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Marrari M.,Servicio de Hidrografia Naval | Signorini S.R.,NASA | McClain C.R.,NASA | Pajaro M.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero Inidep | And 9 more authors.
Fisheries Oceanography | Year: 2013

The mid-shelf front (MSF) of the Buenos Aires province continental shelf in the Southwestern Atlantic Ocean plays a central role in the pelagic ecosystem of the region acting as the main spring reproductive area for the northern population of the Argentine anchovy Engraulis anchoita and supporting high concentrations of chlorophyll as well as zooplankton, the main food of anchovy. To investigate the influence of environmental variability on the reproductive success of E. anchoita, we analyzed a 13-yr time series (1997-2009) of environmental data at MSF including chlorophyll dynamics, as well as zooplankton composition and abundance, ichthyoplankton distributions, and recruitment of E. anchoita. Spring chlorophyll concentrations showed high interannual variability and were mainly influenced by changes in water temperature and vertical stratification, which in turn control nutrient supply to the surface. Chlorophyll dynamics (magnitude, timing, and duration of the spring bloom) explained most of the variability observed in E. anchoita recruitment, most likely via fluctuations in the availability of adequate food for the larvae. Our results suggest that satellite ocean color products can be valuable tools for understanding variability in ecosystem dynamics and its effects on the recruitment of fish. © 2013 Blackwell Publishing Ltd. Source

Pon J.P.S.,Institute Investigaciones Marinas y Costeras IIMyC | Copello S.,Institute Investigaciones Marinas y Costeras IIMyC | Lertora H.P.,University of the Sea | Bruno I.,Fundacion Aquamarina CECIM | And 3 more authors.
Marine and Freshwater Research | Year: 2013

Seabird and marine-mammal attendance and by-catch in mid-water and bottom otter semi-industrial coastal pair-trawl fisheries were assessed for the first time in northern Argentina. Observers were placed onboard trawlers between autumn 2007 and autumn 2008. Fifteen marine top-predator species were associated with the vessels. The most abundant and frequent seabirds (trawl fisheries combined) were the kelp gull, Larus dominicanus (∼70% of total birds and >96% occurrence), and the Olrog's gull, L. atlanticus (∼12% and >50%, respectively). Other seabird taxa such as Procellariiforms and Sphenisciforms, among others, were represented in very low numbers. The only mammal species recorded was the South American sea lion, Otaria flavescens (1% and 2%, respectively). Analysis of environmental and operational variability affecting the abundance of gulls indicated a significant increase in abundance with fishing depth, time of day, seasonality, wind intensity and wind direction. Incidental mortality of top predators was low and comprised only Magellanic penguins, Spheniscus magellanicus, in the mid-water gear. The results of the present study showed that the semi-industrial trawl fisheries operating in coastal waters in northern Argentina may a have a relatively minor impact on marine top-predator populations, at least in terms of incidental capture. © CSIRO 2013. Source

Fanjul E.,Institute Investigaciones Marinas y Costeras IIMyC | Escapa M.,Institute Investigaciones Marinas y Costeras IIMyC | Montemayor D.,Institute Investigaciones Marinas y Costeras IIMyC | Addino M.,Institute Investigaciones Marinas y Costeras IIMyC | And 4 more authors.
Journal of Sea Research | Year: 2014

Organic matter (OM) remineralization plays a key role in controlling the biogeochemistry of marine sediments. Through their burrowing activities, bioturbating macrofauna not only induces physical, chemical and biological modifications, which can affect microbial communities responsible for organic matter remineralization, but it could also directly affect the distribution and bioavailability of sedimentary organic matter. Through in situ experiments manipulating crab and burrow density in intertidal soft-bottoms, we assessed if crab-bioturbation affects benthic metabolism, and the amount, distribution, and bioavailability of sedimentary OM. Crab-bioturbation enhanced overall benthic metabolism and benthic flux of dissolved OM toward the water column at both mudflat and saltmarsh zones. Moreover, our results revealed that bioturbation also changes the quality, bioavailability and distribution of sedimentary OM in mudflats and saltmarshes. Overall, bioturbation enhanced the proportion of labile organic carbon of bioturbated sediments and homogenized the sediment column in terms of their proportion of labile organic carbon. However, crabs also generated biogenic structures (e.g., mounds) that could promote spatial heterogeneity of high nutritional-value OM. Bioturbation-induced changes on benthic metabolism and on OM availability would result in a reduction of the storage capacity of carbon in our intertidal systems. Previous works indicated that crab-burrows trap detritus and OM-rich sediments. Our results suggest that detritus are efficiently remineralized at bioturbated sediment, and finally they are quickly exported to the water column as CO2 and DOC. Thus, crabs are modifying the OM processing at intertidal soft bottoms, and the ways in which carbon is exported to coastal waters. © 2014 Elsevier B.V. All rights reserved. Source

