Ricardo Sahade

Ricardo Sahade
IDEA,Instituto de Diversidad y Ecología Animal, CONICET-UNC · Ecología Marina

About

71
Publications
12,425
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1,140
Citations
Citations since 2016
31 Research Items
713 Citations
2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140

Publications

Publications (71)
Article
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 spec...
Article
Full-text available
When Antarctic glaciers retreat, high sediment loads from geomorphological and glaciological sources can disturb the biota, especially filtering organisms, and thereby significantly alter the ecology of the Antarctic coast. We applied the Finite volumE Sea-ice Ocean-Coastal Model (FESOM-C), a numerical tool equipped with a sediment module, to simul...
Article
Parallel phenotypic divergence is the independent differentiation between phenotypes of the same lineage or species occupying ecologically similar environments in different populations. We tested in the Antarctic limpet Nacella concinna the extent of parallel morphological divergence in littoral and sublittoral ecotypes throughout its distribution...
Thesis
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La Antártida y su océano han estado aislados efectivamente del resto de océanos y continentes del planeta por más de 20 millones de años. El Océano Austral es uno de los ecosistemas marinos más diversos y ricos, compuesto por un ensamble biótico adaptado a condiciones sumamente estables y extremas de vida. Sin embargo, en los últimos 60 años la Pen...
Article
The rapid warming of the West Antarctic Peninsula (WAP) is causing an important expansion of marine coastal areas due to glacier retreat. These new ice-free areas offer additional habitats for the colonization of benthic species in areas formerly occupied by ice. The establishment of benthic species can represent important negative feedback to the...
Article
Ocean acidification (OA) could become a serious threat for the Antarctic marine ecosystem over coming years, as the solubility of atmospheric CO2 and CaCO3 minerals increases at lower temperatures. We evaluated the effect of OA on the stress response of the limpet Nacella concinna by measuring gene expression levels. The experiment was performed wi...
Article
Glacier melting sediment inputs affect coastal ecosystems on the Antarctic Peninsula. In Potter Cove (South Shetland Islands, Antarctica), the shift from an “ascidian dominated” to a “mixed” assemblage has been linked to sedimentation. However, in recently described newly ice-free areas ascidians became dominant in spite of total suspended particul...
Article
Full-text available
The Southern Ocean is one of the most isolated marine ecosystems, characterized by high levels of endemism, diversity, and biomass. Ascidians are among the dominant groups in Antarctic benthic assemblages; thus, recording the evolutionary patterns of this group is crucial to improve our current understanding of the assembly of this polar ocean. We...
Article
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The scallop Argopecten purpuratus is a heavily exploited resource along the coasts of Peru and north-central Chile, especially after El Niño events, when the species undergoes high increases in abundance. Little is known about its genetic structure or demographic history, two important factors to ensure sustainable exploitation. We sequenced the cy...
Article
Full-text available
Ascidians are abundant and well-represented members of worldwide benthic communities, including Antarctica and the Arctic. These organisms exhibit different reproductive patterns usually related to a latitudinal gradient, as do many marine invertebrate species. Reproductive seasonality varies from one or two annual peaks in cold and temperate water...
Article
Full-text available
The Antarctic limpet (Nacella concinna) presents two ecotypes related to different water depths: littoral individuals have a robust and taller shell while sublittoral individuals are thinner and flatter. Among the environmental factors possibly causing this divergence, avian predation upon littoral individuals has been mooted but has received littl...
Article
Full-text available
ABSTRACT. 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 b...
Article
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...
Article
Full-text available
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...
Preprint
Full-text available
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...
Article
Antarctic ecosystems present highly marked seasonal patterns in energy input, which in turn determines the biology and ecology of marine invertebrate species. This relationship is stronger at lower levels of the food web, while upper levels may be less dependent on primary production pulses. The pennatulid Malacobelemnon daytoni, is one of the most...
Presentation
Full-text available
The study of food web structure and complexity is 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 f...
Conference Paper
Full-text available
Increasing atmospheric carbon dioxide concentration alters the chemistry of the oceans towards more acidic conditions. Polar oceans are particularly affected due to their low temperature, low carbonate content and mixing patterns, for instance upwellings. Tolerance to ocean acidification (OA) in metazoans is first linked to acid–base regulation cap...
Conference Paper
Full-text available
