Casey Station Research Articles

Urea amendment decouples nitrification in hydrocarbon contaminated Antarctic soil

Hydrocarbon contaminated soils resulting from human activities pose a risk to the natural environment, including in the Arctic and Antarctic. Engineered biopiles constructed at Casey Station, Antarctica, have proven to be an effective strategy for remediating hydrocarbon contaminated soils, with active ex-situ remediation resulting in significant reductions in hydrocarbons, even in the extreme Antarctic climate. However, the use of urea-based fertilisers, whilst providing a nitrogen source for bioremediation, has also altered the natural soil chemistry leading to increases in pH, ammonium and nitrite. Monitoring of the urea amended biopiles identified rising levels of nitrite to be of particular interest, which misaligns with the long term goal of reducing contaminant levels and returning soil communities to a ‘healthy’ state.Here, we combine amplicon sequencing, microfluidic qPCR on field samples and laboratory soil microcosms to assess the impact of persistent nitrite accumulation (up to 60 months) on nitrifier abundances observed within the Antarctic biopiles. Differential inhibition of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) Nitrobacter and Nitrospira in the cold, urea treated, alkaline soils (pH 8.1) was associated with extensive nitrite accumulation (76 ± 57 mg N/kg at 60 months). When the ratio of Nitrospira:AOB dropped below ∼1:1, Nitrobacter was completely inhibited or absent from the biopiles, and nitrite accumulated. Laboratory soil microcosms (incubated at 7 °C and 15 °C for 9 weeks) reproduced the pattern of nitrite accumulation in urea fertilized soil at the lower temperature, consistent with our longer-term observations from the Antarctic biopiles, and with other temperature-controlled microcosm studies. Diammonium phosphate amended soil did not exhibit nitrite accumulation, and could be a suitable alternative biostimulant to avoid excessive nitrite build-up.

Monitoring of Antarctica's Fragile Vegetation Using Drone-Based Remote Sensing, Multispectral Imagery and AI.

Vegetation in East Antarctica, such as moss and lichen, vulnerable to the effects of climate change and ozone depletion, requires robust non-invasive methods to monitor its health condition. Despite the increasing use of unmanned aerial vehicles (UAVs) to acquire high-resolution data for vegetation analysis in Antarctic regions through artificial intelligence (AI) techniques, the use of multispectral imagery and deep learning (DL) is quite limited. This study addresses this gap with two pivotal contributions: (1) it underscores the potential of deep learning (DL) in a field with notably limited implementations for these datasets; and (2) it introduces an innovative workflow that compares the performance between two supervised machine learning (ML) classifiers: Extreme Gradient Boosting (XGBoost) and U-Net. The proposed workflow is validated by detecting and mapping moss and lichen using data collected in the highly biodiverse Antarctic Specially Protected Area (ASPA) 135, situated near Casey Station, between January and February 2023. The implemented ML models were trained against five classes: Healthy Moss, Stressed Moss, Moribund Moss, Lichen, and Non-vegetated. In the development of the U-Net model, two methods were applied: Method (1) which utilised the original labelled data as those used for XGBoost; and Method (2) which incorporated XGBoost predictions as additional input to that version of U-Net. Results indicate that XGBoost demonstrated robust performance, exceeding 85% in key metrics such as precision, recall, and F1-score. The workflow suggested enhanced accuracy in the classification outputs for U-Net, as Method 2 demonstrated a substantial increase in precision, recall and F1-score compared to Method 1, with notable improvements such as precision for Healthy Moss (Method 2: 94% vs. Method 1: 74%) and recall for Stressed Moss (Method 2: 86% vs. Method 1: 69%). These findings contribute to advancing non-invasive monitoring techniques for the delicate Antarctic ecosystems, showcasing the potential of UAVs, high-resolution multispectral imagery, and ML models in remote sensing applications.

