Macquarie Harbour Research Articles

The non-flowering plants of a near-polar forest in East Gondwana, Tasmania, Australia, during the Early Eocene Climatic Optimum.

The Cenozoic Macquarie Harbour Formation (MHF) hosts one of the oldest and southernmost post-Cretaceous fossil plant assemblages in Australia. Coinciding with the Early Eocene Climatic Optimum (EECO) and predating the breakup of Australia from Antarctica, it offers critical data to study the diversity and extent of the Austral Polar Forest Biome, and the floristic divergence between Australasia and South America resulting from the Gondwana breakup. The micromorphology and macromorphology of new fossil plant compressions from the MHF were described and systematically analyzed. Previously published non-flowering plant records were reviewed and revised. Macrofossil abundance data were provided. The flora was compared with other early Paleogene assemblages from across the Southern Hemisphere. Twelve species of non-flowering plants were identified from the macrofossil record. Conifers include Araucariaceae (Araucaria macrophylla, A. readiae, A. timkarikensis sp. nov., and Araucarioides linearis), Podocarpaceae (Acmopyle glabra, Dacrycarpus mucronatus, Podocarpus paralungatikensis sp. nov., and Retrophyllum sp.), and Cupressaceae (Libocedrus microformis). Dacrycarpus linifolius was designated a junior synonym of D. mucronatus. Further components include a cycad (Bowenia johnsonii, Zamiaceae), a pteridosperm (Komlopteris cenozoicus, Umkomasiaceae), and a fern (Lygodium dinmorphyllum, Schizaeaceae). The fossil assemblage represents a mixed near-polar forest with a high diversity of conifers. The morphology and preservation of several species indicate adaptations to life at high latitudes. The coexistence of large- and small-leaved conifers implies complex, possibly open forest structures. Comparisons with contemporaneous assemblages from Argentina support a circumpolar biome during the EECO, reaching from southern Australia across Antarctica to southern South America.

The Paleocene - Eocene mangroves of southeastern Australia: spatial and temporal occurrences across four geological basins

The advent of the Paleocene-Eocene Thermal Maximum (PETM), a ∼ 200 kyr period of global warming ca. 56 Ma, caused sea-levels to rise, transgressing near-coastal environments in southeastern (SE) Australia over >55,000 km2. During the PETM, warming tropical climates may have extended south to ≥60°S paleolatitude. The PETM in SE Australia is corroborated primarily by stable carbon isotope chemostratigraphy and detailed palynology records in four geological basins. Previous work showed that, in addition to the globally recognised carbon isotope excursion, the PETM interval in coastal SE Australia can be identified using the dual occurrence of the tropical mangrove Nypa palm pollen (Spinizonocolpites prominatus) accompanied by thermophilic marine dinoflagellate cysts (mainly Apectodinium hyperacanthum). We here document a total of twenty-six Gippsland Basin wells that record this Nypa-A.hyperacanthum association in the earliest Eocene Kingfish Formation (Lower Malvacipollis diversus Zone). In the Bass Basin, eight wells record Nypa-A.hyperacanthum association within the Eastern View Group basal Koorkah Formation, or lower part of the Lower M. diversus Zone (earliest Eocene). In the Bass Basin a further thirteen wells with Nypa occurrences near the top of the Cormorant Formation are found, which might be associated with the longer-term warmth of the Early Eocene Climatic Optimum (EECO, ∼53–49 Ma). Government bores and petroleum wells across the Otway Basin record the Nypa-A. hyperacanthum PETM association within the Pember Mudstone Lower M. diversus Zone in twenty-one bores. Nine horizons with Nypa occurrences occur within the Burrungule Member (EECO) at the top of the Dilwyn Formation. In western Tasmania, Nypa occurs in the Sorell Basin and Macquarie Harbour area within the Lower M. diversus Zone. Together, these observations show the remarkable extent of the mangrove-coasts that were established across the mid-high paleolatitudes in SE Australia during the warmest intervals of the Cenozoic, the PETM and EECO.

