Ocean alkalinity enhancement (OAE) is an emerging carbon dioxide removal (CDR) strategy that leverages the natural processes of weathering and acid neutralisation to durably store atmospheric CO2 in seawater. OAE can be achieved with a variety of methods, all of which have different environmental implications. One widely considered method utilizes electrochemistry to remove strong acid from seawater, leaving sodium hydroxide (NaOH) behind. This study evaluates the impacts of OAE via NaOH (NaOH-OAE) on a coastal plankton bloom, with particular focus on how macronutrient regeneration in the aftermath of the bloom responds to the perturbation. To investigate this, we enclosed a natural coastal phytoplankton community, including coccolithophores, in nine microcosms. The microcosms were divided into three groups: control, unequilibrated (512.1 ± 2.5 µmol kg-1 alkalinity increase) and equilibrated (499.3 ±5.65 µmol kg-1 alkalinity increase). Light was provided for 11 days to stimulate a bloom (light phase) and lights were turned off thereafter to investigate alkalinity and nutrient changes for 21 days (dark phase). We found no detectable effect of equilibrated NaOH-OAE on phytoplankton community and bacteria abundances determined with flow cytometry but observed a small yet detectable restructuring of phytoplankton communities under unequilibrated conditions. NaOH-OAE had no significant effect on alkalinity, NOx- and phosphate regeneration, but increased silicate regeneration by 64% over 21 days under darkness in the unequilibrated treatments where seawater pH was highest (8.65 relative to 7.92 in the control). Additional dissolution experiments with two diatom species supported this outcome on silicate regeneration for one of the two species, thereby suggesting that the effect is species specific. Our results point towards the potential of NaOH-OAE to influence regeneration of silicate in the surface ocean and thus the growth of diatoms, at least under the very extreme NaOH-OAE conditions simulated here.

We compare the formulation and emergent dynamics of 11 CMIP6 IPCC marine biogeochemical models. We find that the largest source of uncertainty across model simulations of marine carbon cycling is grazing pressure (i.e. the phytoplankton specific loss rate to grazing). Variability in grazing pressure is driven by large differences in zooplankton specific grazing rates, which are not sufficiently compensated for by offsetting differences in zooplankton specific mortality rates. Models instead must tune the turnover rate of the phytoplankton population to balance large differences in top-down grazing pressure and constrain net primary production. We then run a controlled sensitivity experiment in a global, coupled ocean-biogeochemistry model to test the sensitivity of marine carbon cycling to this uncertainty and find that even when tuned to identical net primary production, export and secondary production remain extremely sensitive to grazing, likely biasing predictions of future climate states and food security.

These files contain the data recorded from a mesocosm experiment conducted in Bergen, Norway 2022 which assessed the effect of simualted mineral-based (silicate or calcium) ocean alkalinity enhancement (OAE) on diatom silicification. Ten mesocosms were used in total, divided into two groups either the silicate- or calcium based group and alkalinity was increased by either 0, 150, 300, 450 or 600 µmol L-1 above natrually occuring levels. The PDMPO-fluorescence (an appropriate proxy for silicification) of diatoms was recorded on eight seperate days during the experiment. Accompanying data includes measured; macronutrients (nitrate, nitrite, phophate, silicate), total alkalinity, biogenic silica in the water column and sediment trap.

Carbon and nitrogen isotope data for J. edwardsii lobsters from eight sites in SE Australia.

Invasive mammal eradications are commonplace in island conservation. However, post-eradication monitoring beyond the confirmation of target species removal is rarer. Seabirds are ecosystem engineers on islands and are negatively affected by invasive mammals. Following an invasive mammal eradication, the recovery of seabird populations can be necessary for wider ecosystem recovery. Seabirds fertilise islands with isotopically heavy nitrogen, which means nitrogen stable isotope analysis (δ15N) could provide a useful means for assessing corresponding change in ecosystem function. We quantified decadal changes in δ15N on eight temperate New Zealand islands subject in pairs to distinct mammal invasion and seabird restoration histories: invaded, never-invaded, invader-eradicated and undergoing active seabird restoration. First, we investigated long-term changes in δ15N values on individual islands. Second, we used a space for time analysis to determine if δ15N levels on islands from which invaders had been removed eventually recovered to values typical of never-invaded islands. On each island soil, plants (Coprosma repens, C. robust and Myrsine australis) and spiders (Porrhothelidae) were sampled in 2006/07 and 2022 allowing δ15N change on individual islands over 16 years to be assessed. Combined, the samples from invader-eradicated islands provided a 7 – 32 year post-eradication dataset. Change in δ15N was only detected on one island across the study period, following the unexpected recolonisation of seabirds to an invaded island. Invader-eradicated islands generally had higher δ15N values than invaded islands however, they were still lower than never-invaded islands and there was no trend in δ15N with time since eradication. This, and the measurable increase in δ15N following seabird recolonisation on one island, may suggest that δ15N change occurs rapidly following invader-eradication, but then slows, with δ15N values staying relatively constant in the time period studied here. Isotope and seabird population studies need to be coupled to ascertain if plateauing in δ15N reflects a slowing of seabird population growth and subsequent basal nutrient input, or if the baseline nutrients are entering the ecosystem but then not propagating up the food web.

