Mean June–August crustacean dissimilarity fell in records from seven Wisconsin lakes, 2002–2013 to 2014–2025

We tested whether crustacean composition differed less between June and August in seven northern Wisconsin lakes. We used open NTL-LTER density data and broad taxon groups in 159 complete summers from 2002–2025. Each lake had equal weight. Mean Bray–Curtis dissimilarity fell from 0.4092 in 2002–2013 to 0.3464 in 2014–2025. The change was −0.0628, or 15.3% of the earlier mean. Its nominal 95% interval from 19,999 shared three-year block draws was −0.1100 to −0.0155. All planned sampling and taxon checks retained negative intervals. Crystal Bog had the largest decrease. Omitting that lake left an uncertain network change. A stricter date-window check retained only 64 summers and was also uncertain. An exploratory squared-Hellinger account placed about 70% of its decrease in deviations among years. The change in the period-mean seasonal vector remained uncertain. Thus, smaller annual distances did not establish weaker mean seasonal succession. The results apply to recorded relative composition at these fixed sites. They do not identify a cause or separate ecological variation from measurement variation. The package preserves source data, provenance, code, all results and draws, four figures, and independent arithmetic checks.

zooplankton · seasonal change · community composition · long-term monitoring · Wisconsin lakes · reproducibility