May–September records showed no clear mean change in relative Daphnia timing at seven Wisconsin lakes between 2002–2013 and 2014–2025

We tested whether Daphnia seasonal density timing changed relative to other crustaceans in seven northern Wisconsin lakes. We used NTL-LTER source version knb-lter-ntl.37.42 and compared 2002–2013 with 2014–2025. The panel has 854 valid dates in 153 lake-years with complete May–September coverage and positive seasonal density in both groups. Each group time index weights month indices by monthly mean density. We gave lakes equal weight and used 9,999 shared calendar-year bootstrap draws with three-year blocks. The mean late-minus-early change in the Daphnia-minus-other index was +0.035 month-index units, with a nominal 95% interval of −0.112 to +0.204. All stated checks with intervals also left the mean change uncertain. Trout had a negative pointwise interval, but its simultaneous interval included zero and its shorter-season estimate changed sign. The records did not resolve a shared relative timing change. They do not establish stable full-year timing, a warming effect, or a trophic mismatch. The package preserves source data, provenance, code, annual and monthly panels, bootstrap draws, figures, and offline repeat instructions.

Daphnia · zooplankton · seasonal timing · lake monitoring · NTL LTER · block bootstrap · reproducible research