Geochemical, mineralogical, and geophysical methods to establish the geoenvironmental characteristics of the King River delta, Queenstown, Western Tasmania

Throughout most of the 20th century, the Mount Lyell Mining and Railway company discharged tailings from the Mount Lyell mine into the Queen River. Tailings migrated downstream of the King River and deposited on riverbanks, the riverbeds and in the King River delta in Macquarie Harbour. This research combines mineralogical, geochemical, and geophysical techniques to characterise the King River delta and to constrain the volume of mine tailings on the King River delta. For this purpose, 25 trenches were excavated across the delta with 145 sediments samples and 20 water samples collected.Tailings in the delta are abundant in quartz (average 50 wt %), muscovite (average 16 wt %), chlorite (mean 11 wt %), pyrite (average 4 wt %), Fe-oxyhydroxides such as goethite (average 0.8 wt %), hematite (average 0.4 wt % and ferrihydrite (average 0.2 wt %), jarosite (average 0.8 wt %) and chalcopyrite (average 0.1 wt %). Sediments are dominated by Fe (average 77,468 ppm) and include high concentrations of Cu (average 1425 ppm) and trace elements such as Co (average 350 ppm). Chalcopyrite is the primary Cu mineral whereas pyrite is the main mineral host for Co. Geoenvironmental tests show tailings in the delta have acid-forming potential, as validated by pore water analyses with pH between 3.1 and 6.3. These conditions enable metal dissolution, with high contents of dissolved heavy metals, especially Fe, Cu, Co and Zn, detected in the pore waters.Apparent resistivity and shear wave profiles suggest the base of tailings is located at depths of 3–5 m. Low resistivity (i.e., <2 Ωm) indicate a saltwater intrusion into likely natural sediments below the tailings, whereas resistivity values between approximately 5 to 12 Ωm, below 15 m depth, suggests a transition to bedrock. The volume of tailings is estimated at ∼14.0 Mt and concentrations of Cu and Co imply that reprocessing of this material could be a feasible option with significant economic and environmental benefits.

Long-Term Impact of Historical Mining on Water Quality at Mount Lyell, Western Tasmania, Australia

During the twentieth century, inadequate management of mine waste at the Mount Lyell Copper Mine affected the ecology of the Queen–King Rivers and Macquarie Harbour, western Tasmania, Australia. Over the past two decades, the water quality of the river system has been measured semi-annually to investigate the long-term hydrochemical and environmental impacts caused by these historical mine practices and the waste associated with the Mount Lyell mine to the Queen–King Rivers. At sample sites below the confluence of Haulage Creek, the water pH was below pH 3.5, remaining below pH 5 across all sites to Macquarie Harbour. Local baseline rivers ranged from pH 4.0 to 8.4. Elemental concentrations of dissolved metals in water samples downstream of Haulage Creek were above the Australian and New Zealand Environment and Conservation Council (ANZECC) water quality guidelines. Copper, Fe, and Zn were not attenuated along the length of the river, with concentrations remaining elevated to the King River Delta. Mineralogical analyses demonstrated secondary minerals in sediments at Haulage Creek and pyrite concentrated at the King River Delta. Static tests on mining-affected sediments indicated risk of AMD and metal(loid) leaching in the river system. Since 2016, after flooding of the Prince Lyell mine, dissolved metal levels in the Queen–King Rivers have decreased; however, concentrations remain above guidelines. Almost three decades after legacy mine waste disposal ended, it still poses a long-term risk to the downstream environment, implying that without effective management of these historical mine wastes, the Queen–King Rivers will continue to be severely impacted.Graphical

