Introduction

It is difficult to generalize about the ecological tolerances and distributions along environmental gradients of a group of organisms as large and diverse as the chrysophytes. Many excellent floristic papers lack quantitative ecological data, while others provide ecological data but lack critical microscopical detail. There are many more detailed studies pertaining to the scale-bearing forms than for non-scaled taxa. Thus, we know more about the forms with scales and have much to learn about the non-scaled species. In addition, many methodologies have been used by the different researchers to assemble their data. Despite the apparent obstacles, many generalizations have been made for the chrysophytes as a group as well as for specific and subspecific taxa.

Although there is much scattered information concerning the ecology of the chrysophytes (Kristiansen 1986; Siver & Hamer 1989; Siver 1991), especially for individual taxa, there are few comprehensive studies (Kristiansen 1986; Hartmann & Steinberg 1989; Wee & Gabel 1989). Sandgren (1988) provided an excellent review of the ecology of the group as a whole. Siver (1991) and Eloranta (1989b) summarized ecological tolerances for many taxa of Mallomonas and Dinobryon, respectively; however, similar works are lacking for most other common genera. Kristiansen (1986) and Smol (1986, 1990, this volume) provide excellent starting points for the use of the chrysophytes as biological indicators and in paleolimnological work, respectively.