ROTIFER ABUNDANCE AND DISTRIBUTION IN THE NORTHERN CASCADE MOUNTAINS,WASHINGTON, USA

Few studies of rotifers have focused on North American western mountai n systems. In this study of Cascade mountain lakes in Washington state , both cluster analysis and detrended correspondence analysis (DCA) gr ouped dominant rotifer taxon. With both statistical techniques, each c luster of lakes was associated with characteristic physico-chemical va riables and dominant crustacean zooplankton. Small, microphagous, lori cate (hard-bodied) rotifers (Keratella or Kellicottia) dominated lakes : in 4 of the clusters; these lakes generally had low to moderate nutr ient concentrations and low cladoceran densities. Conochilus unicornis dominated lakes in a fifth cluster; these lakes had relatively high l evels of alkalinity and conductivity and also had high densities of cl adocerans and diaptomids. Collotheca mutabilis dominated a single lake which composed a sixth cluster; this was a large deep lake with low a lkalinity and conductivity. No significant relationships were evident between vertebrate predation and rotifer taxa.