River Basin Management | Year: 2014

ABSTRACT: The middle and lower sections of most large rivers have fine-grained bed sediments, which may have a strong influence on the functional and taxonomical structure of benthic invertebrates. Based on results from several studies by the authors on the faunal assemblages and habitat structures of the Paraguay–Paraná River system (Brazil, Paraguay, Argentina), from European (Rhine, Loire) River systems, and data from the literature, this review identifies general patterns which appear to have a global character. On one hand, the invertebrate assemblages largely differed between the main channel (MC) and the corresponding floodplain habitats in different sections, and also the floodplain habitats along the river channel revealed great differences in their biodiversity. On the other hand, there was a remarkable homogeneity among the main-channel sections within and even between river systems. We consider physical habitat features as the crucial variables responsible for these patterns. In cross-sections from the MC towards the floodplain habitats, grain size, organic matter content and oxygen supply change dramatically, and different floodplain habitats along the same river system may have different successional stages even at small geographical distances. The sandy structure of potamal habitats (including underwater dunes), however, provides a set of habitat features characterized by continuously changing sediment structures with well-defined grain sizes, low organic matter contents and good oxygenation, which force a set of adaptations by the invertebrates that limits but stabilizes the diversity of invertebrates in these large river sections. A better understanding of the ecohydrological interactions between habitat dynamics and benthic invertebrates is needed to improve sustainable river ecosystem management. We discuss the non-recovery of large benthic invertebrate species in the lower section of large rivers after improvement of the water quality in the context of these ecohydrological features. Conclusions are drawn for river restoration. © 2014, © 2014 International Association for Hydro-Environment Engineering and Research. Source

Frau D.,Instituto Nacional Of Limnologia Inali | Devercelli M.,Instituto Nacional Of Limnologia Inali | Jose De Paggi S.,Instituto Nacional Of Limnologia Inali | Scarabotti P.,Instituto Nacional Of Limnologia Inali | And 3 more authors.
Marine and Freshwater Research | Year: 2015

Bottom-up and top-down control of phytoplankton is one of the most important hypothesis that explains and predicts the structure of aquatic community. Our aim was to elucidate whether predation and resource limitation can control phytoplankton composition and abundance in a subtropical shallow lake with groundwater connection to the river system. During 12 months, the lake was sampled at three points. Physico-chemical parameters, phytoplankton and zooplankton were sampled fortnightly, whereas fish were sampled every 3 months. The results showed that Euglenophyta dominated the total biovolume, followed by Dinophyta and Cryptophyta. As for the species composition, Chlorophyta was the dominant group (80 species recorded), followed by phylum Cyanobacteria (26 species recorded). Redundancy analysis (RDA) indicated that temperature and nitrate + nitrite concentration mainly explained biovolume changes, with zooplankton predation not having any measurable effect on phytoplankton during the high-water (HW) period. During low-water (LW) period top-down by fish was more important. At higher taxonomic resolution (species biovolume), phosphorus was another controlling factor. We concluded that phytoplankton in this lake is mainly regulated by hydrological changes as a macrofactor that affects nutrient availability and other environmental conditions. Even though bottom-up top-down forces do not have a central effect, we found evidence of positive nutrient influences at the HW period and fish effect at the LW period. © 2015 CSIRO. Source

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