The Ross Sea is a major contributor to the primary production of the Southern Ocean, hosting annual phytoplankton blooms from austral spring to austral summer. These events support the marine food web and contribute to CO2 sequestration in Antarctica. The present study investigated the taxonomic composition of the >25 µm size-selected microphytoplankton fraction during late spring and throughout the austral summer of 2018/2019 at the Italian Mario Zucchelli Station (Terra Nova Bay, Ross Sea), with a morphology-based approach combining light and scanning electron microscopy. These analyses resulted in a checklist comprising 77 microalgal taxa (67 diatoms, 8 dinoflagellates, 1 Dictyochophyceae and 1 Bolidophyceae), including the diatom Licmophora belgicae, reported here for the first time in this region. Qualitative temporal variations in the occurrence of major taxonomic groups were observed, with pennate diatoms such as genus Fragilariopsis frequently encountered in late spring and mid-summer, and centric diatoms becoming more prominent in early summer. The detected dinoflagellate diversity was lower than that reported in some previous studies. Overall, this study provides a valuable reference point for assessing Antarctic microphytoplankton diversity and dynamics across temporal and spatial scales.
The present study investigates microzooplankton (MZP) species richness, vertical abundance, and organism dimensions along a transect through the Greenland Sea Gyre from 2 to 10 September 2021, at the end of the productive season. Total MZP abundance varied from 6.25 ind. L− 1 to 721.5 ind. L− 1, and total carbon content from 0.01 µgC L⁻¹ to 1.7 µgC L⁻¹. Microzooplankton abundance and biomass decreased drastically in the presence of cold polar water on the Greenland slope. Vertical distribution profiles showed significantly higher organism abundance in the photic zone (≤ 100 m) compared to the aphotic zone (> 100 m) across the entire transect. Tintinnids, with a maximum of 613 ind. L− 1, dominated the MZP assemblage; among them, Acanthostomella norvegica, Parafavella denticulata, Parafavella parumdentata, and Ptychocylis obtusa were the most common species. Tintinnids appeared to play a major role in the photic zone and exhibited small dimensions, with an oral lorica opening between 15 and 35 μm in 84
In January 2026 a fin whale Balaenoptera physalus was sighted at Cape Evans in the southern Ross Sea, raising the question: was this the southernmost recorded sighting for this species? During the Heroic Age of Antarctic exploration (1900–1911) blue whales and ‘finners’ were sighted at the Bay of Whales (78°33’S, 164°33’W) on the Ross Ice Shelf, the earth’s southernmost navigable point, but ‘finners’ was an ambiguous term also applied to other rorqual whales. Between 1923 and 1926 pioneer Norwegian whalers killed 1142 blue and 37 fin whales in the southern Ross Sea, but catch data are difficult to locate. The 2026 sighting appears to be the furthest south fin whale sighting for at least 100 years, and unless historical data eventually prove otherwise, may be a southernmost record for this heavily whaled and now recovering species.
Limacina rangii (d’Orbigny, 1835) is pelagic pteropod playing a key ecological and biogeochemical role in polar ecosystems, being the prey of a variety of species of higher trophic levels. They are also sensitive indicators that allow gauging environmental change. Despite their recognized ecological relevance, the influence of environmental descriptors on their biometric traits remains largely unexplored. In this study, specimens of L. rangii, including adults and larvae, were collected from the Ross Sea and Terra Nova Bay (Southern Ocean) during the XXXII Italian Antarctic Expedition (late summer 2017). Each sampling event was accompanied by in situ environmental measurements, including temperature, salinity, Chl-a concentration, and conductivity. To identify the most influential environmental drivers of body length, we employed a Random Forest machine learning algorithm. The results revealed that longitude, temperature, and conductivity were among the strongest predictors of body size, underscoring the role of both thermal regimes and oceanographic characteristics in constraining the growth and development of these pelagic gastropods. This study demonstrates that environmental variability exerts a control over the biometric traits of L. rangii, with local thermal regimes and oceanographic features acting as critical constraints on individual growth and population development. These insights are essential for forecasting the responses of pelagic calcifiers to climate-driven changes in the Southern Ocean.
The circumpolar Antarctic rock cod (Trematomus bernacchii) is an important bioindicator species for marine Antarctic coastal waters. Histopathological alterations of key organs in this species provide an indicator of anthropogenic impacts and overall ecological condition. As a long-lived benthic species with a small home range, assessments of histopathology and health status of Trematomus bernacchii are ideal for identifying spatial and temporal changes and impacts resulting from exposure to contaminants in their environment. A collection of microscopic anatomy and histopathological observations of representative normal compared to abnormal histology of key organs including gill, liver, spleen, kidney and gonad was compiled from fish near Davis station, East Antarctica. Fish were collected within 300 m of the wastewater outfall, and at reference sites up to 9 km away from any obvious signs of anthropogenic input or impacts. Sub-lethal histological alterations identified across multiple organs indicates impaired health in fish near the outfall, providing strong evidence of response to contamination. Familiarity with ‘normal’ baseline and common pathologies improves ability to detect changes due to contamination, and reduces the chance of subjective observations and misidentification of alteration. Having a standard microscopic anatomy and histological observation for comparative assessment of tissue samples reduces error associated with subjectivity and differing levels of experience of examiners, and enables direct comparisons between populations in coastal areas around the whole of Antarctica, across temporal and spatial scales. The value of histopathology as a key component in multiple-lines-of-evidence ecological risk assessments, is further strengthened when combined with a numeric histological health index (HHI) which quantifies overall site-specific severity of impact in the environment.
