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Fossette S.,University of Strasbourg | Fossette S.,French National Center for Scientific Research | Fossette S.,University of Swansea | Girard C.,University of Strasbourg | And 13 more authors.
PLoS ONE | Year: 2010

Background: Sea turtles are long-distance migrants with considerable behavioural plasticity in terms of migratory patterns, habitat use and foraging sites within and among populations. However, for the most widely migrating turtle, the leatherback turtle Dermochelys coriacea, studies combining data from individuals of different populations are uncommon. Such studies are however critical to better understand intra- and inter-population variability and take it into account in the implementation of conservation strategies of this critically endangered species. Here, we investigated the movements and diving behaviour of 16 Atlantic leatherback turtles from three different nesting sites and one foraging site during their post-breeding migration to assess the potential determinants of intra- and inter-population variability in migratory patterns. Methodology/Principal Findings: Using satellite-derived behavioural and oceanographic data, we show that turtles used Temporary Residence Areas (TRAs) distributed all around the Atlantic Ocean: 9 in the neritic domain and 13 in the oceanic domain. These TRAs did not share a common oceanographic determinant but on the contrary were associated with mesoscale surface oceanographic features of different types (i.e., altimetric features and/or surface chlorophyll a concentration). Conversely, turtles exhibited relatively similar horizontal and vertical behaviours when in TRAs (i.e., slow swimming velocity/sinuous path/shallow dives) suggesting foraging activity in these productive regions. Migratory paths and TRAs distribution showed interesting similarities with the trajectories of passive satellite-tracked drifters, suggesting that the general dispersion pattern of adults from the nesting sites may reflect the extent of passive dispersion initially experienced by hatchlings. Conclusions/Significance: Intra- and inter-population behavioural variability may therefore be linked with initial hatchling drift scenarios and be highly influenced by environmental conditions. This high degree of behavioural plasticity in Atlantic leatherback turtles makes species-targeted conservation strategies challenging and stresses the need for a larger dataset (>100 individuals) for providing general recommendations in terms of conservation. © 2010 Fossette et al.

Sophia M.D.G.,Federal University of Rio de Janeiro | Perez M.D.C.,Direccion Nacional de Recursos Acuaticos
Iheringia - Serie Botanica | Year: 2010

Merin Lagoon is a large, shallow and subtropical water body shared by the countries Uruguay and Brazil. The desmids composition of Merin Lagoon was analyzed at seven sites in March, July-August, November 1998 and January 1999, based on plankton net samples. The temperature and conductivity of the water presented the lowest values (15°C and 70 μS.cm-1) in July-August 1998 and highest (25°C and 105 μS.cm-1) in January 1999, the pH values varied from neutral to slightly alkaline, between 6.5 and 8.7. A total of 61 desmids taxa belonging to 15 genera were identified and Staurastrum Meyen ex Ralfs (19), Cosmarium Corda ex Ralfs (10), Closterium Nitzsch ex Ralfs (6), and Staurodesmus Teiling (6) were the greatest represented genera. The most frequent taxon was Staurastrum leptocladum Nordstedt var. smithii Grönblad. The high desmid richness in Merin Lagoon and the lack of information about this algal group in this lagoon justify the present study.

Franco-Fraguas P.,University of the Republic of Uruguay | Burone L.,University of the Republic of Uruguay | Mahiques M.,University of Sao Paulo | Ortega L.,Direccion Nacional de Recursos Acuaticos | Carranza A.,University of the Republic of Uruguay
Marine Geology | Year: 2016

