Antarctic environmental change and biological responses

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Science Advances  27 Nov 2019:
Vol. 5, no. 11, eaaz0888
DOI: 10.1126/sciadv.aaz0888


  • Fig. 1 Map of Antarctica, showing locations mentioned in the text, and the Southern Ocean, showing ice-covered and ice-free areas shallower than 200 m, 200- to 1000-m depth, and deeper than 1000 m [modified from (21); image provided by P. Fretwell, British Antarctic Survey].

  • Fig. 2 Satellite images of the area surrounding the original Larsen B ice shelf.

    (A) Ice-covered area in 2000 before its collapse, and (B) in March 2004/5, showing chlorophyll (chl) concentrations from the dense phytoplankton bloom that was present in the newly exposed area (white areas were sea ice covered and gave no signal) [from (266)]. SeaWIFS (Sea-Viewing Wide Field-of-View Sensor) is a satellite borne sensor for measuring Chlorophyll in surface ocean waters; MODIS (Moderate Resolution Imaging Spectroradiometer)is an instrument monitoring the Earth’s atmosphere, ocean, and land surface with a set of visible, NIR, MIR, and thermal channels run by NASA.

  • Fig. 3 Illustration of the major threats to Antarctic biodiversity in the coming century.

    Clockwise from top left: Warming reduces ice cover both in the sea and on land, which, combined with increased human activity, makes the establishment of non-native species much more likely (images are the invasive midge E. murphyi, and the noted but not established marine seaweed U. intestinalis and crab H. araneus); the reduction in sea ice and increased variability affects species dependent on sea ice for habitat, notably krill that are a key ecosystem resource for many penguins, seals, and whales [images are humpback whale, krill, copepod (Calanus propinquus), and emperor penguin chicks]; low-mobility (and many with limited dispersal) marine species affected by multiple factors, including warming, acidification, freshening, increased sedimentation, etc. [images are brachiopods (Liothyrella uva), nemertean worms (Parborlasia corrugatus), anemones (Isotaelia antarctica), and giant isopod (Glyptonotus antarcticus)]; large increases in human activity in terms of more infrastructure, increased tourism, and national field campaigns all directly affect environments on land and sea (images are Dash 7 aircraft, McMurdo station, tourist vessel, Rothera station building, Sir David Attenborough ship, and vehicle tracks on King George Island); reductions in coastal ice make new habitat for new biological productivity in the water column and on the seabed, acting to provide new food for ecosystems and against warming by sequestering carbon; warming, ice melt, and increased precipitation on the continent not only provide new ice-free areas and stimulate increases in populations of native species but also increase likelihood of establishment of non-natives and reduce the isolation and, hence, persistence of native species. Colors on continent show warming and cooling trends over the past 50 years: Red intensity shows warming up to 2°C, and blue shows cooling of up to −1.5°C [following (195)].


  • Table 1 Summary of key features, vulnerabilities, and recommendations for Antarctic marine and terrestrial environments pertinent to consideration of the impacts of environmental change.