Systematic conservation planning for Antarctic research stations

The small ice-free areas of Antarctica are essential locations for both biodiversity and scientific research but are subject to considerable and expanding human impacts, resulting primarily from station-based research and support activities, and local tourism. Awareness by operators of the need to conserve natural values in and around station and visitor site footprints exists, but the cumulative nature of impacts often results in reactive rather than proactive management. With human activity spread across many isolated pockets of ice-free ground, the pathway to the greatest reduction of human impacts within this natural reserve is through better management of these areas, which are impacted the most. Using a case study of Australia's Casey Station, we found significant natural values persist within the immediate proximity (<10 m) of long-term station infrastructure, but encroachment by physical disturbance results in ongoing pressures. Active planning to better conserve such values would provide a direct opportunity to enhance protection of Antarctica's environment. Here we introduce an approach to systematic conservation planning, tailored to Antarctic research stations, to help managers improve the conservation of values surrounding their activity locations. Use of this approach provides a potential mechanism to balance the need for scientific access to the continent with international obligations to protect its environment. It may also facilitate the development of subordinate conservation tools, including management plans and natural capital accounting. By proactively minimising and containing their station footprints, national programs can also independently demonstrate their commitment to protecting Antarctica's environment.

Mapping water content in drying Antarctic moss communities using UAS‐borne SWIR imaging spectroscopy

AbstractAntarctic moss beds are sensitive to climatic conditions, and both their survival and community composition are particularly influenced by the availability of liquid water over summer. As Antarctic regions increasingly face climate pressures (e.g., changing hydrology and heat waves), advancing capabilities to efficiently and non‐destructively monitor water content in moss communities becomes a key research priority. Because of the complexity induced by multiple micro‐climatic drivers and its fragility, tracking the evolution and responses of moss bed moisture requires monitoring methods that are non‐intrusive, efficient, and spatially significant, such as the use of unoccupied aerial systems (UAS). In this study, we combine a multi‐species drying laboratory experiment with short‐wave infrared (SWIR) spectroscopy analyses to first develop a Random Forest regression Model (RFM) capable of predicting Antarctic moss turf water content (~5% error). The RFM was then applied to UAS‐borne SWIR imaging data (900–1700 nm, &lt;16 nm spectral resolution) of the moss beds at high spatial resolution (2 cm) across three sites in the vicinity of Casey Station, Antarctica. The sites differed in terrain, snow cover, and moisture availability to evaluate method capabilities under different conditions. Optimum RFM parameters and input variables (spectral indices and reflectance spectra) were determined. Maps of moss moisture were validated via acquiring moss spectra and water content (using sponges inserted into the moss turf) collected in situ, for which an exponential correlation (R2 = 0.72) was reported. RFM further allowed investigation of the influential spectral variables to model water content in moss and associated spectral water absorption features. We demonstrated that UAS‐borne SWIR imaging is a promising new tool to map and quantify water content in Antarctic moss beds. Hyperspectral mapping facilitates the exploration of the spatial variability of moss health and enables the creation of a baseline against which changes in these moss communities can be measured.

On the chemistry of small waterbodies linked to marine aerosols and local geology on the Windmill Islands and mainland near Casey Station, Antarctica

Context In total, 43 shallow waterbodies were sampled in 1983 in the vicinity of Casey Station and nearby islands in Antarctica. The following physico-chemical parameters were obtained: water and air temperature, pH, conductivity, dissolved oxygen, plus major and minor elements. Aims To identify the physico-chemical characteristics of these waters and determine their origin, and calculate their mineral saturation indices. Methods Waters were analysed using standard methods, including for some elements, flame-atomic absorption spectrometry, spectrophotometry, ion chromatography and gravimetric determination. Mineral saturation indices were calculated using the PHREEQ program. Key results Water salinities were generally low and in the range of 120–1200 mg L−1 (total dissolved solids, TDS), except for one site connected to the sea, and four slightly saline sites. The Na/Cl, Cl/Br and Ca/SO4 ratios of several waters were in the vicinity of seawater ratios, implying a contribution of marine aerosols. However, the Mg/Ca ratio of most waters departed from the seawater ratio, plus there was concordance between the molar ratios of (Na + K)/(Ca + Mg) of many of the waters sampled and those calculated from rock geochemical analyses from diverse lithologies. Such chemical ‘provincialism’ appears to be dictated by rock composition. Nitrate and phosphate concentrations were high in the vicinity of penguin rookeries. Conclusions Two sources of ions are identified, one as marine aerosols as shown by three sets of ratios (Na/Cl, Cl/Br and Ca/SO4) with known marine values, and the other from the weathering of local rocks as shown by (Na + K)/(Ca + Mg) of the lake waters compared to the same ratios for the surrounding rocks. Only a few waterbodies have saturation levels for several carbonate minerals (calcite, aragonite, dolomite and rhodochrosite). Implications Future work is recommended for monitoring the waterbodies surrounding Casey Station as a result of the increased atmospheric CO2 concentration that has occurred over the past 40 years, and likely also with the cessation of building activities around Casey Station.

