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The non-marine diatom flora of the Antarctic continent is currently being revised as recent work within the Maritime and Sub-Antarctic regions has unveiled a number of new endemic species. The under reporting of endemic species is partially due to the historic 'force-fitting' of Antarctic species into European names. Within East Antarctica, the Vestfold Hills are an extensively studied area known for their diversity of lakes spanning a salinity gradient, for whichDiatoms of the saline lakes of the Vestfold Hills, Antarcticaby Roberts & McMinn (1999) has a primary identification resource for over two decades. To determine if improved taxonomic resolution alters the ecological interpretation of these lakes, 30 prepared lake sediment samples first examined by Roberts & McMinn (1999) were re-analysed using an updated, fine-grained taxonomic approach. Our analyses confirmed the role of salinity and alkalinity in structuring Vestfold Hills diatom communities. Thus, the increased taxonomic resolution did not change the original ecological interpretation. However, the revised flora of the Vestfold Hills features 37 species endemic to the Antarctic Region, including members ofLuticola, SabbeaandHalamphora, among others. In total, 183 taxa across 38 genera were observed, in contrast to the 67 taxa reported in the original work. The revised flora, including a larger proportion of endemic species, may improve our understanding of the diatom community in general and has wider implications for both conservation and biodiversity estimates of Antarctica. More widely applied, these data can be incorporated into larger studies of Antarctic microbial biogeography and biodiversity.

Rocky benthic communities are common in Antarctic coastal habitats; yet little is known about their carbon turnover rates. Here, we performed a broad survey of shallow ( < 65 m depth) rocky ice-scoured habitats of South Bay (Doumer Island, Western Antarctic Peninsula), combining (i) biodiversity assessments from benthic imaging, and (ii) in situ benthic dissolved oxygen (O2) exchange rates quantified by the aquatic eddy covariance technique. The 18 study sites revealed a gradual transition from macroalgae and coralline-dominated communities at ice-impacted depths (15–25 m; zone I) to large suspension feeders (e.g., sponges, bivalves) at depth zone II (25–40 m) and extensive suspension feeders at the deepest study location (zone III; 40–65 m). Gross primary production (GPP) in zone I was up to 70 mmol O2 m−2 d−1 and dark ecosystem respiration (ER) ranged from 15 to 90 mmol m−2 d−1. Zone II exhibited reduced GPP (average 1.1 mmol m−2 d−1) and ER rates from 6 to 36 mmol m−2 d−1, whereas aphotic zone III exhibited ER between 1 and 6 mmol m−2 d−1. Benthic ER exceeded GPP at all study sites, with daily net ecosystem metabolism (NEM) ranging from − 22 mmol m−2 d−1 at the shallow sites to − 4 mmol m−2 d−1 at 60 m. Similar NEM dynamics have been observed for hard-substrate Arctic habitats at comparable depths. Despite relatively high GPP during summer, coastal rocky habitats appear net heterotrophic. This is likely due to active drawdown of organic material by suspension-feeding communities that are key for biogeochemical and ecological functioning of high-latitude coastal ecosystems.

Climate change-induced glacial melt affects benthic ecosystems along the West Antarctic Peninsula, but current understanding of the effects on benthic primary production and respiration is limited. Here we demonstrate with a series of in situ community metabolism measurements that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. With little glacial melt disturbance (during cold El Niño spring 2015), clear waters enabled high benthic microalgal production, resulting in net autotrophic benthic communities. In contrast, water column turbidity caused by increased glacial melt run-off (summer 2015 and warm La Niña spring 2016) limited benthic microalgal production and turned the benthic communities net heterotrophic. Ongoing accelerations in glacial melt and run-off may steer shallow Antarctic seafloor ecosystems towards net heterotrophy, altering the metabolic balance of benthic communities and potentially impacting the carbon balance and food webs at the Antarctic seafloor., Ulrike Braeckman et al. use in situ benthic community and benthic biogeochemistry measurements in Potter Cove on the Antarctic Peninsula to show that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. This study sheds light on how future glacial melt and run-off may affect the metabolic balance of Antarctic benthic communities.

