Assessing risks from fuel contamination in Antarctica: Dynamics of diesel ageing in soil and toxicity to an endemic nematode.

Fuel spills are a major source of contamination in terrestrial environments in Antarctica. Little is known of the effects of hydrocarbon contaminants in fuels on Antarctic terrestrial biota, and how these change as fuel ages within soil. In this study we investigate the sensitivity of juveniles of the endemic Antarctic nematode Plectus murrayi to diesel-spiked soil. Toxicity tests were conducted on soil elutriates, and changes in concentrations of hydrocarbons, polar compounds and PAHs were assessed as the spiked soil was artificially aged at 3 °C over a 45-week period, representing multiple summer seasons of fuel degradation. Nematodes were most sensitive to elutriates made from freshly spiked soils (LC50 419 µg/L TPH and 156 µg/L TPH-SG), with a subsequent decline in toxicity observed in the first 6 weeks of laboratory ageing (LC50 2945 µg/L TPH and 694 µg/L TPH-SG). Effects were still evident up to 45 weeks (lowest observed effect concentration 2123 µg/L TPH) despite hydrocarbons being depleted from soils with ageing (84 % loss) and elutriates becoming dominated by polar metabolites (95 % polar). Nematode sensitivity throughout the ageing period showed evidence of a relationship between LC50 and the proportions of the lighter carbon range fraction of TPH in elutriates, the F2 fraction (C10-14). This study is the first to estimate the sensitivity of Antarctic terrestrial fauna to diesel and provides novel data on the dynamics of fuel chemistry under Antarctic conditions and how this influences toxicity. Findings contribute to predicting ecological risk at existing diesel fuel spill sites in Antarctica, to the derivation of site-specific remediation targets, and to environmental guidelines to assess ecosystem health.

Using an expert judgment response matrix to assess the risk of groundwater discharges from remediated fuel spill sites to the marine environment at sub-Antarctic Macquarie Island, Australia.

This study assesses toxicity of groundwater from remediated fuel spill sites, as the final phase of an environmental risk assessment of contaminated sites at sub-Antarctic Macquarie Island, Tasmania, Australia. To complement previous terrestrial ecotoxicological research, we determine risk to marine environments from residual biodegraded hydrocarbon contaminants in groundwater discharges. Direct toxicity assessments were conducted on 7 composite groundwater test solutions, adjusted to ambient seawater salinity. Eleven native marine invertebrates (from varied taxa: gastropods, bivalves, flatworms, amphipods, copepods, isopods) were exposed and observed for up to 21 d. Lethal time estimates (LT10, LT50) showed sensitivity was time dependent (LT10s = 4-15 d) and variable between species. Three species showed no response to any test solution, and most species did not respond for up to 5 d. Data were interpreted using an expert judgment response matrix with multiple lines of evidence to predict risk. No consistent patterns in the relative toxicity of test solutions, based on polar or nonpolar hydrocarbon concentrations, were identified. Although toxicity was observed in some species, this was only under worst-case conditions of undiluted, continuous, extended exposure. Natural dynamics of the site, including low groundwater discharge rates, high rainfall, and a highly energetic receiving environment, ensure groundwater is rapidly diluted and dispersed. In this context, and based on site conditions at the time of testing, these toxicity assessments provide robust evidence that residual contamination in groundwater at remediated sites at Macquarie Island is unlikely to represent a risk to the adjacent marine communities tested. Integr Environ Assess Manag 2021;17:785-801. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Semi-Automated Analysis of Digital Photographs for Monitoring East Antarctic Vegetation.

