Ad H L Huiskes

Continent-wide risk assessment for the establishment of nonindigenous species in Antarctica

Invasive alien species are among the primary causes of biodiversity change globally, with the risks thereof broadly understood for most regions of the world. They are similarly thought to be among the most significant conservation threats to Antarctica, especially as climate change proceeds in the region. However, no comprehensive, continent-wide evaluation of the risks to Antarctica posed by such species has been undertaken. Here we do so by sampling, identifying, and mapping the vascular plant propagules carried by all categories of visitors to Antarctica during the International Polar Years first season (2007–2008) and assessing propagule establishment likelihood based on their identity and origins and on spatial variation in Antarcticas climate. For an evaluation of the situation in 2100, we use modeled climates based on the Intergovernmental Panel on Climate Changes Special Report on Emissions Scenarios Scenario A1B [Nakićenović N, Swart R, eds (2000) Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (Cambridge University Press, Cambridge, UK)]. Visitors carrying seeds average 9.5 seeds per person, although as vectors, scientists carry greater propagule loads than tourists. Annual tourist numbers (∼33,054) are higher than those of scientists (∼7,085), thus tempering these differences in propagule load. Alien species establishment is currently most likely for the Western Antarctic Peninsula. Recent founder populations of several alien species in this area corroborate these findings. With climate change, risks will grow in the Antarctic Peninsula, Ross Sea, and East Antarctic coastal regions. Our evidence-based assessment demonstrates which parts of Antarctica are at growing risk from alien species that may become invasive and provides the means to mitigate this threat now and into the future as the continents climate changes.

The spatial structure of Antarctic biodiversity

Patterns of environmental spatial structure lie at the heart of the most fundamental and familiar patterns of diversity on Earth. Antarctica contains some of the strongest environmental gradients on the planet and therefore provides an ideal study ground to test hypotheses on the relevance of environmental variability for biodiversity. To answer the pivotal question, “How does spatial variation in physical and biological environmental properties across the Antarctic drive biodiversity?” we have synthesized current knowledge on environmental variability across terrestrial, freshwater, and marine Antarctic biomes and related this to the observed biotic patterns. The most important physical driver of Antarctic terrestrial communities is the availability of liquid water, itself driven by solar irradiance intensity. Patterns of biota distribution are further strongly influenced by the historical development of any given location or region, and by geographical barriers. In freshwater ecosystems, free water is also crucial, with further important influences from salinity, nutrient availability, oxygenation, and characteristics of ice cover and extent. In the marine biome there does not appear to be one major driving force, with the exception of the oceanographic boundary of the Polar Front. At smaller spatial scales, ice cover, ice scour, and salinity gradients are clearly important determinants of diversity at habitat and community level. Stochastic and extreme events remain an important driving force in all environments, particularly in the context of local extinction and colonization or recolonization, as well as that of temporal environmental variability. Our synthesis demonstrates that the Antarctic continent and surrounding oceans provide an ideal study ground to develop new biogeographical models, including life history and physiological traits, and to address questions regarding biological responses to environmental variability and change.

Trends in Antarctic Terrestrial and Limnetic Ecosystems, Antarctica as a global Indicator

1. TRENDS IN ANTARCTIC TERRESTRIAL AND LIMNETIC ECOSYSTEMS: ANTARCTICA AS A GLOBAL INDICATOR A.H.L. Huiskes, P. Convey, D.M. Bergstrom 2. THE PHYSICAL SETTING OF THE ANTARCTIC D. M. Bergstrom, D.A. Hodgson, P. Convey 3. COLONISATION PROCESSES K.A. Hughes, S. Ott, M. Boelter, P. Convey 4. BIOGEOGRAPHY S.L. Chown, P. Convey 5. BIOGEOGRAPHIC TRENDS IN ANTARCTIC LAKE COMMUNITIES J.A.E. Gibson, A. Wilmotte, A. Taton, B. van de Vijver, L. Beyens, H.J.G. Dartnall 6. LIFE HISTORY TRAITS P. Convey, S.L. Chown 7. PHYSIOLOGICAL TRAITS OF ORGANISMS IN A CHANGING ENVIRONMENT F. Hennion, A.H.L. Huiskes, S. Robinson, P. Convey 8. PLANT BIODIVERSITY IN AN EXTREME ENVIRONMENT: GENETIC STUDIES OF ORIGINS, DIVERSITY AND EVOLUTION IN THE ANTARCTIC M. L. Skotnicki, P. M. Selkirk 9. THE MOLECULAR ECOLOGY OF ANTARCTIC TERRESTRIAL AND LIMNETIC INVERTEBRATES AND MICROBES M.I. Stevens, I. D. Hogg 10. BIOLOGICAL INVASIONS P. Convey, Y. Frenot, N.J.M. Gremmen, D.M. Bergstrom 11. LANDSCAPE CONTROL OF HIGH LATITUDE LAKES IN A CHANGING CLIMATE A. Quesada, W. F. Vincent, E. Kaup, J.E. Hobbie, I. Laurion, R. Pienitz 12. ANTARCTIC CLIMATE CHANGE AND ITS INFLUENCES ON TERRESTRIAL ECOSYSTEMS P. Convey 13. ANTARCTIC LAKE SYSTEMS AND CLIMATE CHANGE W. B. Lyons, J. Laybourn-Parry, K.A. Welch, J. C. Priscu 14. SUBANTARCTIC TERRESTRIAL CONSERVATION AND MANAGEMENT J. Whinam, G. Copson, J-L. Chapuis 15. ANTARCTIC TERRESTRIAL AND LIMNETIC ECOSYSTEM CONSERVATION AND MANAGEMENT B.B. Hull, D. M.Bergstrom 16. THE ANTARCTIC: LOCAL SIGNALS, GLOBAL MESSAGES D.M. Bergstrom, A.H.L. Huiskes, P. Convey INDEX

