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Polar Lakes and Rivers - Limnology of Arctic and Antarctic Aquatic Ecosystems Edited by Warwick F. Vincent & Johanna Laybourn-Parry Oxford University Press, 2008. ISBN 978-0-19-921388-7, 327 pp, £70 hardback, £37.50 paperback.

There have been few comparative works on the aquatic systems of the Arctic and Antarctic, so this new volume, edited by Warwick Vincent and Johanna Laybourn-Parry, is a very welcome addition to the scientific literature. It is especially timely given the rapid changes occurring in these high latitude environments and climate change is, indeed, among the important issues addressed. The range of subjects covered here is unusually broad and extends from physical limnology to microbial biodiversity and biogeography and includes the most recent studies of subglacial waters, human impacts on loctic and limnic ecosystems and fish in high latitude Arctic lakes. A number of the seventeen chapters in this book call attention to the similarities between the two polar environments, among which, of course, are the lower temperatures and the reduced annual input and extreme seasonality of solar energy. Both regions tend to be characterized by aquatic food webs which are relatively simple and which often feature benthic microbial mats incorporating cyanobacteria. However, there are significant differences, too, and these are highlighted in several chapters. As extensions of northern landmasses, Arctic systems tend to be more species-rich than the more isolated inland waters of the Antarctic. Also, Arctic catchments provide a far greater quantity of allochthonous organic carbon to lakes than do those of Antarctic, whose waters are remarkable for their high percentage of in-lake, autochthonous, organic carbon production. The great rivers of the Arctic have no analogues in Antarctica and the absence of fish in Antarctic lakes and the thicker, perennial, ice covers also distinguish these waterbodies. Although no single chapter is devoted to it, the subject of climate change appears often. Since past climates are revealed in lacustrine sediments, these deposits catalogue changes in both water columns and catchments. Detailed studies on Baffin Island (Arctic) and in the Larsemann Hills (Antarctic) offer a record of climate over the Holocene and earlier interglacials. These sedimentary archives afford glimpses into environmental conditions during the distant past. More recent and often dramatic changes in high latitude conditions are also discussed. Temperature increases of 0.558C/decade on the Antarctic Peninsula have led to massive ice shelf collapse, amounting to some 14 000 sq km of ice loss in recent years. In the High Arctic, where temperature increases of 0.78C/decade are estimated, a loss of Arctic sea ice and a decrease in albedo are among the global consequences of warming. Several authors speculate on how these rapidly changing conditions might impact regional lakes and rivers. Anticipated are higher stream flows, an augmentation in nutrient flux, and consequent shifts toward more productive waters and lower light penetration. Increased fluxes of ultraviolet radiation, on the order of 22% since the 1970s in the Arctic and much higher increases in the Antarctic (180–480% since the early 80s), are likely to have profound effects on aquatic communities at both poles. Low terrestrial DOC and chromophoric DOM in Antarctic lakes make these waters even more vulnerable to enhanced UV levels. Extreme and exotic environments also receive significant attention. A chapter is devoted to Lake Vostok, a vast waterbody the size of Lake Ontario lying 4 km beneath the East Antarctic Ice Sheet and isolated from surface inputs for some 420 000 years. Although no samples have been collected directly from Vostok, deep ice accreted from the lake show an array of microorganisms which portend a fascinating biogeochemistry which may soon be revealed. Possibly unfamiliar systems situated on the ice or in it are reviewed and these diverse environments include the widely-distributed cryoconite holes, common to both polar regions, which form when wind-blown soils melt into glacial surfaces to create small ponds of varying chemistry and microbiology. In the McMurdo Dry Valleys, there are highly saline waters trapped beneath the 19 m ice cover of Lake Vida. Supraand subglacial waters characterize both Arctic and Antarctic environments. The McMurdo Ice Shelf, Antarctica, and the Ward Hunt and Markham ice shelves of the High Arctic have been the subjects of recent investigations. Food-web relationships in Arctic lakes from lower latitudes to the High Arctic are examined at chapter length, as are both regional and global human impacts on these, notably from contaminant inputs, increased ultraviolet light levels and climate change. Comparisons are drawn between the simpler food webs of the Antarctic and the more diverse and wider-ranging communities of the north. Polar Lakes and Rivers contains many useful maps, sixteen colour plates including a striking one depicting subglacial lakes and rivers of the Antarctic crossreferencing among a number of articles and very up-to-date bibliographies. A glossary of possibly unfamiliar terms and a reasonably inclusive index are also features of this welldesigned volume. In reviewing this work, I was reminded of a quote by the geophysicist Emil Weichert who said that “The universe is