Biogeochemical controls on ammonium accumulation in the surface layer of the TD: Southern Ocean

The production and assimilation of ammonium (NH₄⁺) are essential upper-ocean nitrogen (N) cycle pathways. However, in the Southern Ocean where the alternation between biological nitrate drawdown in summer and physical nitrate resupply in winter is central for setting atmospheric CO2, the active cycling of NH₄⁺ in the seasonally-varying mixed layer remains poorly understood. On a cruise from Cape Town (33.9°S) to the Marginal Ice Zone (MIZ; 61.4°S) in winter 2017, surface samples were collected and analysed for nutrient concentrations, planktonic community composition, size-fractionated rates of net primary production and N (as NH₄⁺, urea, and nitrate) uptake, and rates of NH₄⁺ oxidation. NH₄⁺ concentrations, measured every four hours, were five-fold higher than is typical for summer, and lower north than south of the Subantarctic Front (SAF; 0.01–0.26 µM versus 0.19–0.70 µM). Thus, showing that NH₄⁺ accumulates in the Southern Ocean's winter mixed layer, particularly in polar waters. NH₄⁺ uptake rates were highest near the Polar Front (PF; 12.9 ± 0.4 nM day-1 ) and in the Subantarctic Zone (10.0 ± 1.5 nM day-1), decreasing towards the MIZ (3.0 ± 0.8 nM day-1) despite the high ambient NH₄⁺ concentrations, likely due to the low temperatures and limited light. By contrast, rates of NH₄⁺ oxidation were higher south than north of the PF (16.0 ± 0.8 versus 11.1 ± 0.5 nM day-1), perhaps due to the lower light and higher iron concentrations characteristic of polar waters. Additional NH₄⁺ concentration measurements spanning the 2018/2019 annual cycle suggest that mixed-layer NH₄⁺ accumulation south of the SAF is due to sustained heterotrophic NH₄⁺ production in late summer through winter that outpaces NH₄⁺ removal by temperature-, light, and iron-limited microorganisms. The contribution by heterotrophic prokaryotes is supported by observations from winter 2017, where lower ratios of photosynthetic-to-heterotrophic cells were associated with maxima in NH₄⁺ concentrations. These observations imply that the Southern Ocean 27 becomes a biological source of CO₂ to the atmosphere in autumn and winter, not only because nitrate drawdown is weak, but also because the ambient conditions favour net heterotrophy and NH₄⁺ accumulation. High wintertime surface NH4 + concentrations, and the drivers of biological NH4 + cycling, may also have implications for nitrate uptake, through inhibition, and for the air-sea flux of ammonia gas, with the latter influencing the formation of aerosols, clouds, and climate

The kinetics of ammonium uptake and oxidation across the Southern Ocean

International audienceCentral to the Southern Ocean's role in setting atmospheric CO2 is the seasonal alternation between upward mixing of nutrients and their subsequent consumption by phytoplankton. Active nutrient cycling within the mixed layer, including the release of ammonium (NH4+) and its removal by phytoplankton and nitrifiers, also affects Southern Ocean CO2 drawdown, yet remains poorly understood. We conducted kinetics experiments across the Southern Ocean south of Africa to investigate the dependence of NH4+ uptake (summer, winter) and oxidation (winter) on NH4+ concentration. NH4+ uptake followed a Michaelis–Menten function in both seasons, with the maximum rate (Vmax) decreasing poleward, apparently controlled mainly by light in winter and temperature in summer. The half-saturation constant (Km) increased poleward with increasing ambient NH4+ ([NH4+]amb) and was threefold higher in winter (150–405 nM) than in summer (41–115 nM), suggesting that summertime phytoplankton are adapted to low-NH4+ conditions while winter communities typically receive a higher NH4+ supply. NH4+ oxidation showed a high affinity for NH4+ (Km = 28–137 nM), suggesting a dominant role for ammonia-oxidizing archaea, and followed a Michaelis–Menten curve only when [NH4+]amb was ≤ 90 nM. Vmax was near-constant across the region regardless of [NH4+]amb, temperature, or light. From coincident mixed-layer NH4+ oxidation and iron measurements, we hypothesize that iron availability may (co-)limit the Vmax of NH4+ oxidation. If verified, this suggestion has implications for models that parameterize nitrification as a linear function of [NH4+]amb. Additionally, iron depletion may limit the role of mixed-layer nitrification, which is dominant in the winter Southern Ocean, in offsetting phytoplankton CO2 drawdown annually

