Montevideo, Uruguay
Montevideo, Uruguay

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Gimenez L.,Seccion Oceanologia | Gimenez L.,Bangor University | Borthagaray A.I.,Seccion Oceanologia | Borthagaray A.I.,Institute Ecologia y Biodiversidad | And 3 more authors.
Scientia Marina | Year: 2010

We evaluated relationships between (1) salinity and species richness and (2) frontal zones and community structure for the rocky intertidal macrobenthic community of the Uruguayan coast. A large-scale sampling design (extent ~500 km) covering 9 rocky shores across 3 intertidal levels was performed between September and November 2002. The linear relationship between salinity and species richness (minimum at the freshwater extreme) and the lack of correlation between variation in salinity and richness rejected two previous empirical models, explaining variations in species richness along the salinity gradient. Other factors (e.g. turbidity) may explain this discrepancy. The estuarine front defined two communities-freshwater and estuarine-marine-differing in species composition and richness. The freshwater community was characterised by low richness and few individuals confined to crevices or tide pools, and must be structured by physical processes (e.g. desiccation); the estuarine-marine community, with individuals occupying almost all available substrata, must be structured by both physical and biological processes. A marine front, separating estuarine and marine habitats, had a weak effect on community structure although estuarine and marine assemblages differed according to species characterising different functional groups. We conclude that the position of the estuarine frontal zones is important for explaining large-scale patterns of community structure in the study area.

Pires-Vanin A.M.S.,University of Sao Paulo | Muniz P.,Seccion Oceanologia | de Leo F.C.,University of Sao Paulo | de Leo F.C.,University of Hawaii at Manoa
Brazilian Journal of Oceanography | Year: 2011

Structure of intertidal and subtidal benthic macrofauna in the northeastern region of Todos os Santos Bay (TSB), northeast Brazil, was investigated during a period of two years. Relationships with environmental parameters were studied through uni- and multivariate statistical analyses, and the main distributional patterns shown to be especially related to sediment type and content of organic fractions (Carbon, Nitrogen, Phosphorus), on both temporal and spatial scales. Polychaete annelids accounted for more than 70% of the total fauna and showed low densities, species richness and diversity, except for the area situated on the reef banks. These banks constitute a peculiar environment in relation to the rest of the region by having coarse sediments poor in organic matter and rich in biodetritic carbonates besides an abundant and diverse fauna. The intertidal region and the shallower area nearer to the oil refinery RLAM, with sediments composed mainly of fine sand, seem to constitute an unstable system with few highly dominant species, such as Armandia polyophthalma and Laeonereis acuta. In the other regions of TSB, where muddy bottoms predominated, densities and diversity were low, especially in the stations near the refinery. Here the lowest values of the biological indicators occurred together with the highest organic compound content. In addition, the nearest sites (stations 4 and 7) were sometimes azoic. The adjacent Caboto, considered as a control area at first, presented low density but intermediate values of species diversity, which indicates a less disturbed environment in relation to the pelitic infralittoral in front of the refinery. The results of the ordination analyses evidenced five homogeneous groups of stations (intertidal; reef banks; pelitic infralittoral; mixed sediments; Caboto) with different specific patterns, a fact which seems to be mainly related to granulometry and chemical sediment characteristics.

Garcia-Rodriguez F.,Seccion Oceanologia | Hutton M.,Seccion Oceanologia | Brugnoli E.,Seccion Oceanologia | Venturini N.,Seccion Oceanologia | And 5 more authors.
Pan-American Journal of Aquatic Sciences | Year: 2010

Montevideo Bay is an extremely polluted coastal system because of multiple sources of contamination from industrial manufacturing, urban activities, energy production, harbor operations and population increase. Because rehabilitation measures will be implemented, this research project was undertaken to assess the contamination of the system. A sediment core that spanned to 3000 yr BP was taken to reconstruct the Holocene natural changes in salinity and trophic state, and also the effect of human activities on the environmental quality of the system. Before the human impact, the system was controlled by a sea level decrease, during which an increase in trophic state was observed. After the human impact, an intensification of the eutrophication process was observed, mainly due to the industrial activities linked to lack of sanitation. In addition, sharp increases in heavy metal concentration were recorded after 1917, when the leather tanning activities together with the construction and operation of the oil refinery and the thermoelectric generation plant were first documented. Thus, the data presented in this paper provide important chronological evidence of human impacts and environmental degradation, which at the minimum can be used to advise the managers and government agencies about the consequences of bad environmental practices on coastal aquatic systems.

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