DOI: 10.5061/dryad.tx95x6b42
title: Data from: Individual weight estimates for Great Lakes benthic invertebrates

description: We present mean individual weights for common benthic invertebrates of the
 Great Lakes collected from over 2,000 benthic samples and eight years of
 data collection (2012-2019), both as species-specific weights and average
 weights of larger taxonomic groups of interest. The dataset we have
 assembled is applicable to food web energy flow models, calculation of
 secondary production estimates, interpretation of trophic markers, and for
 understanding how biomass distribution varies by benthic invertebrate
 species in the Great Lakes. A corresponding data paper describes
 comparisons of these data to benthic invertebrates in other lakes.
description: <strong>Data Collection</strong>
 Benthic invertebrates were collected from the EPA R/V Lake
 Guardian from 2012-2019 as part of the EPA Great Lakes National Program
 Office GLBMP and Cooperative Science and Monitoring Initiative (CSMI)
 benthic surveys. GLBMP samples are collected in all five of the Great
 Lakes annually and CSMI samples are collected in one of the Great Lakes
 annually. GLBMP includes 57-63 stations each year: 11 in Lake Superior
 (and 2-7 additional stations since 2014), 11 in Lake Huron, 16 in Lake
 Michigan, 10 in Lake Erie, and 10 (9 since 2015) in Lake Ontario. The
 number of CSMI stations vary by year. CSMI surveys for each lake took
 place in the following years: Erie 2014 (97 stations), Michigan 2015 (140
 stations), Superior 2016 (59 stations), Huron 2017 (118 stations), and
 Ontario 2018 (46 stations). Additional CSMI surveys have occurred since
 2019, however, we did not include these survey data in our analysis
 because samples would be unbalanced with some lakes sampled twice and
 other lakes sampled only once. We followed EPA Standard Operating
 Procedures for Benthic Invertebrate Field Sampling SOP LG406 (U.S. EPA,
 2021). In short, triplicate samples were collected from each station using
 a Ponar grab (sampling area = 0.0523 m2 for all surveys except Lake
 Michigan CSMI, for which sampling area = 0.0483 m2) then rinsed through
 500 µm mesh. Samples were preserved with 5-10% neutral buffered formalin
 with Rose Bengal stain.  <strong>Lab
 Processing</strong> Samples were processed in the
 lab after preservation following EPA Standard Operating Procedure for
 Benthic Invertebrate Laboratory Analysis SOP LG407 (U.S. EPA, 2015).
 Briefly, organisms were picked out of samples using a low-magnification
 dissecting microscope then each organism was identified to the finest
 taxonomic resolution possible (usually species). Individuals of the same
 species, or size category, were blotted dry on cellulose filter paper to
 remove external water until the wet spots left by animal(s) on the
 absorbent paper disappeared. Blotting time varied based on the surface
 area/volume ratio of the organisms but was approximately one minute for
 large and medium chironomids and oligochaetes and less time (0.6 min) for
 smaller chironomids and oligochaetes. Care was taken to ensure that the
 procedure did not cause damage to the specimens. Larger organisms (e.g.,
 dreissenids) often took longer to blot dry. All organisms in a sample
 within a given taxonomic unit were weighed together to the nearest 0.0001
 g (WW). Dreissena were weighed by 5 mm size category (size fractions:
 0-4.99 mm, 5-9.99 mm, etc.) to nearest 0.0001 g (shell and tissue
 WW).  <strong>Data
 Analysis</strong> To calculate the total weight
 for each species that was mounted on slides by size groups for
 identification (e.g., Oligochaeta, Chironomidae), we multiplied the number
 of individuals of the species binned into each size category by the
 average weight of individuals in that category. If a species was found in
 more than one size category, we summed the weight of the species across
 all categories per sample. Oligochaetes often fragment in samples, and
 thus, were counted by tallying the number of oligochaete heads (anterior
 ends with prostomium) present in the sample. Oligochaete fragments were
 also counted and weighed for inclusion in biomass calculations. We set the
 cutoff for the minimum number of samples to calculate individual weights
 to ten samples (see companion data paper for details). Therefore, in our
 further analysis we only calculated individual weights when a taxonomic
 unit was found in at least ten samples. Species that were found in fewer
 than ten samples were excluded from the analysis. We
 calculated wet weights by species whenever possible. If species were
 closely related, had similar body size (based on our previous experience),
 and were found in few samples, they were grouped together to achieve our
 minimum sample size of ten. For some taxa (e.g., Chironomidae), individual
 species could not be identified so calculations were made at the finest
 taxonomic resolution possible (usually genus). We hereafter refer to the
 two taxonomic groupings of closely related species and taxa that could not
 be identified to species as “taxonomic units.” For each taxonomic unit, we
 calculated several summary statistics on wet weight: mean, minimum, and
 maximum weight, median weight, standard error of mean weight, and sample
 size (number of samples in which a taxonomic unit was present). 
