The second revised edition of this manual aims at providing students and less experienced professional aquatic biologists with a key to identify some to the more commonly encountered aquatic freshwater algal genera of the United States. In response to reviewers comments, a brief section on diatoms, a section providing a number of possible of dispositions of the genera into a taxonomic hierarchy and a brief glossary of technical terms have been added in this revised edition. A number of nomenclatural changes is reflected as well.
Keys, representative illustrations and general ecological notes are provided for some 300 genera, excluding the diatoms (except for a brief section on them). The keys are based on features observable in freshly collected material. Although there are many excellent taxonomic treatments of freshwater algae, most require detailed familiarity with algal morphology to use the identification keys successfully. To the extent possible, formal terminology common to most taxonomic treatments has been avoided in the preparation of the keys included in this manual.
An extensive bibliography provides references to more detailed taxonomic treatments for those who wish to proceed to species identification. Our concepts of the algal Classes, Orders and Families, due to new information largely provided by electron microscopy and molecular biology, are presently in a state of change. The manual therefore does not include placement of the genera into supra-generic taxa, but the bibliography includes references providing such information.