Recent high-resolution, multidisciplinary studies have provided models of modern and ancient sedimentary processes along the Uruguayan slope (34°S to 36°S), a strategic location in the Southwestern Atlantic margin (SAM). According to these models, modern surface sedimentation is controlled by the transition between the Subtropical Shelf Front and the Brazil-Malvinas Confluence (BMC), and presumably by the summer Rio de la Plata (RdlP) buoyant plume. Ancient sedimentary dynamics is reflected as the northernmost distribution of the contouritic terraces present in the Argentinean margin, reflecting the position of the BMC during glacial stages. In this work, the spatial correlation of previous evidence from modern (surface facies) and ancient (geomorphological features) sedimentation provides a sound framework in order to interpret novel information on the geochemical composition of surface sediments. Proxies for the origins of lithogenic (Nd, Al/Si, and Fe/K) and organic matter (C/N, δ13C, and δ15N), previously calibrated for the SAM, and the elemental compositions (Al, TI, Fe, K, Mn, Ca, P, Mg, Ba, and Si) of surface sediments were used to test working hypotheses on sediment provenance, surface productivity and the environmental control of elementary composition. The distribution of surface sediments is correlated with regional geomorphology, which includes contouritic terraces in the south and a progradational slope in the north. This supports the idea of a strong morphological control on the modern sedimentary processes. However, the distribution and content of terrigenous, biogenic and erosional elements, together with the dominance of Pampean Patagonian sediments, suggests that 1) the RdlP does not contribute with any lithogenic sediments to the slope and, instead, fertilizes open waters with contributions consisting of mixed marine organic matter; 2) in the north, the strong action of the BC and the re-circulated AAIW below promotes redistribution of sediments from the shelf and upper slope towards the middle slope, including sandy spillover/slump transport and hemipelagic sedimentation re-suspended from the continental shelf; 3) with respect to glacial stages, this across-slope sedimentation was displaced southwards dominating even the northernmost distribution of contouritic terraces and 4) sedimentation related to contouritic features, as modern depositional and erosional sedimentation, was restricted to the south accompanying the distribution of the MC. Thus, although the core hypothesis of the previous modern sedimentary model can be retained, considerable improvements in our knowledge of the sediment dynamics in the SAM have emerged from the present analysis of geochemical proxies. © 2016 Elsevier B.V.

Oddone M.C.,Grande Rio University | Paesch L.,Direccion Nacional de Recursos Acuaticos | Norbis W.,Institute Biologia
Journal of Northwest Atlantic Fishery Science | Year: 2010

A total of 1 893 males and 1 124 females of Squalus mitsukurii were collected from latitudes 34o 30' S and 37o 00' S, in the south-western Atlantic Ocean, during early autumn, late autumn and spring 1995, early autumn 1996 and early autumn 1998. Length-frequency distributions significantly varied between sexes for all seasons (P<0.05). Mature males predominated in all seasons throughout the analyzed area, according to their presence in the catches. In all periods sampled, immature females predominated except for late autumn 1995 where mature females were dominant. Significant differences in density among seasons were recorded for immature and mature females and mature males (P<0.05). Density of immature females and mature males were significantly different (P<0.05) for late autumn 1995 and early autumn 1996. Size-at-maturity was 43.1 cm and 55.9 cm total length for males (n = 1 181) and females (n = 862) receptively. The percentage of pregnant females ranged from 21.4% in spring 1995 to 49.8% in late autumn 1995. Ovarian fecundity varied significantly between early autumn 1995 and late autumn 1995 from 1-15 and uterine fecundity from 1-10, respectively. Embryo total length varied from 0.5-22.0 cm, attaining the highest values in autumn months. Sizeat- birth was estimated to be 22-24 cm total length.

Pereyra S.,University of the Republic of Uruguay | Garcia G.,University of the Republic of Uruguay | Miller P.,Direccion Nacional de Recursos Acuaticos | Miller P.,Research Center y Conservacion Marina | And 2 more authors.
Fisheries Research | Year: 2010

The narrownose smooth-hound shark Mustelus schmitti is a coastal species endemic to the Southwest Atlantic Ocean. As this species is an important fishery resource, there is interest in knowing its genetic population structure. In this study, we used mitochondrial cytochrome b gene sequences to examine the genetic structure of the narrownose smooth-hound populations within the Río de la Plata and its Maritime Front in the SW Atlantic Ocean. We found no evidence for genetic structure in the analyzed samples. Low levels of pairwise ΦST values indicated high connectivity and suggested genetic homogeneity at this geographic range. Additionally, notably low nucleotide and haplotype diversities found in this species could indicate that M. schmitti experienced a population bottleneck, recent expansion or selection. The results presented here indicate that M. schmitti exists as a single demographic unit in the Río de la Plata and its Maritime Front. The low genetic diversity values found in the present study, together with the low resilience to exploitation of this species, raise considerable concern over the conservation status of M. schmitti. © 2010 Elsevier B.V.

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