Summer crustacean group differences had no clear mean change across seven Wisconsin lakes, 2002–2013 to 2014–2025

We tested whether summer crustacean group composition became more alike across seven fixed northern Wisconsin lakes. We used open NTL-LTER version 37.42 and five predefined groups. Four groups had positive density in the selected summers. Shares were averaged equally over dates within months, then over June, July and August. The main comparison used 415 dates in 18 complete all-lake summers: seven in 2002–2013 and eleven in 2014–2025. Mean total variation distance across 21 fixed lake pairs changed from 0.2466 to 0.2512. The change was +0.0046, with a nominal 95% shared three-year block interval of −0.0359 to +0.0399. Excluding nauplii, using Hellinger distance, changing the season, selecting one date per month, and changing block length also gave uncertain changes. Larger differences in cladoceran shares offset smaller differences in calanoid and cyclopoid shares. These group contributions are descriptive. A further check using all complete lake-pair years gave +0.0061, with an interval of −0.0274 to +0.0370. The result does not establish stable species composition or identify a cause. It conditions on seven lakes and incomplete year coverage. The package has unchanged source data, provenance, code, figures, independent arithmetic checks and an exact numerical repeat.

zooplankton · lake communities · crustaceans · community composition · temporal change · open data · reproducibility