Benthic trophic interactions in an Antarctic shallow water ecosystem affected by recent glacier retreat

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (delta C-13 and delta N-15 stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling

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Extended glacier retreat is among the main consequences of the rapid warming of the West Antarctic Peninsula. Particularly, in the inner part of Potter Cove (South Shetland Islands, Antarctica) large areas are now exposed to open sea conditions owing to the retreat of Fourcade glacier. During the 2010 austral summer, underwater photographic surveys were undertaken by SCUBA diving up to 30 m in these new ice-free areas 80 m from the glacier front. Our main aim was to investigate colonization and early succession of the benthic assemblages on soft-bottom areas. Here, we reported a total of 1,146 animals belonging to 13 taxa. Filter-feeders comprised the largest trophic group and sessile fauna showed much higher coverages and densities than mobile fauna at all depths. The most abundant groups were ascidians and bryozoans, which together comprised ~90% of all taxa documented. In a region where most of marine-terminating glaciers are in retreat, these results are an important contribution to improve our knowledge on colonization in the newly ice-free areas

Population genetic structure of the Antarctic ascidian Aplidium falklandicum from Scotia Arc and South Shetland Islands

In sessile marine organisms, gene flow between populations depends mainly on free-living reproductive stages (such as larvae and gametes), and usually the strength of genetic structure is related to the time spent in the plankton and physical factors as oceanographic conditions. In Antarctica, abyssal depths that surround the continent and the Polar Front are considered strong barriers for benthic marine fauna, keeping the continent isolated from other shelves. The only available shallow water habitats between South America and the Antarctic continent are those around the Scotia Arc Islands; there are no shallow water habitats between the other southern continents and Antarctica. In this work, ISSRs-PCR markers were used to study the genetic structure of populations of Aplidium falklandicum, a compound ascidian with short-lived lecitotrophic larvae. A highly significant genetic differentiation (ΦST = 0.405; P < 0.05) and a pattern of isolation by distance were found. A genetic landscape approach identified a discontinuity in genetic diversity, coincident with the southernmost registered position of the Polar Front. For A. falklandicum, a species with presumably low capacity of long distance dispersal, the abyssal depths together with the large geographic distances create a barrier for gene flow.Fil: Demarchi, Maria Milagros. Universidad Nacional de Córdoba. Facultad de Cs.exactas Fisicas y Naturales. Departamento de Diversidad Biologica y Ecologica. Cat.de Ecologia Marina; Argentina. Universidad Nacional de Córdoba. Facultad de Cs.exactas Físicas y Naturales. Cátedra de Genética de Poblaciones y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Chiappero, Marina Beatriz. Universidad Nacional de Córdoba. Facultad de Cs.exactas Físicas y Naturales. Cátedra de Genética de Poblaciones y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Tatian, Marcos. Universidad Nacional de Córdoba. Facultad de Cs.exactas Fisicas y Naturales. Departamento de Diversidad Biologica y Ecologica. Cat.de Ecologia Marina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Sahade, Ricardo Jose. Universidad Nacional de Córdoba. Facultad de Cs.exactas Fisicas y Naturales. Departamento de Diversidad Biologica y Ecologica. Cat.de Ecologia Marina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentin

Default versus configured-geostatistical modeling of suspended particulate matter in Potter Cove, West Antarctic Peninsula

The glacier retreat observed during the last decades at Potter Cove (PC) causes an increasing amount of suspended particulate matter (SPM) in the water column, which has a high impact on sessile filter feeder? species at PC located at the West Antarctic Peninsula. SPM presents a highly-fluctuating dynamic pattern on a daily, monthly, seasonal, and interannual basis. Geostatistical interpolation techniques are widely used by default to generate reliable spatial information and thereby to improve the ecological understanding of environmental variables, which is often fundamental for guiding decision-makers and scientists. In this study, we compared the results of default and configured settings of three geostatistical algorithms (Simple Kriging, Ordinary Kriging, and Empirical Bayesian) and developed a performance index. In order to interpolate SPM data from the summer season 2010/2011 at PC, the best performance was obtained with Empirical Bayesian Kriging (standard mean = −0.001 and root mean square standardized = 0.995). It showed an excellent performance (performance index = 0.004), improving both evaluation parameters when radio and neighborhood were configured. About 69% of the models showed improved standard means when configured compared to the default settings following a here proposed guidelineFil: Neder, Camila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Sahade, Ricardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Abele, Doris. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung; AlemaniaFil: Pesch, Roland. Jade University of Applied Sciences; AlemaniaFil: Jerosch, Kerstin. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung; Alemani

Spatial analysis of benthic functional biodiversity in san jorge gulf, Argentina

Anthropogenic pressures on coastal and marine ecosystems are increasing. Current development of spatiotemporal models will improve understanding of how changes to biodiversity distribution resulting from such pressures might affect ecosystem functioning. The objective of this study was to characterize the spatial distribution of benthic biodiversity in San Jorge Gulf (Argentina) to provide insight into the relationship between benthic habitats and biodiversity. First, we characterized the spatial heterogeneity of both sediment types and bottom water variables. Then, we described the ecosystem’s functional diversity considering trophic interactions and behavioral and morphological characteristics of benthic organisms, and we explored whether benthic environment variables can predict functional diversity distribution. Our results showed that the distribution of assemblages of epifauna functional groups in San Jorge Gulf is mainly related to oxygen availability in bottom water and organic matter in sediments. Habitat suitability maps enable us to predict this distribution, improving our knowledge of biodiversity-ecosystem functioning in the gulf, and providing information for designing sustainable management and conservation strategies for ocean ecosystem services.Fil: Kaminsky, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Varisco, Martin Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fernández, Mónica. No especifíca;Fil: Sahade, Ricardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Archambault, Philippe. No especifíca