Three decades of variability and warming of nearshore waters around Tasmania

The ocean region around Tasmania forms an interface between major ocean basins and represents a significant global ocean hotspot due to a rate of warming higher than the global average. Nearshore Tasmanian waters are of central importance for shallow-water ecosystems and a range of human activities, including recreation, aquaculture and fisheries which have become increasingly impacted by warming in recent decades. However, the fine-scale spatial and temporal variability of sea surface temperature (SST) in these waters is not well understood, limiting opportunities for effective local-scale mitigation and adaptation measures in the face of ongoing warming. We use a high-resolution (0.02 °x 0.02°, 1992–2020) satellite SST received at local stations (validated against in situ temperature) to explore variability over seasonal, interannual, decadal and multi-decadal timescales at spatial scales from the nearshore up to the entire study domain. The SST is used as a proxy for seasonal circulation by removal of the broad-scale radiative forcing (estimated by a region-wide latitudinal gradient of SST). The main circulation drivers of nearshore SST are the East Australian Current Extension (EACx) and Zeehan Current (ZC) acting on the east and west coasts with respective peaks in summer and winter. New results include the seasonality of three summer upwelling systems, the first direct evidence of EACx inflow into eastern Bass Strait, a time series of the endpoint of the ZC/EACx intersection, and a full year description of the ZC, from warm winter inflow transitioning into a summer cooler than ambient intrusion. We find that local SST variations are controlled by coastal geometry with intensified atmospheric forcing in enclosed waters. We have identified two modes of low frequency SST variability (including 1, 2 and 10-year periods) associated with the EACx (63% of the variance) and the ZC (12%). The EACx mode induces a rapid adjustment of the entire ocean region around Tasmania. Multi-decadal warming trends occur in all regions, modulated by coastal boundary flows, changes in upwelling mechanisms and local topography. Trends in the eastern shelf arise from intrusions of EACx waters, with local processes driving trends on the western shelf. Both east and west nearshore SST trends are around + 0.4°C decade−1 with the highest value of + 0.55°C decade−1 on the central west coast, possibly associated with outflow from Macquarie Harbour.

Why Sail to Chile? A Reconsideration of the Voyage of the Stolen Brig Frederick from Van Diemen’s Land to Valdivia in January 1834

In January 1834, ten convicts from the secondary penal station of Macquarie Harbour in Van Diemen’s Land seized the newly built brig Frederick and sailed it to Chile along an uncharted sea route. One of them, James Porter, knew Chile and the possibilities for starting new lives for all of them, away from the reach of British justice. But their plans began to founder when they ran out of food and had to land at Valdivia, instead of Valparaiso, only to find that the southern port was a trap just like Macquarie Harbour. Six of them eventually managed to escape but four were sent back to Hobart and long prison sentences. It is clear from examining the internal developments of the young Republic of Chile, the hope of the ten fugitives to live without danger of extradition would have been compromised anyway after Britain established diplomatic relations in 1834.

Network and machine learning analyses of estuarine microbial communities along a freshwater-marine mixed gradient

Microbial communities are important elements in the marine environment, contributing to nutrient cycling and biogeochemical processes. Estuaries comprise environments exhibiting characteristics from freshwater to marine, leading to distinct microbial communities across this environmental gradient. Here, we examine the spatial dynamics of microbial communities in Macquarie Harbour, an estuarine system on the West coast of Tasmania, Australia. Water was sampled along the estuary to explore the structure and composition of the microbial communities using 16S/18S rRNA gene amplicon sequencing. Multivariate analyses showed environmental variables and community compositions varying along a longitudinal (river to adjacent ocean) gradient at the surface. In the Harbour, differences in the microbial community were observed between surface (0–1 m) and intermediate depths (4.5–11 m depth). The results of differential abundance, network and Partial Least Square analyses suggest that Macquarie Harbour is a mixing zone, where the distributions of archaeal, bacterial and eukaryotic communities are influenced by oceanic and riverine inputs. These results provide critical insights into the Macquarie Harbour environment and the importance of understanding the role of microbial communities for similar systems elsewhere.

The influence of mesoscale climate drivers on hypoxia in a fjord-like deep coastal inlet and its potential implications regarding climate change: examining a decade of water quality data