12 pages, 6 figures, 3 tables, We examined the effect of glacial melt-related retreat environmental conditions on the spatial heterogeneity of food sources for Antarctic nearshore marine benthic communities of Potter Cove, a representative fjord on King George Island on the West Antarctic Peninsula. Focusing on Antarctic suspension feeders, we surveyed the variation of carbon (δ13C) and nitrogen (δ15N) stable isotopes in three different stations with contrasting characteristics in terms of glacier-sedimentary regimes and distance from the glacier. Bayesian mixing models were used to estimate the relative contribution of eight potential food sources at the study sites and to the consumers' diet. The isotopically signatures of suspension feeders displayed a broad range of assimilate available food sources with distinct contributions at each site. Overall, for most of the suspension feeders analysed, contributions of suspended particulate matter and macroalgae detritus tended to prevail over the rest of the potential food sources. Additionally, we confirm the assimilation of krill faeces by benthic organisms reinforcing its relevance as food source in nearshore Antarctic ecosystems. Mixing models corroborated the influence of glacier discharge on the spatial distribution of available food sources, since their contribution in the suspension feeders diet was different and more heterogeneous in the internal stations (ice-proximal zone) than in the external one (ice-distal zone). The analysis of isotopic signatures of primary benthic consumers (suspension feeders) indicated the spatial heterogeneity of food sources and its composition in coastal Antarctic nearshore, as consequence of the glacial influence on the local environment and hydrology, This work was supported by the Total Foundation (ECLIPSE Project); Argentinean funds through PICT-Raíces 2011–1320 to IS, PICTO-DNA N° 119; the European Commision under the 7th Framework Programme through the Action – IMCONet (FP7 IRSES, action no. 319718); the American Museum of Natural History (Lerner-Gray Grant for Marine Research)., With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Biofilms were allowed to develop on ceramic tiles placed in closed containers on the shore of Potter Cove, 25 de Mayo (King George) Island. Water pumping from the cove inside the containers extended for 25 days. Diatoms were the dominant microalgae in these biofilms, which were removed from a set of tiles to a) characterize the extracellular mucilage, b) carry out floristic determination and c) perform grazing experiments with the limpet Nacella concinna. Biofilms mucilaginous matrix consisted of proteins and carbohydrates. Room temperature aqueous extraction of the freeze-dried material rendered a fraction enriched in the storage glucan chrysolaminarin, its identity confirmed by methylation structural analyses. Hot water extracted products showed greater heterogeneity in monosaccharide composition, including glucose, mannose, galactose, fucose, xylose and rhamnose. Diatom identification revealed that Pseudogomphonema kamtschaticum was the dominant species followed by several Navicula species, Nitzschia pellucida and Synedra kerguelensis. Photographical survey of colonized tiles placed in glass flasks together with a specimen of Nacella concinna exhibited between 5 and 30% removal of the biofilms coverage after 24 h of exposure to the limpet, suggesting that EPS and chrysolaminarin constitute a C-source for the gastropod., Yasmin Daglio, Hernán Sacristán, Martín Ansaldo, María C.Rodríguez南極キングジョージ島、Potter Coveの海岸に陶器のタイルを設置し、25日間でのバイオフィルムの発達実験を行った。バイオフィルム中では珪藻が優占したが、そこからa）細胞外粘液質の特徴、b）植物相の同定、c）カサガイの一種Nacella concinnaを用いた囓り取り実験を行った。バイオフィルムの粘液層は、タンパク質と炭水化物からなり、グルカノ-クリソラミナリンやグルコースなどの多様な単糖類が含まれていた。珪藻を同定したところ、Pseudogomphonema kamtschaticumが優占し、Naviculaなどがそれに続く事が明らかになった。カサガイによる囓り取りは、24時間で5～30%で、EPSとクリソラミナリンは彼らの炭素源となっていることが示唆された。

15 pages, 7 figures, 5 tables, supplementary data https://doi.org/10.1016/j.marenvres.2019.104790, Sea-ice and coastal glacier loss in the Western Antarctic Peninsula open new ice-free areas. They allowing primary production and providing new seabed for colonisation, both acting as a negative feedback of climate change. However, the injection of sediment-laden runoff from the melting of land-terminating glaciers may reduce this feedback. Changes in particulate matter will affect nutrition and excretion (faeces stoichiometry and properties) of suspension feeders, reshaping coastal carbon dynamics and pelagic-benthic coupling. Absorption efficiency and biodeposition of Euphausia superba and Cnemidocarpa verrucosa were quantified for different food treatments and varying sediment concentrations. Both species showed high overall absorption efficiency for free-sediment diets, but were negatively affected by sediment addition. High sediment conditions increased krill biodeposition, while it decreased in ascidians. Energy balance estimation indicated high carbon sink potential in ascidians, but it is modulated by food characteristics and negatively affected by sediment inputs in the water column, This project benefited from the financial support of the Total Foundation (ECLIPSE Project), Argentinean funds through PICT-Raíces 2011–1320 to IS, PICTO-DNA Nº 119. It has been additionally supported by the European Commision under the 7th Framework Programme through the Action – IMCONet (FP7 IRSES, action no. 319718). It is a contribution to the Coastal Ecology Monitoring programme of Instituto Antártico Argentino/Dirección Nacional del Antártico in Carlini Station and the research program PACES II (topic 1, work package 5) of the Alfred Wegener Institute. GA and TM received a PhD scholarship (CONICET) at the Universidad Nacional de Córdoba