Increasing atmospheric carbon dioxide concentration alters the chemistry of the oceans towards more acidic conditions. Polar oceans are particularly affected due to their low temperature, low carbonate content and mixing patterns, for instance upwellings. Echinodermata were hypothesized to be at risk due to their high-magnesium calcite skeleton. H...
Article
Full-text available
The Antarctic Peninsula is one of the regions on the Earth with the clearest evidence of recent and fast air warming. This air temperature rise has caused massive glacier retreat leading to an increased influx of glacier meltwater which entails hydrological changes in coastal waters, increasing sediment input and ice-scouring impact regime. It has...
Article
The Antarctic Peninsula is among the places on Earth that registered major warming in the last 60 years. Massive ice losses, represented by glacier retreat, ice-shelf collapses and sea-ice reduction are among the main impacts of this regional warming. The loss of sea-bed ice coverage, on the one hand has been affecting benthic assemblages, but on t...
Poster
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This poster presents the results on functional diversity analyses for benthic communities in San Jorge Gulf, Argentina
Article
Full-text available
In the Arctic, the currently observed rising air temperature results in more frequent calving of icebergs. The latter derive from tidewater glaciers. Arctic macrozoobenthic soft-sediment communities are considerably disturbed by direct hits and sediment reallocation caused by iceberg scouring. With the aim to describe the primary succession of macr...
Data
Histology of colony of Malacobelemnon daytoni showing the different spermatogenic and oogenic classes in the longitudinal canal. (a) Oocytes in three stages (I, II and mature) (b) oocytes stage I grouped in clusters and (c) mature oocytes. (d) Spermatocyst stage I (e) stage II and (f) mature spermatocyst in the longitudinal canal. S.I: Stage I. S.I...
Data
All data underlying this work. (XLSX)
Data
Wind speed between January 2009 and December 2010. Data were supplied by the Servicio Meteorológico Nacional (SMN) of the Argentinean Air Force at Carlini Station. datas from Schloss el at. (2012) Vertical bars indicate ± SE. (TIF)
Data
Oocyte size (μm) frequency distribution of individual colonies collected in (a) March 2009, (b) December and c) May 2009 and 2010. (Month, year / number of colony). (TIF)
Article
Full-text available
The pennatulid Malacobelemnon daytoni is one of the dominant species in Potter Cove, Antarctica. Its abundance and range of distribution have increased in recent years probably related to climate change mediated alterations of environmental factors. This work is the second part of a study dealing on the reproductive ecology of Malacobelemnon dayton...
Data
In the Arctic the currently observed rising air temperature results in more frequent calving of icebergs. The latter are derived from tidewater glaciers. Arctic macrozoobenthic soft-sediment communities are considerably disturbed by direct hits and sediment reallocation caused by iceberg scouring. With the aim to describe the primary succession of...
Article
Full-text available
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 pre...
Article
Full-text available
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 diffe...
Poster
Full-text available
In this poster, we present the objectives and methodology for a study on benthic communities in San Jorge Gulf, Argentina
Conference Paper
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La Península Antártica Occidental ha experimentado un rápido incremento en la temperatura del aire y un acelerado retroceso de los glaciares. En Caleta Potter (Isla 25 de Mayo, Antártida), el retroceso del glaciar Fourcade no sólo provocó cambios notables en las comunidades bentónicas sino que además descubrió nuevas zonas libres de hielo disponibl...
Conference Paper
Full-text available
El Atlántico sudoccidental (Mar Argentino) es una región poco conocida en cuanto a su biodiversidad. En particular el Golfo San Matíias (Riío Negro), constituye una zona transicional entre las provincias biogeograáficas Magallánica y Argentina donde confluyen biotas de distintos orígenes. Su sensibilidad como ecosistema transicional demanda la apli...
Article
Full-text available
The muddy bottoms of inner Potter Cove, King George Island (Isla 25 de Mayo), South Shetlands, Antarctica, show a high density and richness of macrobenthic species, particularly ascidians. In other areas, ascidians have been reported to play the role of ecosystem engineers, as they support a significant number of epibionts, increasing benthic diver...
Presentation
Full-text available
For marine invertebrates living at low temperatures of high latitudes Thorson’s rule suggests a comparatively reduced speed of development. Several studies conducted in different climatic zones have revealed the processes involved in the maturation of benthic assemblages. However, the duration and chronology of succession, as well as the influence...
Article
Full-text available
In Antarctica, ascidians are among the most conspicuous and abundant organisms in benthic ecosystems and many species present wide distribution patterns. Two similar forms of ascidians of the colonial genus Synoicum were sampled along the South Shetland Islands, one greenish-yellow with elongated colony stalks and the other yellow-orange with short...
Article
Glacial retreat and subglacial bedrock erosion are consequences of rapid regional warming on the West Antarctic Peninsula. Sedimentation of fine-grained eroded particles can impact the physiology of filter-feeding benthic organisms. We investigated the effect of increasing concentrations of sediment on the oxygen consumption of suspension feeding s...
