Search

Estuaries are transitional systems that link both land and oceans, with particular dynamics regulated by their own characteristics. The main aim of the present study was the assessment of the effects generated by a strong dry period on the distribution of inorganic nutrients and biological production within Mar Chiquita coastal lagoon, comparing this information with that from periods of precipitation regularly conducted. For this study we selected Mar Chiquita coastal lagoon and analyzed a 20-year data series for concentration and distribution of physical and chemical parameters, in particular salinity, inorganic nutrients (i.e. dissolved inorganic nitrogen, phosphate, silicate) and photosynthetical pigments (i.e. chlorophyll a). We also evaluated the association between these parameters and climate conditions within the region, and found a strong relationship and very quick response to changes. As a result, we report, for the first time in the region, rainfall as a main driver of biogeochemical processes within the estuarine system. The obtained results allowed us to confirm the clear transference processes between land and oceanic systems, and the role of climate as a driver of the corresponding transference processes. [ABSTRACT FROM AUTHOR]

Abstract: The semiterrestrial burrowing crab Neohelice granulata is one of the main inhabitants of the supratidal and intertidal zones of brackish salt marshes, estuaries and coastal lagoons from South America''s Atlantic littoral. A large population of this species spreads out Mar Chiquita coastal lagoon (in Argentina) and its corresponding wetlands, and is considered as a key species within this system. Since high values of dissolved heavy metals (including Zn) have been recently reported within Mar Chiquita coastal lagoon, with levels unusually higher than those from other coastal systems within Argentina, it has been explored that the existence of a risk of environmental conditions endanger these populations. So, juveniles of this estuarine crab were experimentally exposed to increasing concentrations of dissolved Zn (i.e., 0, 0.5 and 1mg Zn2+ L−1) during six months, the time involved between two successive molts; in addition, both the size and weight reached after each molt were also studied in this assay. It can be concluded that zinc can be toxic to crabs only at high concentrations. Considering that levels up to 1mg ZnL−1 were recently reported in Mar Chiquita coastal lagoon waters, the potential occurrence of mean chronic effects on the crab population within the coastal lagoon is discussed. [Copyright &y& Elsevier]

Abstract: Total mercury contents from both abiotic and biological compartments within several estuaries from Argentina have been studied since the 1980s. The assessment of mercury occurrence in surface sediments, suspended particulate matter and crab and fish species from Mar Chiquita coastal lagoon, Bahía Blanca estuary and Samborombón Bay (in La Plata river estuary) are included in the present study. All samples were analyzed through Cold Vapor-Atomic Absorption Spectroscopy, following internationally standardized methods. In all cases analytical quality was checked against international reference materials. During the 1980s, Hg contents in sediments and SPM, as well as in edible fish species from Bahía Blanca estuary were significantly higher (p <0.01) than those of the 1990s and 2000s, and the large industrial nucleus located in the northern margin of this estuary was elsewhere identified as the main source of this metal. A permanent monitoring program carried out in 1986 and that is being implemented up to the present has demonstrated that Hg concentration values have significantly decreased (p <0.01) compared to the values of the 1980s. Both, Mar Chiquita coastal lagoon and Samborombón Bay have intermediate mercury levels in their biological compartments. In both cases, the possible occurrence of remote sources of this metal was considered. Even though, Hg values as determined in sediments and suspended particulate matter from Samborombón Bay were the highest ones for the whole analyzed period. Both mercury bioaccumulation and biomagnification processes were evaluated in the studied estuaries, as well as the potential qualification of estuarine foodstuffs for human consumption. [Copyright &y& Elsevier]