Susie M. Grant

Challenges to the Future Conservation of the Antarctic

Changing environments and resource demands present challenges to Antarctic conservation. The Antarctic Treaty System, acknowledged as a successful model of cooperative regulation of one of the globes largest commons (1), is under substantial pressure. Concerns have been raised about increased stress on Antarctic systems from global environmental change and growing interest in the regions resources (2, 3). Although policy-makers may recognize these challenges, failure to respond in a timely way can have substantial negative consequences. We provide a horizon scan, a systematic means for identifying emerging trends and assisting decision-makers in identifying policies that address future challenges (2, 3). Previous analyses of conservation threats in the Antarctic have been restricted to matters for which available evidence is compelling (4). We reconsider these concerns because they might escalate quickly, judging from recent rapid environmental change in parts of Antarctica and increasing human interest in the region (see the map). We then focus on a more distant time horizon.

Spatial variation in seabed temperatures in the Southern Ocean: Implications for benthic ecology and biogeography

The Antarctic seabed has traditionally been regarded as cold and thermally stable, with little spatial or seasonal variation in temperature. Here we demonstrate marked spatial variations in continental shelf seabed temperature around Antarctica, with the western Antarctic Peninsula shelf significantly warmer than shelves around continental Antarctica as a result of flooding of the shelf by Circumpolar Deep Water from the Antarctic Circumpolar Current. The coldest shelf seabed temperatures are in the Weddell Sea, Ross Sea, and Prydz Bay as a consequence of seasonal convection associated with strong air-sea heat fluxes and sea-ice formation. These waters constitute the dense precursors of Antarctic Bottom Water, and can descend down the adjacent slope to inject cold water into the Southern Ocean deep sea. Deep sea seabed temperatures are coldest in the Weddell Sea and are progressively warmer to the east. There is a distinct latitudinal gradient in the difference between seabed temperatures on the shelf and in the deep sea, with the deep sea warmer by up to similar to 2 K at high latitudes and colder by similar to 2 K around sub-Antarctic islands. These differences have important consequences for benthic ecology and biogeography, understanding the evolutionary history of the Antarctic marine biota, and the impact of regional climate change.

Bayesian inference of a historical bottleneck in a heavily exploited marine mammal

Emerging Bayesian analytical approaches offer increasingly sophisticated means of reconstructing historical population dynamics from genetic data, but have been little applied to scenarios involving demographic bottlenecks. Consequently, we analysed a large mitochondrial and microsatellite dataset from the Antarctic fur seal Arctocephalus gazella, a species subjected to one of the most extreme examples of uncontrolled exploitation in history when it was reduced to the brink of extinction by the sealing industry during the late eighteenth and nineteenth centuries. Classical bottleneck tests, which exploit the fact that rare alleles are rapidly lost during demographic reduction, yielded ambiguous results. In contrast, a strong signal of recent demographic decline was detected using both Bayesian skyline plots and Approximate Bayesian Computation, the latter also allowing derivation of posterior parameter estimates that were remarkably consistent with historical observations. This was achieved using only contemporary samples, further emphasizing the potential of Bayesian approaches to address important problems in conservation and evolutionary biology.

Ecosystem services of the Southern Ocean: trade-offs in decision-making

Abstract Ecosystem services are the benefits that mankind obtains from natural ecosystems. Here we identify the key services provided by the Southern Ocean. These include provisioning of fishery products, nutrient cycling, climate regulation and the maintenance of biodiversity, with associated cultural and aesthetic benefits. Potential catch limits for Antarctic krill (Euphausia superba Dana) alone are equivalent to 11% of current global marine fisheries landings. We also examine the extent to which decision-making within the Antarctic Treaty System (ATS) considers trade-offs between ecosystem services, using the management of the Antarctic krill fishery as a case study. Management of this fishery considers a three-way trade-off between fisheries performance, the status of the krill stock and that of predator populations. However, there is a paucity of information on how well these components represent other ecosystem services that might be degraded as a result of fishing. There is also a lack of information on how beneficiaries value these ecosystem services. A formal ecosystem assessment would help to address these knowledge gaps. It could also help to harmonize decision-making across the ATS and promote global recognition of Southern Ocean ecosystem services by providing a standard inventory of the relevant ecosystem services and their value to beneficiaries.