Several fish species of the suborder Notothenioidei (Perciformes) predominate in the Antarctic Convergence Zone; nevertheless, reproductive studies are scarce due to difficulties on regular sampling. This study takes the research area of reproductive biology of notothenioids to a new level by providing, for the first time, data on sex hormone and vitellogenin detection in the blood of females of Notothenia rossii and N. coriiceps and correlates this data with morphological maturity indices as well as ovarian histology. Fish were captured during the Antarctic summer at Potter Cove, 25 de Mayo (King George) Island, and blood and ovary were collected. Histological analysis revealed that females of both fish possess group synchronous ovarian development with two distinct clutches of oocytes: a more advanced batch of vitellogenic oocytes ready for spawning and a second batch of previtellogenic oocytes for the next spawning event. Since liver vitellogenin synthesis is stimulated by estradiol produced by the ovaries, gonadal development, estradiol levels, and vitellogenin showed that both species were at a more advanced stage of maturation in March than in January. On the other hand and irrespectively of the month, gonadosomatic index and plasma estradiol levels of N. coriiceps were higher than those of N. rossii. Furthermore, females of N. coriiceps showed an advanced stage of vitellogenesis or were ready for spawn, contrary to results of previous studies. Our results indicate the successful use of gonadal morphology, estradiol, and vitellogenin detection for the estimation of sexual maturity stage of female adults. Fil: Ferreira, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina Fil: Varela, María Luisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina Fil: Lo Nostro, Fabiana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina Fil: Ansaldo, Martin. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Genovese, Griselda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina

Food web analyses are powerful tools to understand the structure, dynamics and stability of communities. Potter Cove (25 de Mayo/King George Island) is one of the most biodiverse and studied fjords on the West Antarctic Peninsula (WAP), where climate change is affecting benthic and pelagic communities. This fjord ecosystem presents a considerable degree of environmental and species distribution heterogeneity across space: the outer portion of the cove is dominated by hard bottoms meanwhile the inner portion is dominated by soft bottoms. In this work, we have incorporated habitat type to a highly-resolved Antarctic food web, and evaluated its effects on different network metrics and proxies for various dimensions of stability. We considered a multidimensional perspective and employed simulation techniques to encompass variability. Our results showed that the incorporation of habitat type to Potter Cove food web analysis led to two different functional types of networks segregated on space: a green food web (in the outer cove) and a brown food web (in the inner cove). The green and the brown food webs showed significant differences in network structure and in some proxies for multidimensional stability (i.e. quasi sign-stability and omnivory), suggesting that these two food webs have different resilience to perturbations. However, there were no changes in network robustness when in silico experiments were performed. We conclude that habitat type plays a significant role in the structure and stability of Antarctic food webs, and should be taken into account to design effective conservation strategies.

Glaciers along the western Antarctic Peninsula are retreating at unprecedented rates, opening up sublittoral rocky substrate for colonization by marine organisms such as macroalgae. When macroalgae are physically detached due to storms or erosion, their fragments can accumulate in seabed hollows, where they can be grazed upon by herbivores or be degraded microbially or be sequestered. To understand the fate of the increasing amount of macroalgal detritus in Antarctic shallow subtidal sediments, amesocosm experiment was conducted to track 13C- and 15N-labeledmacroalgal detritus into the benthic bacterial, meiofaunal, and macrofaunal biomass and respiration of sediments from Potter Cove (King George Island).We compared the degradation pathways of two macroalgae species: one considered palatable for herbivores (the red algae Palmaria decipiens) and other considered nonpalatable for herbivores (the brown algae Desmarestia anceps). The carbon from Palmaria was recycled at a higher rate than that of Desmarestia, with herbivores such as amphipods playing a stronger role in the early degradation process of the Palmaria fragments and the microbial community taking over at a later stage. In contrast, Desmarestia was more buried in the subsurface sediments, stimulating subsurface bacterial degradation. Macrofauna probably relied indirectly on Desmarestia carbon, recycledby bacteria and microphytobenthos. The efficient cycling of the nutrients and carbon from the macroalgae supports a positive feedback loop among bacteria, microphytobenthos, and meiofaunal and macrofaunal grazers, resulting in longer term retention ofmacroalgal nutrients in the sediment, hence creating a food bank for the benthos. Fil: Braeckman, U.. University of Ghent; Bélgica Fil: Pasotti, F.. University of Ghent; Bélgica Fil: Vázquez, Susana Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentina Fil: Zacher, K.. Alfred Wegener Institute; Alemania Fil: Hoffmann, R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentina Fil: Elvert, M.. Alfred Wegener Institute; Alemania Fil: Marchant, H.. Max Planck Institute for Marine Microbiology; Alemania Fil: Buckner, C.. Max Planck Institute for Marine Microbiology; Alemania Fil: Quartino, M. L.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Mac Cormack, Walter Patricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentina Fil: Soetaert, K.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Wenzhöfer, F.. Utrecht University; Países Bajos Fil: Vanreusel, A.. University of Ghent; Bélgica

