Admiralty Bay Research Articles

Waterfall notch-filtering for restoration of acoustic backscatter records from Admiralty Bay, Antarctica

A series of multibeam sonar surveys were conducted from 2009 to 2013 around Admiralty Bay, Shetland Islands, Antarctica. These surveys provided a detailed bathymetric model that helped understand and characterize the bottom geology of this remote area. Unfortunately, the acoustic backscatter records registered during these bathymetric surveys were heavily contaminated with noise and motion artifacts. These artifacts persisted in the backscatter records despite the fact that the proper acquisition geometry and the necessary offsets and delays were applied during the survey and in post-processing. These noisy backscatter records were very difficult to interpret and to correlate with gravity-core samples acquired in the same area. In order to address this issue, a directional notch-filter was applied to the backscatter waterfall in the along-track direction. The proposed filter provided better estimates for the backscatter strength of each sample by considerably reducing residual motion artifacts. The restoration of individual samples was possible since the waterfall frame of reference preserves the acquisition geometry. Then, a remote seafloor characterization procedure based on an acoustic model inversion was applied to the restored backscatter samples, generating remote estimates of acoustic impedance. These remote estimates were compared to Multi Sensor Core Logger measurements of acoustic impedance obtained from gravity core samples. The remote estimates and the Core Logger measurements of acoustic impedance were comparable when the shallow seafloor was homogeneous. The proposed waterfall notch-filtering approach can be applied to any sonar record, provided that we know the system ping-rate and sampling frequency.

Changes in bird communities of Admiralty Bay, King George Island (West Antarctic): insights from monitoring data (1977–1996)

AbstractThe paper summarizes results of twenty years of seabird observations carried out between 1977 and 1996 on the western shore of Admiralty Bay (King George Island, South Shetlands, Antarctic). Changes in population size, distribution and phenology of the breeding species as well as the appearance of non-breeding species are reported. A total of 34 species of birds were observed, including 13 breeding species. Among the non-breeding species, four were observed to visit the site regularly, six rarely, and the remaining 11 were observed only occasionally. Among breeding populations, three Pygoscelis penguin species, the main krill consumers, were most numerous. The Adélie Penguin (P. adeliae) dominated among the penguins nesting in the investigated areas, reaching 23,661 breeding pairs in 1978. Two other penguin species were less abundant with population sizes of approximately 7,200 breeding pairs for the Chinstrap Penguin (P. antarcticus) and 3,100 breeding pairs for the Gentoo Penguin (P. papua) in the same year. During the following two decades, breeding populations of pygoscelid species experienced a declining trend and their numbers were reduced by 68.0% for Chinstrap, 67.1% for Gentoo, and 33.9% for Adélie Penguins. The data reported here represent a unique reference basis and provide valuable information about indicator species, suitable for comparison with contemporary observations of bird populations in the Antarctic Peninsula region, a place of rapidly occurring climate changes and intensive harvesting of marine living resources.

Low abundance and high species richness: the structure of the soft-bottom isopod fauna of a West Antarctic glacial fjord

Isopods belong to the most speciose groups of the Antarctic benthic fauna, although the knowledge on their diversity and small-scale distribution patterns is still limited. Here we analyze the diversity of the isopod fauna in the Admiralty Bay, a glacial fjord on the King George Island. The basin is located in the region of the Antarctic Peninsula, the fastest warming area of the Southern Ocean. The study provides important baseline data for future research, particularly with respect to temporal fluctuations in benthic fauna, associated with global changes observed in that part of the world. Forty species of isopods representing 19 families were recorded on the soft bottom of the Admiralty Bay. The analyses were based on 99 quantitative samples collected, within the 20–502-m depth range, with a 0.1 m2 van Veen grab. The materials for the analyses were obtained in the austral summer seasons of 1984/1985 and 1985/1986. The data revealed a high number of isopod species occurring at a low abundance, the mean abundance amounting to 4.8 ± 8.6 ind./0.1 m2. Most of the species occurred at low abundances, 25% of the species being represented by singletons. Caecognathia polaris, the most abundant species, showed the mean abundance of merely 1.2 ± 4.2 ind./0.1 m2. Species richness, diversity and abundance of the isopod fauna were much higher in the central basin of the Admiralty Bay than in the Ezcurra Inlet, an area affected by a strong disturbance of glacial origin.

