Methods for Collection and Characterization of Samples From Icy Environments

Environments where the prevailing temperature is below 0°C include both solid (frozen) substrates, such as glacier ice and permafrost, and liquid environments such as cold springs and cryopegs. Some of these environments have low solute concentrations, whereas others have very high levels of salts and other solutes, with corresponding freezing point depression. Some have high microbial density, while others represent the limits of cell survival. All of these present specific challenges for identifying microorganisms by direct imaging or -omics techniques. In this chapter, we discuss specific cryoenvironments—sea ice, glacier ice, and permafrost—and begin with issues of sampling, from researcher safety to sample contamination and osmotic shock. We then present methods for imaging both live and fixed specimens. These include methods that may be performed in the field, such as light, fluorescence, and holographic microscopy, as well as methods that are performed upon sample return to the laboratory, such as confocal and electron microscopy. Microscope designs for field use are presented and discussed. Considerations of sample return are also presented in the context of downstream analysis.