Salinity regulation of zooplanktonic abundance and vertical distribution in two saline meromictic lakes in south central British Columbia

Zooplankton species abundance and vertical distribution were followed in two south-central British Columbia saline meromictic lakes during the recent decade of their declining water levels. The lower salinity mixolimnion (0–7 m) of both lakes circulates partially most years down to their primary chemoclines marked by a 10–15 cm layer of purple sulfur bacteria (Amoebobacter purpureus) heavily grazed upon mainly by late copepodite stages and adults of Diaptomus connexus, possibly by some rotifers, but apparently not by cladocerans. Vertical distribution profiles, over an 8-year period, are presented mainly for the rotifer Brachionus plicatilis, two cladocerans Ceriodaphnia lacustris, and Daphnia pulicaria, as well as copepodite and adult D. connexus during normal periods of unimeromixis and a period of weak bimeromixis caused by shallow upper low salinity layers coming from drainage basin inputs.