Page 194 - Freshwater-Biology-and-Ecology-Handbook

CHAPTER 4 3.2 Finally, there are freeze-coring techniques. These involve macroinvertebrates (Figure 4.11). However, although useful
passing either liquid nitrogen (Figure 4.9) or pressurised
for research investigations, it is unlikely to be practical for
most monitoring purposes because of its cost and the
carbon dioxide gas (Figure 4.10) down a sealed standpipe
precautions required for health and safety.
such that a freezing front advances outwards into the river
gravel. The frozen sample attached to the outside of the
Information about the hyporheic invertebrate communities in
standpipe is then winched free from the surrounding gravels
and defrosted into compartments. This sophisticated
(61)
technique gives a large, vertically intact sample
and their relevance to wider environmental management in
Buss et al. (2009).
(62)
comprising undisturbed gravels and freshwater hyporheic Britain is included in the review by Robertson et al. (2008)

Figure 4.9
Liquid nitrogen freeze corer (Photo John Davy-Bowker)

194 | Freshwater Biology and Ecology Handbook
–