Stable isotope analyses were used to investigate the diet of Weddell seals in Terra Nova Bay (Ross Sea) and the potential variation of their foraging behaviour with age, sex and body mass. For this purpose, skin samples were collected from adult breeding seals and pups, together with muscle samples of their potential prey. Our results showed variation in foraging behavior between age classes, with pups reporting lower ?C values than adults, while no significant differences in ?N were recorded. In addition, contrary to expectations, a mixing model analysis showed that adult seals foraged mainly on shallow benthic prey, such as Trematomus spp. (34.1%) and Dissostichus mawsoni (21.1%), rather than on pelagic fish, such as Pleuragramma antarcticum (9.8%). Overall, with this paper we provide novel diet information on a seal colony not previously sampled, adding new insight into the feeding ecology of a top Antarctic predator.

Biotic interactions are particularly relevant in stable environments, such as the High Antarctic areas. Among them, predation has a key role in structuring community and population variables, including size-frequency distribution. This study aims to quantify the impact of predation by the notothenioid fish Trematomus bernacchii on the Antarctic scallop Adamussium colbecki-size distribution. We developed a model of this impact that estimates the size distribution of the preyed scallop population, taking into account for the predator-size distribution, sex structure, and daily consumption. Comparing this size distribution of the preyed A. colbecki with the living populations at Terra Nova Bay (Ross Sea, Antarctica), we were able to detect a relevant impact of fish predation. Fish-size frequency resulted to be the major factor shaping prey-size structure, with significant differences between predation by males and females. Our findings, given the key role of the two species in the littoral ecosystem of Terra Nova Bay (Antarctic Special Protected Area 161), fall into the framework of ecosystem management of High Antarctic coastal areas, particularly in the actual context of climate change, and increasing anthropogenic impact.

In this study the accumulation of the 3,3'-dichlorobiphenyl (PCB-11) in monitoring organisms from the Antarctic and Mediterranean coastal environments has been investigated. This lesser-known PCB congener, unrelated to the industrial use of commercial mixtures, continues to be generated and released into the environment mainly as an unintentional by-product of pigment manufacturing. Specimens of the filter-feeders Adamussium colbecki from Terra Nova Bay and of Mytilus galloprovincialis and Ruditapes philippinarum from the north-western Adriatic coasts were collected and analyzed for PCB-11 by Gas Chromatography coupled both to Low-Resolution and High-Resolution Mass Spectrometry (LRMS, HRMS). In order to assess the influence of PCB-11 with respect to the legacy contamination, 126 PCB congeners related to the Aroclor commercial mixtures were simultaneously analyzed. PCB-11 was detected in all the samples, regardless of the species and of the geographical area, representing on average 17.6% and 15.6% of the total PCBs (n 127) in Antarctic and Mediterranean samples, respectively. In the Adriatic area the highest concentrations were related to the influence of industrial activities or ship traffic, while the highest value found in Antarctic specimens, namely those collected in the austral summer 1997-1998, was ascribed to a local anthropogenic source. The occurrence of PCB-11 in the other samples from Terra Nova Bay may be related to Long-Range Atmospheric Transport (LRAT), facilitated by the higher volatility of the analyte compared to the heavier PCB congeners. Nevertheless, more in-depth studies are needed in order to evaluate the relative contribution of local and distant sources.(C) 2017 Elsevier Ltd. All rights reserved.

The Antarctic silverfish, Pleuragramma antarctica, is ecologically important for connecting lower and upper trophic levels within the coastal marine Antarctic food web. In recent decades, populations of silverfish have exhibited a declining trend in some regions of the Antarctic, in particular the western Antarctic Peninsula. It is of paramount importance to elucidate its life history and to characterize the areas that are crucial for the reproduction of the species: spawning, hatching and nursery areas. Presently, the overall available knowledge is scant and spatially restricted. In this study, we assessed the spatial scales of variation in the distribution patterns of eggs and newly hatched larvae, and their vertical distribution within the platelet ice layer underlying fast ice at Terra Nova Bay. We found that (1) distribution patterns of eggs and larvae abundance significantly changed at a spatial scale of kilometers, while they did not at scale of tens of kilometers and hundreds/tens meters, and (2) eggs were not homogeneously distributed under the solid ice; in particular, the egg abundance was highest at -2.5 m within the platelet ice and dramatically declined more in depth. This study thus allowed shed light on distribution patterns of eggs and early-hatched larvae of the Antarctic silverfish. Such information will be useful to better understand the ecological processes possibly producing the patterns we have observed and then identify further reproduction and nursery areas around the Antarctic continent.

Underwater acoustic measurements have been recently carried out in Tethys Bay (Ross Sea, Antarctica) during the XXIX Italian Antarctic Expedition to support acoustic propagation studies in the area and to investigate the environmental noise. Tethys Bay is a small deep cove close to the Antarctic Italian base Mario Zucchelli Station (Baia Terra Nova -74°42' S e 164°07' E) and covered with sea-ice for most of the year. During the period of the experiment (November 2013) the pack-ice had an almost constant thickness of about 2.2 m, so that the measurements were performed deploying the instruments into the sea from holes drilled through the pack ice. The holes were located along the bay axis at a distance of about 500 m each other. The sea depth was around 200 m except for the hole close to the coast, where the sea depth was only 25 m. An hydrophone RESON TC 4032 was located in the outermost hole, while the acoustic source, a transceiver transmitting FSK pulses at 11 kHz, was placed in sequence in the other three holes. Every time, the measurements were performed at 0, 20 and 45 m depth for each configuration. Furthermore during the experiment, sea temperature, salinity and currents, as well as the main meteorological parameters were continuously measured. The analysis here reported mainly focuses on the acquired acoustic passive data. The passive measurements evidenced that the signal was generally dominated by different sounds from seals, which was prevailing on the noise due to human activities.

