DOI: 10.5061/dryad.0p2ngf1xq
title: Littoral macroinvertebrate and water quality data for 32 lakes across the boreal-tundra transition in the Northwest Territories

description: This dataset includes macroinvertebrate and water quality data from 32
 lakes sampled in the Northwest Territories, Canada, from the Dempster and
 Inuvik-Tuktoyaktuk Highways during July and August of 2017 and 2018. It
 was collected as part of a project to determine how physicochemical
 variables affect macroinvertebrate and fish communities in small Arctic
 lakes.
description: <strong>Study sites</strong> Our
 32 study lakes were located within the boreal to tundra transition area.
 Eight of the lakes were sampled in August 2017 in the boreal forest region
 within the Gwich'in Settlement Area (GSA), and 24 of the lakes were
 sampled in August 2018 in the Inuvialuit Settlement Region (ISR) where
 tundra vegetation dominates. Our selection of lakes was not random, but
 was determined by a combination of logistical, licensing, and scientific
 considerations. As our project included fish community sampling, we had
 heavy gear, including gill nets and motorboats to transport to each lake,
 limiting the distance we could travel from the highway. Peat hummocks in
 the tundra and boggy terrain in the boreal region made it especially
 difficult to traverse long distances carrying heavy gear. Licenses were
 required for the research project as a whole (Northwest Territories
 Scientific License), and for fish collection in particular (Department of
 Fisheries and Oceans Scientific Collection Permit). These licenses
 required community consultation in the choice of lakes sampled so that
 lakes of cultural or recreational value to communities could be excluded.
 Therefore, for logistical reasons we considered all lakes within 300 m of
 the highways as possible sites. We also included five sites further away
 from the highway (0.6-3.5 km from the highway) that were accessible from
 the Trail Valley Creek Field Station (68.741°N, -133.499°W) north of
 Inuvik. For licensing reasons, and to respect the wishes of the
 communities, we excluded culturally significant lakes such as the Husky
 Lakes near Tuktoyaktuk or Dolomite Lake near Inuvik. Finally, for
 scientific reasons, we deliberately attempted to select lakes that varied
 in latitude and surface area. Our rationale was that we were hoping to
 examine environmental gradients, so lakes at different latitudes and of
 different sizes would be likely to vary in temperature, depth, fish
 presence/absence, and other important environmental variables.
 <strong>Biological data</strong>
 We collected macroinvertebrate samples using a modified version
 of the Ontario Benthic Biomonitoring Network protocol (OBBN) (Jones et al.
 2007). We collected three replicate samples using a 500 μm D-net to kick
 and sweep macroinvertebrates. The modifications to the original OBBN
 protocol were that each replicate was collected over three minutes, and
 replicates were taken along parallel transects from the shore until 1 m
 depth was reached. We used a three-minute traveling kick and sweep per
 replicate rather than ten minutes because of the abundance of organic
 matter on the lake bottom that quickly clogged the D-net, preventing
 further sample collection. To conduct a traveling kick and sweep, the
 researcher “vigorously kicks the substrate to disturb it to a depth of ~5
 cm” and sweeps the net “back and forth and up and down” to capture
 disturbed invertebrates (Jones et al. 2007). We did not take replicates at
 random locations in the lake as in the conventional OBBN protocol due to
 inaccessibility of different parts of the shoreline. A boat was not always
 available when we were collecting macroinvertebrate samples, and the boggy
 terrain often made it difficult to walk the shoreline without sinking into
 the peat. We were able to discern three types of substrate in our study
 lakes: mats of sphagnum moss, sphagnum moss with floating and emergent
 vegetation, and mixed gravel/cobble. For most lakes we visited, the
 littoral zone was quite homogeneous, consisting primarily of sphagnum
 moss, below which was a layer of fine silt. Many lakes also had floating
 vegetation, such as water lilies, and emergent sedges or grasses
 nearshore. A smaller number of lakes had cobble/gravel habitats in
 addition to sphagnum substrate. In cases where there were no clear
 indications of differing habitat types along the shore, we collected
 replicate samples at least 10 m apart. In cases where obvious habitat
 heterogeneity existed (e.g. sphagnum bottom versus rocky bottoms), we
 collected at least one sample in each habitat type. Each sample was
 preserved in 95% ethanol and brought back to the laboratory for
 identification. Using a 500 µm sieve and a dissecting
 microscope, we identified macroinvertebrates to the order and family level
 in the laboratory according to the OBBN tally sheet (Jones et al. 2007).
 We performed quality assurance and quality control on taxonomic accuracy
 and sorting efficiency following the Canadian Aquatic Biomonitoring
 Network (CABIN) protocol (McDermott et al. 2014). We counted full samples
 from the eight lakes collected in 2017 from the GSA, while we used
 subsampling by weight for the 24 lakes sampled the next year in the ISR
 due to large sample sizes and high abundances of macroinvertebrates. For
 the ISR samples, we weighed an entire sample, and then weighed out a small
 amount of sediment representing approximately 10% of the sample for
 analysis. If we did not count at least 100 individuals in this subsample,
 then we added more sediment until at least 100 individuals were identified
 for that particular subsample. We counted two more subsamples for each
 lake in the same manner, such that a minimum of 300 individuals were
 identified from each lake. If fewer than 300 individuals were present in
 the whole sample, we processed the entire sample. This methodology
 resulted in a mean of 437 individuals identified for each ISR lake with a
 standard deviation of 148. We conducted subsampling without replacement,
 meaning that we did not return sediment to the sample after each
 subsample. We collected fish community data in both
 sampling years. In 2017, we performed gillnetting according to the Ontario
 Broadscale Monitoring (BsM) protocol (Sandstrom et al. 2013). In 2018, we
 modified the BsM protocol in that we checked nets every 45-60 minutes and
 deployed nets an average of 11 hours in small to medium lakes (&lt;500
 ha) and 37 hours in larger lakes (&gt;500 ha). We changed the sampling
 methodology to address community concerns regarding the more lethal method
 of the BsM protocol where gillnets are left overnight (16-22 hours).