Large-scale map and 3D modelling of the Henryk Arctowski Polish Antarctic Station

ABSTRACTThis paper presents survey measurements carried out during the 39th Polish Antarctic Expedition to the Henryk Arctowski Polish Antarctic Station in March 2015. The measurements were used to create a map on a 1:500 scale and for 3D modelling of the station buildings and vicinity. The paper also presents the geodetic control network established around the station. We discuss the issue of creating a digital elevation model for the station and its surroundings. The elevation models were generated using terrestrial laser scanning data integrated with Global Navigation Satellite System real time kinematic and tacheometric surveying. The accuracy of these models was estimated using height differences in relation to survey data. The mean height difference was 0.03 m and root mean square error was 0.05 m. Furthermore, an analysis of changes to the coastline was conducted using archival cartographic materials to assess the threat of Admiralty Bay to the station buildings. The results are important for continued scientific activity and safety at Arctowski Station, and may be useful for future research on King George Island.

Assemblages and habitat preferences of soft bottom Antarctic Amphipoda: Admiralty Bay case study

Amphipoda belong to enormously diverse benthic invertebrate groups in the Southern Ocean, playing a very important role in the Antarctic communities. However, in the majority of ecological studies they are identified only to the order level. Rare ecological studies, where amphipods were identified to the species level, concern mainly shallow sublittoral. There is also poor knowledge about the environmental features that are important in the habitat selection by these crustaceans. The aims of this study were to recognize and describe the soft bottom sublittoral amphipod assemblages of the Antarctic fjord and observe the habitat preferences of dominant species. Additionally, we investigated the usefulness of surrogacy methods in the description of amphipod assemblages. The series of 101 quantitative samples from wide depth range (25–502 m) from Admiralty Bay were studied. The cluster analysis allowed to distinguish four assemblages representing: shallow sublittoral (A), middle sublittoral (B) and deep sublittoral (C) of central basin of the bay and Ezcurra Inlet (D) fauna. The study of habitat preferences led to the recognition of the species whose distribution depended on the depth and type of the sediment. The first group encompassed shallow water species characteristic of assemblage (A). The second set of species was related to the presence of colonial organisms identifying the assemblage (B). Third group of deep water species represented assemblage C, while the group of species preferring fine-grained sediments was found in assemblage D. The surrogacy analysis demonstrated low usefulness of this method in the description of Antarctic amphipod assemblages in non-disturbed areas.

Genetic and biochemical characterization of yeasts isolated from Antarctic soil samples

The Polish Arctowski Station is situated in the maritime Antarctic on the western shore of Admiralty Bay and encompasses terrestrial habitats which are not permanently covered by ice, in contrast to more than 90% of the island’s surface area. Over the past several decades, studies exploring the soils of those habitats have revealed a considerable diversity of bacteria, filamentous fungi, and, to a lesser extent, yeasts; however, characterization of this complex microbiome, especially at the molecular level, is still far from satisfactory. The isolates were assigned to their respective genera and species based on genetic analysis of the D1/D2 and ITS1-5.8S-ITS2 regions of rDNA. In the studied soil samples, the most abundant microorganisms belonged to the genera Cryptococcus, Rhodotorula, and Debaryomyces. Physiological and biochemical analysis of Cryptococcus gilvescens (pro tempore Goffeauzyma gilvescens) and Rhodotorula mucilaginosa showed only a limited level of intraspecies diversity. Cellular DNA content and karyotypes were determined using flow cytometry and pulsed-field gel electrophoresis for several selected strains. For the first time, genome size and electrophoretic karyotypes were investigated in C. gilvescens (pro tem G. gilvescens), Cryptococcus saitoi (pro tem Naganishia globosa), Cryptococcus gastricus (pro tem Goffeauzyma gastrica), and Cryptococcus albidus (pro tem Naganishia albida). In addition, plate tests showed Antarctic yeasts to be a potential source of biotechnologically important enzymes. This study in biodiversity, presenting physiological and molecular characterization of psychrotolerant yeast strains isolated from the soils of western Admiralty Bay, contributes to a better understanding of the microbial ecology of this unique ecosystem.