Abstract. Deep coastal inlets are sites of high sedimentation and organic carbon deposition that account for 11 % of the world's organic carbon burial. Australasia's mid- to high-latitude regions have many such systems. It is important to understand the role of climate forcings in influencing hypoxia and organic matter cycling in these systems, but many such systems, especially in Australasia, remain poorly described. We analysed a decade of in situ water quality data from Macquarie Harbour, Tasmania, a deep coastal inlet with more than 180 000 t of organic carbon loading per annum. Monthly dissolved oxygen, total Kjeldahl nitrogen, dissolved organic carbon, and dissolved inorganic nitrogen concentrations were significantly affected by rainfall patterns. Increased rainfall was correlated to higher organic carbon and nitrogen loading, lower oxygen concentrations in deep basins, and greater oxygen concentrations in surface waters. Most notably, the Southern Annular Mode (SAM) significantly influenced oxygen distribution in the system. High river flow (associated with low SAM index values) impedes deep water renewal as the primary mechanism driving basin water hypoxia. Climate forecasting predicts increased winter rainfall and decreased summer rainfall, which may further exacerbate hypoxia in this system. Currently, Macquarie Harbour's basins experience frequent (up to 36 % of the time) and prolonged (up to 2 years) oxygen-poor conditions that may promote greenhouse gas (CH4, N2O) production altering the processing of organic matter entering the system. The increased winter rainfall predicted for the area will likely promote the increased spread and duration of hypoxia in the basins. Further understanding of these systems and how they respond to climate change will improve our estimates of future organic matter cycling (burial vs. export).

Life history traits and conservation actions for the Maugean skate (Zearaja maugeana), an endangered species occupying an anthropogenically impacted estuary

AbstractThe Maugean skate,Zearaja maugeana, is endemic to two isolated western Tasmanian (Australia) estuaries. The species' persistence in one of these estuaries (Bathurst Harbour) is uncertain, while the other estuary (Macquarie Harbour), potentially the remaining stronghold for the species, is an anthropogenically impacted system.Key life‐history parameters were studied to inform conservation actions for this species. Reproductive information was obtained using non‐lethal methodologies, circulating concentrations of sex steroids and ultrasonography. Growth and age parameters were estimated based on vertebral sections from a small sample of individuals.Females and males reached 870 and 760 mm total length, respectively. The species reached a maximum age of at least 10 years. Females and males attained 50% sexual maturity at 665 and 633 mm total length, respectively, probably maturing somewhere between four and six years of age. Females displayed an asynchronous, discontinuous reproductive cycle, being able to reproduce throughout the year, with a probable decline in reproductive activity during summer. No egg cases were observedin‐utero. Males produce sperm all year round, with a peak in testosterone production during spring–autumn.Conservation strategies for Z. maugeanawill need to focus on reducing anthropogenic impacts on the environmental health, the primary impacts being altered river flows associated with the production of hydroelectricity and increased nutrient load associated with salmonid aquaculture. There is a need to better understand how reproductive success, egg survival and recruitment are affected by these environmental challenges if the future well‐being of this species is to be secured.

Environmental influences shaping microbial communities in a low oxygen, highly stratified marine embayment

Microbial communities in the marine environment drive biogeochemical and nutrient cycles. However, microbial composition and therefore their role in ecosystems is likely to be strongly influenced by the environment. Here, we examined Macquarie Harbour, a highly stratified system on the west coast of Tasmania, Australia, to determine environmental factors driving microbial diversity. Water was sampled along spatial and environmental gradients to examine the structure and composition of the microbial communities, using high-throughput sequencing. The spatial distribution of the communities was found to be homogenous throughout the harbour’s surface, although it differed from riverine and oceanic samples. In contrast, the distribution and composition of microbial communities varied with depth-related changes in salinity and oxygen. Prokaryotes associated with riverine and brackish waters dominated the oxic surface waters. Phytoplankton metabolite-related bacteria and nitrite oxidizers were abundant at the halocline, whereas microbes linked to the consumption of organic matter, nitrogen and sulphur metabolization inhabited the hypoxic bottom waters and may be acting as major players in oxygen consumption throughout the harbour’s water column. This study provides valuable insights into microbial community ecology in a semi-enclosed and highly stratified environment and will improve our knowledge on how bacterial and archaeal distribution may be influenced by a changing environment.