The South Georgia and the South Sandwich Islands MPA: Protecting a biodiverse oceanic island chain situated in the flow of the Antarctic Circumpolar Current

South Georgia and the South Sandwich Islands (SGSSI) are surrounded by oceans that are species-rich, have high levels of biodiversity, important endemism and which also support large aggregations of charismatic upper trophic level species. Spatial management around these islands is complex, particularly in the context of commercial fisheries that exploit some of these living resources. Furthermore, management is especially complicated as local productivity relies fundamentally upon biological production transported from outside the area. The MPA uses practical management boundaries, allowing access for the current legal fisheries for Patagonian toothfish, mackerel icefish and Antarctic krill. Management measures developed as part of the planning process designated the whole SGSSI Maritime Zone as an IUCN Category VI reserve, within which a number of IUCN Category I reserves were identified. Multiple-use zones and temporal closures were also designated. A key multiple-use principle was to identify whether the ecological impacts of a particular fishery threatened either the pelagic or benthic domain.

Understanding the structure and functioning of polar pelagic ecosystems to predict the impacts of change

The determinants of the structure, functioning and resilience of pelagic ecosystems across most of the polar regions are not well known. Improved understanding is essential for assessing the value of biodiversity and predicting the effects of change (including in biodiversity) on these ecosystems and the services they maintain. Here we focus on the trophic interactions that underpin ecosystem structure, developing comparative analyses of how polar pelagic food webs vary in relation to the environment. We highlight that there is not a singular, generic Arctic or Antarctic pelagic food web, and, although there are characteristic pathways of energy flow dominated by a small number of species, alternative routes are important for maintaining energy transfer and resilience. These more complex routes cannot, however, provide the same rate of energy flow to highest trophic-level species. Food-web structure may be similar in different regions, but the individual species that dominate mid-trophic levels vary across polar regions. The characteristics (traits) of these species are also different and these differences influence a range of food-web processes. Low functional redundancy at key trophic levels makes these ecosystems particularly sensitive to change. To develop models for projecting responses of polar ecosystems to future environmental change, we propose a conceptual framework that links the life histories of pelagic species and the structure of polar food webs.

Valuing biodiversity and ecosystem services: a useful way to manage and conserve marine resources?

Valuation of biodiversity and ecosystem services (ES) is widely recognized as a useful, though often controversial, approach to conservation and management. However, its use in the marine environment, hence evidence of its efficacy, lags behind that in terrestrial ecosystems. This largely reflects key challenges to marine conservation and management such as the practical difficulties in studying the ocean, complex governance issues and the historically-rooted separation of biodiversity conservation and resource management. Given these challenges together with the accelerating loss of marine biodiversity (and threats to the ES that this biodiversity supports), we ask whether valuation efforts for marine ecosystems are appropriate and effective. We compare three contrasting systems: the tropical Pacific, Southern Ocean and UK coastal seas. In doing so, we reveal a diversity in valuation approaches with different rates of progress and success. We also find a tendency to focus on specific ES (often the harvested species) rather than biodiversity. In light of our findings, we present a new conceptual view of valuation that should ideally be considered in decision-making. Accounting for the critical relationships between biodiversity and ES, together with an understanding of ecosystem structure and functioning, will enable the wider implications of marine conservation and management decisions to be evaluated. We recommend embedding valuation within existing management structures, rather than treating it as an alternative or additional mechanism. However, we caution that its uptake and efficacy will be compromised without the ability to develop and share best practice across regions.