Primary production and mineralization are key processes and living organisms key components of the biological carbon cycle. Their dynamics are controlled by abiotic and biotic factors, which can also be inter-dependently linked with each other. Changes in the polar cryosphere and related secondary effects, associated with global temperature increase, can have a great impact on processes and components of the biological carbon cycle. For example, nutrients and particles are released into the marine realm by glacial and permafrost soil melt, while thinning, diminishing, and retreating sea ice leads to increased light availability but suppresses nutrient upwelling. These secondary effects are known to influence primary productivity, organismal community structures and mineralization rates. The investigation of how changes in polar ice conditions alter primary production, the benthic biota, and benthic mineralization is the overall aim of this thesis and was addressed in three manuscripts.

The West Antarctic Peninsula (WAP) is a climatically sensitive region where periods of strong warming have caused significant changes in the marine ecosystem and food-web processes. Tight coupling between phytoplankton and higher trophic levels implies that the coastal WAP is a bottom-up controlled system, where changes in phytoplankton dynamics may largely impact other food-web components. Here, we analysed the inter-decadal time series of year-round chlorophyll-a (Chl) collected from three stations along the coastal WAP: Carlini Station at Potter Cove (PC) on King George Island, Palmer Station on Anvers Island and Rothera Station on Adelaide Island. There were trends towards increased phytoplankton biomass at Carlini Station (PC) and Palmer Station, while phytoplankton biomass declined significantly at Rothera Station over the studied period. The impacts of two relevant climate modes to the WAP, the El Niño-Southern Oscillation and the Southern Annular Mode, on winter and spring phytoplankton biomass appear to be different among the three sampling stations, suggesting an important role of local-scale forcing than large-scale forcing on phytoplankton dynamics at each station. The inter-annual variability of seasonal bloom progression derived from considering all three stations together captured ecologically meaningful, seasonally co-occurring bloom patterns which were primarily constrained by water-column stability strength. Our findings highlight a coupled link between phytoplankton and physical and climate dynamics along the coastal WAP, which may improve our understanding of overall WAP food-web responses to climate change and variability. This article is part of the theme issue 'The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change'. Fil: Kim, Hyewon. Columbia University; Estados Unidos Fil: Ducklow, Hugh W.. Columbia University; Estados Unidos Fil: Abele, Doris. Alfred Wegener Institute for Polar and Marine Research; Alemania Fil: Ruiz Barlett, Eduardo M.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Buma, Anita G. J.. University of Groningen; Países Bajos Fil: Meredith, Michael. British Antarctic Survey; Reino Unido Fil: Rozema, Patrick D.. University of Groningen; Países Bajos Fil: Schofield, Oscar M.. Rutgers University. School of Environmental and Biological Sciences. Department of Marine and Coastal Sciences. Center for Ocean Observing Leadership; Estados Unidos Fil: Venables, Hugh J.. British Antarctic Survey; Reino Unido Fil: Schloss, Irene Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Universidad Nacional de Tierra del Fuego; Argentina

Background: Scavenger guilds are composed of a variety of species, co-existing in the same habitat and sharing the same niche in the food web. Niche partitioning among them can manifest in different feeding strategies, e.g. during carcass feeding. In the bentho-pelagic realm of the Southern Ocean, scavenging amphipods (Lysianassoidea) are ubiquitous and occupy a central role in decomposition processes. Here we address the question whether scavenging lysianassoid amphipods employ different feeding strategies during carcass feeding, and whether synergistic feeding activities may influence carcass decomposition. To this end, we compared the relatively large species Waldeckia obesa with the small species Cheirimedon femoratus, Hippomedon kergueleni, and Orchomenella rotundifrons during fish carcass feeding (Notothenia spp.). The experimental approach combined ex situ feeding experiments, behavioural observations, and scanning electron microscopic analyses of mandibles. Furthermore, we aimed to detect ecological drivers for distribution patterns of scavenging amphipods in the Antarctic coastal ecosystems of Potter Cove. In Potter Cove, the climate-driven rapid retreat of the Fourcade Glacier is causing various environmental changes including the provision of new marine habitats to colonise. While in the newly ice-free areas fish are rare, macroalgae have already colonised hard substrates. Assuming that a temporal dietary switch may increase the colonisation success of the most abundant lysianassoids C. femoratus and H. kergueleni, we aimed to determine their consumption rates (g food x g amphipods−1 x day−1) and preferences of macroalgae and fish.Results: We detected two functional groups with different feeding strategies among scavenging amphipods during carcass feeding: carcass 'opener' and 'squeezer'. Synergistic effects between these groups were not statistically verified under the conditions tested. C. femoratus switched its diet when fish was not available by consuming macroalgae (about 0.2 day−1) but preferred fish by feeding up to 80% of its own mass daily. Contrary, H. kergueleni rejected macroalgae entirely and consumed fish with a maximal rate of 0.8 day−1.Conclusion: This study reveals functional groups in scavenging shallow-water amphipods and provides new information on coastal intraguild niche partitioning. We conclude that the dietary flexibility of C. femoratus is a potential ecological driver and central to its success in the colonisation of newly available ice-free Antarctic coastal habitats.