Contamination of the marine environment by Antarctic research stations: Monitoring marine pollution at Casey station from 1997 to 2015.

The contamination of the marine environment surrounding coastal Antarctic research stations remains insufficiently understood in terms of its extent, persistence, and characteristics. We investigated the presence of contaminants in marine sediments near Casey Station, located in the Windmill Islands of East Antarctica, during the period spanning from 1997 to 2015. Metals, hydrocarbons, PBDEs, PCBs, and nutrients were measured in sediments at anthropogenically disturbed sites, including the wastewater outfall, the wharf area, two former waste disposal sites, and various control locations. Sampling was carried out at three spatial scales: Locations, which were generally kilometres apart and formed the primary scale for comparison; Sites, which were 100 meters apart within each location; and Plots, which were 10 meters apart within each site. Consistently higher concentrations of most contaminants, and in some cases nutrients, were observed at disturbed locations. Some locations also exhibited an increase in contaminant concentrations over time. The spatial distribution of sediment properties (such as grain size and organic matter) and contaminants displayed intricate patterns of variation. Variation in grain size depended on the size category, with fine grains (e.g., <63 μm) showing the greatest variation at the Location scale, while coarse grains exhibited minimal variation at this scale. Contaminant levels demonstrated significant differences between Locations, accounting for approximately 55% of the overall variation for metals, while the variation within the 10-meter scale generally exceeded that within the 100-meter scale. Residual variation among replicate samples was also very high, demonstrating the need for adequate replication in studies of sediments and contaminants around stations. Some contaminants exceeded international guidelines for sediment quality, including metals, hydrocarbons, and PCBs. We conclude that Antarctic research stations such as Casey are likely to pose a moderate level of long-term ecological risk to local marine ecosystems through marine pollution. However, contamination is expected to be confined to areas in close proximity to the stations, although its extent and concentration are anticipated to increase with time. Raising awareness of the contamination risks associated with Antarctic stations and implementing monitoring programs for marine environments adjacent to these stations can contribute to informed decision-making and the improvement of environmental management practices in Antarctica.

Preliminary investigation of effects of copper on a terrestrial population of the antarctic rotifer Philodina sp.

Terrestrial microinvertebrates in Antarctica are potentially exposed to contaminants due to the concentration of human activity on ice-free areas of the continent. As such, knowledge of the response of Antarctic microinvertebrates to contaminants is important to determine the extent of anthropogenic impacts. Antarctic Philodina sp. were extracted from soils and mosses at Casey station, East Antarctica and exposed to aqueous Cu for 96 h. The Philodina sp. was sensitive to excess Cu, with concentrations of 36 μg L−1 Cu (48 h) and 24 μg L−1 Cu (96 h) inhibiting activity by 50%. This is the first study to be published describing the ecotoxicologically derived sensitivity of a rotifer from a terrestrial population to metals, and an Antarctic rotifer to contaminants. It is also the first study to utilise bdelloid rotifer cryptobiosis (chemobiosis) as a sublethal ecotoxicological endpoint. This preliminary investigation highlights the need for further research into the responses of terrestrial Antarctic microinvertebrates to contaminants.