Climate change is affecting Antarctica and minimally destructive long-term monitoring of its unique ecosystems is vital to detect biodiversity trends, and to understand how change is affecting these communities. The use of automated or semi-automated methods is especially valuable in harsh polar environments, as access is limited and conditions extreme. We assessed moss health and cover at six time points between 2003 and 2014 at two East Antarctic sites. Semi-automatic object-based image analysis (OBIA) was used to classify digital photographs using a set of rules based on digital red, green, blue (RGB) and hue-saturation-intensity (HSI) value thresholds, assigning vegetation to categories of healthy, stressed or moribund moss and lichens. Comparison with traditional visual estimates showed that estimates of percent cover using semi-automated OBIA classification fell within the range of variation determined by visual methods. Overall moss health, as assessed using the mean percentages of healthy, stressed and moribund mosses within quadrats, changed over the 11 years at both sites. A marked increase in stress and decline in health was observed across both sites in 2008, followed by recovery to baseline levels of health by 2014 at one site, but with significantly more stressed or moribund moss remaining within the two communities at the other site. Our results confirm that vegetation cover can be reliably estimated using semi-automated OBIA, providing similar accuracy to visual estimation by experts. The resulting vegetation cover estimates provide a sensitive measure to assess change in vegetation health over time and have informed a conceptual framework for the changing condition of Antarctic mosses. In demonstrating that this method can be used to monitor ground cover vegetation at small scales, we suggest it may also be suitable for other extreme environments where repeat monitoring via images is required.

Sensitivity to Copper and Development of Culturing and Toxicity Test Procedures for the Antarctic Terrestrial Nematode Plectus murrayi.

Environmental quality guideline values and remediation targets, specific to Antarctic ecosystems, are required for the risk assessment and remediation of contaminated sites in Antarctica. Ecotoxicological testing with Antarctic soil organisms is fundamental in determining reliable contaminant effect threshold concentrations. The present study describes the development of optimal culturing techniques and aqueous toxicity test procedures for an endemic Antarctic soil nematode, Plectus murrayi, which lives within interstitial waters between soil particles. Toxicity tests were of extended duration to account for the species' physiology and life-history characteristics. Plectus murrayi was sensitive to aqueous copper with a 50% effective concentration for egg-hatching success of 139 µg/L. Hatched juveniles that were first exposed to copper as eggs appeared to be less sensitive than those first exposed at the hatched J2 stage, indicating a potential protective effect of the egg. Sensitivity of juveniles to copper increased with exposure duration, with 50% lethal concentrations of 478 and 117 µg/L at 21 and 28 d, respectively. The present study describes new methods for the application of an environmentally relevant test species to the risk assessment of contaminants in Antarctic soil and provides the first estimates of sensitivity to a toxicant for an Antarctic terrestrial microinvertebrate. Environ Toxicol Chem 2020;39:482-491. © 2019 SETAC.

Sensitivity of a Large and Representative Sample of Antarctic Marine Invertebrates to Metals.

There are limited data on the sensitivity to contaminants of marine organisms in polar regions. Consequently, assessments of the risk of contaminants to marine biota in polar environments typically include extrapolations from temperate and/or tropical species. This is problematic because the taxonomic composition of organisms differs between polar and temperate/tropical waters, and both the toxicity of chemicals and the physiology of organisms are very different at the stable low temperatures experienced in polar marine systems. Collecting high-quality sensitivity data for a wide range of marine polar organisms using traditional toxicity assessment approaches is a time-consuming and difficult process, especially in remote and hostile environments. We applied a rapid toxicity testing approach, which allowed a much larger number of species to be tested than would be possible with traditional toxicity test methods, albeit with lower replications and fewer exposure concentrations. With this rapid approach, sensitivity estimates are less precise, but more numerous. This is important when constructing species sensitivity distributions (SSDs), which aim to represent the sensitivity of communities. We determined the approximate sensitivity (4- and 10-d median lethal concentration [LC50] values) of a large and representative sample of Antarctic marine invertebrates to copper (Cu), zinc (Zn), and cadmium (Cd). Up to 88 LC50 values (from 88 different taxa) were used in the construction of SSDs. The hazardous concentrations for 1% of taxa (HC1) based on 10-d LC50 values were 37, 346, and 792 µg/L for Cu, Zn, and Cd, respectively. Our results provide a basis for estimating the risk of exposure to metals for a large representative sample of marine polar invertebrates. Environ Toxicol Chem 2019;38:1560-1568. © 2019 SETAC.