 We performed Kruskal-Wallis tests (Kruskal & Wallis,
 1952) to determine when individuals within a species could be grouped by
 depth zone and/or lake when sample size was large enough (species found in
 ≥10 samples per group) to permit splitting because we expected species
 weight to differ by depth zone and/or lake. In all five Great Lakes,
 benthic density and species richness are greater at stations ≤70 m than at
 stations deeper than 70 m (Burlakova et al., 2018; Cook & Johnson,
 1974). The 70 m depth contour separation of benthos mirrors a breakpoint
 in spring chlorophyll concentrations observed for these stations,
 suggesting that lake productivity is likely the major driver of benthic
 abundance and diversity across lakes (Burlakova et al., 2018). Therefore,
 we used two categories of depth zones: ≤70 m and &gt; 70 m. If
 Kruskal-Wallis tests showed that weights did not differ by lake or depth,
 the average weight for a species was calculated as an average of all lakes
 and depths. If Kruskal-Wallis tests showed significant separation (α
 &lt; 0.05) by lake or depth, then means were calculated for each group
 and we also compared the group means. Individuals in different lakes or
 depth zones were combined if the mean difference between most groups was
 less than 25%, even when Kruskal-Wallis tests were significant because
 small differences were likely not biologically significant. Oligochaete
 fragments for finer taxonomic units were reported separately from
 oligochaete species because it was rarely apparent which species the
 fragments came from. Mean individual wet weights were
 calculated for a total of 187 groupings within taxonomic units (data file
 “IndividualWeights_AllData.csv”). For 117 taxonomic units, weights were
 calculated across all lakes, depths, and basins because weights were
 similar in all regions or because of small sample size, for seven
 taxonomic units, weights were calculated by lake, and for the rest summary
 statistics were calculated by both lake and depth zone. In addition, five
 species were considered as “special cases” where some areas were similar
 while others were not. For example, some species had similar weights in
 multiple lakes, thus those lakes were grouped together while other were
 kept separate. Dreissena rostriformis bugensis weights were calculated by
 lake and depth zone except for Lake Erie, where the western, central, and
 eastern basins were separated because previous research demonstrated that
 D. rostriformis bugensis size structure is drastically different in each
 of Lake Erie’s basins (Karatayev et al., 2021). Other special cases were:
 Heterotrissocladius marcidus group (Huron, Michigan, and Ontario were
 similar and grouped together, while mean weight in Lake Superior was
 different), Pisidium spp. (grouped as Ontario/Michigan, Erie, and
 Huron/Superior), Unidentified Chironomidae (Lake Erie was separated and
 all other lakes were grouped together), and Spirosperma ferox (Lake Erie
 was separated and all other lakes were grouped together).
 To calculate mean individual weights for commonly reported larger
 taxonomic groups (e.g., Oligochaeta, Chironomidae), we combined species or
 taxonomic units that belonged to this group (see “SpeciesList.csv” for
 information on groupings). Summary statistics were calculated on the mean
 individual weight for all individuals within a group in a given sample,
 i.e., total biomass for a given group was divided by total density for
 that group, repeated for each sample. Results are given for each major
 group as a mean/minimum/maximum for each lake, and for each depth zone
 within each lake as groups are often made up of different species with
 different body sizes in each lake and depth zone. Because densities of
 oligochaetes were counted based on the number of oligochaetes with heads
 in a sample (excluding fragments), but the fragments were weighed to
 calculate biomass, the mean individual weight for oligochaetes within a
 sample was calculated by dividing the weight of all oligochaetes
 (including fragments) in a sample by the number of oligochaetes (not
 including fragments). Calculations of mean individual
 weight by major group were performed both by lake and lake plus depth zone
 (data file “IndividualWeights_MajorGroups.csv”). Summary statistics were
 reported for 14 major taxa and were broken down by depth zone when sample
 size was sufficient (data file
 “IndividualWeights_MajorGroups.csv”). 
 REFERENCES Burlakova, L. E., Barbiero, R. P.,
 Karatayev, A. Y., Daniel, S. E., Hinchey, E. K., & Warren, G. J.
 (2018). The benthic community of the Laurentian Great Lakes: Analysis of
 spatial gradients and temporal trends from 1998 to 2014. Journal of Great
 Lakes Research, 44(4), 600–617.
 https://doi.org/10.1016/j.jglr.2018.04.008 Cook, D. G.,
 & Johnson, M. G. (1974). Benthic Macroinvertebrates of the St.
