Lake Mendota Microbial Observatory Nutrient Data 2013-2018

Pelagic water samples were collected from Lake Mendota as part of routine microbial observatory sampling and analyzed for total and dissolved nitrogen and phosphorus, as well as inorganic nitrogen compounds. On a typical sampling trip, a 12m tube approximating the depth of the epilimnion layer was used to collected an integrated epilimnion water sample from the central, deepest location in the lake. Two separate water grabs, which we refer to here as biological replicates, were typically taken from different sides of the small motor boat and processed separately. Water samples were stored frozen at -20 C until nutrient analysis was performed using a segmented flow analyzer. These samples differ in several key ways from the other routine NTL-LTER nutrient measurements, namely in that they reflect a mixed water column sample rather than a discrete depth, that the dissolved fraction is collected using the microbial observatory's 0.22 um filter instead of 0.45 um, and that the nitrate/nitrite speciation is included by repeating the analysis with and without the standard reducing column. This nutrient data is collected from the same water samples used for microbial analysis, and the collection site is also co-located with the Lake Mendota weather buoy.