An exploration of the trajectory of psychological distress associated with exposure to smoke during the 2014 Hazelwood coal mine fire

Due to climate change, catastrophic events such as landscape fires are increasing in frequency and severity. However, relatively little is known about the longer-term mental health outcomes of such events. Follow-up was conducted of 709 adults exposed to smoke from the 2014 Hazelwood mine fire in Morwell, Victoria, Australia. Participants completed two surveys evaluating posttraumatic distress, measured using the Impact of Events Scale-Revised (IES-R), three and six years after the mine fire. Mixed-effects regression models were used to evaluate longitudinal changes in distress. IES-R total scores increased on average by 2.6 points (95%CI: 1.2 to 3.9 points) between the two survey rounds, with increases across all three posttraumatic distress symptom clusters, particularly intrusive symptoms. This increase in distress was evident across all levels of fine particulate matter (PM2.5) exposure to the mine fire smoke. Age was an effect modifier between mine fire PM2.5 exposure and posttraumatic distress, with younger adults impacted more by exposure to the mine fire. Greater exposure to PM2.5 from the mine fire was still associated with increased psychological distress some six years later, with the overall level of distress increasing between the two survey rounds. The follow-up survey coincided with the Black Summer bushfire season in south-eastern Australia and exposure to this new smoke event may have triggered distress sensitivities stemming from exposure to the earlier mine fire. Public health responses to disaster events should take into consideration prior exposures and vulnerable groups, particularly younger adults. © 2022 Elsevier Gmb

An exploration of the trajectory of psychological distress associated with exposure to smoke during the 2014 Hazelwood coal mine fire

Due to climate change, catastrophic events such as landscape fires are increasing in frequency and severity. However, relatively little is known about the longer-term mental health outcomes of such events. Follow-up was conducted of 709 adults exposed to smoke from the 2014 Hazelwood mine fire in Morwell, Victoria, Australia. Participants completed two surveys evaluating posttraumatic distress, measured using the Impact of Events Scale-Revised (IES-R), three and six years after the mine fire. Mixed-effects regression models were used to evaluate longitudinal changes in distress. IES-R total scores increased on average by 2.6 points (95%CI: 1.2 to 3.9 points) between the two survey rounds, with increases across all three posttraumatic distress symptom clusters, particularly intrusive symptoms. This increase in distress was evident across all levels of fine particulate matter (PM2.5) exposure to the mine fire smoke. Age was an effect modifier between mine fire PM2.5 exposure and posttraumatic distress, with younger adults impacted more by exposure to the mine fire. Greater exposure to PM2.5 from the mine fire was still associated with increased psychological distress some six years later, with the overall level of distress increasing between the two survey rounds. The follow-up survey coincided with the Black Summer bushfire season in south-eastern Australia and exposure to this new smoke event may have triggered distress sensitivities stemming from exposure to the earlier mine fire. Public health responses to disaster events should take into consideration prior exposures and vulnerable groups, particularly younger adults