Dissolved oxygen consumption in a fjord-like estuary, Macquarie Harbour, Tasmania

Microbial respiration of organic matter (OM) is a key driver of deoxygenation and hypoxia. In fjord-like estuaries with established aquaculture industries understanding drivers of oxygen demand, and the relative importance of different drivers, is crucial for improving fish farming management in those systems. We designed a study to examine patterns of pelagic oxygen demand (POD) in a fjord-like estuary on the west coast of Tasmania, Macquarie Harbour, and relate those observations to physical forcings and major OM sources. Monthly water column sampling and bottle incubation experiments were conducted from June to November 2017. Water was collected throughout the harbour including river and oceanic endmembers as well as transects leading away from fish farms. Water was incubated from 4 different depths spanning the surface water to the seabed. Regression modelling was used to examine the relationship between POD, riverine OM loading, proximity to fish farms and the major system endmembers, depth, harbour region, concentration of dissolved oxygen, and month. POD reached rates as high as 0.108 mg L−1 hour−1 with the greatest POD observed above the halocline and during high river flow/OM loading months. Regression modelling showed that important drivers of POD are spatially specific along vertical and longitudinal gradients. The importance of riverine OM loading waned with depth primarily due to mixing dynamics of dissolved organic carbon across the halocline. Proximity to fish farms was an important but localized explanatory variable for POD in the halocline and basin waters, but not a significant driver of POD compared to the Gordon River. Based on the POD rates observed in this study, hypoxia can be established in less than 9 days in the basin waters and is primarily driven by pelagic oxygen sinks (95%–98%), not sediment sinks. It is crucial that aquaculture management accounts for natural, and/or preexisting, variation in endmember OM loading and its effect on DO dynamics, in these systems.

Colonial penal stations and uneven legal reform after the Bigge Commission of Inquiry: the Port Macquarie absconders at Macquarie Harbour

Between 1822 and 1824, just under 100 convict absconders from the mainland penal settlement at Port Macquarie were relocated to Van Diemen’s Land under executive orders they be retained at the island’s new penal station at Macquarie Harbour. The subsequent fate of this cohort reveals an early moment of divergence in policy and practice between the two colonies. Two years later, when the New South Wales government tacitly acknowledged that many convicts had been illegally sentenced to penal stations by magistrates, the benefits of that disclosure were not extended to those mainland convicts who had been relocated south to Van Diemen’s land. Nor, importantly, were they extended to Vandemonian convicts whose sentences were equally suspect. This article considers how developments in New South Wales which served to sharpen thinking about the nature and role of colonial penal settlements passed virtually unnoticed in Van Diemen’s Land, allowing the local authorities to evade much larger questions about magisterial sentencing practices and the application of English criminal transportation law.

The endemic and endangered Maugean Skate (Zearaja maugeana) exhibits short-term severe hypoxia tolerance.

The endangered and range-restricted Maugean skate (Zearaja maugeana) is subjected to large environmental variability coupled with anthropogenic stressors in its endemic habitat, Macquarie Harbour, Tasmania. However, little is known about the basic biology/physiology of this skate, or how it may respond to future environmental challenges predicted from climate change and/or increases in human activities such as aquaculture. These skate live at a preferred depth of 5–15 m where the dissolved oxygen (DO) levels are moderate (~55% air saturation), but can be found in areas of the Harbour where DO can range from 100% saturation to anoxia. Given that the water at their preferred depth is already hypoxic, we sought to investigate their response to further decreases in DO that may arise from potential increases in anthropogenic stress. We measured oxygen consumption, haematological parameters, tissue–enzyme capacity and heat shock protein (HSP) levels in skate exposed to 55% dissolved O2 saturation (control) and 20% dissolved O2 saturation (hypoxic) for 48 h. We conclude that the Maugean skate appears to be an oxyconformer, with a decrease in the rate of O2 consumption with increasing hypoxia. Increases in blood glucose and lactate at 20% O2 suggest that skate are relying more on anaerobic metabolism to tolerate periods of very low oxygen. Despite these metabolic shifts, there was no difference in HSP70 levels between groups, suggesting this short-term exposure did not elicit a cellular stress response. The metabolic state of the skate suggests that low oxygen stress for longer periods of time (i.e. >48 h) may not be tolerable and could potentially result in loss of habitat or shifts in their preferred habitat. Given its endemic distribution and limited life-history information, it will be critical to understand its tolerance to environmental challenges to create robust conservation strategies.