En el oeste de la Península Antártica se ha registrado un retroceso de los sistemas glaciarios como consecuencia de un incremento de la temperatura, de aproximadamente 2°C, en los últimos 50 años. Este proceso ha originado “nuevas áreas libres de hielo” (NALH) las cuales son aptas para la colonización de algas marinas bentónicas, como ocurre en el caso de estudio de Caleta Potter en donde se ha observado un notable retroceso del Glaciar Fourcade. Simultáneamente, estas áreas presentan distinto grado de perturbaciones asociadas al retroceso glaciario como es incremento en la descarga de sedimento, que genera un menor grado de la penetración de la luz. Se realizaron mediciones de variables ambientales tales como Radiación Fotosintéticamente Activa (400-700nm) (PAR), temperatura, salinidad y turbidez en la columna de agua (de 0 a 30 m de profundidad) en cuatro NALH con distinto grado de influencia glaciaria y en un área control no afectada por el glaciar (Peñón de Pesca) durante los años 2010 y 2014 inclusive. Se llevó a cabo un muestreo fotográfico de 0.5 a 30 m de profundidad durante el verano de 2013 en Peñón de Pesca y en tres NALH. Se caracterizó la distribución espacial y vertical de las comunidades de macroalgas presentes en cada área. A su vez, se compararon temporalmente los resultados obtenidos con estudios previos realizados en las mismas áreas durante el año 2008 (Quartino et al. 2013). Por otro lado, se realizaron estudios ecofisiológicos con cinco especies de macroalgas (Desmarestia anceps, Himantothallus grandifolius, Ascoseira mirabilis, Iridaea cordata y Palmaria decipiens) durante el verano 2010 y la primavera 2011 en Peñón de Pesca y en tres NALH. Se determinaron curvas de fotosíntesis vs irradiancia obteniéndose los valores de los parámetros fotosintéticos y el balance diario metabólico de carbono (BC). Por último, se analizó el proceso de colonización y sucesión en dos NALH; se instalaron placas sucesionales (46 sustratos artificiales) a 5 m de profundidad que fueron analizadas entre los años 2010 y 2014. El aporte de sedimento aumentó en relación directa con el aumento de las temperaturas del aire. Los valores de PAR resultaron significativamente menores en las NALH con mayor influencia glaciaria. Se reveló la permanencia y continuidad de las comunidades de algas en las NALH, y una composición de especies de algas diferentes entre áreas con diferente influencia glaciaria y entre profundidades. Luego de cinco años se identificó la presencia de especies nuevas de macroalgas en cada área, y un aumento en el % cobertura de algas en NALH. Los resultados ecofisiológicos revelaron un BC significativamente menor en áreas con menor penetración de la luz, mientras que no se registraron signos de foto aclimatación reflejados en la falta de variación de los parámetros fotosintéticos de las especies en estudio. Asimismo, la colonización y la sucesión resultaron diferentes en NALH con las condiciones de influencia glaciaria diferentes. En un contexto de cambio climático, es esperable que continúen los procesos de colonización y expansión de las macroalgas y se produzcan cambios significativos en la productividad primaria en sistemas costeros antárticos. Estos estudios, sumados a estudios que incluyan el efecto de otros factores como el sustrato, el disturbio de hielo, la duración del mar congelado, la herbivoría y la competencia entre otros también son fundamentales para predecir la evolución de las comunidades macroalgales antárticas en el contexto del cambio global. The West Antarctic Peninsula has been experiencing marked glacier retreat as a consequence of increased temperatures, of approximately 2°C, in the last 50 years. This process has originated “newly ice-free areas” (NIFA) with are available for macroalgal colonization, as it is the case of Potter Cove where a significant retreat of glacier Fourcade has been observed. Simultaneously, these areas present different degree of glacial disturbance associated with glacier retreat, as the increase of sediment run off, which diminishes a lower degree of light penetration. Environmental factors have been measured as Photosynthetically Active Radiation (400-700nm) (PAR), temperature, salinity and turbidity in the water column (from 0 to 30 m depth) in four NIFA with different degree of glacial influence, and in a control area not affected by the glacier (Peñón de Pesca) between the years 2010 and 2014. A photographic sampling was performed from 0.5 to 30 m depth during summer 2013 in Peñón de Pesca and three NIFA. The spatial and vertical distribution of the macroalgal communities were characterized in each area. At the same time, the results were compared temporally against previous studies performed in the same areas during the year 2008 (Quartino et al. 2013). On the other hand, ecophysiological studies were carried out with five macroalgal species (Desmarestia anceps, Himantothallus grandifolius, Ascoseira mirabilis, Iridaea cordata y Palmaria decipiens) during summer 2010 and spring 2011 in Peñón de Pesca and in three NIFA. Photosynthetic vs. Irradiance curves were obtained, and photosynthetic parameters and the daily metabolic carbon balance (CB) were calculated. Finally, colonization and succession processes were analyze in two NIFA; artificial substrates were installed (46 artificial tiles) at a 5 m depth with were analyzed between the years 2010 and 2014. The sediment input increased directly with the increases of air temperature. PAR was significantly lower at NIFA with more glacier influence. It was revealed the permanence and continuity of algae at the NIFA, and different composition of algal species was found associated to the increased degree of glacier impact in each area. After five years, the presence of new macroalgal species was identified in each área, and an increase in the macroalgal