Depositional history and inventories of polychlorinated biphenyls (PCBs) in sediment cores from an Antarctic Specially Managed Area (Admiralty Bay, King George Island)

Temporal patterns, fluxes and inventories of polychlorinated biphenyls (PCBs) were assessed in nine sediment cores collected from selected areas of Admiralty Bay off the Antarctic Peninsula. Concentrations of total PCBs were low, but slightly higher in comparison to low-impacted, remote environments in the world, ranging from below the detection limit to 11.9ngg−1 in dry weight. PCB concentrations and inventories suggest a possible minor influence related to the nearby logistic activities, especially in the sediment core collected close to the Ferraz Station. Despite being the most remote and protected area on the planet, the Antarctic continent is no longer a pristine environment.

Erythrocyte nuclear abnormalities and leukocyte profile in the Antarctic fish Notothenia coriiceps after exposure to short- and long-term heat stress

Several studies suggest that Antarctic endemic stenothermic fish species, such as Notothenia coriiceps, have a limited ability to acclimate to warmer conditions. In the present study, we evaluated the effects of exposure to short- and long-term temperature increases on the occurrence of erythrocytic nuclear abnormalities (ENAs) and changes in the leukocyte profile of N. coriiceps. For the experiments, 30 specimens of N. coriiceps were captured in Admiralty Bay and transferred to the Commandant Ferraz Brazilian Antarctic Station where they were acclimated to water at 0 °C for 6 days and subsequently subjected to treatments of temperature increases (2–4 °C) on a short- (1 day) or long- (6 days) term basis. At the end of exposure, peripheral blood samples were collected and blood smears were prepared for qualitative and quantitative analysis of the ENAs and the leukocyte profile. Significant responses were observed for both ENAs and leukocyte profile. The responses of ENAs were characterized by an increased incidence of bilobed nuclei in erythroblasts following 1-day exposure to water at 2–4 °C, as well as increased incidence of bilobed nuclei in erythrocytes following 1-day and 6-day exposure to water at 4 °C. In the leukocyte profile, 1-day exposure to water at 2 °C promoted a stress response characterized by diminished levels of circulating lymphocytes (lymphopenia) and elevated levels of circulating monocytes (monocytosis). In conclusion, our results indicate that elevation of water temperature during short periods provoked cellular and physiological stress in N. coriiceps. Furthermore, we conclude that in terms of nuclear alterations, erythrocytes and erythroblasts respond differently to thermal stress. Finally, we conclude that the methodology proposed was efficient in quantifying thermal stress in N. coriiceps and we recommend the utilization of this technique in the biomonitoring of thermal stress in this species and other notothenioids.

High Prevalence of Gammaproteobacteria in the Sediments of Admiralty Bay and North Bransfield Basin, Northwestern Antarctic Peninsula.

