High mercury levels in Antarctic toothfish Dissostichus mawsoni from the Southwest Pacific sector of the Southern Ocean

Mercury is a bioaccumulating toxic pollutant which can reach humans through the consumption of contaminated food (e.g. marine fish). Although the Southern Ocean is often portrayed as a pristine ecosystem, its fishery products are not immune to mercury contamination. We analysed mercury concentration (organic and inorganic forms – T-Hg) in the muscle of Antarctic toothfish, Dissostichus mawsoni, a long-lived top predator which supports a highly profitable fishery. Our samples were collected in three fishing areas (one seamount and two on the continental slope) in the Southwest Pacific Sector of the Southern Ocean during the 2016/2017 fishing season. Mercury levels and the size range of fish varied between fishing areas, with the highest levels (0.68 ± 0.45 mg kg−1 wwt) occurring on the Amundsen Sea seamount where catches were dominated by larger, older fish. The most parsimonious model of mercury concentration included both age and habitat (seamount vs continental slope) as explanatory variables. Mean mercury levels for each fishing area were higher than those in all previous studies of D. mawsoni, with mean values for the Amundsen Sea seamount exceeding the 0.5 mg kg−1 food safety threshold for the first time. It might therefore be appropriate to add D. mawsoni to the list of taxa, such as swordfish and sharks, which are known to exceed this threshold. This apparent increase in mercury levels suggests a recent contamination event which affected the Southwest Pacific sector, including both the Amundsen and Dumont D'Urville seas

Shearwater Foraging in the Southern Ocean: The Roles of Prey Availability and Winds

Background Sooty (Puffinus griseus) and short-tailed (P. tenuirostris) shearwaters are abundant seabirds that range widely across global oceans. Understanding the foraging ecology of these species in the Southern Ocean is important for monitoring and ecosystem conservation and management. Methodology/Principal Findings Tracking data from sooty and short-tailed shearwaters from three regions of New Zealand and Australia were combined with at-sea observations of shearwaters in the Southern Ocean, physical oceanography, near-surface copepod distributions, pelagic trawl data, and synoptic near-surface winds. Shearwaters from all three regions foraged in the Polar Front zone, and showed particular overlap in the region around 140°E. Short-tailed shearwaters from South Australia also foraged in Antarctic waters south of the Polar Front. The spatial distribution of shearwater foraging effort in the Polar Front zone was matched by patterns in large-scale upwelling, primary production, and abundances of copepods and myctophid fish. Oceanic winds were found to be broad determinants of foraging distribution, and of the flight paths taken by the birds on long foraging trips to Antarctic waters. Conclusions/Significance The shearwaters displayed foraging site fidelity and overlap of foraging habitat between species and populations that may enhance their utility as indicators of Southern Ocean ecosystems. The results highlight the importance of upwellings due to interactions of the Antarctic Circumpolar Current with large-scale bottom topography, and the corresponding localised increases in the productivity of the Polar Front ecosystem

Splenic T-cell lymphoma in a North American River Otter (Lontra canadensis)

Background: Splenic lymphoma is commonly reported in domestic ferrets (Mustela putorious furo), but very rarely reported in wild Mustelidae species, including otters. One report described B-cell splenic lymphoma in an Asian smallclawed otter (Aonyx cinerea) that metastasized and was the primary reasoning for humane euthanasia (Stedman and Mills, 2014).Case Description: The current report describes a case of splenic T-cell lymphoma in a captive North American river otter (Lontra canadensis). The otter died several weeks after splenectomy and no evidence of metastasis was found on gross necropsy or histopathological evaluation.Conclusion: The splenectomy performed on this individual was presumptively curative for its splenic lymphoma. Extensive myocardial fibrosis was found, and suspected to have caused severe cardiac arrhythmia leading to acute death. Keywords: Fibrosis, Mustelid, Neoplasia, Splenectom

High-pressure liquid chromatography (HPLC) pigment concentration data and flow-cytometry picophytoplankton abundance and fluorescence data from serial dilution experiments conducted with surface mixed-layer water in 'Experimental stations' during TAN1702

Here we present data of phytoplankton pigment and flow cytometry (FCM) data from initial (T0) and final (T24) samples obtained from serial dilution grazing experiments set up with surface mixed layer water from subantarctic waters across the Campbell Plateau region southeast of New Zealand. Experiments were incubated onboard of the RV Tangaroa using deck flow-through incubators simulating in situ light and temperature conditions

High-pressure liquid chromatography (HPLC) pigment concentration data and flow-cytometry picophytoplankton abundance and fluorescence data from depth-resolved CTD profiles at 'Biomass stations' during RV Tangaroa expedition TAN1702

Here we present data of phytoplankton pigment and flow cytometry (FCM) depth-resolved data collected from the water column (0-100 m) during TAN1702 voyage (March-April 2017) in subantarctic waters across the Campbell Plateau region southeast of New Zealand on board of the RV Tangaroa

Apparent growth rates estimated in each incubation bottle of dilution experiments and photoacclimation correction index (Phi) assessed from changes in cell fluorescence measured by flow-cytometry during 24-h dilution experiments during during TAN1702

Here we present taxon-specific apparent growth rate data obtained from high-pressure liquid chromatography (HPLC) pigment and flow cytometry (FCM) analisis of initial (T0) and final (T24) samples in serial dilution grazing experiments conducted with surface mixed layer water from subantarctic waters across the Campbell Plateau region southeast of New Zealand

Phytoplankton taxon-specific growth and microzooplankton grazing rates in subantarctic HNLC waters on and off Campbell Plateau southeast of New Zealand during austral autumn

Here we present data of phytoplankton pigment and flow cytometry (FCM) data in the water column (CTD_HPLC_FCM_May2022.xlsx) and dilution grazing experiments (DILEX_HPLC_FCM_Conc_May2022.xlsx), and derived apparent growth rates for specific pigment markers and picophytoplankton groups assessed by FCM (APPARENT_GROWTHRATES_May2022.xlsx). Samples and experiments were collected and carried out in subantarctic waters across the Campbell Plateau region southeast of New Zealand. We distinguish between a subset of 'Experimental' stations (n = 8), where serial dilution experiments were conducted and a subset of additional 'Biomass' stations (n = 7), where depth-resolved physico-chemical and biological measurements (e.g., nutrients, size-fractionated chlorophyll a (SF-Chla), optical microscopy, FCM and HPLC) were also undertaken throughout the euphotic zone. 'Experimental' stations were used to characterize phytoplankton group-specific growth and grazing rates and associated carbon production and microzooplankton consumption dynamics in surface-mixed layer waters (10 m) On-plateau (n = 5) and Off-plateau (n = 3) with 'Biomass' stations providing a broader context of the environmental conditions and phytoplankton biomass and taxonomic composition across the region

14C-uptake and net primary productivity in the Southwest Pacific

The data describes net primary productivity data obtained from 14C-uptake standard 24h incubations during several cruises across the Southwest Pacific. The data spans 25 years (1993 - 2018) and includes measurements obtained in subantarctic and subtropical water masses and in the Subtropical Front that separates both. The dataset contains depth-resolved chlorophyll a concentration (mgChla/m³) and primary productivity measurements (mgC/m³/day) as well as areal chlorophyll a (mgChla/m²) and primary productivity (mgC/m²/day) calculated for the euphotic zone using trapezoidal integration. Environmental data including surface temperature, daily incident irradiance, attenuation coefficient and depth of the euphotic zone are provided when available