 Because of differences in sampling between field seasons, we used the
 occurrence of fish species instead of catch-per-unit-effort. In our
 statistical analysis, we used occurrence data for the most common fish
 that were caught, including whitefish (<em>Coregonus
 clupeaformis</em> or <em>Coregonus nasus</em>), northern
 pike (<em>Esox lucius</em>) and least cisco
 (<em>Coregonus sardinella</em>).
 <strong>Water quality and chemistry
 data</strong> We measured a suite of water
 quality and chemistry parameters in lakes where macroinvertebrates were
 sampled. We obtained water clarity measurements using a Secchi depth at
 the deepest point of the lake by lowering the Secchi disk over the shady
 side of the boat. We used a Eureka Manta multiparameter probe (Eureka
 Water Probes) to take water quality measurements in the littoral zone at
 the same locations where macroinvertebrates were collected. The
 measurements were taken before collection of the invertebrates to avoid
 changes that might result from disturbing the sediment. The probe measured
 pH, conductivity, turbidity, and water temperature. Additionally, we
 collected a nearshore water sample to measure total suspended solids
 (TSS), chlorophyll-a¸ total phosphorus, total nitrogen, dissolved organic
 carbon, and calcium. To measure TSS, we followed standard operation
 procedures according to method 2540 D (Rice et al. 2017). We measured
 chlorophyll-a concentrations by filtering 250 mL of each water sample
 through Fisherbrand G4 glass fiber filters. We then used methanol to
 extract the chlorophyll-a from the filters and measured the concentration
 dissolved in the methanol using a fluorometer (Turner TD700) (Symons et
 al. 2012). We used a Perkin Elmer Optima 8000 Inductively Coupled Plasma
 Optical Emission Spectroscopy (ICP-OES) to measure calcium concentrations,
 and a Shimadzu TOC-LCPH carbon and nitrogen analyzer (Shimadzu Corp.) to
 measure dissolved organic carbon and total nitrogen. We measured total
 phosphorus by first digesting a portion of the sample in an autoclave
 using ammonium persulfate and sulfuric acid according to EPA method 365.1.
 Then, we used a SEAL Continuous Segmented Flow Analyzer (SEAL Analytical,
 Inc.) to measure total phosphorus colorimetrically. In
 addition to the described water quality parameters, we collected
 sediments, as they have been shown to be important in determining the
 structure of macroinvertebrate communities in lakes (De Sousa et al. 2008;
 Namayandeh and Quinlan 2011). We determined sediment size distribution by
 drying sediment samples at 105 °C for eight hours and then using a sieve
 shaker for ten minutes per sample to separate grain sizes using seven
 different sieve sizes (4 mm, 2 mm, 1 mm, 500 µm, 250 µm, 125 µm, 63 µm).
 To calculate % organic matter and % CaCO3 in sediments we used 5 g of
 sediment from each sample that was &lt;2 mm and followed the standard
 operating procedure for loss on ignition (Santisteban et al.
 2004).
 <strong>References</strong> De
 Sousa, S., Pinel-Alloul, B., and Cattaneo, A. 2008. Response of littoral
 macroinvertebrate communities on rocks and sediments to lake residential
 development. Can. J. Fish. Aquat. Sci. 65(6): 1206–1216.
 doi:10.1139/F08-031. Jones, F.C., Somers, K.M., Craig,
 B., and Reynoldson, T.B. 2007. Ontario benthos biomonitoring network:
 protocol manual. Available from
 https://desc.ca/sites/default/files/OBBN2007finalapril18c.pdf.
 McDermott, H., Paull, T., and Stachan, S. 2014. Canadian Aquatic
 Biomonitoring Network (CABIN) laboratory methods: Processing, taxonomy,
 and quality control of benthic macroinvertebrate samples.
 <i>In</i> Environment Canada.
 doi:10.1089/dna.1998.17.321. Rice, E.W., Baird, R.B.,
 and Eaton, A.D. (<i>Editors</i>). 2017. Standard methods for
 the examination of water and wastewater, 23rd edition. American Public
 Health Association, American Water Works Association, Water Environment
 Federation, Washington, D.C. Sandstrom, S., Rawson, M.,
 and Lester, N. 2013. Manual of instructions for broad-scale fish community
 monitoring; using North American (NA1) and Ontario small mesh (ON2)
 gillnets. Ontario Minist. Nat. Resour. Peterborough, Ontario. Version
 2013.2 35 p. + Append. Symons, C.C., Arnott, S.E., and
 Sweetman, J.N. 2012. Grazing rates of crustacean zooplankton communities
 on intact phytoplankton communities in Canadian Subarctic lakes and ponds.
 Hydrobiologia 694(1): 131–141. doi:10.1007/s10750-012-1137-6.