Geophysical investigation of mine waste in the King River Delta, Macquarie Harbour, Tasmania

The majority of discharged mine waste from the Mt Lyell copper mine was deposited as deltaic sediments at the mouth of the King River, Macquarie Harbour, Tasmania. These waste materials are compose...

Drivers of deep water renewal in Macquarie Harbour, Tasmania

Abstract Macquarie Harbour is a fjord-like estuary located on the west coast of Tasmania and is home to a growing aquaculture industry. The harbour is oriented with the mouth on its north west end and two main tributaries located on its northeast and southeast ends. Both of the system's major tributaries have hydroelectric power schemes controlling catchment discharge into the harbour. The harbour has a history of low oxygen concentrations and the bottom water is often oxygen poor. No study to date has described the underlying mechanisms of deep water renewal and oxygenation in the system. Approximately 5 years of data from monthly dissolved oxygen, salinity, and temperature profiles, located throughout the harbour, and 3 continuous logger stations was analysed with water level and meteorological data. These data were used to describe the drivers of water level and deep water oxygen renewal in the system. This study provides a first order estimate of the net mass of dissolved oxygen entering via these marine water intrusion events. Data analysis indicates that deep water renewal appears to occur episodically, with only 2 significant events recorded over a 5 year period, though a number of smaller events were also recorded on a monthly basis. The largest events were observed during winter and late autumn and are associated with strong north westerly winds and a sudden drop in atmospheric pressure. The drop in pressure results in an increase in water level that allows marine water to enter the harbour via the mouth. The north westerly winds act to push surface water to the southern end of the harbour allowing more water to flood over the sill into the Sophia basin. Analysis of oxygen, temperature and salinity logger data indicates that larger renewal events create water column instabilities which can provide a potential threat to the salmon aquaculture industry situated in the harbour. The frequency of renewals also has implications on the standing oxygen concentrations in the harbour, with fewer events likely resulting in greater periods of hypoxia in the bottom and mid water column.

Dietary analysis reveals the vulnerability of the endangered Maugean skate (Zearaja maugeana) to benthic changes in Macquarie Harbour

Species occupying high trophic positions with a small population size, limited diet and restricted range are vulnerable to extinction. The endangered Maugean skate (Zearaja maugeana) in Macquarie Harbour is potentially threatened by changing benthic environmental conditions (declining dissolved oxygen concentrations and decreased macrofaunal diversity). To inform investigations on potential indirect impacts of benthic environmental changes on the Maugean skate and its prey, non-lethal techniques were used to identify dietary composition and trophic position of the species. The Maugean skate occupies a high trophic position (3.70) in the food web, with both stable-isotope (median 86% contribution to isotopic signatures, credible interval (CI)=44–100%) and stomach-content analysis showing crustaceans, particularly brachyuran crabs (58.5% index of relative importance), as the dominant prey type. Aquaculture feed from salmonid fish farms operating in the harbour was not found to be important in skate diet. This study showed that the Maugean skate consumes a small number of benthic prey species, highlighting its vulnerability to changing environmental conditions in the harbour.

Population genetics of the endangered Maugean skate (Zearaja maugeana) in Macquarie Harbour, Tasmania

The Maugean skate (Zearaja maugeana) has only been recorded in two remote and isolated estuaries on the west coast of Tasmania, Australia. While the population status in one of these estuaries (Bathurst Harbour) is uncertain, it is likely that Macquarie Harbour now represents the sole remaining habitat for this species. Environmental conditions, in particular dissolved oxygen levels and benthic biodiversity, in Macquarie Harbour have deteriorated in recent years, impacted by increased nutrient inputs from an expanding salmonid aquaculture industry. These environmental changes are believed to pose a threat to the persistence of the Maugean skate. In assessing the risks for this rare and range-restricted species, it is vital to consider genetic information when developing management strategies. Both mitochondrial and microsatellite markers showed that the species has low genetic diversity; with no detectable genetic diversity in over 3000 base pairs surveyed from the mitochondrial genome, low average microsatellite heterozygosity (0.35 ± 0.11), a low average number of alleles per locus (2.1 ± 0.4) across eight microsatellite loci and no overall population structure within the microsatellite loci (Fst = − 0.002, p = 0.718 ± 0.012). There was also evidence of a recent bottleneck or founder event, which may explain the low observed genetic diversity. While the species may have existed with low genetic diversity for many generations, the results of this study represent a flag for conservation concern for the Maugean skate. Given that Macquarie Harbour may be its last remaining habitat, any threats to the species resulting in local extinction could equate to global loss of this unique skate species.