Stellatelli O.A.,Institute Investigaciones Marinas y Costeras IIMyC | Block C.,Institute Investigaciones Marinas y Costeras IIMyC | Vega L.E.,Institute Investigaciones Marinas y Costeras IIMyC | Cruz F.B.,National University of Comahue
Wildlife Research | Year: 2014

Context. Exotic forestations may modify habitat quality, affecting native animal populations that require specific microhabitats to remain viable. Aims. We determined whether abundances and body condition of the lizard species Liolaemus wiegmannii and L. multimaculatus differed between forested and non-forested dunes. We also examined what environmental attributes are important in explaining the potential differences. Methods. We sampled six sites of 300ha each. Three of these sites had original vegetation and three were forested with exotic Acacia longifolia. We traced 120 transects per site searching for lizards. Key results. Lizards were two times more abundant in non-forested sites than in sites covered by acacia trees (even as low as a fourth of the area). Sites with high densities of acacia (≥78% of coverage) had the lowest abundance of lizards. In forested sites, the snout-vent length of L. wiegmannii was 10% smaller and relative body mass 22% lower than in non-forested sites. We found no differences in the body size of L. multimaculatus. Conclusions. The replacement of the native vegetation by A. longifolia has negative effects on lizard species, representing a substantial threat to L. wiegmannii and particularly to L. multimaculatus, a threatened status species. Structural and thermal characteristics of the non-forested sites seemed to be more favourable for the abundance and body condition, whereas the dense vegetation and the low temperatures on the forested sites might explain the lower presence of lizards. Implications. We recommend that before the implementation of future forestation plans in the pampasic coastal dunes, the deleterious consequences that this practice generates on native lizard fauna must be considered. When necessary, we recommend that A. longifolia be planted so that the coverage does not exceed a quarter of the total area, so as to prevent the formation of continuous (or closed) forest patches and to maintain the structural heterogeneity of the habitat that these lizards need to survive. In the most affected areas, eradication and control strategies may help reduce the advancement of this exotic plant over the areas intended for conservation. © CSIRO 2014. Source

Stellatelli O.A.,Institute Investigaciones Marinas y Costeras IIMyC | Block C.,Institute Investigaciones Marinas y Costeras IIMyC | Vega L.E.,Institute Investigaciones Marinas y Costeras IIMyC | Cruz F.B.,National University of Comahue
Herpetologica | Year: 2015

The introduction of nonnative plant species might generate habitat modifications that, in turn, increase the predation risk for animals, either by making prey species more conspicuous, limiting the availability of refuges, or by offering vantage points to potential predators. We compared predation pressure and escape behavior of two sympatric species (Liolaemus wiegmannii and Liolaemus multimaculatus) of Sand Lizards inhabiting forested and nonforested grasslands of the pampasic coastal sand dunes of Argentina. Predation pressure was evaluated by measuring the predation rate on plasticine replicas of lizards and the abundance of avian predators. We also recorded flight initiation distance (FID) of lizards in the different habitat types and the microhabitat used as refuge. Both lizard species prefer refuges in native plants but, when they are scarce, the nonnative Acacia longifolia is selected as alternative refuge. In forested habitats, sand-burying behavior is a complementary strategy used by L. multimaculatus to avoid predation. The FID of L. wiegmannii was greater in forested habitats than in nonforested ones. In contrast, L. multimaculatus exhibited a short FID in forested habitats, mostly because sand-burying behavior appears to reduce the risks typically associated with exposed areas. Plasticity in antipredatory behavior suggests that these lizards could recognize predators and develop a suitable antipredatory behavior. We conclude that increased predation pressure and structural alterations of the habitat in the presence of nonnative A. longifolia affect the decisions that determine how, when, and where these lizards flee. © 2015 by The Herpetologists' League, Inc. Source

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