Microorganisms dominate most Antarctic marine ecosystems, in terms of biomass and taxonomic diversity, and play crucial role in ecosystem functioning due to their high metabolic plasticity. Admiralty Bay is the largest bay on King George Island (South Shetland Islands, Antarctic Peninsula) and a combination of hydro-oceanographic characteristics (bathymetry, sea ice and glacier melting, seasonal entrance of water masses, turbidity, vertical fluxes) create conditions favoring organic carbon deposition on the seafloor and microbial activities. We sampled surface sediments from 15 sites across Admiralty Bay (100–502 m total depth) and the adjacent North Bransfield Basin (693–1147 m), and used the amplicon 454-sequencing of 16S rRNA gene tags to compare the bacterial composition, diversity, and microbial community structure across environmental parameters (sediment grain size, pigments and organic nutrients) between the two areas. Marine sediments had a high abundance of heterotrophic Gammaproteobacteria (92.4% and 83.8% inside and outside the bay, respectively), followed by Alphaproteobacteria (2.5 and 5.5%), Firmicutes (1.5 and 1.6%), Bacteroidetes (1.1 and 1.7%), Deltaproteobacteria (0.8 and 2.5%) and Actinobacteria (0.7 and 1.3%). Differences in alpha-diversity and bacterial community structure were found between the two areas, reflecting the physical and chemical differences in the sediments, and the organic matter input.

Identifying Risk: Concurrent Overlap of the Antarctic Krill Fishery with Krill-Dependent Predators in the Scotia Sea.

Mitigating direct and indirect interactions between marine predators and fisheries is a motivating factor for ecosystem-based fisheries management (EBFM), especially where predators and fisheries compete for a shared resource. One difficulty in advancing EBFM is parameterizing clear functional responses of predators to indices of prey availability. Alternative characterizations of fishery-predator interactions may therefore benefit the implementation of EBFM. Telemetry data identify foraging areas used by predators and, therefore, represent critical information to mitigate potential competition between predators and fisheries. We analyzed six years (2009–2014) of telemetry data collected at Cape Shirreff, Livingston Island and Admiralty Bay, King George Island, Antarctica, on three species of Pygoscelid penguins and female Antarctic fur seals. In this region, all four species are primarily dependent on Antarctic krill. The tracking data demonstrate local movements near breeding colonies during the austral summer and dispersal from breeding colonies during the winter. We then assessed overlap between predators and the Antarctic krill fishery on a suite of spatiotemporal scales to examine how different data aggregations affect the extent and location of overlap. Concurrent overlap was observed on all spatiotemporal scales considered throughout the Antarctic Peninsula and South Orkney Islands region, including near tagging locations and in distant areas where recent fishing activity has concentrated. Overlap occurred at depths where mean krill densities were relatively high. Our results demonstrate that direct overlap of krill-dependent predators with the krill fishery on small spatiotemporal scales is relatively common throughout the Antarctic Peninsula region. As the krill fishery continues to develop and efforts to implement ecosystem-based management mature, indices of overlap may provide a useful metric for indicating where the risks of fishing are highest. A precautionary approach to allocating krill catches in space would be to avoid large increases in catch where overlap on small spatiotemporal scales is common.

Eocene paleosols on King George Island, Maritime Antarctica: Macromorphology, micromorphology and mineralogy

We investigated the origin of reddish layers between basalt flows in an Early Eocene volcanic succession in King George Island, Maritime Antarctica. Previous studies in the area classified these layers as regolith surfaces, baked zones and paleosols, but the properties of these layers and the reasons for their classification are not clarified. Since the Early Eocene epoch was one of the warmest phases on Earth during the Cenozoic, a proper investigation of these layers is crucial to obtain additional regional information about the paleoenvironment.The focus of this study is on three profiles located in the Admiralty Bay on King George Island. They were classified as paleosols based on field, micromorphological and mineralogical properties. Main soil forming processes identified by micromorphological analyses were clay neoformation, pedo-/bioturbation and a weak redoximorphosis. The occurrence of plant residues in all profiles was a reliable indicator that these soils formed a land surface during the Early Eocene. Abundant weathered volcanic glass and pyroclasts may indicate andosolization although the main diagnostic features for Andosols, which are the presence of nanocrystalline minerals and organic matter accumulation, were not detected or only in small amounts, respectively. The long-term burial of the paleosol could be a reason for lacking of these diagnostic features. Clay minerals associated with moderately weathered volcanic soils (smectite) were detected in the X-ray diffraction analysis. A predominantly reddish colour of most of the soil horizons is given by hematite, confirmed by the determination of pedogenic oxides. Nevertheless, rubification was not solely a result of pedogenesis but also of reddening of oxyhydroxides by dehydration during diagenesis. Other diagenetic processes were burial compaction, loss of organic matter and induration. In the horizons directly buried by a basalt flow, voids were filled by zeolite crystals, an effect related to lava cooling. Another possible diagenetic effect was the geochemical rejuvenation and homogenization of the profiles. Despite the occurrence of these features, the results are in agreement with previous studies, indicating a humid temperate paleoclimate for King George Island during the Early Eocene.

