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Rodriguez-Gallego L.,Centro Universitario Regional del Este UdelaR | Achkar M.,Institute Ecologia y Ciencias Ambientales | Vidal L.,Institute Ecologia y Ciencias Ambientales | Meerhoff E.,Católica del Norte University | Conde D.,Institute Ecologia y Ciencias Ambientales
Estuarine, Coastal and Shelf Science | Year: 2017

Five catchment areas in Uruguay were selected to conduct a nutrient exportation analysis and to evaluate the effects of current land use on the eutrophication of coastal lagoons. Satellite images and national agriculture censuses were used for a quantitative analysis of land use changes from 1974 to 2005, and a nutrient export coefficient approximation was used to determine long-term changes in annual loads. Several eutrophication indicators (water, sediment and autotrophic communities) were assessed seasonally in the lagoon basins during 2005 and 2006. The areal annual load of nutrients exported to the lagoons increased over time. Population and extensive livestock ranching were the most important nutrient sources, while agriculture is increasing in importance. Buffer effects of riparian forests on eutrophication indicators were observed in contrast to the wetlands surrounding the lagoons, which seem to be acting as a source of nutrients. Catchment size was inversely related to most eutrophication indicators. Afforestation and agriculture were found not to directly impact eutrophication indicators, however, catchments with larger agricultural areas showed higher concentrations of suspended solids, which may indicate the export of particulate nutrients. Salinity was inversely related to most eutrophication indicators, suggesting that the manipulation of the sand bar of the lagoons is a critical management issue. Sediment-related eutrophication indicators were more sensitive to changes in land uses and covers, in contrast with the more variable water column indicators, suggesting their potential use as enduring indicators. This research provides a rapid and integral assessment for qualitatively linking catchment changes with eutrophication indicators in coastal environments, which can easily be replicated to track pollutants in locations that lack standardized monitoring programs needed for more complex catchment modeling approaches. © 2017 Elsevier Ltd

Ferigolo J.,Seccao de Paleontologia | Meneghel M.,Institute Ecologia y Ciencias Ambientales | Laurin M.,CNRS Center for Research on Palaeobiodiversity and Palaeoenvironments
Historical Biology | Year: 2012

The earliest undisputed crown-group amniotes date back to the Late Carboniferous, but the fossil record of amniotic eggs and embryos is very sparse, with the oldest described examples being from the Triassic. Here, we report exceptional, well-preserved amniotic mesosaur embryos from the Early Permian of Uruguay and Brazil. These embryos provide the earliest direct evidence of reproductive biology in Paleozoic amniotes. The absence of a recognisable eggshell and the occurrence of a partially articulated, but well-preserved embryo within an adult individual suggest that mesosaurs were viviparous or that they laid eggs in advanced stages of development. Our finds represent the only known documentation of amniotic embryos in the Paleozoic and the earliest known case of viviparity, thus extending the record of these reproductive strategies by 90 and 60 Ma, respectively. © 2012 Copyright Taylor and Francis Group, LLC.

Domenico F.C.D.,University of Sao Paulo | Bentos-Pereira A.,Institute Ecologia y Ciencias Ambientales
Journal of Orthoptera Research | Year: 2011

This paper proposes new synonyms and combinations for species of Bolidorhynchus, Cephalocoema, Orienscopia, Pseudastroma and Scleratoscopia; phallic complexes, seminal receptacles and distributions are illustrated. Most of the synonymized species were originally described by Dr. Salvador de Toledo Piza Jr., whose types were found in the collection of the Museu da Escola Superior de Agricultura Luiz de Queiroz, Piracicaba, São Paulo, Brasil.

PubMed | Institute Investigaciones Biologicas Clemente Estable and Institute Ecologia y Ciencias Ambientales
Type: | Journal: Harmful algae | Year: 2017

The development of cyanobacterial blooms in inland aquatic ecosystems is greatly promoted by nutrient availability, especially nitrogen and phosphorous. When blooms are dominated by toxigenic species the harmful effects of nutrient loading becomes particularly relevant. Among toxic species, Cylindrospermopsis raciborskii found in South American ecosystems is characterized by the production of saxitoxin and analogs (Paralytic Shellfish Poisoning, PSP), for which the factors that trigger their production have not been elucidated. In this study, the effect of nitrate availability on the relative transcript abundance of two genes (sxtU and sxtI), both involved in different steps of PSP biosynthetic pathway, was addressed in C. raciborskii MVCC19 by qPCR. The relative transcript abundance of both genes significantly increased from the beginning to the end of growth, independent of nitrate availability in the culture medium. Differences between the genes in terms of the levels of relative expression were also found, implying that during growth in nitrate-rich or nitrate-deprived conditions C. raciborskii MVCC19 has the ability to produce different kind of PSP molecules. The presence of nifH transcripts in the nitrogen-depleted treatment confirmed that in the absence of nitrate C. raciborskii fixed atmospheric N