Underwater acoustic measurements have been recently carried out in Tethys Bay (Ross Sea, Antarctica) during the XXIX Italian Antarctic Expedition to support acoustic propagation studies in the area and to investigate the environmental noise. Tethys Bay is a small deep cove close to the Antarctic Italian base Mario Zucchelli Station (Baia Terra Nova -74°42' S e 164°07' E) and covered with sea-ice for most of the year. During the period of the experiment (November 2013) the pack-ice had an almost constant thickness of about 2.2 m, so that the measurements were performed deploying the instruments into the sea from holes drilled through the pack ice. The holes were located along the bay axis at a distance of about 500 m each other. The sea depth was around 200 m except for the hole close to the coast, where the sea depth was only 25 m. An hydrophone RESON TC 4032 was located in the outermost hole, while the acoustic source, a transceiver transmitting FSK pulses at 11 kHz, was placed in sequence in the other three holes. Every time, the measurements were performed at 0, 20 and 45 m depth for each configuration. Furthermore during the experiment, sea temperature, salinity and currents, as well as the main meteorological parameters were continuously measured. The analysis here reported mainly focuses on the acquired acoustic passive data. The passive measurements evidenced that the signal was generally dominated by different sounds from seals, which was prevailing on the noise due to human activities.

Interannual and seasonal variability of the biogeochemical characteristics of fast ice were analysed in relation to ambient conditions, water column properties and ice biota. According to Zubov's Law, the annual atmospheric cooling should generate 2.5m thick fast ice sheets in this coastal zone, but katabatic wind peaks in July-August often cause ice breakouts, resulting in highly variable growth periods (2-9 months) and thickness (1.0-2.5 m). In spring, atmospheric forcings significantly modulate brine content (5-20%) and drainage in fast ice, as well as salinity oscillations in bottom and platelet layers (15 psu). In the water column, the formation of nutrient-impoverished Summer Surface Waters is triggered by seawater warming (-1.9 to 0.78 C), ice melting (0.03 m d-1) and pelagic production. Negative NO3 and SiO2 balances and positive NH4 balances (-41, -153 and 1173 kg km-2, respectively) were estimated in fast ice in spring, whereas nutrient budgets in the platelet layer are regulated by its variable level of isolation from seawater. The large accumulation of dissolved organic carbon (3890 kg km-2) in the ice system and its release in seawater in late spring are important features of the carbon cycle in these Antarctic coastal zones, with possible implications for the modulation of climate.

Pleuragramma antarcticum is the dominant pelagic fish in the waters of the continental shelf in high Antarctic regions, where it plays a key role in the food web. A nursery ground for eggs of this species was first identified in 2002 in Terra Nova Bay (Ross Sea), where eggs were found trapped in ice platelets under the sea-ice during the spring. As part of a monitoring program aimed at understanding the geographic and temporal characteristics of this nursery ground, the present study reports on surveys carried out in the austral springs of 2005 and 2006 using a simple and effective method for sampling from the sea-ice. These surveys enabled the evaluation of the spatial range of the nursery area of the Antarctic silverfish in the sea-ice of the coastal area of Victoria Land between the Coulman Island and the Drygalski Glacier Tongue. P. antarcticum eggs were concentrated in an area of Terra Nova Bay of about 270 km(2), encompassing two adjacent sites, Gerlache Inlet and Silverfish Bay. The present results add information on life cycle and hatching period of the Antarctic silverfish and confirm the importance of the Terra Nova Bay as a nursery area for this important species. Moreover, the survey points to the sea-ice cover and platelet ice as important environmental features of the nursery area.

The aim of this study was to assess the role of platelet ice microalgal communities in seeding pelagic blooms. Nutrient dynamics, microalgal biomass, photosynthetic parameters, cell densities and species succession were studied in two mesocosm experiments, designed to simulate the transition of microalgal communities from platelet ice habitat to pelagic conditions. The microalgal assemblages were dominated by diatoms, 70% of which were benthic species such as Amphiprora kufferathii, Nitzschia stellata, and Berkeleya adeliensis. Photoacclimation of benthic species was inadequate also at relatively low irradiances. Exceptional growth capacity at different light levels was observed for pelagic species such as Fragilariopsis cylindrus and Chaetoceros spp. which may be important in seeding blooms at ice breakup. Fragilariopsis cylindrus showed high growth rates both at 65 and 10% of incident light and in nutrient replete as well as in nutrient depleted conditions. Five days after inoculation, phytoplankton biomass increased and nutrient concentrations decreased in both light conditions.

The aim of the study was to investigate the capacity of microalgae from the extremely low light habitat of bottom ice to acclimate to different light conditions. During austral spring 1997 the bottom layer of land-fast ice in Terra Nova Bay displayed high values of microalgal biomass concentrated in a few centimetres ice layer. The algal assemblage was dominated by benthic pennate diatoms. Photoacclimation of the microalgae was addressed in terms of pigment spectra and photosynthetic parameters. Immediate and long term (minutes to days) changes in the photoprotective pigments (DD-cycle) were analysed. Severe photodamage occurred in microalgal assemblages exposed to high light. However, part of the bottom ice algal community showed a notable ability to acclimate to high irradiance levels. Changes in photosynthetic parameters preceded the sudden abrupt changes in pigment synthesis and the rapid increase in biomass and growth rates.