Response of the Native Springtail Parisotoma insularis to Diesel Fuel-Contaminated Soils Under Field-Realistic Exposure Conditions at Subantarctic Macquarie Island.

A number of sites contaminated by petroleum hydrocarbons from past fuel spills are currently undergoing remediation on subantarctic Macquarie Island (under the jurisdiction of Tasmania, Australia). To assess the environmental risks these spills pose, and to establish remediation targets and guideline values, toxicity data for a range of native biota are required. The availability of data for local biota is limited, especially for soil invertebrates, which are critical to soil health. To examine the response of naturally occurring soil invertebrate communities to fuel contamination, intact soil cores from a range of soil types were collected along an organic carbon (OC) gradient. Organic carbon was factored into the toxicity assessment due to its toxicity-modifying potential. Soil cores were spiked with Special Antarctic Blend diesel, to mimic a fresh fuel spill at the soil surface. Springtails were the most abundant taxa, with the community heavily dominated by the native species Parisotoma insularis. This species was sensitive to fuel contamination (EC20 48 mg/kg, CI 5-188), irrespective of soil organic content. This study is the first to derive critical effect concentrations (CECs) for a subantarctic springtail species and provides important data that will be incorporated into future derivation of site-specific soil quality guideline values for fuels for Macquarie Island soils and the broader subantarctic region. Integr Environ Assess Manag 2019;15:565-574. © 2019 SETAC.

Moving beyond presence and absence when examining changes in species distributions.

Species distributions are often simplified to binary representations of the ranges where they are present and absent. It is then common to look for changes in these ranges as indicators of the effects of climate change, the expansion or control of invasive species or the impact of human land-use changes. We argue that there are inherent problems with this approach, and more emphasis should be placed on species relative abundance rather than just presence. The sampling effort required to be confident of absence is often impractical to achieve, and estimates of species range changes based on survey data are therefore inherently sensitive to sampling intensity. Species niches estimated using presence-absence or presence-only models are broader than those for abundance and may exaggerate the viability of small marginal sink populations. We demonstrate that it is possible to transform models of predicted probability of presence to expected abundance if the sampling intensity is known. Using case studies of Antarctic mosses and temperate rain forest trees, we demonstrate additional insights into biotic change that can be gained using this method. While species becoming locally extinct or colonising new areas are extreme and obviously important impacts of global environmental change, changes in abundance could still signal important changes in biological systems and be an early warning indicator of larger future changes.

Soil invertebrate community change over fuel-contaminated sites on a subantarctic island: An ecological field-based line of evidence for site risk assessment.

A number of fuel spills, of both recent and historic origins, have occurred on World Heritage-listed subantarctic Macquarie Island. Sites contaminated by mainly diesel fuels are undergoing remediation by the Australian Antarctic Division. The risks posed by these sites are being managed using a "weight of evidence" approach, for which this study provides a preliminary line of evidence for the ecological assessment component of this site management decision framework. This knowledge is pertinent, given the absence of environmental guidelines for fuel contaminants in subantarctic ecosystems. We provide a field-based, site-specific ecological risk assessment for soil invertebrate communities across the fuel spill sites, before the commencement of in situ remediation activities. Springtails (Collembola) were the most abundant taxa. Springtail community patterns showed only limited correlations with the level of fuel contamination at the soil surface, even when elevated levels occurred in the substratum layers. Of the environmental variables measured, community patterns were most strongly correlated with vegetation cover. We identify a suite of 6 species that contribute most to the community dynamics across these sites. A subset of these we propose as useful candidates for future development of single-species toxicity tests: Folsomotoma punctata, Cryptopygus caecus, Cryptopygus antarcticus and Parisotoma insularis. Findings from this study advance our understanding of soil invertebrate community dynamics within these contaminated sites, directly contributing to the improved management and restoration of the sites. Not only does this study provide an important line of evidence for the island's ecological risk assessment for fuel contaminants, it also enhances our understanding of the potential impact of fuels at other subantarctic islands.

Impact of hydrocarbons from a diesel fuel on the germination and early growth of subantarctic plants.

