DOI: 10.5061/dryad.31zcrjf1t
title: Macroinvertebrate diversity, community structure, and dispersal in a regulated river are affected by tributary identity and confluence conditions

description: Tributaries are essential components of river ecosystems that provide
 habitat and resources for many species, especially during ontogenetic
 shifts. The role of tributaries in creating heterogeneous physical
 conditions and resource supply for riverine macroinvertebrates and fishes
 could be critical, especially given homogenization by mainstem dams, yet
 little is known about how variable conditions in different tributaries
 influence mainstems. Using field observations in five tributaries on the
 Madison River, Montana, USA, we found that tributaries within 61 river km
 of each other varied greatly in environmental conditions,
 macroinvertebrate densities, and macroinvertebrate community structure.
 Downstream of confluences, macroinvertebrate richness in the mainstem
 increased, drift density increased, and average mass of a drifting
 individual decreased, suggesting that confluences may act as biodiversity
 and resource supply hotspots in regulated rivers. The magnitude of a
 tributary’s influence on richness and body size of drifting
 macroinvertebrates was positively related to greater US Forest Service
 land, steeper slope in the watershed, cooler water temperature, and lower
 discharge. In contrast, a tributary’s influence on benthic density and
 biomass was negatively related to these same drivers. The opposing effects
 on different metrics that we uncovered suggest that a suite of drivers
 influence physical and resource heterogeneity imparted by tributaries in
 complex ways. Future research will need to test the ubiquity of the
 patterns we observed in other river networks and in relationship to other
 global changes such as pollution or drought. Continued understanding of
 the importance of tributaries for diversity, density, and biomass of
 freshwater species may help guide restoration efforts aimed at improving
 river resilience.
description: # Macroinvertebrate diversity, community structure, and dispersal in a
 regulated river are affected by tributary identity and confluence
 conditions **Author Information** Principal Investigator Contact
 Information Name: Lindsey Albertson Institution: Montana State University
 Address: 310 Lewis Hall, Bozeman, MT 59717 USA Email:
 [lindsey.albertson@montana.edu](mailto:lindsey.albertson@montana.edu)
 **Date of data collection**: 2020-07-15 - 2021-07-26 **Geographic location
 of data collection:** near Ennis, Montana, USA (45.349209, -111.732765)
 **Information about funding sources that supported the collection of the
 data:** Funding was provided by Montana State University, The Montana
 Water Center, NorthWestern Energy, Sitka Gear, and The Madison River
 Foundation. ## DATA & FILE OVERVIEW **File List:** InvertAbundance.csv
 Density of invertebrate taxa collected across 4 sampling dates at 3
 sampling sites near each of 5 tributary confluences on the upper Madison
 River, USA. InvertBiomass.csv Biomass of invertebrate taxa collected
 across 4 sampling dates at 3 sampling sites near each of 5 tributary
 confluences on the upper Madison River, USA. InvertAll.csv Various
 community metrics pooled for all invertebrate taxa with corresponding
 environmental variables cross 4 sampling dates at 3 locations near each of
 5 tributary confluences on the upper Madison River, USA. InvertDrift.csv
 Invertebrate density and individual weight in the drift samples across 4
 sampling dates at 3 sampling sites near each of 5 tributary confluences on
 the upper Madison River, USA. Environmental.csv Characteristics of each
 tributary site. PCAScores.csv Scores from principle components analysis
 (PCA) used for linear regressions of PCA scores against invertebrate
 response ratios. ### DATA-SPECIFIC INFORMATION FOR: InvertAbundance.csv
 Variable List: ``` season - Season when the sample was collected -Summer
 -Spring -Fall; Indian trib has no fall sample because it was dry date -
 Date when sampling occurred -7/20/20 -7/21/20 -7/23/20 -7/24/20 -7/26/20
 -10/30/20 -10/31/20 -11/1/20 -11/2/20 -11/3/20 -4/1/21 -4/2/21 -4/3/21
 -4/4/21 -4/5/21 -7/23/21 -7/24/21 -7/25/21 -7/26/21 -7/27/21 stream - Five
