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Pampean streams constitute a drainage network which discharges continental freshwater into the associated marine coastal zone. The present study concerned a set of streams within General Pueyrredón district, Southeastern province of Buenos Aires, Pampa's region, Argentina, which deserves particular attention, since they flow in the area of influence of Mar del Plata, one of the most important tourist destination in the country. Different physical–chemical (i.e., temperature, conductivity, pH, dissolved oxygen), hydrographical and eco-physiological parameters were studied within five streams along an annual cycle, searching for seasonal variations and possible relations with land use. The behavior of physical–chemical parameters was consistent with previous reports on similar environments; inorganic nutrients presented high levels along the whole period, and have never been completely depleted. Within N nutrients, nitrate demonstrated to be the dominant along the whole period, with global mean values of ~ 18 µM and reaching values up to ~ 50 µM (total discharge of N ~ 1.23 Ton DIN y−1). A very high load of organic matter (from ~ 2000 mg Cm−3 in the fall up to ~ 4000 mg Cm−3 during summer) is discharged from these streams into the marine coastal zone (which represents ~ 214 Ton POC y−1) and, even until now, response effects have not been recorded there. The obtained results allowed us to sustain that anthropic activities (i.e., agriculture, cattle raising), continental runoff and climate conditions seem to be the main drivers of the hydrographical/biogeochemical behavior of the studied streams. Therefore, changes concerning them should also be included in future monitoring programs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 μg/L and zinc levels ranged between n.d. and 1224.38 μg/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. LC50 96-h values were 2.24 mg Cd2+/L and 7.07 mg Zn2+/L at 5 psu, and 15.42 mg Cd2+/L and 11.41 mg Zn2+/L at 25 psu. Higher salinities resulted in lower metal toxicity. This effect was stronger for Cd than for Zn. C. granulatus juveniles LC50 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. [ABSTRACT FROM AUTHOR]

Total Hg contents from abiotic (surface sediments and suspended particulate matter) and biological (crabs, fishes and halophytes) compartments from Bahía Blanca estuary and Mar Chiquita Coastal Lagoon, Argentina, have been monitored since the 1980's. At Bahía Blanca estuary, high Hg concentrations were recorded during the early 1980's in surface sediments (0.34 ± 0.22 μg/g) and suspended particulate matter (0.19 ± 0.10 μg/g). Fish species, Mustelus schmitti (0.89 ± 0.29 μg/g), Paralichthys brasiliensis (0.85 ± 0.18 μg/g) and Micropogonias furnieri (0.37 ± 0.11 μg/g) also presented high Hg concentrations. The large industrial nucleus located within the estuary has been identified as the main metal source for this environment. Hg contents from the same area during 1996–1998 were significantly lower: surface sediments (0.164 ± 0.023 μg/g), suspended particulate matter (0.048 ± 0.0017 μg/g), fish Micropogonias furnieri (0.13 ± 0.02 μg/g) and crab Chasmagnathus granulata (0.334 ± 0.071 μg/g). This trend of environmental detoxification is probably related with (i) the technological changes incorporated by the local industry, (ii) a most adequate management of industrial effluents, and (iii) the removal of great sediment volume by dredging and refill. During the 1980's Mar Chiquita Lagoon Hg concentrations reached 0.08 ± 0.01 μg/g in surface sediments and 0.09 ± 0.025 μg/g in suspended particulate matter, and 0.14 ± 0.04 μg/g in the fish Basilichthys bonariensis and 0.22 ± 0.08 μg/g in Paralichthys brasiliensis, and 0.08 ± 0.01 μg/g in the crab C. granulata, Hg concentrations were lower than at Bahía Blanca. Remote Hg sources for this Coastal Lagoon and atmospheric and stream transport of Hg is proposed as major Hg sources, since no Hg point sources exists nearby. Mercury concentrations recorded in the 1996–1998 period were lower than those recorded in the previous decade: surface sediments (0.019 ± 0.004 μg/g), suspended particulate matter (0.030 ± 0.008 μg/g), halophyte Spartina densiflora (0.013 ± 0.008 μg/g) or crab C. granulata (0.011 ± 0.009 μg/g). Both Hg bioaccumulation and biomagnification processes were verified in Bahía Blanca estuary and in Mar Chiquita Coastal Lagoon. This apparent recovery of both estuarine environments deserves to be carefully analyzed, in order to fully understand the foundations of these processes. [ABSTRACT FROM AUTHOR]