Water quality, temperature, ash-free dry mass, photosynthetic activate radiation (PAR), and zooplankton data from a warming and DOC subsidy experiment, 2020 - 2021.

This dataset includes chlorophyll-a concentrations, periphyton
biomass estimates, water quality measurements, and qualitative
observations from a large-scale mesocosm experiment conducted in the
Green Lakes Watershed, Colorado. The experiment was designed to test
how earlier lake ice-off and increased dissolved organic material
(DOM), associated with terrestrial plant encroachment in alpine
watersheds, interactively influence aquatic food webs. In fall 2019,
twenty 2600L “megacosms” were established at Sandy Corner (3300 m
ASL; 40.042289, -105.584006), left to fill with snowmelt, and
maintained throughout the 2020 open water season. The experiment
followed a 2 × 2 randomized block design manipulating ice-off timing
(via black vs. beige tank coloration) and DOM inputs
(presence/absence of willow leaf packs), with five replicates per
treatment. All tanks were seeded with sediments and zooplankton from
both alpine and montane lakes (Green Lake 1 and Green Lake 4), and
instrumented with thermistors recording surface and hypolimnion
temperature every two hours year-round. Periphyton growth was
monitored using clay tiles, sampled across five time points.
Chlorophyll-a concentrations were extracted from filtered water
samples and analyzed spectrophotometrically. Periphyton biomass was
estimated via ash-free dry mass (AFDM) determinations, based on the
mass lost on combustion of material scraped from tiles. Water
quality was measured 1–2 times weekly using a YSI ProPlus multiprobe
and Li-Cor quantum sensor, and snow/ice cover was qualitatively
assessed monthly during winter.