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El Calafate, Argentina

Escapa M.,Institute Investigaciones Marinas y Costeras | Perillo G.M.E.,Instituto Argentino Of Oceanografia | Iribarne O.,Institute Investigaciones Marinas y Costeras
Geomorphology | Year: 2015

Salt-marshes are under increasing threat, particularly from sea-level rise and increased wave action associated with climate change. The development and stability of these valuable habitats largely depend on complex interactions between biotic and abiotic processes operating at different scales. Also, interactions between biotic and abiotic processes drive internal morphological change in salt-marshes. In this paper we used a biogeomorphological approach to assess the impact of biological activities and interactions on salt pan formation in Sarcocornia-dominated salt marshes. Salt pans represent a key physiographic feature of salt-marshes and recent studies hypothesized that biogeomorphic processes could be related to salt pan formation in SW Atlantic salt-marshes. The glasswort Sarcocornia perennis is one of the dominant plants in the salt-marshes of the Bahía Blanca Estuary (Argentina) where they form patches up to 8m in diameter. These salt-marshes are also inhabited in great densities by the burrowing crab Neohelice (Chasmagnathus) granulata whose bioturbation rates are among the highest reported for salt-marshes worldwide. A set of biological interactions between N. granulata and S. perennis appears to be responsible for salt pan development in these areas which has not been described elsewhere. The main objective of this work was to determine the ecological interactions occurring between plants and crabs that lead to salt pan formation by using field-based sampling and manipulative experiments. Our results showed that S. perennis facilitated crab colonization of the salt-marsh by buffering otherwise stressful physical conditions (e.g., temperature, desiccation). Crabs preferred to construct burrows underneath plants and, once they reach high densities (up to 40 burrowsm-2), the sediment reworking caused plant die-off in the central area of patches. At this state, the patches lose elevation and become depressed due to the continuous bioturbation by crabs. Thus, salt pans are generated in this case by a set of biogeomorphic processes that include pure ecological interactions such as plant facilitation of crab settlement and also indirect negative effects of crabs on plant survival. Furthermore, crab bioturbation affects sediment structure due to concentration of burrowing activity under plant canopies promoting elevation loss and leading, after a few years, to salt pan formation in a previously vegetated substrate. © 2014 Elsevier B.V.

Beltrame M.O.,Instituto Argentino Of Oceanografia | Beltrame M.O.,FASTA University | De Marco S.G.,FASTA University | De Marco S.G.,University of the Sea | And 3 more authors.
Archives of Environmental Contamination and Toxicology | Year: 2010

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. © 2009 Springer Science+Business Media, LLC.

Fiori S.M.,Instituto Argentino Of Oceanografia | Fiori S.M.,National University of the South | Carcedo M.C.,Instituto Argentino Of Oceanografia
Journal of Shellfish Research | Year: 2015

The yellow clam Amarilladesma mactroides (Reeve, 1854), is an intertidal species that prospers mainly on dissipative sandy beaches along the temperate Atlantic coast of South America, from Brazil to Argentina (24-41° S). This large clam is considered a fast burrower, which lives buried in the sediment, migrating seasonally into the intertidal zone. The present study explores the effect of sediment grain size on the burrowing performance of this species, to elucidate the influence of granulometry on the alongshore distribution of the A. mactroides population. Laboratory trials were performed with clams of different sizes, to study the influence of grain size on the burial rate. Clam distribution was analyzed along a 32 km coastal fringe whose granulometric composition varies from very fine to coarse sand. The values of the mean burrowing rate index, a measurement of clam mobility, suggest that burrowing is fast to very fast in fine and medium sand and becomes slower toward areas with extreme particle size (very fine and coarse sand). The burial time of A. mactroides was positively correlated with shell length: small animals can burrow into substrates that may exclude larger animals. Adults clams burrowed in a very limited range of sand grain sizes. They displayed fastest burial times in grain sizes typical of dissipative beaches, i.e., fine to medium sand. Patchy distribution and density variation of A. mactroides alongshore reflect the relation between grain size and burrowing performance: the population is absent in sites with the highest proportion of coarse sands, its density increases in patches with the highest proportion of fine and medium sand and peaks at a site with the highest proportion of fine sand. Results indicate that the discontinuous distribution of A. mactroides along its range could be due to a postsettlement process. Clams can potentially recruit on a wide morphodynamic range, but only may thrive in beaches which sand grain size allows them a rapid reburial during migratory and local movements.

Fiori S.M.,Instituto Argentino Of Oceanografia | Fiori S.M.,National University of the South | Simonetti P.,Instituto Argentino Of Oceanografia | Dos Santos E.P.,Instituto Argentino Of Oceanografia
Aquatic Invasions | Year: 2012

The present work reports the finding of an exotic bivalve, Barnea (Anchomasa) truncata, in the intertidal zone of the Bahía Blanca Estuary Argentina (38° Lat S), more than 2000 km south from the edge of its native range in South America (21° Lat S, Brazil). Lines of evidence suggest that larval transport by shipping is the probable entry route of this species. The most apparent modification created by the introduction of this species is the generation of greater complexity and habitat heterogeneity in the mud tidal plain of the estuary; the consequent effects on the local biota should therefore be evaluated. © 2012 The Author(s).

The life cycle and growth of the mud-snail Heleobia australis was studied in the Bahía Blanca estuary (Argentina) from April 2008 to April 2010. Four age classes were identified. This species recruits once a year, during summer. In general, the recruits (< 2.5 mm) represented a small percentage of the total population. The growth rate of H. australis declined with increasing animal size and showed a marked seasonal pattern for the population under study: lower rate during winter and higher rate in summer. A life cycle of approximately 30 months (~2.5 years) was estimated for the population of H. australis in the Bahía Blanca estuary. This population shows variations in growth rate, abundance of recruits, and shell size in relation to more northerly populations. Several factors like parasitism, predation, environmental features, and anthropogenic action may be interacting to produce these differences. This work constitutes the first long-term study of the life cycle of cochliopids. Heleobia australis appears to be a long-lived species and exhibits variations in its life cycle that seem to be influenced by biological and physical variables. Long-term studies that include biological interactions and spatial features of the microhabitats are needed to elucidate patterns in life-history traits of H. australis along its distribution range.

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