Pereira G.,Institute Ecologia y Ciencias Ambientales | Abadie M.,Federal University of Rio Grande do Sul | Maneyro R.,Institute Ecologia y Ciencias Ambientales
Studies on Neotropical Fauna and Environment | Year: 2015

We analyzed the reproductive pattern in males of Physalaemus riograndensis (n = 276). To identify the potential breeder males (n = 100), the presence of secondary sexual characters were recorded. These males were found mainly from September to April, and two peaks of abundance were observed. Breeding activity was positively correlated with temperature, but did not correlate with rainfall. As occurs with females of P. riograndensis, the fat bodies increased synchronously with the gametogenic activity, coinciding with the period of highest reproductive activity for the species (October to April). Therefore, these structures could be used as reserves of energy for reproduction in males. © 2015 Taylor & Francis.

Masciadri S.,Institute Ecologia y Ciencias Ambientales | Masciadri S.,Federal University of Rio Grande do Norte | Stutz S.,CONICET | Garcia-Rodriguez F.,Institute Ecologia y Ciencias Ambientales
Revista Brasileira de Botanica | Year: 2013

Modern pollen-vegetation relationships are the basis for any paleo-study and are especially needed to understand fossil pollen assemblages and their ecological inferences. Some authors have proposed that lakes and ponds represent the surrounding vegetation through pollen grains captured by the lake. The aim of this work was to establish the modern pollen-vegetation relationships of coastal plant communities and pollen spectra represented in the surface sediments of a coastal shallow lake, and to evaluate whether spatial heterogeneity was captured by the Lake Chaparral in Perla de Rocha, Rocha, Uruguay. Pollen grains of five surface sediment samples were analyzed and related with a stratified sampling of vegetation communities surrounding the lake. Correspondence analysis and t test were used to determine plant communities and analyze the diversity of pollen assemblages. Several plant species relevant to conservation were registered, and plant communities were differentiated: coastal forest, dunes, prairies, and wetlands. However, due to limitations in taxonomic identification level for the grains of graminoids (Poaceae, Cyperaceae) in pollen assemblages, herbaceous communities highly represented by these botanical families were inferred as open environments. Pollen spectra registered at Chaparral Lake represented local and nearby vegetation well, according to both old and new theoretical models of lakes as a catchment pollen system. Several pollen grains were good indicators of the coastal forest (Myrsine sp., Ephedra tweediana Fisch. & C. A. Mey., Lithraea sp. and Tripodanthus acutifolius (Ruiz & Pav.) Tiegh.), and dunes (Chenopodiaceae, and Ambrosia sp. and Senecio sp.). The modern pollen-vegetation relationship established in this work is similar to those registered for the southern coast of Brazil, due to a shared forest component in both vegetation and pollen spectra. These results constitute primary data for the area, and we think this system is very appropriate for the historic reconstruction of coastal vegetation, particularly the coastal forest. © 2013 Botanical Society of Sao Paulo.

Rodriguez-Gallego L.,Institute Ecologia y Ciencias Ambientales | Masciadri S.,Institute Ecologia y Ciencias Ambientales | Nin M.,Vida Silvestre Uruguay
Estuaries and Coasts | Year: 2012

Pollen studies and their relationship with modern vegetation facilitate paleoecological reconstructions while changes in pollen abundance are indicators of environmental fluctuations. We analyzed the relationships between recent pollen deposits in the sediments of four Uruguayan coastal lagoons and catchment vegetation and analyzed the temporal dynamics of submerged aquatic vegetation (SAV). We mapped terrestrial vegetation, sampled SAV biomass, and analyzed the pollen record in each lagoon. The sediment samples represented the last 49-76 years of deposition, and most vegetation types were well represented in the pollen records. Pollen of Chenopodiaceae, proposed as indicators of saltmarshes, decreased in the surface samples of all lagoons, possibly due to the salinity reduction promoted by precipitation changes in the region. Pollen of SAV was found in all lagoons but with gaps in the record, and a submerged vegetated phase was recorded. Simultaneous botanical and pollen analyses better captured the large fluctuations of SAV in coastal lagoons. © 2012 Coastal and Estuarine Research Federation.

