I like to use glass slides because they can easily be mounted in slide holders and anchored at
various depths in the water. One can also observe ecologically-significant internal features of the
algae, such as parasites or endosymbionts, and see algae at the bottom of a stack or aggregation
of cells. Upon retrieval, slides bearing algae can be transported back to the lab in 1%
glutaraldehyde; this prevents decomposition or other changes. Back at the lab, slides are rinsed to
remove sand and sediment, and algae removed from one side by wiping with a paper towel. Then
the algae are dehydrated by submerging slides in increasing concentrations of ethanol for 15
minutes each, and stained with fast green dissolved in 95% ethanol. Rinsing with 100% ethanol
removes excess stain and completes the dehydration process. Slides should then be submersed
briefly in xylenes in a fume hood, whereupon they are removed and a drop of permount added to
the algae-coated surface. A large cover slip is added at an angle to avoid bubble formation, then
the slide is left to dry on a slide drier. Addition of a lead weight helps to flatten the preparation.
When the permount is hard, excess permount is removed and slides are ready to label, store, and
examine by LM.