The distribution of scaled chrysophytes along a pH gradient

Abstract

Frequency distributions versus pH and weighted mean pH values are reported for 25 and 40 species of scaled chrysophytes, from water bodies in Connecticut and the Adirondacks, respectively, and are compared with those assembled from a survey of the literature. For most species, similar distributions with respect to a pH gradient and weighted mean pH values were found. However, in Connecticut and Adirondack lakes, Mallomonas punctifera and Synura spinosa were more restricted to slightly acidic conditions and M. hamata was more abundant in conditions below a pH of 5.5. Groups of taxa with similar distributions with respect to pH were clearly defined. One group, consisting of Mallomonas acaroides var. muskokana, M. paludosa, M. pugio, M. canina, M. hindonii, S. sphagnicola, and S. echinulata, was dominant in waters with a pH < 5.5. Another group, including M. acaroides var. acaroides, M. corymbosa, M. tonsurata, M. psuedocoronata, and M. alpina, was primarily restricted to pH values above 6.5. A third group, including M. punctifera, M. akrokomas, M. crassisquama, M. galeiformis, M. caudata, Spiniferomonas bourrellyi, Sp. serrata, S. spinosa, and Chrysosphaerella longispina, had a significant decline in occurrence as the pH lowered to the 5–5.5 interval. The importance of scaled chrysophytes as a group in the biomonitoring of acid deposition is discussed.