 Lawrence Great Lakes. Journal of the Fisheries Research Board of Canada,
 31, 763–782. https://doi.org/10.1139/f74-101 Karatayev,
 A. Y., Burlakova, L. E., Mehler, K., Hinchey, E. K., Wick, M., Bakowska,
 M., & Mrozinska, N. (2021). Rapid assessment of Dreissena
 population in Lake Erie using underwater videography. Hydrobiologia,
 848(9), 2421–2436. https://doi.org/10.1007/s10750-020-04481-x
 Kruskal, W. H., & Wallis, W. A. (1952). Use of Ranks in
 One-Criterion Variance Analysis. Journal of the American Statistical
 Association, 47(260), 583–621.
 https://doi.org/10.1080/01621459.1952.10483441 USEPA.
 (2015). Standard Operating Procedure for Benthic Invertebrate Laboratory
 Analysis. (LG 407, Version 09).
 https://www.epa.gov/sites/default/files/2017-01/documents/sop-for-benthic-invertebrate-lab-analysis-201504-13pp.pdf USEPA. (2021). Standard Operating Procedure for Benthic Invertebrate Field Sampling. (LG 406, Version 14). https://www.epa.gov/system/files/documents/2021-08/lg406.v14-benthos-sampling_rfa.pdf
description: # Data from: Individual weight estimates for Great Lakes benthic
 invertebrates
 [https://doi.org/10.5061/dryad.tx95x6b42](https://doi.org/10.5061/dryad.tx95x6b42) The files in this data set give information for benthic invertebrate weights for the Laurentian Great Lakes. See companion data manuscript text for calculation methods. All files are formatted as comma-separated values and missing data are denoted with "NA." ## Description of the data and file structure Description for file "IndividualWeights_AllData.csv" This file gives summary statistics of individual weights for species to the highest possible taxonomic resolution, and separates by lake, depth, and/or basin when necessary. The column headers are as follows: Name (character string) = Name of the taxonomic unit represented. Species in most cases. Lake (character string) = Great Lake(s) represented in grouping. "All" indicates that all possible data from the Great Lakes was combined. DepthZone_m (character string) = Depth zone represented in grouping, either &gt;=70 m or &lt; 70 m. "All" indicates that data from all lake depths were combined. Basin (character string) = Lake basin represented in grouping. "All" indicates that data from all lake basins are included. AverageIndividualWeight_g (numeric) = Mean weight of an individual benthic invertebrate of the given taxonomic unit in grams. SE_weight (numeric) = Standard error of mean individual weight. MedianIndividualWeight_g (numeric) = Median weight of an individual benthic invertebrate of the given taxonomic unit in grams. MinimumIndividualWeight_g (numeric) = Minimum weight of an individual benthic invertebrate of the given taxonomic unit in grams. MaximumIndividualWeight_g (numeric) = Maximum weight of an individual benthic invertebrate of the given taxonomic unit in grams. SampleSize_Nsamples (integer) = Sample size for a given taxonomic unit. Represents the number of samples in which the taxonomic unit was present. \----- Description for file "IndividualWeights_MajorGroups.csv" This file has summary statistics for major taxonomic groups of benthic macroinvertebrates in different lakes, depth zones, and for Dreissena, the three basins of Lake Erie. The column headers are as follows: Name (character string) = Name of the taxonomic unit represented. Lake (character string) = Great Lake(s) represented in grouping. "All" indicates that all possible data from the Great Lakes was combined. DepthZone_m (character string) = Depth zone represented in grouping, either &gt;=70 m or &lt; 70 m. "All" indicates that data from all lake depths were combined. Basin (character string) = Lake basin represented in grouping. "All" indicates that data from all lake basins are included. AverageIndividualWeight_g (numeric) = Mean weight of an individual benthic invertebrate of the given taxonomic unit in grams. SE_weight (numeric) = Standard error of mean individual weight. MedianIndividualWeight_g (numeric) = Median weight of an individual benthic invertebrate of the given taxonomic unit in grams. MinimumIndividualWeight_g (numeric) = Minimum weight of an individual benthic invertebrate of the given taxonomic unit in grams. MaximumIndividualWeight_g (numeric) = Maximum weight of an individual benthic invertebrate of the given taxonomic unit in grams. SampleSize_Nsamples (integer) = Sample size for a given taxonomic unit. Represents the number of samples in which the taxonomic unit was present. \----- Description for file "SpeciesList.csv" This file shows which taxa were grouped for calculations. The column headers are as follows: Name (character string) = Name of the taxonomic unit represented following the format “Genus species” or “Genus species subspecies” if subspecies is known. Abbreviations: sp. = unknown species; spp. = unknown species but genus likely encompasses multiple species. Group (character string) = Higher taxonomic used to classify the species for calculations in file "IndividualWeights_MajorGroups.csv."