Special Antarctic Blend (SAB) is a diesel fuel dominated by aliphatic hydrocarbons that is commonly used in Antarctic and subantarctic regions. The past and present use of SAB fuel at Australia's scientific research stations has resulted in multiple spills, contaminating soils in these pristine areas. Despite this, no soil quality guidelines or remediation targets have been developed for the region, primarily due to the lack of established indigenous test species and subsequent biological effects data. In this study, twelve plant species native to subantarctic regions were collected from Macquarie Island and evaluated to determine their suitably for use in laboratory-based toxicity testing, using germination success and seedling growth (shoot and root length) as endpoints. Two soil types (low and high organic carbon (OC)) were investigated to reflect the variable OC content found in soils on Macquarie Island. These soils were spiked with SAB fuel and aged for 14 days to generate a concentration series of SAB-contaminated soils. Exposure doses were quantified as the concentration of total petroleum hydrocarbons (TPH, nC9-nC18) on a soil dry mass basis. Seven species successfully germinated on control soils under laboratory conditions, and four of these species (Colobanthus muscoides Hook.f., Deschampsia chapmanii Petrie, Epilobium pendunculare A.Cunn. and Luzula crinita Hook.f.) showed a dose-dependent inhibition of germination when exposed to SAB-contaminated soils. Contaminated soils with low OC were generally more toxic to plants than high organic carbon soils. Increasing soil-TPH concentrations significantly inhibited shoot and root growth, and root length was identified as the most sensitive endpoint. Although the test species were tolerant to SAB-contaminated soils in germination assays, development of early life stages (up to 28 days) were generally more sensitive indicator of exposure effects, and may be more useful endpoints for future testing.

Toxicity of fuel-contaminated soil to Antarctic moss and terrestrial algae.

Fuel pollution is a significant problem in Antarctica, especially in areas where human activities occur, such as at scientific research stations. Despite this, there is little information on the effects of petroleum hydrocarbons on Antarctic terrestrial biota. The authors demonstrate that the Antarctic mosses Bryum pseudotriquetrum, Schistidium antarctici, and Ceratodon purpureus, and the Antarctic terrestrial alga Prasiola crispa are relatively tolerant to Special Antarctic Blend (SAB) fuel-contaminated soil (measured as total petroleum hydrocarbons). Freshly spiked soils were more toxic to all species than were aged soils containing degraded fuel, as measured by photosynthetic efficiency (variable fluorescence/maximum fluorescence [Fv/Fm]), pigment content, and visual observations. Concentrations that caused 20% inhibition ranged from 16,600 mg/kg to 53,200 mg/kg for freshly spiked soils and from 30,100 mg/kg to 56,200 mg/kg for aged soils. The photosynthetic efficiency of C. purpureus and S. antarctici was significantly inhibited by exposure to freshly spiked soils with lowest-observed-effect concentrations of 27,900 mg/kg and 40,400 mg/kg, respectively. Prasiola crispa was the most sensitive species to freshly spiked soils (Fv/Fm lowest-observed-effect concentration 6700 mg/kg), whereas the Fv/Fm of B. pseudotriquetrum was unaffected by exposure to SAB fuel even at the highest concentration tested (62,900 mg/kg). Standard toxicity test methods developed for nonvascular plants can be used in future risk assessments, and sensitivity data will contribute to the development of remediation targets for petroleum hydrocarbons to guide remediation activities in Antarctica.

Phytoremediation of hydrocarbon contaminants in subantarctic soils: an effective management option.