Kandratavicius N.,Institute Ecologia y Ciencias Ambientales | Muniz P.,Institute Ecologia y Ciencias Ambientales | Venturini N.,Institute Ecologia y Ciencias Ambientales | Gimenez L.,Bangor University
Estuarine, Coastal and Shelf Science | Year: 2015

This study aimed to determine if estuarine meiofaunal communities of Uruguay (South America) vary between permanently open estuaries and open/closed coastal lagoons, or if they respond to the sediment composition. In Uruguay, estuaries and coastal lagoons vary in the degree of connectivity to the sea and in the sediment composition; sediments in estuaries are characterized by fine-medium sands but sediments vary from lagoon to lagoon (either fine-medium or coarse sand). Taxa richness (total=16) showed less temporal variability in lagoons than in estuaries, due to patterns of presence/absence of the less abundant taxa. However, no major response to habitat was found in the most abundant groups: polychaetes (6% of total fauna) were on average 5% more abundant in lagoons than in estuaries. Some level of zonation, within estuaries and lagoons, was found in the most abundant groups, nematodes (63% of total fauna) and copepods (15%) in response to medium and fine sands. In addition, sediment type modulated seasonal patterns in the frequency of presence/absence in ostracods, polychaetes and oligochaetes. For instance, in polychaetes and ostracods the increase in the frequency of absences, occurring from summer to winter, was stronger in lagoons and estuaries dominated by fine sands. The lagoon habitat appears to ameliorate the effects of unfavourable (winter) conditions in less abundant meiofaunal taxa. In summary, sediment fractions explain spatial patterns in the average abundance of organisms (e.g. nematodes) as well as the seasonal changes in frequency of presence/absence (e.g. polychaetes). © 2015 Elsevier Ltd.

Segura A.M.,Institute Ecologia y Ciencias Ambientales | Segura A.M.,University of Montevideo | Calliari D.,Institute Ecologia y Ciencias Ambientales | Kruk C.,Institute Ecologia y Ciencias Ambientales | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2011

The mechanisms that drive species coexistence and community dynamics have long puzzled ecologists. Here, we explain species coexistence, size structure and diversity patterns in a phytoplankton community using a combination of four fundamental factors: organism traits, size-based constraints, hydrology and species competition. Using a 'microscopic' Lotka-Volterra competition (MLVC) model (i.e. with explicit recipes to compute its parameters), we provide a mechanistic explanation of species coexistence along a niche axis (i.e. organismic volume). We based our model on empirically measured quantities, minimal ecological assumptions and stochastic processes. In nature, we found aggregated patterns of species biovolume (i.e. clumps) along the volume axis and a peak in species richness. Both patterns were reproduced by the MLVC model. Observed clumps corresponded to niche zones (volumes) where species fitness was highest, or where fitness was equal among competing species. The latter implies the action of equalizing processes, which would suggest emergent neutrality as a plausible mechanism to explain community patterns. © 2010 The Royal Society.

Cayssials V.,Institute Ecologia y Ciencias Ambientales | Rodriguez C.,Institute Ecologia y Ciencias Ambientales
Evolutionary Ecology | Year: 2013

The amount of light available for photosynthesis is a key environmental factor that shapes the form and function of plants. Several plant traits affect the manner in which different species fix carbon during vegetative growth. Under the hypothesis that grasses respond to environmental selective pressures, we analyzed the differences in certain leaf, culm, and regenerative traits of 283 native Uruguayan grasses growing in open (grassland) and shaded (forest) habitats. In order to differentiate the phylogenetic effects from the adaptive changes to current local conditions, we used phylogenetically controlled comparative analysis. We found that the divergence of grass species between grasslands and forests was accompanied by changes in leaf traits. Narrow and filiform blades (higher length/width ratio) were favored in species growing in grasslands, while wider and oval blades were favored in species growing in forests. The response of the leaf blades in forests was probably directed towards maximizing light interception, while in grasslands could be linked to the loss of water and heat. In contrast, we found that neither the culm nor the caryopsis length exhibited significant evolutionary changes associated with open or shaded habitats. Our results highlight the functional significance and adaptive value of the width and shape of the grass blades to the current environment. © 2012 Springer Science+Business Media B.V.

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