Unravelling the function of dolphin leaps using the dusky dolphin (Lagenorhynchus obscurus) as a model species

The prevalence of leaping across delphinids indicates it has an adaptive benefit. I examined leaping behaviour in dusky dolphins (Lagenorhynchus obscurus) according to signalling, social facilitation, and prey capture hypotheses. I quantified the effect of leaping on group behaviour and fission-fusion and the behavioural context of leaping. I observed dolphins in Admiralty Bay, New Zealand during 171 focal follows totalling 157 h. Data were analysed using generalized estimating equations. Clean leaping had a positive effect on party fission () and foraging behaviour (). Coordinated leaping caused a short-term wane in foraging behaviour () and had a positive effect on party fusion (). Noisy leaping had a negative effect on perpetuating resting and traveling cessation (both ). The signalling hypothesis was the most strongly supported. The social facilitation and prey capture hypotheses were moderately supported. Leaping may provide adaptive benefits such as reduced scramble competition, increased foraging efficiency, and social bonding.

Heavy metal concentration in selected soils and sediments of Livingston Island, Deception Island, King George Island, James Ross Island (Antarctica)

This paper evaluated the heavy metal concentration in fine earth and skeleton fraction of the Antarctic soil and sediments in the Admiralty Bay (King George Island); Livingston Island; Whaler´s Bay (Deception Island); James Ross Island and the Trinity peninsula (Antarctica). Total concentrations of eight elements (arsenic, chromium, copper, nickel, lead, strontium, vanadium, and zinc) were determined in sixteen sediments/soils samples and skeleton fraction. For the analyses, eight samples were taken from James Ross Island, four samples from Deception Island, two samples from Trinity peninsula, one sample from Livingston Island, and one sample from King George Island. The contents the elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). Most affected by human activity was the sample collected near permanent station General Bernardo O'Higgins Riquelme - Chile on Trinity peninsula. On this site, the highest concentration of copper in fine-earth (201 ppm), zinc in skeleton (163 ppm) and fine-earth (771 ppm) and strontium in skeleton (733 ppm) and fine-earth (1297 ppm) were found. This location was also exceptional by the residues of penguins’ eggs shells and excrements. Samples of skeleton had significantly higher maximum values of analyzed elements compare to the available literature data. Results from all sampled localities are summarized in the text.

Antarctic strict anaerobic microbiota from Deschampsia antarctica vascular plants rhizosphere reveals high ecology and biotechnology relevance.

The Antarctic soil microbial community has a crucial role in the growth and stabilization of higher organisms, such as vascular plants. Analysis of the soil microbiota composition in that extreme environmental condition is crucial to understand the ecological importance and biotechnological potential. We evaluated the efficiency of isolation and abundance of strict anaerobes in the vascular plant Deschampsia antarctica rhizosphere collected in the Antarctic's Admiralty Bay and associated biodiversity to metabolic perspective and enzymatic activity. Using anaerobic cultivation methods, we identified and isolated a range of microbial taxa whose abundance was associated with Plant Growth-Promoting Bacteria (PGPB) and presences were exclusively endemic to the Antarctic continent. Firmicutes was the most abundant phylum (73%), with the genus Clostridium found as the most isolated taxa. Here, we describe two soil treatments (oxygen gradient and heat shock) and 27 physicochemical culture conditions were able to increase the diversity of anaerobic bacteria isolates. Heat shock treatment allowed to isolate a high percentage of new species (63.63%), as well as isolation of species with high enzymatic activity (80.77%), which would have potential industry application. Our findings contribute to the understanding of the role of anaerobic microbes regarding ecology, evolutionary, and biotechnological features essential to the Antarctic ecosystem.