'Weather@home ANZ' is a global citizen science distributed computing project being run as part of the Oxford-based 'weather@home' project, which is part of 'climateprediction.net'. In this experiment, a detailed limited area (regional) climate model is embedded within the less detailed 'driving' global model. This higher-resolution regional model is able to tell us in unprecedented detail about potential changes to patterns of weather as climate changes. In the initial 'weather@home' experiment launched in 2010, the project team released this regional modelling capability for three regions: Europe, Southern Africa and the Western USA. This capability has been extended to other regions around the world and the first such new region to be developed was the Australasian region encompassing Australia, New Zealand and surrounding areas, which was launched to the public in 2014. This particular part of the project - 'weatherathome ANZ' - has received support from the University of Oxford (U.K.), the U.K. Met. Office, the Universities of Melbourne and Tasmania (Australia), the Tasmanian Partnership for Advanced Computing and the New Zealand National Institute for Water and Atmospheric Research (NIWA). 'weather@home' has also been supported by Microsoft Research.

Southeastern Australia's marine waters are undergoing a trend of increased warming, surpassing the global average. This area has emerged as an alluring location for research on planktic microfossils, particularly dinoflagellate cysts, which are abundant in contemporary and Late Quaternary sediments. The composition of dinoflagellate cyst assemblages offers valuable information about the physical and biogeochemical properties of mid-latitude waters in this region. This study presents an analysis of cyst assemblages from marine sediment cores from waters inshore and offshore Maria Island, Tasmania, southeast Australia, up to 9 kyrs BP. The dominant cysts were Protoceratium reticulatum, Protoperidinium spp. (P. avellana, P. conicum, P.minutum, P. oblongum, P. subinerme, P. shanghaiense) and Spiniferites spp. (S. bulloideus, S. hyperacanthus, S. membranaceus, S. mirabilis, S. pachydermus, and S. ramosus). Inshore, Spiniferites spp. were more abundant (up to 61%), while P. reticulatum was dominant (up to 80%) at the offshore site. Impagidinium spp. and Nematosphaeropsis labyrinthus were exclusively detected offshore, with their increasing occurrence from 6 kyrs BP to present suggesting a transition from shallow coastal to stable deep-water habitat. Cysts of the Alexandrium tamarense complex were detected over the past 140 years and 9 kyrs BP at the inshore and offshore sites respectively, indicating an endemic long-term presence. Low abundances of Gymnodinium catenatum cysts were detected exclusively inshore from 50 years ago to present, suggesting recent bloom events. The limited southward penetration of the East Australian Current is indicated by the lack of warm-water cyst taxa such as Lingulodinium machaerophorum. Unlike coccolithophores, previously studied in the same sediment core, no discernible shift from cold to warm-water dinoflagellate cyst species was observed. The documentation of dinoflagellate cyst assemblages presented in this study will aid in predicting the effects of climate change, eutrophication, and introduction of novel species on local and broader community dynamics.

1. Workforce Tasmania’s commercial fishing industry workforce is defined as those people engaged in economic activity (work) within the sector across or at a given time, either in paid employment or self-employment. For fisheries this includes skippers and crew employed as sub-contractors and paid on a share of catch arrangement. It can include people engaged in unpaid work undertaken as part of these activities, although this has not been included in this assessment. Monitoring workforce changes is important because these changes indicate changes in social and economic benefits at a statewide and regional community level. Factors which affect workforce size include the extent to which a policy of maximizing technical efficiency is pursued through management, which typically reduces the fleet size and therefore the number of people employed. Other factors include the level of stock availability and access, the cost of entry into the fishery, and the financial profitability of fishing. Because of these factors, many fishers are engaged in employment in multiple fisheries or other marine sectors in order to supplement fishing incomes and pursue full-time employment. 1.1. Abalone The commercial harvesters catching abalone species operate within the Tasmanian Abalone Fishery. Assessment of workforce indicators is undertaken at fishery level. The data provided for this fishery is for the Tasmanian Abalone Fishery as a whole, which includes harvesting activity for this species as well as all other species caught in this fishery. 1.2. Commercial Dive species The commercial harvesters catching these species operate within the Tasmanian Commercial Dive Fishery. Assessment of workforce indicators is undertaken at fishery level. The data provided here is for the Tasmanian Commercial Dive species as well as all other species caught in this fishery. 1.3. Giant crab species The commercial harvesters catching giant crab operate within the Tasmanian Giant Crab Fishery. Assessment of workforce indicators is undertaken at fishery level. 1.4. Scalefish species The commercial harvesters catching this scalefish species operate within the Tasmanian Scalefish Fishery. Assessment of workforce indicators is undertaken at fishery level. The data provided here is for the Tasmanian Scalefish Fishery as a whole, which includes harvesting activity for this species as well as all other species caught in this fishery. 1.5. Scallop species The commercial harvesters catching species of scallop operate within the Tasmanian Scallop Fishery. Assessment of workforce indicators is undertaken at fishery level. 1.6. Southern rock lobster The commercial harvesters catching southern rock lobster operate within the Tasmanian Rock Lobster Fishery. Assessment of workforce indicators is undertaken at fishery level. 2. Workforce Indicators 2.1. Persons Workforce size (the total number of people directly employed) includes both skippers and crew, and those employed full time and part time. 2.2. Employment FTE The number of Full Time Equivalent (FTE) positions in each fishery is also estimated. This indicator shows that while a higher number of people may be employed in a fishery, some of these jobs may be part-time. Therefore, the number of FTEs is typically lower than the number of people in the workforce. In this iteration of the dataset, this value is unavailable for the abalone fishery in 2016, 2017, and 2019, and does not apply to the scallop fishery in any of the years available (2016-2020). 2.3. Active Supers The number of supervisors (skippers) employed in the fishery. 2.4. Harvest Units (TAS HP) The number of harvest units (combination of licensed vessel and fishing entitlement) active in a fleet and the number of people who actively harvest fish as supervisors (skippers) in a commercial fishery are directly linked to the size of the workforce in each fishery. In many cases, multiple supervisors may be linked to the same harvest unit, so the number of supervisors is often higher.