Temporal variations of water quality and the taxonomic structures of phytoplankton and zooplankton assemblages in mountain lakes, Mount Rainier National Park, Washington USA

A synoptic inventory of physical and chemical properties and plankton assemblages of 27 mountain lakes was conducted at Mount Rainier National Park in 1988. From 1990–1993, die opportunity was presented to resurvey six of these lakes to determine inter-annual change within die set of characteristics surveyed in 1988. If changes were evident, a second objective was to provide guidance to park management about the value of a long-term lake monitoring program.

Secchi-disk clarity, water temperature, and pH of the lakes in 1988 were within the range of values obtained between 1990 and 1993. Conductivities and concentration of nutrients in some lakes were not consistent in 1990–1993 with the values recorded in 1988. Although the dominant phytoplankton taxa in die lakes varied among years, die taxa in individual lakes were in consistent among years, with die exception of two lakes. Rotifer assemblages were consistent among years, but most of die lakes exhibited dramatic changes in some years, as did crustacean zooplankton assemblages. Suggestions were made about die need for a long-term monitoring program to evaluate die status and trends of park lakes.