Life in Ancient Ice. Edited by John D. Castello and Scott O. Rogers. Princeton, New Jersey: Princeton University Press, 2005. 336 pp. $69.50. ISBN 0691074755.
This book might well have been titled Life in Ancient Ice! because it reports the unexpected finding that all the ice realms, polar, glacial, and permafrost, are part of the biosphere. Since more than 80% of the earth's surface (including oceans) is permanently cold (<5°C), this represents an important expansion of our understanding of life on earth.
The book results from a symposium in 2001 organized by the editors and sponsored by the National Science Foundation. The 20 chapters in the book are, presumably, edited versions of papers presented at that symposium. Each chapter reports the methods and findings of an investigation into the presence and viability of viruses, prokaryotes, or eukaryotes (diatoms, yeast, fungi) from a particular icy environment. Protocols are described in sufficient detail to allow evaluation and emulation. The chapter on human viruses presents no empirical data (but does include the interesting idea that it may be possible to isolate the virus that caused the 1918 Spanish Flu from frozen victims of the pandemic). Six of the chapters are by Russian investigators, and these chapters have valuable references to work published in Russian journals. One chapter is a report of an attempt to design a new tool for in situ identification of living organisms using auto-fluorescence signals. The first and last chapters are by the editors, and they do a superb job of laying out the significance of these investigations and raising important procedural questions. Like all organizers, they lay large claims for the importance of this work, but they are also scrupulously honest about the need for replicative experiments before accepting initial results: “This is an immediate need that must be met by those of us working in this field of science. This is an important priority because unless it is accomplished we risk disbelief by the general scientific community” (p. 290). In the last chapter, the editors make recommendations on how to address that need.
This book might also have been titled Life in Ancient Ice? because considerable skepticism is to be expected about the extraordinary claims presented: Cyanobacterial doubling time of nine years (Lake Bonney, Antarctic Dry Valleys)? Viable bacteria, not in a frozen resting state, from three million-year-old permafrost (Kolyma tundra, Siberia)? Human viral pathogens released from ancient ice by global warming?
Foremost, there are procedural questions about the various decontamination protocols utilized. Each author presents data about the efficacy of their protocols, but that data needs scrutiny. And contamination is only one barrier to replication, as the excellent chapter on studies of the Lake Vostok ice core points out: “… the apparent inability to precisely replicate the findings of other laboratories …” has “… many possible reasons, none of which is mutually exclusive” (p. 257). Then there are basic questions in biology that need addressing. As the editors point out, the question of microbial metabolism in ice in situ must be resolved: “Are some microorganisms immured in ice for millennia able to maintain viability, and if so what are the mechanisms involved?” (p. 298). And so far, “No one has yet carried out a thorough study of the depth dependence of types of microbes, or of the fractions that are metabolizing, dormant, or dead” (p. 268). How stable is DNA over millennia?
There is also unfamiliar physics to ponder, including evidence for microscopic layers of liquid water around ice inclusions, and little-understood biological phenomena to consider, including symbiotic effects in biological aggregations. And then there is the meaning of the word “Life” in the title. As usually applied, the term refers to organisms carrying out normal life processes in a selected ecological niche. But several chapters make clear that birds or wind deposited the organisms found in the ice. Rather than “living” in ice, they are preserved there—which has different implications.
Finally, there are questions of scientific validity. What are we to make of a study on yeasts in ancient permafrost that isolates viable organisms from only two of seven samples, one 3 million years old (p. 120)? How can that be compared statistically to the finding that “… viable fungi have been recovered from all (glacial) ice subcores examined to date, including ice from both Antarctica and Greenland” (p. 162)? One chapter states in its introduction: “We hypothesize that the worldwide distribution of the yeasts may be influenced by ablation of glacial ice” (p. 181). But the finding of yeast in ice reported in this chapter does not of itself establish this hypothesis. In the immediately preceding sentence in the introduction these investigators point out: “These organisms are ubiquitous on leaf surfaces, they commonly occur in soils; fresh, estuarine, and marine waters; indoor and outdoor air; and clouds and fog.” So why would not the worldwide distribution be driven in the opposite direction, into the ice?
Taking a clue from the jacket cover photograph of a scientist climbing an ice cliff, perhaps this book could have been titled Life on Ancient Ice, in this case “Life” referring to the scientists who are attempting to unlock a new paradigm. It is this aspect of the book that is most fascinating to me, and most problematic. My academic position is in a teaching college where I challenge first-year biology majors to define “life.” This book would be a useful tool in complicating my students' assignment. But, because this book is a compilation of research papers, it would be difficult reading for an undergraduate. In fact, because the investigations use the full range of modern technology, including molecular, optical, and chemical methods, the book is difficult reading for anyone. And although the editors apparently made a sincere effort to produce a useful book, the diversity of tools utilized in these investigations means figures require extensive study, and minor editorial lapses make understanding difficult. A diagram (Fig. 7.1) of methane and nitrite content in a cross section of Late Cenozoic permafrost has the x-axis labeled “H(m),” which I think means “Horizon in meters,” but I cannot be sure. Fig. 4.1 is a “plot of the inverse of the square root of the generation time versus temperature” for Antarctic sea ice bacteria compared to “the predicted value for the entire biokinetic temperature range and determined from fitting the Ratkowsky (square root) growth rate model to the experimental data.” I puzzled over this diagram a long time; presumably investigators in the field know why this information is presented in this manner. (Curiously, in my copy, one line of the caption of this figure is printed in a smaller font than the rest of the book.)
Clearly, the book was not produced for a general audience. However, both a general audience and a professional audience would undoubtedly have enjoyed at least a summary of the questions and answers that must have followed each presentation at the symposium. And I suspect that discussions between formal sessions produced even more interesting ideas and speculations. None of this is reported. But these are minor quibbles that are elicited only because the topic is so fascinating and the book so important. Two compelling reasons why progress in this field matters are: (1) these studies are required to guide the search for extraterrestrial life because conditions on Mars and Europa are icy, and (2) “… in situ biological alteration of gases and ions may skew paleoclimatic interpretations of ice core records” (p. 236).
This book documents how far the study of life in ice has advanced in the decade since Abyzov's chapter on microorganisms in the Antarctic ice in the 1993 book Antarctic Microbiology (edited by E. Imre Friedmann, Wiley-Liss, 1993). As the new field of study of life in extreme conditions continues to expand, this book will be a constant reference. Someday it will be seen to have been seminal.