Brominated Flame Retardants in Antarctic Air in the Vicinity of Two All-Year Research Stations

Continuous atmospheric sampling was conducted between 2010–2015 at Casey station in Wilkes Land, Antarctica, and throughout 2013 at Troll Station in Dronning Maud Land, Antarctica. Sample extracts were analyzed for polybrominated diphenyl ethers (PBDEs), and the naturally converted brominated compound, 2,4,6-Tribromoanisole, to explore regional profiles. This represents the first report of seasonal resolution of PBDEs in the Antarctic atmosphere, and we describe conspicuous differences in the ambient atmospheric concentrations of brominated compounds observed between the two stations. Notably, levels of BDE-47 detected at Troll station were higher than those previously detected in the Antarctic or Southern Ocean region, with a maximum concentration of 7800 fg/m3. Elevated levels of penta-formulation PBDE congeners at Troll coincided with local building activities and subsided in the months following completion of activities. The latter provides important information for managers of National Antarctic Programs for preventing the release of persistent, bioaccumulative, and toxic substances in Antarctica.

Hydration/dehydration behaviour of geosynthetic clay liners in the Antarctic environment

This paper examines the hydration/dehydration behaviour of geosynthetic clay liner (GCL) under polar conditions for four simulated conditions experienced at Australia's Casey Station in Antarctica: (a) hydration during summer, (b) dehydration during a winter-summer cycle, (c) hydration through a fine Antarctic soil, and (d) hydration through a coarse Antarctic soil. Hydration during the summer is found to occur if there is direct contact with the water table. In contrast, the low relative humidity of the environment tends to dehydrate the GCL along a path that depends on the field conditions the GCL is exposed to. Hydration from either fine or coarse Antarctica soil is function of the original gravimetric water content of the subgrade soil and its grain size distribution as well as the low relative humidity prevailing in Antarctica.

Diversity, Abundance, Spatial Variation, and Human Impacts in Marine Meiobenthic Nematode and Copepod Communities at Casey Station, East Antarctica

The composition, spatial structure, diversity and abundance of Antarctic nematode and copepod meiobenthic communities was examined in shallow (5–25 m) marine coastal sediments at Casey Station, East Antarctica. The sampling design incorporated spatial scales ranging from 10 meters to kilometers and included testing for human impacts by comparing polluted (metal and hydrocarbon contaminated sediments adjacent to old waste disposal sites) and control areas. A total of 38 nematode genera and 20 copepod families were recorded with nematodes being dominant, comprising up to 95% of the total abundance. Variation was greatest at the largest scale (km’s) but each location had distinct assemblages. At smaller scales there were different patterns of variation for nematodes and copepods. There were significant differences between communities at control and impacted locations. Community patterns had strong correlations with concentrations of metals introduced by human activity in sediments as well as sediment grain size and total organic content. Given the strong association with environmental patterns, particularly those associated with human impacts, we provide further evidence that meiofauna are very useful indicators of anthropogenic environmental changes in Antarctica.

Antarctic sea anemone distribution, abundance and relationships with habitat composition, community structure and anthropogenic disturbance

AbstractUnderstanding the distribution, abundance and habitat preferences of species in the Southern Ocean provides a foundation for assessing the impacts of environmental change and anthropogenic disturbance on Antarctic ecosystems. In near-shore waters at Casey and Davis Stations, photoquadrat surveys were used to determine sea anemone distribution and abundance, habitat preferences, associations with other species and the impact of human disturbance on sea anemone distribution. Two distinct sea anemone morphotypes were found in this study: large sea anemones that require hard substrate for attachment and small, burrowing sea anemones found in muddy sediment. The large sea anemones were found in rocky habitats, with the exception of some sedimentary habitats where other biota were used as substrate. The large sea anemones were associated with a diverse community of epibenthic species found in rocky habitats. The burrowing sea anemones were associated with a less diverse assemblage of sediment-dwelling epibenthos. At Casey Station, sea anemones were more abundant in habitats adjacent to a former waste disposal site than at control sites. The reason for this is not yet known, but may be due to high organic matter inputs or, alternatively, a longer sea ice duration providing protection from ice scour.

Development of an environmental impact reduction strategy for Australia's Antarctic infrastructure

AbstractIn this article, we first describe aspects of the environmental impact reduction strategy that was developed in conjunction with a life cycle assessment undertaken for the operations necessary to support Australia's largest Antarctic research station, Casey Station. The article then identifies future research and operational improvement opportunities for the Australian Antarctic Division, who is responsible for Australia's presence in Antarctica. These insights are mapped against knowledge, treaties, plans, and policies framing how the Australian Antarctic Division operates on the southern continent, making operational planning from the strategy relevant and actionable. The article concludes by posing recommendations, for future environmental management practice, that cover making improvements to data quality collection, undertaking a strategic approach, utilizing a new ice breaker, and facilitating behavior change via engagement and active support of staff.