percent cover in the NIFA. The ecophysiological results indicated a CB significantly lower in areas with lower light penetration, while no signs of photoacclimation were registered reflected by the lack of variation of photosynthetic parameters of the studied species. Likewise, the complexity of the colonization and successional states were also found to be related to the conditions of glacial influence in each area. In a climate change scenario, it is expected that the processes of colonization and expansion of the macroalgal community will continue, and significant changes in primary productivity are predicted in Antarctic coastal systems. These studies, together with the study of other factors such us substrate, ice scouring, fast ice duration, herbivory and competition among others are fundamental to predict the fate and evolution of macroalgal communities in this context of global change. Fil: Deregibus, Dolores. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Se estudiaron las dinámicas temporal y espacial de las comunidades de mesozooplancton del Canal Beagle y de Caleta Potter, con énfasis en la fracción de tamaño más pequeño. Para tal fin, serealizaron muestreos con una red de 100 μm de poro. Además, se investigaron las causas de 3eventos de mortandad masiva del krill antártico Euphausia superba, observados en las costas de Caleta Potter en 2008 y 2009. La comunidad del Canal Beagle se estudió durante un ciclo estacionalentre noviembre-2005 y septiembre-2006. Los copépodos fueron el grupo más abundante, siendolas especies dominantes Oithona similis, Ctenocalanus citer y Drepanopus forcipatus. Otros taxonescaracterísticos fueron la apendicularia Fritillaria borealis y el rotífero Synchaeta sp. La comunidadexhibió una marcada variación temporal, presentando una mayor diversidad en septiembre ynoviembre, cuando se registraron elevadas abundancias de larvas meroplanctónicas y una mayorconcentración de clorofila-a. Esto indicaría un fuerte acoplamiento bento-pelágico. La ausencia deun claro patrón espacial del mesozooplancton, sugiere que el área estudiada se comporta como uncuerpo de agua semicerrado. En Antártida, se estudió el mesozooplancton en los sectores interno yexterno de Caleta Potter, entre octubre-2008 y junio-2009. La mayor abundancia se registró enotoño. Las especies características fueron los copépodos O. similis, C. citer, Calanus propinquus, y laapendicularia F. borealis. El krill se halló con mayor frecuencia en el sector externo. Se observó unamarcada variación temporal en la comunidad, diferente en cada sector. La diversidad fue superiordurante el período octubre-marzo en el sector externo, y durante marzo-junio en el sector interno. Se investigó el contenido estomacal e intestinal de krill hallado muerto durante los eventos demortandad masiva, y de krill capturado en las aguas de Caleta Potter. El volumen total de partículasen los estómagos del krill hallado muerto estuvo compuesto principalmente por partículaslitogénicas, y por diatomeas en los estómagos del krill vivo. Además, las partículas litogénicasencontradas en krill vivo resultaron de menor tamaño. Se concluye que partículas litogénicas de granvolumen en la columna de agua, al ser ingeridas por el krill, podrían obstruir su sistema digestivo,ocasionando los eventos de mortandad masiva observados. Palabras clave: zooplancton, copépodos marinos, krill antártico, mortandad masiva, Canal Beagle, Caleta Potter, Antártida The temporal and spatial dynamics of the mesozooplankton communities of the Beagle Channel and Potter Cove were studied with emphasis on the smaller size fraction. Mesozooplankton sampleswere collected with a 100 μm mesh net. In addition, the causes of 3 mass mortality events observedon the coasts of Potter Cove during 2008 and 2009 were investigated. The community of the Beagle Channel was studied during a seasonal cycle between 2008 and 2009. Copepods were the mostabundant group. Among them, Oithona similis, Ctenoacalanus citer and Drepanopus forcipatus werethe dominant species. Other important taxa were the appendicularian Fritillaria borealis and therotifer Synchaeta sp. The community showed a strong temporal variation, with a higher diversity in September and November, in coincidence with higher densities of meroplanktonic larvae andchlorophyll-a concentration. This may indicate a strong bentho-pelagic coupling. The absence of aclear spatial pattern, suggests that the studied area behaves as a semi-enclosed water body. In Antarctica, the mesozooplankton community was studied in both the inner and outer areas of Potter Cove, between October 2008 and June 2009. The highest abundance was registered in autumn. Themost important species were the copepods O. similis, C. citer, Calanus propinquus, and theappendicularian F. borealis. Krill was found more frequently in the outer cove. The communityshowed a strong temporal variation, which was different among areas. Diversity was higher during October-March in the outer cove, but it was higher during March-June in the inner cove. Thestomach and gut contents of dead krill from the mass mortality events, were investigated in relationto the stomach and gut contents of live krill caught in Potter Cove. The total volumes of particles inthe stomachs of dead krill and live krill were mainly composed of lithogenic particles and diatoms,respectively. Moreover, lithogenic particles found in live krill were smaller than in dead krill. It isconcluded that the ingestion of large lithogenic particles in the water column may interrupt thepassage of food in the digestive tract of krill, causing the mass mortality events studied here. Keywords: zooplankton, marine copepods, Antarctic krill, mass mortality, Beagle Channel, Potter Cove, Antarctica Fil: Aguirre, Gastón Ezequiel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

