Molecular, morphological and chemical diversity of two new species of Antarctic Diatoms, Craspedostauros ineffabilis sp. nov. and Craspedostauros zucchellii sp. nov.

The current study focuses on the biological diversity of two strains of Antarctic diatoms (strains IMA082A and IMA088A) collected and isolated from the Ross Sea (Antarctica) during the XXXIV Italian Antarctic Expedition. Both species presented the typical morphological characters of the genus Craspedostauros: cribrate areolae, two “fore-and-aft” chloroplasts and a narrow “stauros”. This classification is congruent with the molecular phylogeny based on the concatenated 18S rDNArbcL-psbC alignment, which showed that these algae formed a monophyletic lineage including six taxonomically accepted species of Craspedostauros. Since the study of the evolution of this genus and of others raphe-bearing diatoms with a “stauros” is particularly challenging and their phylogeny is still debated, we tested alternative tree topologies to evaluate the relationships among these taxa. The metabolic fingerprinting approach was implemented for the assessment of the chemical diversity of IMA082A and IMA088A. In conclusion, combining (1) traditional morphological features used in diatoms identification, (2) phylogenetic analyses of the small subunit rDNA (18S rDNA), rbcL and psbC genes, and (3) metabolic fingerprint, we described the strains IMA082A and IMA088A as Craspedostauros ineffabilis sp. nov. and Craspedostauros zucchellii sp. nov. as new species, respectivelyinfo:eu-repo/semantics/publishedVersio

Antarctic food web architecture under varying dynamics of sea ice cover

open7noIn the Ross Sea, biodiversity organisation is strongly influenced by sea-ice cover, which is characterised by marked spatio-temporal variations. Expected changes in seasonal sea-ice dynamics will be reflected in food web architecture, providing a unique opportunity to study effects of climate change. Based on individual stable isotope analyses and the high taxonomic resolution of sampled specimens, we described benthic food webs in contrasting conditions of seasonal sea-ice persistence (early vs. late sea-ice break up) in medium-depth waters in Terra Nova Bay (Ross Sea). The architecture of biodiversity was reshaped by the pulsed input of sympagic food sources following sea-ice break up, with food web simplification, decreased intraguild predation, potential disturbance propagation and increased vulnerability to biodiversity loss. Following our approach, it was possible to describe in unprecedented detail the complex structure of biodiverse communities, emphasising the role of sympagic inputs, regulated by sea-ice dynamics, in structuring Antarctic medium-depth benthic food webs.openRossi L.; Sporta Caputi S.; Calizza E.; Careddu G.; Oliverio M.; Schiaparelli S.; Costantini M.L.Rossi, L.; Sporta Caputi, S.; Calizza, E.; Careddu, G.; Oliverio, M.; Schiaparelli, S.; Costantini, M. L

Cross-Disciplinarity in the Advance of Antarctic Ecosystem Research

The biodiversity, ecosystem services and climate variability of the Antarctic continent, and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds - Ecosystem Resilience and Adaption of the Scientific Committee on Antarctic Research, which focused on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas, and first steps in their implementation, were clustered into eight themes, ranging from scale problems, risk maps, organism and ecosystem responses to multiple environmental changes, to evolutionary processes. Scaling models and data across different spatial and temporal scales were identified as an overarching challenge. Approaches to bridge gaps in the research programmes included multi-disciplinary monitoring, linking biomolecular findings and simulated physical environments, as well as integrative ecological modelling. New strategies in academic education are proposed. The results of advanced cross-disciplinary approaches can contribute significantly to our knowledge of ecosystem functioning, the consequences of climate change, and to global assessments that ultimately benefit humankind

Buoyancy of post-fertilised Dissostichus mawsoni eggs and implications for early life history

Gametes from gravid Antarctic toothfish (Dissostichus mawsoni) were combined in vitro and buoyancy measurements were made on fertilised eggs during early development. Eggs were strongly positively buoyant, indicating that they would ascend quickly in the water column and reside near or in association with the underside of sea ice, which covers most of the spawning habitat during winter. An association with sea ice may provide: protection from the turbulence of ice-free surface waters, a mechanism that modifies the velocity of advection by surface currents, and a habitat with a concentrated planktonic food source during spring months. An association with sea ice would also create spatial differences in egg advection patterns for eggs produced spanning a large geographic area. The effects of climate change on sea ice formation and melting patterns, or fishery-induced changes in the spatial density of adults could then influence juvenile advection patterns and influence survival

Visual imaging of benthic carbonate-mixed factories in the ross sea region marine protected area, Antarctica

Marine biogenic skeletal production is the prevalent source of Ca-carbonate in today\u2019s Antarctic seas. Most information, however, derives from the post-mortem legacy of calcifying or-ganisms. Prior imagery and evaluation of Antarctic habitats hosting calcifying benthic organisms are poorly present in the literature, therefore, a Remotely Operated Vehicle survey was carried out in the Ross Sea region Marine Protected Area during the 2013\u20132014 austral summer. Two video surveys of the seafloor were conducted along transects between 30 and 120 m (Adelie Cove) and 230 and 260 m (Terra Nova Bay \u201cCanyon\u201d), respectively. We quantified the relative abundance of calcifiers vs non-calcifiers in the macro-and mega-epibenthos. Furthermore, we considered the ty-pology of the carbonate polymorphs represented by the skeletonized organisms. The combined evidence from the two sites reveals the widespread existence of carbonate-mixed factories in the area, with an overwhelming abundance of both low-Mg and (especially) high-Mg calcite calcifiers. Echi-noids, serpulids, bryozoans, pectinid bivalves and octocorals prove to be the most abundant animal producers in terms of abundance. The shallower Adelie Cove site also showed evidence of seabed coverage by coralline algae. Our results will help in refining paleoenvironmental analyses since many of the megabenthic calcifiers occur in the Quaternary record of Antarctica. We set a baseline to monitor the future response of these polar biota in a rapidly changing ocean