Molecular responses of a key Antarctic species to sedimentation due to rapid climate change

Rapid regional warming causing glacial retreat and melting of ice caps in Antarctica leads benthic filter-feeders to be exposed to periods of food shortage and high respiratory impairment as a consequence of seasonal sediment discharge in the West Antarctic Peninsula coastal areas. The molecular physiological response and its fine-tuning allow species to survive acute environmental stress and are thus a prerequisite to longer-term adaptation to changing environments. Under experimental conditions, we analyzed here the metabolic response to changes in suspended sediment concentrations, through transcriptome sequencing and enzymatic measurements in a highly abundant Antarctic ascidian. We found that the mechanisms underlying short-term response to sedimentation in Cnemidocarpa verrucosa sp. A involved apoptosis, immune defense, and general metabolic depression. These mechanisms may be understood as an adaptive protection against sedimentation caused by glacial retreat. This process can strongly contribute to the structuring of future benthic filter-feeder communities in the face of climate change.Fil: Ruiz, Micaela Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Servetto, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Alurralde, Roque Gastón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Abele, Doris. Alfred-Wegener-Institut. Helmholtz-Zentrum für Polar und Meeresforschung; AlemaniaFil: Harms, Lars. Alfred-Wegener-Institut. Helmholtz-Zentrum für Polar und Meeresforschung; AlemaniaFil: Sahade, Ricardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Held, Christoph. Alfred-Wegener-Institut. Helmholtz-Zentrum für Polar und Meeresforschung; Alemani

The Food Web of Potter Cove (Antarctica): complexity, structure and function

Knowledge of the food web structure and complexity are central to better understand ecosystem functioning. A food-web approach includes both species and energy flows among them, providing a natural framework for characterizing species’ ecological roles and the mechanisms through which biodiversity influences ecosystem dynamics. Here we present for the first time a high-resolution food web for a marine ecosystem at Potter Cove (northern Antarctic Peninsula). Eleven food web properties were analyzed in order to document network complexity, structure and topology. We found a low linkage density (3.4), connectance (0.04) and omnivory percentage (45), as well as a short path length (1.8) and a low clustering coefficient (0.08). Furthermore, relating the structure of the food web to its dynamics, an exponential degree distribution (in- and out-links) was found. This suggests that the Potter Cove food web may be vulnerable if the most connected species became locally extinct. For two of the three more connected functional groups, competition overlap graphs imply high trophic interaction between demersal fish and niche specialization according to feeding strategies in amphipods. On the other hand, the prey overlap graph shows also that multiple energy pathways of carbon flux exist across benthic and pelagic habitats in the Potter Cove ecosystem. Although alternative food sources might add robustness to the web, network properties (low linkage density, connectance and omnivory) suggest fragility and potential trophic cascade effects.Fil: Marina, Tomas Ignacio. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; ArgentinaFil: Salinas, Vanesa Anabella. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cordone, Georgina Florencia. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campana, Gabriela Laura. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Moreira, María Eugenia. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Deregibus, Dolores. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Torre, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Sahade, Ricardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Tatian, Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Barrera Oro, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; ArgentinaFil: De Troch, Marleen. University College Ghent; BélgicaFil: Doyle, Santiago Raúl. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Quartino, Maria Liliana. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Saravia, Leonardo Ariel. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Momo, Fernando Roberto. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentin

Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem

The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a “filter feeders–ascidian domination” to a “mixed assemblage” suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP

Baixa concordância entre a classificação da NYHA e as variáveis do teste de exercício cardiopulmonar em pacientes com insuficiência cardíaca e fração de ejeção reduzida

FUNDAMENTO: A classificação funcional da New York Heart Association (NYHA) é o sistema de classificação mais utilizado para a insuficiência cardíaca (IC), enquanto o teste de exercício cardiopulmonar (TECP) é o padrão ouro para a avaliação do estado funcional na IC. OBJETIVO: Analisar a correlação e a concordância entre as classes da NYHA e as variáveis do TECP. MÉTODOS: Foram selecionados pacientes com IC com indicação clínica para TECP e fração de ejeção (FE) < 50%. A correlação (coeficiente de Spearman) e a concordância (kappa) entre a classificação da NYHA e as classificações baseadas no TECP foram analisadas. Um valor de p < 0,05 foi considerado significativo. RESULTADOS: No total, foram incluídos 244 pacientes no estudo. A idade média foi de 56±14 anos, e a FE média foi de 35,5%±10%. A distribuição de pacientes de acordo com a classificação da NYHA foi a seguinte: classe I (31,2%), classe II (48,3%), classe III (19,2%) e classe IV (1,3%). A correlação (r) entre as classes da NYHA e de Weber foi de 0,489 (p < 0,001), e a concordância foi de 0,231 (p < 0,001). A correlação (r) entre as classes da NYHA e ventilatórias (inclinação da ventilação minuto/produção de dióxido de carbono [VE/VCO(2)]) foi de 0,218 (p < 0,001), e a concordância foi de 0,002 (p = 0,959). A correlação de Spearman entre as classes da NYHA e do escore TECP foi de 0,223 (p = 0,004), e a concordância kappa foi de 0,027 (p = 0,606). CONCLUSÃO: Foi identificada uma associação moderada entre as classes da NYHA e de Webber, embora a concordância tenha sido baixa. As classes ventilatórias (inclinação VE/VCO(2)) e do escore TECP apresentaram uma associação fraca e uma baixa concordância com as classes da NYHA