5 pages, 3 figures, Jubanyella plemmyris, a new genus and species of aeginid narcomedusan, is described from one complete specimen stranded on Potter Cove beach, King George Island, Southern Ocean. The new genus and species is proposed in order to accommodate the specimen described in the family Aeginidae; Jubanyella gen. nov. contains undivided stomach pouches, therefore necessitating a new diagnosis for this family. © The Author 2006. Published by Oxford University Press. All rights reserved, The first author is indebted to the German Academic Exchange Service (DAAD) for financing her scientific stay in Germany and to Sigrid Schiel for providing working facilities at the Alfred-Wegener-Institute. We thank A. [...] This study has been performed in the frame of the Census of Marine Zooplankton (CMARZ—COML) and supported by the following project PICT-O 1-11566 from the Argentinean Antarctic Institute

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 determined the abundance of the different seston particles which constituted the stomach contents of the Antarctic ascidian Cnemidocarpa verrucosa (Lesson, 1830) at Potter Cove. Stomach repletion was highest in November and lowest in June. Ascidians took in a wide range of particles from large detritus (macroalgal debris and faecal pellets) to minute particles < 5 μm. Large detritus and minute particles together represent the main percentage of contents throughout the year (mean 91%). Diatoms were a low percentage (mean 4.5%). Unidentified flagellates, dinoflagellates and coccolithophorids were scarce, with mean values lower than 4%. Among diatoms benthic species were more abundant in summer and pelagic ones prevailed from March to November. Resuspension of benthic material due to wind mixing and the input of allochthonous particles by currents are important mechanisms that ensure food for ascidians and the community of suspension feeders in Potter Cove. Fil:Esnal, G.B. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

The West Antarctic Peninsula is one of the fastest warming regions on Earth. Faster glacier retreat and related calving events lead to more frequent iceberg scouring, fresh water input and higher sediment loads, which in turn affect shallow water benthic marine assemblages in coastal regions. In addition, ice retreat creates new benthic substrates for colonization. We investigated three size classes of benthic biota (microbenthos, meiofauna and macrofauna) at three sites in Potter Cove (King George Island, West Antarctic Peninsula) situated at similar water depths but experiencing different disturbance regimes related to glacier retreat. Our results revealed the presence of a patchy distribution of highly divergent benthic assemblages within a relatively small area (about 1 km2). In areas with frequent ice scouring and higher sediment accumulation rates, an assemblage mainly dominated by macrobenthic scavengers (such as the polychaete Barrukia cristata), vagile organisms and younger individuals of sessile species (such as the bivalve Yoldia eightsi) was found. Macrofauna were low in abundance and very patchily distributed in recently ice-free areas close to the glacier, whereas the pioneer nematode genus Microlaimus reached a higher relative abundance in these newly exposed sites. The most diverse and abundant macrofaunal assemblage was found in areas most remote from recent glacier influence. By contrast, the meiofauna showed relatively low densities in these areas. The three benthic size classes appeared to respond in different ways to disturbances likely related to ice retreat, suggesting that the capacity to adapt and colonize habitats is dependent on both body size and specific life traits. We predict that, under continued deglaciation, more diverse, but less patchy, benthic assemblages will become established in areas out of reach of glacier-related disturbance.