Could Ecosystem Assessment improve the protection of Antarctic ecosystems

John Muir’s century-old observation about the interconnectedness of nature ‘‘When we try to pick out anything by itself, we find it hitched to everything else in the Universe.’’ has important implications for managing human activities. The diverse benefits that people want and need from ecosystems are not always mutually compatible, and a decision to reap one benefit from nature can impact the availability or quality of others. The human activities that affect ecosystems are also diverse, and the responsibility for managing them is devolved to multiple organizations. These organizations are constrained by their individual remits and the spatial scales at which they operate. Yet the need to manage the wider consequences of decisions made within each organization implies the additional need to coordinate these decisions across organizations. Critically, this requires a standardized form of communication so that these organizations, and those whose interests they serve, can understand each others’ objectives and the values they place on particular benefits. The Antarctic Treaty System (ATS) has played a leading role in developing ecosystem management that acknowledges interconnectedness. The Protocol on Environmental Protection recognizes the intrinsic value of Antarctica beyond the financial value of its exploitable resources, while the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) charges fishery managers with maintaining ecosystem health and resilience. The ATS has some advantages compared to the complex mosaics of governance systems that exist in more populated parts of the world. Firstly, the Antarctic Treaty operates at the scale of a whole continent and the CCAMLR extends this to include a whole ocean. The ATS therefore encompass entire ecosystems. Secondly, there are relatively few activities that need to be managed including fishing, shipping and other transport, and the various activities associated with scientific presence. However, the ATS has a very diverse group of constituents who must reach consensus in order to make decisions. These constituents are national governments who, in turn, have diverse relationships with their own constituents, NGOs and industries. Furthermore, the set of signatory governments, and the government departments responsible, varies between the instruments of the ATS. Better understanding of the benefits that people obtain from the Antarctic, and improved coordination and communication, could allow the ATS to deal more effectively with future challenges such as the increasing pressure from climate change and a growing global population. This suggestion is not novel, and it is often presented in terms of an increasingly complex lexicon of potential tools: Ecosystem Services, Ecosystem Assessment, Ecosystem Services Valuation, State of the Environment Reporting, Ecosystem-Based Management and so on. But what does this really mean and are these tools of any actual use? Daniel Pauly summed up the concerns of many about this when observing that the term ‘‘ecosystem-based fisheries management is bandied about as if people know what it is.’’ The specific terminology is less important than two basic principles. Firstly, every benefit derived from nature impacts the availability of other benefits now and in the future. Secondly, a shared understanding of these benefits and their value is a vital step towards coordinated decision-making that appropriately recognizes the trade-offs between benefits while achieving the objectives of the ATS. Ecosystem Assessment is now standard practice for much of the world. However, the Antarctic has to date been under-represented in global and sub-global Ecosystem Assessments. Adopting an Ecosystem Assessment approach might therefore help to achieve one of the implicit objectives of the ATS institutions: to ensure that the value of the Antarctic is appropriately recognized at the global scale and its contribution adequately recognized in decision-making.

Benthic biodiversity in the South Orkney Islands Southern Shelf Marine Protected Area

ABSTRACT The South Orkney Islands Southern Shelf (SOISS) Marine Protected Area (MPA) was the first MPA to be designated entirely within the high seas and is managed under the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). To assist with research and monitoring of the MPA, an international expedition (‘SO-AntEco’) was undertaken in the austral summer of 2016 to contribute towards a better understanding of selected benthic habitats within the region. The benthic assemblages of the SOISS MPA region were found to be strongly correlated with the texture of the seafloor, where hard substrates hosted a greater number of individuals, taxa and biomass with a dominance of filter feeding vulnerable marine ecosystem (VME) taxa, and soft sediments were dominated mostly by deposit feeders. Substantial differences in the abundance of VME taxa were found between sampling gears (shallow underwater camera system and Agassiz trawl). We conclude that camera systems may be more suitable for VME assessments, but additional trawling is advisable for collecting all faunal types and for higher taxonomic resolution. The designation of VME locations based purely on large scale geomorphic classification is not advisable, due to small scale variation in substrate and other local physical influences.

Conservation and Management of Antarctic Silverfish Pleuragramma antarctica Populations and Habitats

One of the main conservation objectives for marine systems is to identify areas of ecological importance for biodiversity and essential species habitats which can be used as scientific reference areas for monitoring global change in the absence of major human impacts. The Antarctic silverfish, Pleuragramma antarctica is a keystone pelagic species, that has been assessed on the IUCN Red list of threatened species as a species with “Least Concern”. However, this species is unique as it is placed at one extreme of the notothenioid evolutionary/ecological axis that ranges from benthic to secondary pelagic life style. Its different life stages occur in unique environments such as the platelet ice for eggs, some of the inner shelf canyons for young larvae and at the shelf break with Antarctic krill swarms for juveniles and adults. The winter habitats are not known. In addition to the effects of climate change, a threat to this species is its bycatch in krill fisheries; however it has not been directly harvested since the 1980s. As a midtrophic species, P. antarctica is sensitive to environmental changes and should be monitored in protected scientific reference areas to obtain information on global change. For a midtrophic fish in a supposed wasp-waist ecosystem, strict regulation of bycatch and monitoring should be carried out in parallel with the monitoring of Antarctic krill and ice krill. The designation of protected areas is an important mechanism for preserving the essential habitats of P. antarctica in the Southern Ocean.