 tributary confluences where data were collected -jack -odell -ruby -indian
 -standard site - Three locations at each of the 5 tributary confluences
 where data were collected -up is in the mainstem upstream of the
 confluence -down is in the mainstem downstream of the confluence -trib is
 inside the tributary rep - Surber sample replicate from each site -1 -2 -3
 Acari onward - Density in number per meter squared for each taxon
 identified from the invertebrate samples ``` ### DATA-SPECIFIC INFORMATION
 FOR: InvertBiomass.csv Variable List: ``` season - Season when the sample
 was collected -Summer -Spring -Fall; Indian trib has no fall sample
 because it was dry date - Date when sampling occurred -7/20/20 -7/21/20
 -7/23/20 -7/24/20 -7/26/20 -10/30/20 -10/31/20 -11/1/20 -11/2/20 -11/3/20
 -4/1/21 -4/2/21 -4/3/21 -4/4/21 -4/5/21 -7/23/21 -7/24/21 -7/25/21
 -7/26/21 -7/27/21 stream - Five tributary confluences where data were
 collected -jack -odell -ruby -indian -standard site - Three locations at
 each of the 5 tributary confluences where data were collected -up is in
 the mainstem, just upstream of the confluence -down is in the mainstem,
 just downstream of the confluence -trib is inside the tributary rep -
 Surber sample replicate from each site -1 -2 -3 Acari onward - Biomass in
 grams per meter squared for each taxon identified from the invertebrate
 samples ``` ### DATA-SPECIFIC INFORMATION FOR: InvertAll.csv Variable
 list: ``` Year - Year when sample was collected -2020 -2021 Season -
 Season when the sample was collected -Summer; could be year 2020 or 2021
 -Spring -Fall; Indian trib has no fall sample because it was dry Tributary
 - Five tributary confluences where data were collected -Jack -Odell -Ruby
 -Indian -Standard Site - Three locations at each of the 5 tributary
 confluences where data were collected -up is in the mainstem, just
 upstream of the confluence -down is in the mainstem, just downstream of
 the confluence -trib is inside the tributary Date - Date when sampling
 occurred -7/20/20 -7/21/20 -7/23/20 -7/24/20 -7/26/20 -10/30/20 -10/31/20
 -11/1/20 -11/2/20 -11/3/20 -4/1/21 -4/2/21 -4/3/21 -4/4/21 -4/5/21
 -7/23/21 -7/24/21 -7/25/21 -7/26/21 -7/27/21 Rep - Surber sample replicate
 from each site -1 -2 -3 Abundance - Total density in number per meter
 squared of all invertebrates pooled across taxa Dry_Mass - Total mass in
 grams per meter squared of all invertebrates pooled across taxa Shannon -
 Shannon-Weaver diversity index estimated for the invertebrate community;
 not used for subsequent analysis Eveness - Eveness estimated for the
 invertebrate community; not used for subsequent analysis Simpson -
 Simpson's diversity index estimated for the invertebrate community;
 not used for subsequent analysis Richness - Number of taxa identified in
 the invertebrate community omDiff_v1 - Benthic organic matter in grams per
 meter squared collected from the sample taken for invertebrates with an
 oversized, custom surber net MWMT - Mean weekly maximum temperature in
 degrees celsius mean_b_axis - Diameter of the b-axis (intermediate) for
 gravels in the pebble count in millimeters sedimentFiltered - Fine
 sediment mass in a water column sample in milligrams per liter; also
 called Suspended sediment AFDM_biofilm - Benthic biomass ash free dry mass
 in milligrams per 3 centimeters squared. Converted to milligrams per 1
 meter squared (mg/m2) for Table 1 in the associated manuscript published
 at RRA. NRCS - Natural Resources Conservation Service score for riparian
 land use, which can range from 0-100 ``` ### DATA-SPECIFIC INFORMATION
 FOR: InvertDrift.csv Variable List: ``` date - Date when sampling occurred
 -7/20/20 -7/21/20 -7/23/20 -7/25/20 -7/26/20 -10/30/20 -10/31/20 -11/1/20
 -11/2/20 -11/3/20 -4/1/21 -4/2/21 -4/3/21 -4/4/21 -4/5/21 -7/23/21
 -7/24/21 -7/25/21 -7/26/21 -7/27/21 trib - Five tributary confluences
 where data were collected -jack -odell -ruby -indian -standard site -
 Three locations at each of the 5 tributary locations where data were
 collected -up is in the mainstem, just upstream of the confluence -down is
 in the mainstem, just downstream of the confluence -trib is inside the
 tributary rep - Drift net replicate -1 -2 soak_second - Length of
 deployment of the drift nets in seconds v1 - Velocity measurement 1 at the