The environmental impacts of operating an Antarctic research station

AbstractWe present a life cycle assessment (LCA) of the operation of Casey Station in Antarctica. The LCA included quantifying material and energy flows, modeling of elementary flows, and subsequent environmental impacts. Environmental impacts were dominated by emissions associated with freight operations and electricity cogeneration. A participatory design approach was used to identify options to reduce environmental impacts, which included improving freight efficiency, reducing the temperature setpoint of the living quarters, and installing alternative energy systems. These options were then assessed using LCA, and have the potential to reduce environmental impacts by between 2% and 19.1%, depending on the environmental indicator.

Assessing the Risk of Metals and Their Mixtures in the Antarctic Nearshore Marine Environment with Diffusive Gradients in Thin-Films.

Robust environmental assessments and contaminant monitoring in Antarctic near-shore marine environments need new techniques to overcome challenges presented by a highly dynamic environment. This study outlines an approach for contaminant monitoring and risk assessment in Antarctic marine conditions using diffusive gradients in thin-films (DGT) coupled to regionally specific ecotoxicology data and environmental quality standards. This is demonstrated in a field study where DGT samplers were deployed in the near-shore marine environment of East Antarctica around the operational Casey station and the abandoned Wilkes station to measure the time-averaged biologically available fraction of metal contaminants. The incorporation of DGT-labile concentrations to reference toxicity mixture models for three Antarctic organisms predicted low toxic effects (<5% effect to the growth or development of each organism). The comparison of metal concentrations to the Australian and New Zealand default water quality guideline values (WQGVs) showed no marine site exceeding the WQGVs for 95% species protection. However, all sites exceeded the 99% WQGVs due to copper concentrations that are likely of geogenic origin (i.e., not from anthropogenic sources). This study provides evidence supporting the use of the DGT technique to monitor contaminants and assess their environmental risk in the near-shore marine environment of Antarctica.

Spatio-temporal variation of skeletal Mg-calcite in Antarctic marine calcifiers.

Human driven changes such as increases in oceanic CO2, global warming, petroleum hydrocarbons and heavy metals may negatively affect the ability of marine calcifiers to build their skeletons/shells, especially in polar regions. We examine spatio-temporal variability of skeletal Mg-calcite in shallow water Antarctic marine invertebrates using bryozoan and spirorbids as models in a recruitment experiment of settlement tiles in East Antarctica. Mineralogies were determined for 754 specimens belonging to six bryozoan species (four cheilostome and two cyclostome species) and two spirorbid species from around Casey Station. Intra- and interspecific variability in wt% MgCO3 in calcite among most species was the largest source of variation overall. Therefore, the skeletal Mg-calcite in these taxa seem to be mainly biologically controlled. However, significant spatial variability was also found in wt% MgCO3 in calcite, possibly reflecting local environment variation from sources such as freshwater input and contaminated sediments. Species with high-Mg calcite skeletons (e.g. Beania erecta) could be particularly sensitive to multiple stressors under predictions for near-future global ocean chemistry changes such as increasing temperature, ocean acidification and pollution.

Effect of temperature on bacterial community in petroleum hydrocarbon-contaminated and uncontaminated Antarctic soil