Mercury in the ecosystem of Admiralty Bay, King George Island, Antarctica: Occurrence and trophic distribution

Mercury (Hg) can reach the environment through natural and human-related sources, threatening ecosystems all over the planet due to its well known deleterious effects. Therefore, Antarctic trophic webs, despite being relatively isolated, are not exempt of its influence. To evaluate Hg concentrations in an Antarctic ecosystem, different tissues from 2 species of invertebrates, 2 of fish, 8 of birds, 4 of pinnipeds and at least 5 of vegetation were investigated (n=176). For animals, values ranged from 0.018 to 48.7μgg−1 dw (whole Antarctic krill and Antarctic Fur Seal liver). They were generally correlated to trophic position (assessed by δ15N and δ13C) but also to cephalopods and myctophids consumption. For vegetation, values ranged from 0.014 to 0.227μgg−1 dw (Colobanthus quitensis and an unidentified lichen), with lichens presenting significantly higher values than mosses, likely due to year-round exposure and absorption of animal derived organic matter, as hypothesized by literature.

Composition, density and size-structure of the autotrophic plankton community in a shallow coastal zone at King George Island, West Antarctic Peninsula (WAP), during early summer 2010

The planktonic microorganism community of Admiralty Bay, Antarctic Peninsula is being monitored since 2002. This study describes composition, size-structure and biomass of the phytoplankton communities observed during early summer 2010/2011 in the area. Organisms were counted by microscopy and scored as belonging to three size classes: <10 µm, 10 - 80 µm and 80 - 400 µm. In terms of density, this phytoplankton community was dominated by cells < 10 µm (~106 - 107 cells L-1), confirming the increasing presence of small planktonic autotrophs in West Antarctic Peninsula waters. Organisms > 10 µm dominated in terms of biomass (> 50% of Chlorophyll a) with densities of up to 1.6 x 104 cells L-1, which is approximately 0.6 times higher than observed for early summer in recent years. Additionally, our results confirm a previously observed phenomenon whereby large-size phytoplankton (> 80 µm), especially pennate diatoms, are replaced by mid-size centric diatoms (10- 80 µm), such as Thalassiosira spp., and small dinoflagellates (e.g. Prorocentrum antarcticum) during warmer early summers.

CHARACTERISTICS OF MARINE ENVIRONMENTAL GEOCHEMISTRY FROM HA TINH TO QUANG NAM (60-100M WATER DEPTH)

CHARACTERISTICS OF MARINE ENVIRONMENTAL GEOCHEMISTRY FROM HA TINH TO QUANG NAM (60-100M WATER DEPTH)

Culture-independent characterization of novel psychrophilic magnetotactic cocci from Antarctic marine sediments.

