The Madison lake zooplankton data are from a long-term study in seasonal dynamics of zooplankton, collected by the Richard Lathrop. The data were collected from a chain of lakes in Wisconsin (Mendota, Monona, Kegnonsa, and Waubesa) approximately bi-weekly from 1976 to 1994. They consist of samples of the zooplankton communities, taken from the deepest point of each lake via vertical tow. The data are provided by the Wisconsin Department of Natural Resources and their collection and processing are fully described in Lathrop (2000).
Source
Pedersen EJ, Miller DL, Simpson GL, Ross N. 2018. Hierarchical generalized additive models: an introduction with mgcv. PeerJ Preprints 6:e27320v1 doi:10.7287/peerj.preprints.27320v1 .
Details
Each record consists of counts of a given zooplankton taxon taken from a subsample from a single vertical net tow, which was then scaled to account for the relative volume of subsample versus the whole net sample and the area of the net tow and rounded to the nearest 1000 to give estimated population density per m2 for each taxon at each point in time in each sampled lake.