It is generally accepted that bacterial diversity in a community confers resistance to environmental perturbation. Communities with high bacterial diversity are less likely to be impacted by environmental changes such as warming. As such, hydrocarbon-contaminated Antarctic soil that are typically characterised by low bacterial diversity and highly selective taxonomic composition are expected to be more sensitive to changes in temperature than uncontaminated Antarctic soil. To test this hypothesis, we evaluated the response of bacterial community structure to warming of hydrocarbon-contaminated and uncontaminated soil collected from Casey Station, Windmill Island, East Antarctica by using microcosms incubated at 5, 10 and 15 °C over a period of 12 weeks. Our results showed that shifts occurred in the bacterial community in relation to the incubation temperatures in both the hydrocarbon-contaminated and uncontaminated soil, with a stronger response observed in the contaminated soil. Taxa referred as comprising hydrocarbon-degrading genera such as Rhodococcus, was the most prevalent genus in the contaminated soil after incubation at 15 °C, accounting for approximately 32–50% of the total detected genera. However, there were no significant differences in the selected functional genes, potentially suggesting high levels of metabolic plasticity in the studied soil bacterial communities. Overall, we showed that hydrocarbon contamination in soil might lead to lower bacterial community stability against environmental perturbation such as temperature variation.

Biofilm communities and biodegradation within permeable reactive barriers at fuel spill sites in Antarctica

Determining the composition of the complex microbial communities within biofilms can aid us in understanding the potential for biodegradation on different permeable reactive barrier materials. Microbial communities were examined under Antarctic conditions across laboratory and field studies using amplicon pyrosequencing, and the reaction of these communities to petroleum hydrocarbon contamination and NH4+ supplementation was assessed. Putative hydrocarbon degrading bacteria in the orders Actinomycetales and Burkholderiales were identified in laboratory flow cells and within the upper PRB and lower PRB at Casey Station, Antarctica. The release of NH4+ from ammonium exchanged zeolite was shown to reduce the microbial diversity of biofilms, when compared to natural zeolite. Bacteria from the orders Sphingomonadales, Rhodocyclales, Pseudomonadales and Xanthomonadales were also observed across the Zeopro™/granular activated carbon permeable reactive barrier mixtures. The bacterial species were observed within a uniform microbial biofilm layer, embedded within extracellular polymeric substances on the surface of the materials. This study demonstrates that petroleum hydrocarbon contamination can contribute to the enrichment of certain hydrocarbon degrading species on permeable reactive barrier materials.

The effects of hydrocarbons on meiofauna in marine sediments in Antarctica

The effects of hydrocarbons in marine sediments on Antarctic meiofaunal communities (nematodes and copepods) were investigated in a five year field experiment at Casey Station, East Antarctica. The effects of four different types of hydrocarbons were examined: clean mineral lube oil, used mineral lube oil, synthetic lube oil marketed as being rapidly biodegradable, and diesel fuel (Special Antarctic Blend). Sediments were sieved to remove macrofauna and then treated with one of the oils, then deployed in trays on the seabed (12–18m) under sea ice, along with control, uncontaminated sediment. Samples of the meiofaunal communities were collected at one, two and five years and nematodes identified to genus and copepods to family. There were significant differences between meiofaunal communities in hydrocarbon-treated sediment compared to controls, but each hydrocarbon type had quite different effects. Effects persisted to five years and communities showed no signs of recovery or becoming more similar to controls. Nematodes were more sensitive to hydrocarbons than copepods, showing very distinct community differences between different treatments which persisted over the five years. In contrast, copepod communities showed less distinct, more variable changes, which decreased in severity over five years. Nematode abundance initially decreased in hydrocarbon treatments in comparison to controls, except for the biodegradable oil treatment, and this persisted also over five years. In contrast, copepod abundance initially increased in hydrocarbon treatments compared to controls, and then declined, and by five years abundances were lower in hydrocarbon treatments than in controls. Whilst structural community, abundance and diversity differences for nematodes and copepods remained after 5years, the nematode functional parameters based on feeding types and maturity characteristics showed a substantial degree of recovery after 5years, suggesting some functional recovery of the nematode community. This experiment demonstrates that different hydrocarbons can have very different effects on sediment meiofauna and that despite strong patterns of community effects it was very difficult to characterize effects on different taxa. The effects of oils in sediments are also likely to persist for periods greater than five years and could take decades to recover.

Is the Antarctic Ophryotrocha orensanzi (Annelida: Dorvilleidae) a circumpolar non-specialized opportunist?

