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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.

Although many notothenioid fishes are primarily carnivorous, some species consistently feed on macroalgae and are therefore omnivorous. Among fish, the degree of herbivory is usually reflected in the morphology of the gastrointestinal system especially intestine length. We examined a large number of juvenile and adult specimens of nine sympatric notothenioid species collected sequentially over eight summer seasons at Potter Cove, South Shetland Islands. We provide relative intestine lengths (RIL), distinct proportions of algae and animal prey in the diets (W%), and numbers of pyloric caeca for all species. The sister species Notothenia coriiceps (NOC) and N. rossii (NOR) evidenced significantly different intestinal growth over ontogeny and ate distinctly different proportions of algae and animal prey. We establish a ranking of the degree of herbivory for the fish species in the local ecosystem, and this was found to be related to their distinct feeding types and strategies. There is a correspondence between intestine length/RILs and degree of herbivory in six of the nine species analysed but no clear association between the number of pyloric caeca and degree of omnivory or carnivory. Compared to other teleosts, our results, and those in the literature, indicate modest divergence in notothenioids that include a phylogenetic decrease in the number of pyloric caeca, from 6 to 7 in most nototheniids to 2–3 in channichthyids, and a 1.8-fold difference in average relative intestine lengths which are most frequently 50–70% of body length and never exceed body length. This is consistent with the unspecialized gastrointestinal morphology that reflects the dietary and ecological plasticity of many notothenioids, exemplified by the high degree of omnivory in species such as NOC and NOR. Fil: 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. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina Fil: Novillo, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Eastman, Joseph T.. Ohio State University; Estados Unidos Fil: Barrera Oro, Esteban. 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

Coastal areas of the West Antarctic Peninsula (WAP) constitute a rich and biodiverse marine zone. Despite these ecosystems being supported by the microorganism’s activity, the structure of microbial communities is insufficiently studied. As WAP is the area most affected by global warming worldwide, the increased glacier melting caused by the global warming and the consequent increase of the water runoff could be deeply affecting these microbial communities. To advance knowledge about the structure of microbial communities and its response to the environmental factors, a full-year study of marine bacterioplankton was conducted at Potter Cove, Antarctica. Multivariate analysis based on denaturing gradient gel electrophoresis (DGGE) and environmental data revealed a seasonal pattern in the structure of the bacterioplankton community, with spring–summer clustering separately from autumn–winter samples. Salinity, temperature and particulated matter werethe main environmental driving forces. Based on the seasonal patterns, five bacterial clone libraries were performed from three sampling sites (E1, inner cove; E2, outer cove; and E3, mouth of a creek). Phylogenetic analysis of libraries generated 301 operational taxonomic units (OTUs), revealing the enormous richness and high diversity of these communities. Proteobacteria (68%), Bacteroidetes (20%) and Actinobacteria (8%) were the most represented phyla. During summer, bacterial community from E1 resembled that observed in E3, whereas during winter it resembled the E2 community. Results evidencedthe influence of glacial meltwater input and showed the high variability of the bacterioplankton from inner cove. This study contributes to the better understanding of the structure of the Potter Cove marine ecosystems and could be reflecting the behavior of other similar ecosystems from WAP.

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

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.