Macroinvertebrate diversity, community structure, and dispersal in a regulated river are affected by tributary identity and confluence conditions
Data files
Dec 18, 2025 version files 305.40 KB
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Environmental.csv
7.11 KB
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InvertAbundance.csv
113.96 KB
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InvertAll.csv
31.87 KB
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InvertBiomass.csv
126.54 KB
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InvertDrift.csv
10.51 KB
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PCAScores.csv
4.20 KB
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README.md
11.21 KB
Abstract
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.
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
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
- Licenses/restrictions placed on the data:
None - 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.