Descripción: The coastline position in Claromecó, Buenos Aires province was determined, featuring character elements identified in relation to the position of the shoreline. In comparison on the determination of coastline and shoreline, it appears that the first results of the geomorphologic interpretation, while the position of the shoreline is subject to a number of uncertainties if there are no long-term measurements. The nomenclature for the coastal areas is not always clear, hampering the interpretation of the processes occurring in the coast and shore. The correct identification is important technical, scientific and legal. Current legislation states that the boundary between public and private territory corresponds to the shoreline. The use of plant species in the determination of the coastline and shoreline, by itself is not determinative if not accompanied by the geomorphologic reconnaissance of the area. The exact determination of shoreline and coastline is essential in the implementation of geological surveys of major importance for the proper planning and development of the coastal area. In the task of delimitation of the coastal area beach ridges were found; one located about 5 m a.s.l has an age of 4,370 years BP.

Descripción: The objective of this research is to study the main variability modes of the frequency of extreme temperatures in the south of South Amenica, their relation to sea surface temperatures (SSTs), and some indices of atmospheric circulation in the Southern Hemisphere. Observational data and reanalysis data were used for this purpose over the 1964-2003 period. An initial analysis showed that between the months of March and June, the frequency of wann events (especially warm nights) is highly associated with the SST in coastal zones. A wavelet analysis showed that the main variability mode found at a seasonal scale was an 8-year wave signal present in spning that remains active until the 1990s; it was noticeable in the analysis of cold nights, Atlantic SSTs, Pacific SSTs, and the Southern Annular Mode (SAM). A cross-wavelet analysis among them reflected this signal as a common variability mode, with the positive phase of the SAM congruent with the warmest conditions in the coastal zones of the Atlantic Ocean and lower cases with cold nights at the reference meteorological stations analyzed. Although longer series are desirable for low-frequency variability analysis, the results agree with previous studies that take into account an 8-year periodicity of the baroclinic waves at the Southern Hemisphere, supporting the relevance of the 8-year signal. Copyright 2008 by the American Geophysical Union.

Descripción: Nauplii of the branchiopod crustacean Artemia spp. are widely used as live food in aquaculture. Their nutritional value depends essentially on the fatty acid profile of their lipids, which can be very variable. Study of this variability (often species- and/or ecology-related) proposes interesting theoretical and applied questions. In the present study, cysts (dehydrated dormant eggs) from Argentinean Artemia spp. populations were analysed for their fatty acid profile. Most of the cyst samples analysed (n = 16) were obtained from Artemia persimilis populations, but 3 belonged to A. franciscana. Previous research indicated that A. persimilis populations are confined to inland biotopes, but in this study we report the presence of A. persimilis populations in coastal ecosystems. Cysts from all populations exhibited fatty acid profiles typical of either marine or freshwater, irrespective of the inland or coastal origin of their biotope. This study represents the first time that a significant amount of eicosapentaenoic acid (EPA, 20:5n-3) was detected in A. persimilis cyst samples. We hypothesize on some factors that presumably influence the fatty acid profiles of Artemia spp. cysts: (1) food resources from different habitats, which in turn can be influenced by environmental parameters, (2) the genetic make-up of each population, and/or (3) mechanisms of selective feeding. © Inter-Research 2007.

Descripción: Several species of ecosystem engineers inhabiting coastal environments have been reported structuring different kinds of communities. The magnitude of this influence often depends on the habitat complexity introduced by the engineers. It is commonly accepted that an increase in habitat complexity will result in an increase in diversity and/or abundance in the associated fauna. The rocky salt marshes along the coast of Patagonia are dominated by cordgrasses, mussels, and barnacles forming a mosaic of engineered habitats with different complexity. This system allows us to address the following questions: how different is a macroinvertebrate assemblage when dominated by different ecosystem engineers? And, is there a positive relationship between increasing habitat complexity and the species richness, diversity and total density of the assemblages? To address these questions, we compared the three ecological scenarios with decreasing habitat complexity: cordgrass-mussel, mussel, and barnacle-engineered habitats. We found a total of 22 taxa mostly crustaceans and polychaetes common to all scenarios. The three engineered habitats showed different macroinvertebrate assemblages, mainly due to differences in individual abundances of some taxa. The cryptogenic amphipod Orchestia gammarella was found strictly associated with the cordgrass-mussel habitat. Species richness and diversity were positively related with habitat complexity while total density showed the opposite trend. Our study suggests that species vary their relative distribution and abundances in response to different habitat complexity. Nevertheless, the direction (i. e., neutral, positive or negative) and intensity of the community's response seem to depend on the physiological requirements of the different species and their efficiency to readjust their local spatial distribution in the short term. © 2010 Springer-Verlag and AWI.