Changing biogeochemistry of the Southern Ocean and its ecosystem implications

The datasets published here apply only to unpublished nutrient data from the wintertime trans-Southern Ocean sections WOCE line IO6 (2017) and A12 (2019) and one summertime surface ocean A12 ammonium dataset. Nutrient concentrations are in units micromole per liter. Variables measured from the CTD (pressure, temperature and salinity) for the two wintertime datasets are provided at 1 m resolution. Winter nutrient sampling was conducted aboard the R/V SA Agulhas II in 2017 (WC-17; 28 June – 13 July 2017) along WOCE line IO6 (Indian sector) and in 2019 (SCALE; 18 July – 12 August 2019) along WOCE line A12 (the GoodHope repeat hydrographic line; Atlantic sector). Seawater was collected at regular depth intervals in 12-L Niskin bottles attached to a CTD rosette. Samples for the analysis of nitrate, nitrite, dissolved silicon and phosphate concentrations were decanted into replicate 50 mL HDPE tubes that were copiously rinsed prior to filling. Duplicate tubes were immediately frozen at -20°C for later measurement of nitrate and dissolved silicon, whilst nitrite and phosphate samples that were to be measured shipboard within a few hours were stored in the fridge. Duplicate samples of unfiltered seawater (~40 mL) were also collected at each depth between the surface and 500 m for the analysis of ammonium concentrations in 50 mL HDPE Nalgene bottles that had been stored (“aged”) with orthophthaldialdehyde working reagent (OPA-WR) prior to sample collection. The OPA-WR was decanted just prior to sample collection and bottles were rinsed three times with sample seawater prior to filling.The datasets published here apply only to unpublished nutrient data from the wintertime trans-Southern Ocean sections WOCE line IO6 (2017) and A12 (2019) and one summertime surface ocean A12 ammonium dataset. Nutrient concentrations are in units micromole per liter. Variables measured from the CTD (pressure, temperature and salinity) for the two wintertime datasets are provided at 1 m resolution. Winter nutrient sampling was conducted aboard the R/V SA Agulhas II in 2017 (WC-17; 28 June – 13 July 2017) along WOCE line IO6 (Indian sector) and in 2019 (SCALE; 18 July – 12 August 2019) along WOCE line A12 (the GoodHope repeat hydrographic line; Atlantic sector). Seawater was collected at regular depth intervals in 12-L Niskin bottles attached to a CTD rosette. Samples for the analysis of nitrate, nitrite, dissolved silicon and phosphate concentrations were decanted into replicate 50 mL HDPE tubes that were copiously rinsed prior to filling. Duplicate tubes were immediately frozen at -20°C for later measurement of nitrate and dissolved silicon, whilst nitrite and phosphate samples that were to be measured shipboard within a few hours were stored in the fridge. Duplicate samples of unfiltered seawater (~40 mL) were also collected at each depth between the surface and 500 m for the analysis of ammonium concentrations in 50 mL HDPE Nalgene bottles that had been stored (“aged”) with orthophthaldialdehyde working reagent (OPA-WR) prior to sample collection. The OPA-WR was decanted just prior to sample collection and bottles were rinsed three times with sample seawater prior to filling.

Development of an Australia and New Zealand Lung Cancer Clinical Quality Registry: a protocol paper

Introduction: Lung cancer is the leading cause of cancer mortality, comprising the largest national cancer disease burden in Australia and New Zealand. Regional reports identify substantial evidence-practice gaps, unwarranted variation from best practice, and variation in processes and outcomes of care between treating centres. The Australia and New Zealand Lung Cancer Registry (ANZLCR) will be developed as a Clinical Quality Registry to monitor the safety, quality and effectiveness of lung cancer care in Australia and New Zealand. Methods and analysis: Patient participants will include all adults >18 years of age with a new diagnosis of non-small-cell lung cancer (NSCLC), SCLC, thymoma or mesothelioma. The ANZLCR will register confirmed diagnoses using opt-out consent. Data will address key patient, disease, management processes and outcomes reported as clinical quality indicators. Electronic data collection facilitated by local data collectors and local, state and federal data linkage will enhance completeness and accuracy. Data will be stored and maintained in a secure web-based data platform overseen by registry management. Central governance with binational representation from consumers, patients and carers, governance, administration, health department, health policy bodies, university research and healthcare workers will provide project oversight. Ethics and dissemination: The ANZLCR has received national ethics approval under the National Mutual Acceptance scheme. Data will be routinely reported to participating sites describing performance against measures of agreed best practice and nationally to stakeholders including federal, state and territory departments of health. Local, regional and (bi)national benchmarks, augmented with online dashboard indicator reporting will enable local targeting of quality improvement efforts.</p

The Weddell Sea Expedition 2019: Cruise Scientific Report

Cruise Scientific Report associated with the Weddell Sea Expedition, 2019. Edited by J. A. Dowdeswell (Chief Scientist).This research was funded by the Flotilla Foundation and Marine Archaeology Consultants Switzerland