DOI: 10.5061/dryad.rfj6q57k5
title: Data from: Multiple stressors in river networks: Local and downstream effects on freshwater macroinvertebrates

description: River networks are complex ecosystems characterized by a continuous
 exchange of material and energy through longitudinal gradients. These
 ecosystems are threatened by various human-induced stressors, which
 frequently co-occur and may interact in complex ways, potentially
 triggering cascading effects in the river network. Aiming at assessing the
 single and combined effects of flow intermittency and light pollution on
 macroinvertebrate communities, we performed a multiple stressor experiment
 in 18 flow-through mesocosms. Each mesocosm was designed to mimic a
 simplified river network, with two upstream tributaries merging
 downstream, to assess both local and cascading effects. The experiment was
 performed in Summer 2021 for seven weeks, applying the stressors either
 separately or co-occurring in the upstream sections, following a
 randomized block design. Flow intermittency was simulated as the ponded
 phase of the drying process, whereas light pollution was applied with LED
 strips (set at 10 lux). Drifting macroinvertebrates were sampled weekly
 during the treatment phase, and benthic macroinvertebrates were sampled at
 the end of the treatment phase. Both stressors individually applied
 reduced benthos richness and abundance, whereas drift decreased with flow
 intermittency and increased with light pollution. When co-occurring
 upstream, stressors showed dominant effects of flow intermittency on the
 benthos and interactive effects on the drift. The effects of the single
 stressors and their interactions cascaded along the river network, with
 stronger downstream effects when stressors co-occurred upstream. These
 findings showed that the spatial distribution of multiple stressors along
 the river network can affect their resultant downstream effects,
 highlighting the importance of framing multiple stressors research in a
 spatial context. Considering the pressing needs of the growing human
 population, our results represent a step forward in anticipating
 cumulative stressors' effects, informing efficient conservation
 strategies for protecting freshwater ecosystems.
description: Data were collected during a field experiment in Summer 2021,
 using the Disconnected system, a system of 18 flow-through mesocosms, at
 the Eußerthal Ecosystem Research Station (EERES, RPTU
 Kaiserslautern-Landau), in the Palatinate Forest (Rheinland-Pfalz,
 Germany). The Disconnected system is a mesocosm system designed to mimic a
 simplified river network, with two upstream tributaries merging together
 downstream. The experiment lasted seven weeks, with three weeks of
 colonisation and four weeks of treatment. Drift data were collected weekly
 during the treatment phase of the experiment. Benthos data were collected
 at the end of the experiment.  Drift samples were
 collected by placing drift nets at the outlet of each upstream section.
 Benthos samples were collected from sampling areas of 150
 cm<sup>2</sup> with two replicates in each section (six
 samples per flume). All macroinvertebrate samples were
 processed, counting and identifying organisms to a mixed taxonomic level
 (family or genus). 
description: # Data from: Multiple stressors in river networks: Local and downstream
 effects on freshwater macroinvertebrates
 [https://doi.org/10.5061/dryad.rfj6q57k5](https://doi.org/10.5061/dryad.rfj6q57k5) ## Description of the data and file structure The experiment was performed to assess the local and downstream effects of multiple stressors (flow intermittency and light pollution) on macroinvertebrate communities in a river network. The study took place in a system of 18 flow-through mesocosms, with each mesocosm unit designed to mimic a simplified river network. The experiment ran for seven weeks in summer 2021, consisting of 26 days of colonization followed by 23 days of treatment. The Excel spreadsheet includes four sheets (drift, benthos, background_data, and README) that are described below.  ### Files and variables #### File: DISCONNECTED_alldata.xlsx **Description:** Data from the Disconnected project ##### Variables * drift (sheet 1): data for drifting macroinvertebrates * ID (column A): unique identifier of each drift sample collected during the experiment * HT (column B): header tank identifier (HT1-HT6) * flume (column C): mesocosm unit (i.e. flume) number identifier (F1-F18) * side (column D): identifier of the side (left or right for the two upstream tributaries) * treatment_up (column E): identifier of the treatment applied for each drift sample. This column has four levels, being: CT (control treatment in upstream sections), L (light treatment in upstream sections), F (flow treatment in upstream sections), L+F (light and flow treatment in upstream sections) * treatment_down (column F): identifier of the treatment applied at flume level. This column is used in the script when considering the total downstream export. This column has three levels, being CT (control flume), CS (flume with co-occurring stressors), and SS (flume with separated stressors) * date (column G): sampling day (in date format) for each drift sample * time (column H): sampling day in factor format (from T1 to T4) * columns I-AT: drifting macroinvertebrate taxa with abundances for each sample * benthos (sheet 2): data for benthic macroinvertebrates. * ID (column A): unique identifier of each benthos sample collected during the experiment * HT (column B): header tank identifier (HT1-HT6) * flume (column C): mesocosm unit (i.e. flume) number identifier (F1-F18) * section (column D): section of each flume (being up for upstream tributaries and down for the downstream part) * side (column E): identifier of the side (left or right for the two upstream tributaries). Samples collected in downstream sections are marked with "__" * treatment (column F): identifier of the treatment applied for each sample. This column has sevel levels being: CT_up (control treatment in upstream sections), L (light treatment in upstream sections), F (flow treatment in upstream sections), L+F (light and flow treatment in upstream sections), CT_down (control treatment in downstream sections), CS (flume with co-occurring stressors), and SS (flume with separated stressors) * columns G-AT: benthic macroinvertebrate taxa with abundances for each sample. * background_data (sheet 3): physical (conductivity, dissolved oxygen, pH, and water temperature, with multiparametric probe WTW Multi 3630 IDS Set G) and hydraulic (flow velocity and water depth, with an OTT MF pro electromagnetic current meter) parameters monitored weekly throughout the experiment (during both colonisation and treatment phases). * ID (column A): unique identifier of each measurement * flume (column B): mesocosm unit (i.e. flume) number identifier (F1-F18) * section (column C): section of each flume (being up for upstream tributaries and down for the downstream part) * side (column D): identifier of the side (left or right for the two upstream tributaries). Samples collected in downstream sections are marked with "__" * date_probe(column E): measuring day (in date format) for physical parameters * date_hydro (column F): measuring day (in date format) for hydraulic parameters * time (column G): measuring day in factor format (from T-3 to T4) * phase (column H): phase of the experiment (being colonisation or treatment phase) * treatmet (column I): identifier of the treatment applied. This column has sevel levels being: CT_up (control treatment in upstream sections), L (light treatment in upstream sections), F (flow treatment in upstream sections), L+F (light and flow treatment in upstream sections), CT_down (control treatment in downstream sections), CS (flume with co-occurring stressors), and SS (flume with separated stressors) * O2_perc (column J): dissolved oxygen (percentage) * O2_conc (column K): dissolved oxygen (concentration) * temp (column L): water temperature * pH (column M): water pH * cond (column N): water conductivity * vel (column O): flow velocity * depth (column P): water depth * README (sheet 4): a summary of the physical and hydraulic parameters, reporting the meaning of the abbreviations in sheet 3 and the units. ## Code/software R code used for this study can be found at [https://github.com/GSBurg/Disconnected](https://github.com/GSBurg/Disconnected). A list of the R package used is reported at the beginning of the script.