Magnetotactic bacteria (MTB) are a heterogeneous group of ubiquitous aquatic microorganisms capable of biomineralizing nano-sized, membrane-bound, magnetic iron-rich mineral particles called magnetosomes. MTB are found in chemically-stratified aquatic sediments and/or water columns with a wide range of salinities, moderate to high temperatures, and pH varying from neutral to strongly alkaline. MTB from very cold environments have not been investigated to any great degree and here we characterize MTB from the low temperature Antarctic maritime region. Sediment samples were collected at nine sampling sites within Admiralty Bay, King George Island (62°23'S 58°27'W) from 2009 to 2013. Samples from five sites contained MTB and those from two of these sites contained large number of magnetotactic cocci that were studied using electron microscopy and molecular techniques. The magnetotactic cocci contained magnetosomes either arranged as two or four chains or as a disorganized cluster. The crystalline habit and composition of all magnetosomes analyzed with high-resolution transmission electron microscopy and energy dispersive X-ray microanalysis were consistent with elongated prismatic crystals of magnetite (Fe3 O4 ). The retrieved 16S rRNA gene sequences from magnetically-enriched magnetotactic cocci clustered into three distinct groups affiliated with the Alphaproteobacteria class of the Proteobacteria. Novel sequences of each phylogenetic cluster were confirmed using fluorescent in situ hybridization. Metagenomic data analysis of magnetically-enriched magnetotactic cocci revealed the presence of mam genes and MTB-specific hypothetical protein coding genes. Sequence homology and phylogenetic analysis indicated that predicted proteins are related to those of cultivated alphaproteobacterial MTB. The consistent and continuous low temperature of the sediment where the magnetotactic cocci are present (always below 1°C) suggests that these MTB from maritime Antarctica are psychrophiles. Moreover, similar morphotypes and 16S gene sequences were retrieved from samples collected from different sites from maritime Antarctica for several years suggesting that these new strains of MTB are indigenous members of Antarctic microbiota.

Species composition, seasonal abundance and population structure of chaetognaths in Admiralty Bay (Antarctic)

Abstract Although chaetognaths inhabiting polar ecosystems are relatively well known, there are few reports on their functioning in the Antarctic coastal plankton community. The presented results provide the first comprehensive description of population structure of chaetognaths in the neritic zone west of the Antarctic Peninsula. The studies were performed on samples collected in Admiralty Bay, from December 1994 to June 1995. Following six chaetognath species were determined: Eukrohnia hamata, E. bathypelagica, E. fowleri, Pseudosagitta gazellae, P. maxima and Solidosagitta marri. The representatives of Eukrohnia were observed almost throughout the research period, whereas those of Pseudosagitta and Solidosagitta were found only during first four months of our investigation. Eukrohnia hamata showed a strong dominance in respect to abundance (max. 445 ind./1000 m3). The mean abundance of all taxa significantly fluctuated in the study period and across weeks. Generally, all species were represented by the first three maturity stages (I-III), individuals stage IV occurred sporadically, and mature specimens (stage V) were not recorded at all. Morphometric analysis of the most abundant species showed distinct differences in their total length and body proportions. Our findings may suggest that chaetognath populations in Admiralty Bay are migrant, dependent on the inflow of water from the Bransfield Strait, but to prove this statement further, round year study is necessary.

Aliterella atlantica gen. nov., sp. nov., and Aliterella antarctica sp. nov., novel members of coccoid Cyanobacteria.

Two Cyanobacteria isolated from South Atlantic Ocean continental shelf deep water and from a marine green algae inhabiting the Admiralty Bay, King George Island, Antarctica were investigated based on morphological and ultrastructural traits, phylogeny of 16S rRNA gene sequences, secondary structure of the 16S-23S internal transcribed spacer regions and phylogenomic analyses. The majority of these evaluations demonstrated that both strains differ from the genera of cyanobacteria with validly published names and, therefore, supported the description of the novel genus as Aliterella gen. nov. The identity and phylogeny of 16S rRNA gene sequences, together with the secondary structure of D1D1' and BoxB intergenic regions, further supported the two strains representing distinct species: Aliterella atlantica gen. nov., sp. nov. (type SP469036, strain CENA595T) and Aliterella antarctica sp. nov. (type SP469035, strain CENA408T). The phylogenomic analysis of A. atlantica sp. nov. CENA595T, based on 21 protein sequences, revealed that this genus belongs to the cyanobacterial order Chroococcidiopsidales. The isolation and cultivation of two geographically distant unicellular members of a novel cyanobacterial genus and the sequenced genome of the type strain bring new insights into the current classification of the coccoid group, and into the reconstruction of their evolutionary history.