    Most isolated marine environment on Earth, no shelf links to other continents, no water masses flowing to/from other continents through the barrier of the circumpolar current.
    There is no year-round ice-free intertidal or shallow subtidal habitat.
    Much higher native biodiversity than expected by area, several groups more diverse than the average for the planet. Crushing predators (e.g., brachyuran crabs, lobsters, and most sharks) very rare to absent. High overall endemism.
    Gigantism well developed, linked to low metabolic rates and high levels of dissolved oxygen dissolved at low temperatures.
    Some of the most stable temperatures globally, but other factors among the most variable, e.g., light regime, phytoplankton productivity, and ice cover.
    Sea temperatures west of the Antarctic Peninsula among the fastest warming globally in the 20th century. Warming predicted to become more widespread around the continent.
    Biological responses to change vary with the rate of the change, from instantaneous biochemical buffering to migration and evolution; most important immediate responses are acclimatization of physiology through plasticity or genetic adaptation.
    Biological assemblages developing in areas exposed by glacier and ice shelf retreat (blue carbon) may be the second largest biological response on Earth mitigating warming by sequestering carbon.
    Many species have poor abilities to cope with warming compared with lower latitude species.
    Ocean acidification has variable impacts, with some groups such as pteropods negatively affected while others appear resilient to predicted end century acidification.
    Increased freshwater runoff and lowered salinities, as well as increased sediment input, are expected to have large local impacts especially in fiordic and other coastal systems.
    High oxygen in cold waters has led to evolution of strong antioxidant defenses. The challenge could lessen with warming. However, warming will increase metabolic costs and reduce available oxygen, likely reducing capacity to raise metabolic rates to do work.
    In situ experimental manipulations exposing biological communities to predicted end century temperatures for up to 2 years produced unexpected results with greater than expected increases in growth with 1°C of warming and several species showing signs of inability to cope at 2°C of warming.
    The Southern Ocean was the first to use an ecosystem-based approach to fisheries management, with more sustainable long-term management of living resources than elsewhere.
    Antarctica contains a repository of global pollution records, increasingly including plastics. Pollution is a concern in marine systems, especially in relation to station sewage outputs. Natural levels of some trace metals from rock erosion may be very high in both marine and terrestrial systems.
    Viruses from lower latitude sources can infect birds and mammals, and humans are the likely vector.
    Non-native species invasions in the Antarctic marine environment are currently rare to absent, but warming and loss of ice may allow establishment before the end of the century.
    Ship traffic has increased 10-fold since the 1960s, with strong regional hot spots where establishment is more likely. Further strong increase expected, with multiple new operator and cruise ships being built.
    Continent strongly isolated from lower latitude land by geographical distance, oceanic, and atmospheric circulation.
    Ice-free ground constitutes tiny proportion of continental area (<0.5%), mostly as “islands” in varying degrees of isolation.
    Low overall diversity, restricted to microarthropods, microinvertebrates, mostly lower plants, lichens, and microbes.
    Generally highly endemic biota, with multimillion year or longer presence. Very strong regionalization (ACBRs).
    Many unknowns remain in terms of lack of survey of many areas or of specific taxonomic groups, meaning “discovery science” is still required. Lack of repeat survey or monitoring restricts ability to detect biodiversity changes.
    Multiple and highly variable environmental stresses, particularly temperature, desiccation, light/radiation climate, and low nutrients. Liquid water availability is primary driver of biodiversity on the continent. Marine vertebrate nutrient also inputs an important diversity driver in coastal regions and subjects to predicted climate-related changes in vertebrate distribution.
    Stress tolerance adaptations well developed, in typically “stress-selected” life histories but take up many resources and quid pro quo is that competitive abilities are low. Abiotic variables typically structure biodiversity.
    Antarctic Peninsula air temperatures among the fastest warming globally in the 20th century, predicted to resume; continent also predicted to face similar warming in next century. Increased precipitation and melt also around the fringes of the continent and Peninsula.
    At “business-as-usual” warming rates, ice-free area predicted to increase by 25% in next century across entire continent and 300% in Peninsula. Increased area for native and non-native species colonization, and distribution spread, but threat of genetic homogenization.
    Already well-developed physiological tolerances mean native biota generally not likely to be stressed beyond limits by predicted century-scale changes, although this may occur in specific instances especially considering interactions between multiple variables.
    Experimental field manipulations generally support these predictions, although representativeness of methodologies has been subject to scrutiny.
    Continental and peninsula ecosystems to date have suffered relatively little direct human impact, unlike those of sub-Antarctic islands. No extractive or exploitative industries on land. Human presence today limited to national scientific operators and tourism industry. However, multiple direct pressures now increasing, in particular competition for land/land use change, pollution, and inadvertent introduction of non-native species.
    Rates of anthropogenic introduction already two orders of magnitude or more greater than natural colonization rates.
    Major, possibly now irreversible, effects of non-native species on several sub-Antarctic islands. Although historical vertebrate introductions have had marked visible effects, contemporary concern relates to invertebrates and plants. Possible step changes or tipping points in ecosystem function in terms of, e.g., predation, pollination, and nutrient turnover. Virtually no knowledge of microbial introductions.
    Negative impacts of non-native species on Antarctic ecosystems are likely to be greater on a “next-century” time scale than those of other aspects of environmental change.
    Major station and infrastructure (re)construction programs from multiple national operators, particularly in Victoria Land and Antarctic Peninsula regions.
    Achieve a comprehensive genetic archive of all Antarctic species, including microbial, so at least their genetic material may be used for societal benefit in future years. Given the poor resistance capacities of Southern Ocean biota in particular, ex situ conservation measures should be encouraged through gene banks that screen and store the DNA sequences of as many species as can be obtained.
    Environmental change, genetic homogenization, and direct human impacts (particularly non-native species introductions) present urgent conservation challenges to the Antarctic Treaty Parties requiring timely action and delivery of an effective conservation strategy for both land and ocean.
    Baseline survey and research are still required to properly document and describe Antarctic biodiversity, with the widespread establishment of ongoing monitoring of natural ecosystems backed by appropriate taxonomic expertise to detect and then investigate changes. There is also an urgent need for higher levels of monitoring and research to identify species and ecosystems that are vulnerable to change, to both predict future outcomes and also to ensure that the best conservation practices are used.
    There remains a need to link large-scale studies of changes in physical climate with monitoring and identification of change trends (if any) at biologically relevant scales, for instance, as proposed by the SCAR ANTOS (Antarctic Terrestrial and Nearshore Observing System;
    There is a prescient need for commitment to long-term and multidisciplinary evaluations of environmental change and the responses of the biota in terms of their distributions, physiologies, population genetic modification, and community and ecosystem structure and function.
    Increased emphasis is required in experimental studies to the inclusion of multiple interacting stressors, realistic timescales of exposure and rates of change, and multiple ecosystem elements, in studies attempting to clarify or predict biological responses.
    Avoiding and mitigating the impacts of direct human activities requires organizational and personal commitment to active education and adherence to existing procedures and advice; this inherently requires appropriate investment in monitoring (increasingly through remote sensing) of both impacts and recovery.
    Greater recognition is required of the combination of climate similarity and human operational connectivity between the different biogeographic regions within Antarctica, which further compounds the risk of human-assisted introduction of regionally non-native species.
    Of the currently known non-native species established in Antarctica (including the sub-Antarctic) since the mid-20th century, virtually all can most plausibly be linked with national operations. Education and awareness are therefore required of the major sources of risk and their mitigation measures, with commitment to investment in monitoring and effective rapid response protocols in place in the event of future transfer events.
    Greater awareness of and adherence to appropriate and stringent biosecurity procedures are required at both operator and personal individual levels; compared with other continents, the numbers of gateway departure and arrival ports, vessels and aeroplanes, quantities of cargo, and individuals involved make this tractable in terms of applying these measures effectively.
    Develop means of assessing how successful conservation measures are currently in the Antarctic marine environment, including programs to collect the required data.

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