The effect of environmental change on vascular plant and cryptogam communities from the Falkland Islands and the Maritime Antarctic

BackgroundAntarctic terrestrial vegetation is subject to one of the most extreme climates on Earth. Currently, parts of Antarctica are one of the fastest warming regions on the planet. During 3 growing seasons, we investigated the effect of experimental warming on the diversity and abundance of coastal plant communities in the Maritime Antarctic region (cryptogams only) and the Falkland Islands (vascular plants only). We compared communities from the Falkland Islands (51°S, mean annual temperature 7.9°C), with those of Signy Island (60°S, -2.1°C) and Anchorage Island (67°S, -2.6°C), and experimental temperature manipulations at each of the three islands using Open Top Chambers (OTCs).ResultsDespite the strong difference in plant growth form dominance between the Falkland Islands and the Maritime Antarctic, communities across the gradient did not differ in total diversity and species number.During the summer months, the experimental temperature increase at 5 cm height in the vegetation was similar between the locations (0.7°C across the study). In general, the response to this experimental warming was low. Total lichen cover showed a non-significant decreasing trend at Signy Island (p < 0.06). In the grass community at the Falkland Islands total vegetation cover decreased more in the OTCs than in adjacent control plots, and two species disappeared within the OTCs after only two years. This was most likely a combined consequence of a previous dry summer and the increase in temperature caused by the OTCs.ConclusionThese results suggest that small temperature increases may rapidly lead to decreased soil moisture, resulting in more stressful conditions for plants. The more open plant communities (grass and lichen) appeared more negatively affected by such changes than dense communities (dwarf shrub and moss).

Food choice of Antarctic soil arthropods clarified by stable isotope signatures

Antarctic soil ecosystems are amongst the most simplified on Earth and include only few soil arthropod species, generally believed to be opportunistic omnivorous feeders. Using stable isotopic analyses, we investigated the food choice of two common and widely distributed Antarctic soil arthropod species using natural abundances of 13C and 15N and an isotope labelling study. In the laboratory we fed the isotomid springtail Cryptopygus antarcticus six potential food sources (one algal species, two lichens and three mosses). Our results showed a clear preference for algae and lichens rather than mosses. These results were corroborated by field data comparing stable isotope signatures from the most dominant cryptogams and soil arthropods (C. antarcticus and the oribatid mite Alaskozetes antarcticus). Thus, for the first time in an Antarctic study, we present clear evidence that these soil arthropods show selectivity in their choice of food and have a preference for algae and lichens above mosses.

Global Movement and Homogenisation of Biota: Challenges to the Environmental Management of Antarctica?

Globally, many thousands of species have been redistributed beyond their natural dispersal ranges as a result of human activities. The introduction of non-native species can have severe consequences for indigenous biota with changes in both ecosystem structure and function. The Antarctic region has not escaped this threat. The introduction of invasive species, including vertebrates, invertebrates and plants, has altered substantially the ecosystems of many sub-Antarctic islands. In contrast, the Antarctic continent itself currently has few confirmed non-native species, but numbers are increasing. Possible future increases in human presence in the region, either through tourism, governmental operators or other commercial activities, will increase the risk of further non-native species introductions, while climate change may enhance the likelihood of establishment and range expansion. Ensuring effective biosecurity measures are implemented throughout the Antarctic region in a timely manner is an urgent challenge for the Antarctic Treaty nations and the Antarctic community as a whole.

The instrumental period

The instrumental period began with the first voyages to the Southern Ocean during the Seventeenth and Eighteenth centuries when scientists such as Edmund Halley made observations of quantities such as geomagnetism. During the early voyages information was collected on the meteorological conditions across the Southern Ocean, ocean conditions, the sea ice extent and the terrestrial and marine biology. The continent itself was discovered in 1820, although the collection of data was sporadic through the remainder of the Nineteenth Century and it was not possible to venture into the inhospitable interior of Antarctica. At the start of the Twentieth Century stations were first operated year-round and this really began the period of organised scientific investigation in the Antarctic. Most of these stations were not operated for long periods, which is a handicap when trying to investigate climate change over the last century.

Physiological Traits of Organisms in a Changing Environment

Antarctic ecosystems represent one extreme of the continuum of environmental conditions across the planet. To our eyes, the environment appears harsh but, even though terrestrial biological diversity is restricted, a wide range of life is present and, locally, thrives. In the Antarctic, unusually, environments exist in which physical characteristics are dominant and overcome biological considerations. These are at the extreme ends of the ranges of many characteristics (temperature, snow, ice and solar radiation) found across environments globally. However, the Antarctic is also a large continent, comparable in area to continental Europe, and further surrounded by the cold Southern Ocean, within which lie a ring of subantarctic islands. Together, these islands and the continent give a natural environmental gradient with which to study the biological impacts of climate variables. Antarctica is also a focus for studies of responses to regional and global change (eg Bergstrom and Chown 1999, Convey 2001, 2003, Robinson et al. 2003). Some of the fastest changing regions on earth (air temperatures along the western Antarctic Peninsula and Scotia Arc) are found here (King and Haranzogo 1998, Skvarca et al. 1998, Smith 2002, Quayle et al. 2002, 2003). Evaluations of change in this area are expected to provide a vital ‘early warning system’ for change consequences worldwide (Convey et al. 2003a, b). This chapter addresses an area central to our ability to understand and evaluate biotic responses to climate change predictions – that of organism physiology