The dorvilleid polychaete Ophryotrocha orensanzi is reported from the vicinity of Casey station, East Antarctica, an astounding range extension from its previous records in the South Shetland Islands to the opposite side of the Antarctic continent, suggesting that it is a circumpolar species. Genetic studies confirmed the conspecificity and the inferred haplotype network suggests that the two populations studied are genetically connected. Morphological studies of the newly collected material revealed that the jaw apparatus consists of the P- and K-type, in accordance with other members of the ‘lobifera’ clade. We are reporting a previously undocumented button-like structure that we are referring to as ‘nuchal papilla’ for its association with the nuchal region, and present an emended diagnosis for the species. The Casey station population was collected in a clean, unpolluted intertidal environment associated with stones and seaweeds. We are challenging the generally held opinion that Ophryotrocha species are specialists of organically enriched substrates, suggesting that, at least for the particulars of O. orensanzi, they might also be unspecialized opportunists, able to exist in the most pristine environments and having the ability to rapidly increase their population sizes under favourable conditions.

Third xFOCE Workshop: Present Status and Future Developments of In Situ Ocean Acidification Experiments

One of the major challenges facing ocean acidification research is the need to expand from single species to communities and ecosystems (Riebesell and Gattuso 2015). Free Ocean CO2 Enrichment (FOCE) experiments were developed to address the need for long term, in situ CO2 manipulation in benthic ecosystems (Gattuso et al. 2014), and to enable community level investigations of the effects of ocean acidification. Theoretically these experiments allow for the precise control of pH in benthic chambers, while maintaining open flow-through conditions including natural background variation in other parameters. xFOCE is the open source technology developed by the Monterey Bay Aquarium Research Institute (MBARI) to enable cost effective and adaptable system design. With support from the Australian Antarctic Division (AAD) and the 4th International Symposium on the Ocean in a High-CO2 World, a group of 18 past, present and future FOCE users met in Kingston, Hobart (Australia) on 29th April 2016. Problems with the shallow water FOCE (swFOCE) in Monterey Bay were described by engineer K. Headley (MBARI), including electrical ground faults and software interfacing. Despite these issues MBARI is at the forefront of FOCE design and has contributed to all other FOCE systems. Valuable lessons in chamber design, power supply and habitat choice were reviewed by F. Gazeau (Laboratoire d'Océanographie de Villefranche, France) from the Mediterranean Sea FOCE (eFOCE) conducted in seagrass beds. J. Stark (AAD) gave a comprehensive overview of the recent successful Antarctic FOCE (antFOCE) experiment (Fig. 1) and was followed by further antFOCE insights including: deployment under ice in Antarctica (G. Johnstone AAD); engineering of pump systems and enriched seawater (S. Whiteside, AAD); surface based sensors and control of pH via feedback loops (M. Milnes, AAD); carbonate chemistry demonstrating the antFOCE system's effectiveness in obtaining a 0.4 pH offset (N. Roden, University of Tasmania, UTAS); and preliminary results from work on bioturbation (A. Queiros, Plymouth Marine Laboratories). A very successful addition to FOCE systems was described by J. Black (UTAS), which consisted of smaller chambers designed for short term (48–96h) in situ incubation experiments using water from the antFOCE system. The antFOCE experiment was deployed in 14m of water under sea ice at Casey Station, in East Antarctica. Mixing ducts 40m long were required to allow pH to equilibrate following the addition of CO2 enriched seawater into the flow-through system. Although FOCE experiments present many challenges, group consensus was that FOCE systems are now proven to be viable and worthwhile. There are a range of solutions and options to overcome site specific difficulties and adapt FOCE systems to particular scientific needs. Using the combined experience of past efforts we now can make estimates of resources (including personnel) and skills required for successful FOCE experiments. A paper on this topic is being prepared as a result of the workshop. The next challenge for FOCE systems will be to incorporate additional drivers beyond a pH offset, such as temperature or oxygen. The xFOCE website contains additional information including a list of meeting participants and can be found at http://www.xfoce.org. Jonathan S. Stark, Antarctic Conservation and Management, Australian Antarctic Division, Channel Hwy, Kingston, Tasmania, Australia, email: jonny.stark@aad.gov.au Jean Pierre Gattuso, Laboratoire d'Océanographie de Villefranche, CNRS-UPMC-IDDRI, Villefranche-sur-mer, France, e-mail: Gattuso@obs-vlfr.fr