Data for: Climate change is poised to alter mountain stream ecosystem processes via organismal phenological shifts

Climate change is affecting the phenology of organisms and ecosystem processes across a wide range of environments. However, the mechanisms linking organismal to ecosystem process change in complex communities are uncertain. Here we examined how earlier snowmelt will alter the phenology of stream organisms and ecosystem processes, via a large-scale field experiment in outdoor stream channels. Extended low flows increased water temperature, reducing production-to-respiration ratios by 32%. The stream invertebrate community shifted due to phenological shifts in two-thirds of the taxa, and emergent flux pulses of the dominant insect group (Chironomidae) almost doubled, benefitting a generalist riparian predator. Our study shows that climate change in mountain streams is poised to alter the dynamics of stream food webs via fine-scale changes in phenology—leading to novel predator-prey ‘matches’ or 'mismatches’ even when community structure and ecosystem processes appear stable at the annual..., Time frame: Begin date 4/21/2019 - End date 8/25/2019.
General study design- We subjected nine large-scale, flow-through outdoor stream mesocosms in California’s Sierra Nevada to three flow regime treatments: a flow regime based on historic average conditions (current treatment), a mitigated climate change scenario where low flow begins three weeks earlier than currently (3-week treatment), and an unmitigated climate change scenario where low flow begins six weeks earlier than currently (6-week treatment). Over the course of a season, we regularly measured primary production; community composition, production, and emergence of benthic and emergent stream invertebrates; and Brewer’s Blackbird (Euphagus cyanocephalus) feeding activity. We tested for immediate vs. delayed effects of advanced low flows by combining the period of the study (i.e., start, middle, and end) with the treatment, creating a variable that captures both timing and treatment effects (i.e., period-treatment). We ran a ..., , # Climate change is poised to alter mountain stream ecosystem processes via organismal phenological shifts

## Description of the Data and file structure

[https://doi.org/10.6078/D10712](https://doi.org/10.6078/D10712)

### Details for: Discharge\_dryad.csv

* Dataset description: The dataset includes the average discharge of each channel on each day of the experiment taken with U20 Onset sensors recording every 15 minutes. Sensors were located in pools near the downstream end of channels and secured to cinder blocks at the streambed.

Variables

* Date: Date with day, month, and year. The format is month/day/year and the year is 2019.
* Channel: Channel number beginning at the upstream channel closest to Convict Creek as #1 and ending with the downstream channel farthest from Convict Creek being #9
* Treatment: The treatment of the channel as described above in methods
* Discharge_Av_Chan_L_s: Average daily discharge (L/s). Raw water depth data is collected from sensors and ...