Made available in DSpace on 2019-09-12T16:53:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2015 Ministério do Meio Ambiente (MMA) Ministério da Ciência, Tecnologia e Inovação (MCTI) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Secretariat of the Interministerial Commission for the Resources of the Sea (SeCIRM) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) The well-being, feeding habits and energetic and plasmatic parameters of the notothenioids Notothenia rossii and Notothenia coriiceps were assessed in specimens collected at a depth of up to 25 m in the Admiralty Bay region, King George Island, Antarctic Peninsula. The population structure of N. rossii (n = 221) was composed of juveniles, and that of N. coriiceps (n = 151) was composed of adults. The greatest mean length and weight measurements of N. coriiceps may be related to warming waters in the Antarctic Peninsula region. Salps were the dominant item in the diet of both species responsible for high protein quantity item found in muscle tissues and liver. The krill and amphipods were an important food item and related to lipid reserves. Among the indices evaluated, greater variation was observed in the hepatosomatic index of N. coriiceps and was related to the greater sizes and ages attained by this species. The liver and muscle energetic components showed great variability between different months may be related by the variability in diet. The plasma components did not exhibit seasonal patterns but displayed large monthly variation. Long-term analysis of the biological parameters evaluated in this study should be continued to monitor the species present in Admiralty Bay, a region with great biological diversity. [Raga, Gabriela; Pichler, Helen Audrey; Zaleski, Tania; Vaz da Silva, Flavia Baduy; Machado, Cintia; Rios, Flavia Sant'Anna; Donatti, Lucelia] Univ Fed Parana, Dept Cell Biol, Adapt Biol Lab, BR-80060000 Curitiba, Parana, Brazil [Rodrigues, Edson] Universidade de Taubaté (Unitau), Basic Biosci Inst, Sao Paulo, Brazil [Kawall, Helena Goncalves] Univ Sao Paulo, Oceanog Inst, Sao Paulo, Brazil

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 (d13C and d15N 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.

Sensitivity to photoinhibition from near-surface irradiance was determined in coastal phytoplankton from Potter Cove (King George Island, Antarctica) in relation to hydrographic conditions shaped by summertime meltwater influx. Slow (indicative for PSII damage) and fast (indicative for xanthophyll cycle activity) relaxing non-photochemical chlorophyll fluorescence quenching (NPQ) was measured during recovery from excess photosynthetically active radiation (PAR) and PAR + ultraviolet radiation (UVR) for 3 stations differentially affected by sediment influx. Additionally, assemblages were incubated outside to study xanthophyll cycle activity during PAR and PAR+UVR exposure. For comparison, NPQ and xanthophyll cycle activity were determined for high (125 mu mol photons m(-2) s(-1)) and low (20 mu mol photons m(-2) s(-1)) light acclimated Chaetoceros brevis (Bacillariophyceae) and Phaeocystis antarctica (Haptophyceae) cultures. Pigment analysis (CHEMTAX) revealed diatom dominance (average 74%) at all locations, with haptophytes being of minor importance (average 13%). All stations were stratified by a vertical density gradient, whereas sediment influx was significantly higher at the innermost station. Taxonomic composition, NPQ characteristics, and photoprotective pigment ratios were not different among stations. At the chlorophyll maximum, phytoplankton showed high light acclimation at all locations, and fast relaxing NPQ dominated after excess PAR and PAR+UVR. Samples from below the chlorophyll maximum were enriched in haptophytes, showed lower photoprotective pigment ratios, reduced capacity for NPQ, and increased contribution of slow relaxing NPQ. The photoprotective capacity of high and low light acclimated C. brevis and P. antarctica differed significantly. P. antarctica induced less NPQ and there was a stronger slow relaxing NPQ component than in the diatom, particularly after low light acclimation. Although total NPQ decreased and slow relaxing NPQ increased after UVR in field samples, NPQ and the xanthophyll cycle de-epoxidation state of cultures were not affected by UVR. A higher photoprotective capacity of diatoms over haptophytes may explain their dominance in stratified meltwater-affected coastal Antarctic waters.