Salmon, sensors, and translation: The agency of Big Data in environmental governance

This paper explores the emerging role of Big Data in environmental governance. We focus on the case of salmon aquaculture management from 2011 to 2017 in Macquarie Harbour, Australia, and compare this with the foundational case that inspired the development of the concept of ‘translation’ in actor-network theory, that of scallop domestication in St Brieuc Bay, France, in the 1970s. A key difference is the salience of environmental data in the contemporary case. Recent dramatic events in the environmental governance of Macquarie Harbour have been driven by increasing spatial and temporal resolution of environmental monitoring, including real-time data collection from sensors mounted on the fish themselves. The resulting environmental data now takes centre stage in increasingly heated debates over how the harbour should be managed: overturning long-held assumptions about environmental interactions, inducing changes in regulatory practices and institutions, fracturing historical alliances and shaping the on-going legitimacy of the industry. Environmental Big Data is now a key actor within the networks that constitute and enact environmental governance. Given its new and unpredictable agency, control over access to data is likely to become critical in future power struggles over environmental resources and their governance.

The reverse precautionary principle: science, the environment and the salmon aquaculture industry in Macquarie Harbour, Tasmania, Australia

Science is frequently used by opposing sides in environment–development debates. Scientific input from an environmental perspective can be inhibited if those in favour of development control research funding. We test whether such a situation can result in outcomes desired by neither of the protagonists, and seek to identify how negative outcomes can be avoided, using the example of fish farming in Macquarie Harbour, Tasmania. A marked decline in dissolved oxygen (DO) at 19–21m depth in Macquarie Harbour, Tasmania, occurred between 2009 and 2011. DO continues to be low. DO change was associated with changes in the benthic biota, with effects extending from fish farms into the Tasmanian Wilderness World Heritage Area and threatening a Tasmanian endemic fish. The reverse precautionary response of industry and government was to undertake further research because the causes of the changes were not fully understood. We present simple graphs and analyses that suggest that the only substantial predictor of benthic DO reduction is fish production from marine farms, with variability in discharge, catchment rainfall, wind speed, sea surface temperatures and sea level pressure having no effect. Adaptive management of fish farming in Macquarie Harbour seems to require an estuary-wide approach rather than the current attention to the effects of single pens. The broader implications of the case study are that the science related to the environmental impacts of an industry needs to be undertaken by scientists in secure positions funded independently of industry and government.

Application of environmental DNA to detect an endangered marine skate species in the wild.

Environmental DNA (eDNA) techniques have only recently been applied in the marine environment to detect the presence of marine species. Species-specific primers and probes were designed to detect the eDNA of the endangered Maugean skate (Zearaja maugeana) from as little as 1 L of water collected at depth (10–15 m) in Macquarie Harbour (MH), Tasmania. The identity of the eDNA was confirmed as Z. maugeana by sequencing the qPCR products and aligning these with the target sequence for a 100% match. This result has validated the use of this eDNA technique for detecting a rare species, Z. maugeana, in the wild. Being able to investigate the presence, and possibly the abundance, of Z. maugeana in MH and Bathurst harbour (BH), would be addressing a conservation imperative for the endangered Z. maugeana. For future application of this technique in the field, the rate of decay was determined for Z. maugeana eDNA under ambient dissolved oxygen (DO) levels (55% saturation) and lower DO (20% saturation) levels, revealing that the eDNA can be detected for 4 and 16 hours respectively, after which eDNA concentration drops below the detection threshold of the assay. With the rate of decay being influenced by starting eDNA concentrations, it is recommended that samples be filtered as soon as possible after collection to minimize further loss of eDNA prior to and during sample processing.