Article
Full-text available
Many species of the genus Octopus are important resources for fisheries worldwide. Its approximately 200 species show a strong similarity in structural morphology and a wide diversity in skin coloration and patterning, behaviour and life strategies that have hampered the study of phylogenetic relationships. We used a Bayesian approach to estimate a...
Article
Full-text available
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 Pola...
Data
Appendix 1 Description of the outline of the shell using increasing number of harmonics. The first 15 harmonics represents 99.99% of the total Fourier power spectrum. Graphically this number of harmonics represents better the contour of shells than previous harmonics. The red line represents the original shape of shell and the light blue line repre...
Article
Full-text available
The Antarctic limpet Nacella concinna (Strebel 1908) presents two ecotypes (littoral and sublittoral) differing in morphological and behavioral characteristics and more recently discovered, in physiological traits and genetic population structure. Previous works, based on traditional morphometry, used only three measurements (length, width and heig...
Article
Full-text available
Octacnemids represent a different pathway in the evolution of the typical filter-feeding ascidians. We examine and identify the prey items in the gut contents and describe the cell types that constitute the inner wall of different sections of the gut of the macrophagous octacnemid Cibacapsa gulosa collected in the South Sandwich Islands, Antarctica...
Conference Paper
Full-text available
Las comunidades del intermareal rocoso son sensibles tanto a cambios de las condiciones naturales como a los causados por la actividad humana, siendo escasos los estudios a ese nivel en las costas argentinas. El trabajo se llevo a cabo en dos y tres comunidades intermareales de la localidad de Las Grutas (40º 49’ S, 65º 05’ O) en los años 2007 y 20...
Conference Paper
Full-text available
El presente estudio se llevó a cabo en la zona del intermareal de La Rinconada en la localidad de Las Grutas (65º 05 O; 40º 48 S) ubicada en el Golfo San Matías (Río Negro, Argentina) (Fig. 1). El sitio presenta un ciclo de marea semidiurno, por lo que el muestreo se realizó durante la máxima bajamar del mes de noviembre de 2008. Se muestrearon 8 p...
Article
The actual Arctic biota shows a strong affinity with that of the Boreal Atlantic and Pacific ones, as a result of an active recolonization process after the Quaternary glaciations. The geographic distribution of sessile species is usually linked to larvae dispersive capabilities which can be directly related with time spent in the plankton. Ascidia...
Article
An in situ experiment on metazoan meiofauna colonisation and succession was carried out at Brandal (78°56.88′N, 11°51.63′E), situated in arctic glacial Kongsfjorden (Spitsbergen). 28 soft sediment containers were deployed at a depth of 20 m and sampled after a one-, two-and three-year immersion period. The main taxonomic groups, abundance of coloni...
Article
Full-text available
The limpet Nacella concinna (Strebel 1908) was the focus of numerous studies dealing with Antarctic benthos. One of the main characteristics of the species is the presence of two distinguishable morphotypes, one inhabiting the intertidal (during summer) and the other inhabiting the subtidal. For a long time these forms were considered as an express...
Article
Full-text available
A rich benthic filter-feeding community is present at Potter Cove, South Shetland, in spite of some usually unfavorable conditions affecting their feeding ecology, such as low phytoplankton production in summer and high sedimentation rates. However, organic material that could fuel the benthic system, such as macroalgal fragments, was detected in t...
Article
Full-text available
und Meeresforschung Am Handelshafen 12 -Geb. E 27570 Bremerhaven * This work is dedicated to the memory of Augusto "Alfa" Thibaud and Teófilo González, who lost their lives in a glacier crevasse near Jubany during the overwintering in 2005.
Article
Full-text available
Ascidians are found in all the oceans. The Polar Front is considered a strong barrier, especially for benthic organisms, separating the Southern Ocean from other oceans. Its influence on ascidian species present at the boundary of the Magellan and Antarctic regions along the Scotia Arc and on the species composition at each station is inferred from...
Article
Full-text available
Coupling between pelagic and benthic systems has been described in numerous shallow water communities. In Potter Cove, where pelagic primary production is low (not only during the Antarctic winter but also during the summer), the rich benthic community present there must depend on other food sources than phytoplankton. Over a year-round period we d...
Article
Full-text available
The reproductive biology of the common Antarctic ascidian Cnemidocarpa verrucosa (Lesson) (Tunicata, Ascidiacea) was studied in a shallow-water population at Potter Cove, South Shetland Islands. Samples were taken monthly by SCUBA diving over a 15 mo period during 1996 and 1997. The reproductive cycle was examined by histological analysis of the go...
Article
A high seasonality characterizes Antarctic environments, and generates marked differences in availability and composition of food for benthic filter feeders. During a year-round period at Potter Cove, Antarctica, algal pigment concentration (chlorophyll a) and organic matter were measured in water column and sediment samples. Chemical composition o...