RESUMEN
Cadmium, chromium, copper, and manganese concentrations were determined in hepatopancreas of both sexes as well as in eggs at different embryonic development stages of the burrowing crab Neohelice granulata (Brachyura, Varunidae) from Mar Chiquita Coastal Lagoon, a biosphere reserve from Argentina, during a period of 1 year, to assess the bioaccumulation of metals associated with sex and seasonality. Furthermore, metal levels in associated superficial sediment samples were also determined. Two different "cangrejales," one in a mudflat and another one in a salt marsh, were studied. The results showed high concentrations of copper within the hepatopancreas, which was considered a strong reflection of high exposure of N. granulata to this metal. Metal accumulation in hepatopancreas from both study sites and sexes did not present significant differences, as did seasonality. In this sense, both spring and summer metal levels in hepatopancreas were the greatest. Eggs did not present differences in metal accumulation, with the exception of manganese, between sites or between crabs at different embryonic stages. For this metal, eggs from female crabs inhabiting mudflats showed higher levels than those from inhabiting salt marshes. Moreover, eggs in the late embryonic stage also showed the highest manganese concentrations. Metal levels in sediments, however, were similar in both sites. These are the first results of metal level in biota and sediments in this particular environment. Such results could be used as a baseline for the monitoring of metal levels in future studies in Mar Chiquita Coastal Lagoon.
Asunto(s)
Braquiuros/química , Ecosistema , Metales Pesados/análisis , Contaminantes Químicos del Agua/análisis , Animales , Argentina , Cromo/análisis , Cobre/análisis , Monitoreo del Ambiente , Femenino , Masculino , Manganeso/análisis , Óvulo/química , Páncreas/química , Estaciones del Año , Factores SexualesRESUMEN
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 1 mg Zn(2+)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 1 mg 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.
Asunto(s)
Peso Corporal/efectos de los fármacos , Braquiuros/efectos de los fármacos , Muda/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Zinc/toxicidad , Animales , Argentina , Peso Corporal/fisiología , Braquiuros/crecimiento & desarrollo , Braquiuros/fisiología , Geografía , Muda/fisiología , Agua de Mar , América del Sur , Factores de TiempoRESUMEN
The large Argentine marine littoral zone is characterized by great number of wetlands and includes only one coastal lagoon, Mar Chiquita, which has been declared as a Biosphere Reserve by the Man and Biosphere Reserve Program from UNESCO. Its margins present populations of Chasmagnathus granulatus, a semiterrestrial crab distributed along wide salinity gradients that plays an important role as a key species within the corresponding trophic web. Dissolved cadmium (Cd) and zinc (Zn) concentrations present in this ecosystem were determined. Cadmium concentrations ranged between n.d. and 0.82 mug/L and zinc levels ranged between n.d. and 1224.38 mug/L within the mentioned coastal lagoon. Cd and Zn acute semistatic toxicity bioassays were carried out for 96 h on juvenile crabs of C. granulatus. LC(50) 96-h values were 2.24 mg Cd(2+)/L and 7.07 mg Zn(2+)/L at 5 psu, and 15.42 mg Cd(2+)/L and 11.41 mg Zn(2+)/L at 25 psu. Higher salinities resulted in lower metal toxicity. This effect was stronger for Cd than for Zn. C. granulatus juveniles LC(50) 96-h values determined for Cd were three to four orders of magnitude higher than the corresponding dissolved metal concentrations in the Mar Chiquita coastal lagoon; nevertheless, those Zn values determined were similar to several ones corresponding to natural water samples.
Asunto(s)
Braquiuros/efectos de los fármacos , Cadmio/toxicidad , Salinidad , Contaminantes Químicos del Agua/toxicidad , Zinc/toxicidad , Animales , Argentina , Dosificación Letal Mediana , Agua de MarRESUMEN
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.