Preservation techniques for benthic invertebrate samples

[Fraser R. Sime]

The Northern District of the Calif. Dept. of Water Resources has an
extensive benthic invertebrate sampling program in the north state. I am
heavily involved in the coordination of this program. For many years, we
have used formaldehyde as our main preservative for benthic samples
collected in the field. These are archived, sometimes for many months,
before being id'd and enumerated, etc..

Recent changes in safety regulations, disposal problems and concerns for
the environmental health of workers has forced us to look at other
alternatives for preserving our benthic samples. We do use ethanol for
short-term work, but have found it to be less than ideal over extended
time.

I know there have been many studies done in the past on preservation
techniqes re; biomass, dry weight, etc.. However, I would really appreciate
receiving any comments, references,or other materials anyone may have on
the comparison of various techniques, with emphasis on their ability to
preserve important, often minute taxonomic characteristics.
I am particularly interested in the potential for freezing as an
alternative. In the course of this investigation, I would like to conduct a
small study on the various methods, to compare effectiveness.

Any and all suggestions will be greatly appreciated.