 drift net opening in meters per second v2 - Velocity measurement 2 at the
 drift net opening in meters per second avg_v - Mean velocity averaging
 columns v1 and v2 in meters per second volume_m3 - Volume of water passing
 through the drift net estimated as the product of soak_second * avg_v *
 area of the drift net, which was 25 cm x 45 cm fraction - Fraction (also
 called subsample) of a complete drift sample that was picked for
 invertebrates -0.0625 -0.125 -0.25 -0.5 -1 bugCount - Number of aquatic
 invertebrates enumerated from the fraction. terrestrial - Number of
 terrestrial invertebrates enumerated from the fraction; not included in
 further analyses totalBug - Number of invertebrates in the full sample
 estimated as the product of fraction * bugCount bugs_m3 - Number of
 invertebrates per volume in meters cubed estimated from totalBug divided
 by volume_m3; also called drift density mean_weight - Average mass of an
 individual invertebrate in the drift in grams; also called weight of
 individuals in drift ``` ### DATA-SPECIFIC INFORMATION FOR:
 Environmental.csv Variable List: ``` Date - Date when sampling in the
 tributary occurred -7/20/20 -7/21/20 -7/23/20 -7/24/20 -7/26/20 -10/30/20
 -10/31/20 -11/1/20 -11/3/20 -4/1/21 -4/2/21 -4/3/21 -4/4/21 -4/5/21
 -7/23/21 -7/24/21 -7/25/21 -7/26/21 -7/27/21 Tributary - Five tributary
 confluences where data were collected -Jack -Odell -Ruby -Indian -Standard
 Site - Location at each of the 5 tributary confluences where data were
 collected -trib is inside the tributary Rep - Surber sample replicate from
 each site, most relevant in this csv file for the omDiff_v1 column below
 -1 -2 -3 Season - Season when the sample was collected -Summer; could be
 year 2020 or year 2021 -Spring -Fall; Indian has no fall sample because it
 was dry Year - Year when sample was collected -2020 -2021 MWMT - Mean
 weekly maximum temperature in degrees celsius d50_b_axis - Diameter of the
 b-axis (intermediate) for gravels in the pebble count in millimeters
 sedimentFiltered - Fine sediment mass in a water column sample in
 milligrams per liter; also called Suspended sediment AFDM_biofilm -
 Benthic biomass ash free dry mass in milligrams per 3 centimeters squared.
 Converted to milligrams per 1 meter squared (mg/m2) for Table 1 in the
 associated manuscript published at RRA. omDiff_v1 - Benthic organic matter
 in grams per meter squared collected from the sample taken for
 invertebrates with an oversized, custom surber net prop_USFS - Proportion
 of land use that was classified as U.S. Forest Service land prop_ag -
 Proportion of land use that was classified as agriculture land prop_resid
 - Proportion of land use that was classified as residential land NRCS -
 Natural Resources Conservation Service score for riparian land use, which
 can range from 0-100 Elevation_confluence - Elevation in meters at the
 confluence Length (km) - Stream length in kilometers Elevation_loss -
 Difference in elevation in meters at the start and at the confluence of
 each stream Discharge_trib - Discharge in cubic meters per second ``` ###
 DATA-SPECIFIC INFORMATION FOR: PCAScores.csv Variable List: ``` PC1 -
 Principle component 1 score PC2 - Principle component 2 score Tributary -
 Five tributary confluences where data were collected -Jack -Odell -Ruby
 -Indian -Standard Date - Date when sampling occurred -7/20/20 -7/21/20
 -7/23/20 -7/25/20 -7/26/20 -10/30/20 -10/31/20 -11/01/20 -11/02/20
 -11/03/20 -04/01/21 -04/02/21 -04/03/21 -04/04/21 -04/05/21 -07/23/21
 -07/24/21 -07/25/21 -07/26/21 -07/27/21 Site - Location at each of the 5
 tributary confluences where data were collected -trib is inside the
 tributary Rep - Surber sample replicate from each site -1 -2 -3 Season -
 Season when the sample was collected -Summer; could be year 2020 or year
 2021 -Spring -Fall; Indian has no fall sample because it was dry ``` ##
 SHARING/ACCESS INFORMATION 1. Licenses/restrictions placed on the data:
 None 2. Was data derived from another source? Basin attributes and
 land-use categories for each tributary were mapped and calculated with
 ArcGIS Pro 2.9 (ESRI, Redlands, CA, USA). The basin boundaries and
 land-use shape files were obtained from Montana State Library’s geographic
 database. ```