Accidental fuel spills on world heritage subantarctic Macquarie Island have caused considerable contamination. Due to the island's high latitude position, its climate, and its fragile ecosystem, traditional methods of remediation are unsuitable for on-site clean up. We investigated the tolerance of a subantarctic native tussock grass, Poa foliosa (Hook. f.), to Special Antarctic Blend (SAB) diesel fuel and its potential to reduce SAB fuel contamination via phytoremediation. Toxicity of SAB fuel to P. foliosa was assessed in an 8 month laboratory growth trial under growth conditions which simulated the island's environment. Single seedlings were planted into 1 L pots of soil spiked with SAB fuel at concentrations of 1000, 5 000, 10,000, 2000 and 40,000 mg/kg (plus control). Plants were harvested at 0, 2, 4 and 8 months and a range of plant productivity endpoints were measured (biomass production, plant morphology and photosynthetic efficiency). Poa foliosa was highly tolerant across all SAB fuel concentrations tested with respect to biomass, although higher concentrations of 20,000 and 40,000 mg SAB/kg soil caused slight reductions in leaf length, width and area. To assess the phytoremediation potential of P. foliosa (to 10 000 mg/kg), soil from the planted pots was compared with that from paired unplanted pots at each SAB fuel concentration. The effect of the plant on SAB fuel concentrations and the associated microbial communities found within the soil (total heterotrophs and hydrocarbon degraders) were compared between planted and unplanted treatments at the 0, 2, 4 and 8 month harvest periods. The presence of plants resulted in significantly less SAB fuel in soils at 2 months and a return to background concentration by 8 months. Microbes did not appear to be the sole driving force behind the observed hydrocarbon loss. This study provides evidence that phytoremediation using P. foliosa is a valuable remediation option for use at Macquarie Island, and may be applicable to the management of fuel spills in other cold climate regions.

Toxicity of diesel contaminated soils to the subantarctic earthworm Microscolex macquariensis.

Several fuel spills have occurred on subantarctic Macquarie Island (54°30' S 158°57' E) associated with storing fuel and generating power for the island's research station. The Australian Antarctic Division began full-scale, on-site remediation of these sites in 2009. To develop appropriate target concentrations for remediation, acute and chronic tests were developed with the endemic earthworm, Microscolex macquariensis, using avoidance, survival, and reproduction as endpoints. Uncontaminated low (3%), medium (11%), and high (38-48%) carbon content soils from Macquarie Island were used to examine the influence of soil carbon on toxicity. Soils were spiked with Special Antarctic Blend (SAB) diesel and used either immediately to simulate a fresh spill or after four weeks to simulate an aged spill. Earthworms were sensitive to fresh SAB, with significant avoidance at 181 mg/kg; acute 14-d survival median lethal concentration (LC50) of 103 mg/kg for low carbon soil; and juvenile production median effective concentration (EC50) of 317 mg/kg for high carbon soil. Earthworms were less sensitive to aged SAB than to fresh SAB in high carbon soil for juvenile production (EC50 of 1,753 and 317 mg/kg, respectively), but were more sensitive for adult survival (LC50 of 2,322 and 1,364 mg/kg, respectively). Using M. macquariensis as a surrogate for soil quality, approximately 50 to 200 mg SAB/kg soil would be a sufficiently protective remediation target.

Some like it wet - biological characteristics underpinning tolerance of extreme water stress events in Antarctic bryophytes.

Antarctic bryophyte communities presently tolerate physiological extremes in water availability, surviving both desiccation and submergence events. We investigated the relative ability of three Antarctic moss species to tolerate physiological extremes in water availability and identified physiological, morphological, and biochemical characteristics that assist species performance under such conditions. Tolerance of desiccation and submergence was investigated using chlorophyll fluorescence during a series of field- and laboratory-based water stress events. Turf water retention and degree of natural habitat submergence were determined from gametophyte shoot size and density, and δ13C signatures, respectively. Finally, compounds likely to assist membrane structure and function during desiccation events (fatty acids and soluble carbohydrates) were determined. The results of this study show significant differences in the performance of the three study species under contrasting water stress events. The results indicate that the three study species occupy distinctly different ecological niches with respect to water relations, and provide a physiological explanation for present species distributions. The poor tolerance of submergence seen in Ceratodon purpureus helps explain its restriction to drier sites and conversely, the low tolerance of desiccation and high tolerance of submergence displayed by the endemic Grimmia antarctici is consistent with its restriction to wet habitats. Finally the flexible response observed for Bryum pseudotriquetrum is consistent with its co-occurrence with the other two species across the bryophyte habitat spectrum. The likely effects of future climate change induced shifts in water availability are discussed with respect to future community dynamics.