ASSESSING THE PREVALENCE OF SUB-ICE PRODUCTIVITY IN IOWA LAKES

Historically, biological productivity has only rarely been measured in ice-covered lakes. However, a trend towards increased winter limnological studies in recent decades has revealed that primary producers are common in mid- and high-latitude lakes in winter. In some cases, diatom blooms have reached or surpassed equivalent summer biomass in a matter of days to weeks. Reports of diatoms, in particular the filamentous diatom, Aulacoseira islandica, indicate that diatoms are commonly found below the ice and are occasionally attached to the ice. This represents both a significant oversight in both annual primary productivity estimates from ice covered lakes and also an untapped potential proxy for lake ice in paleoclimate studies. To date, most analyses of the winter phytoplankton community have been conducted on water samples collected from below the ice in places such as Poland, the Canadian Arctic, Lake Baikal in Russia, and the US Great Lakes. Only rarely has lake ice itself been analyzed for phytoplankton and never from lakes in Iowa. In this project, we will use a Kovaks Mark V Ice Corer to collect lake ice cores from six lakes and marshes across Iowa. Then, thawed cores will be filtered to concentrate phytoplankton. The filters will be examined visually using light and scanning electron microscopy to identify diatoms and soft algal groups such as chrysophytes, nanoflagellates, ciliates, rotifers, and cyanobacteria. Visual analysis will be complemented by molecular analysis, consisting of extracting DNA from the filters, amplifying the 16s rRNA gene (or equivalent from eukaryotic phytoplankton) with taxon-specific polymerase chain reaction (PCR) primers. A further goal will be to quantify the relative abundances of different algal groups using quantitative PCR. We will present our results of phytoplankton communities present in these lakes during three time intervals throughout the winter.