Chrysophycean stomatocyst flora from south-central Ontario lakes

Chrysophycean stomatocyst morphotypes were identified and enumerated from the sediments of 55 Muskoka-Haliburton south-central Ontario lakes. Principal components analysis (PCA) and TWINSPAN cluster analysis showed that the distribution of cyst assemblages was most closely related to lake water pH. Cyst abundance varied with lake trophic status, decreasing in highly productive lakes. The diversity of the observed cyst assemblages was similar to that seen in other stomatocyst studies from temperate regions, with a total of 246 morphotypes noted. The Muskoka-Haliburton cyst flora contained a high proportion (22.8%) of as yet undescribed morphotypes and an abundance of cysts ornamented with circuli and small ridges. Fifty-six previously unidentified morphotypes were observed, 29 of which were studied in detail using scanning electron microscopy, and described using International Statospore Working Group guidelines. Six variants of common morphotypes, characterized by the presence of a siliceous envelope, are also described. Twelve new distinct morphotypes observed only using light microscopy are documented as unidentified forms.