Data from: Effect of canal lock presence on macroinvertebrate diversity and community composition

We assessed the influence of canal lock presence on macroinvertebrate diversity and community composition by comparing two stretches of the Leeds-Liverpool canal using a cost-effective, replicable method. Specifically, our investigation sought to: (1) assess whether the diversity of aquatic macroinvertebrates is linked to the presence of canal locks and to differences in biophysical conditions; (2) assess differences in water pollution using biotic indices across the lock and control areas; (3) examine how macroinvertebrate community structure varies between a lock-dominated and lock-lacking (‘control’) area. Methods We sampled two areas of the Leeds-Liverpool canal in Lancashire: an area with high lock density in Lathom (53.590°N 2.820°W) and a control area without locks in Halsall (53.584°N 2.953°W). Six sites were sampled per area, with each site spaced ~400m apart along a 2.5 km transect route (Fig. 1). See "Context_of_twelve_sampling_sites" for characteristics on each sampling site. Distance from urban settlement was measured by canal length from the closest sampling site to an urban source. Urban settlements were defined using the Major Towns and Cities boundaries dataset (Office for National Statistics, 2015). Each site was visited three times between June and August 2022, on the same day and within a four hour window. Salinity, temperature and pH were measured using a Hanna Waterproof Salinity Tester (model HI-98319) and Preciva pH Meter (model 2011). Invertebrate samples were collected using sweep sampling: a pond net attached to an extendable pole was used to sweep along the bottom of the canal to disturb the canal bed at ~1.5 m distance from the canal edge, then was moved in figure-of-eight motion six times before being removed. Invertebrates were identified ex situ to family level on the same day as collection to minimise the likelihood of predation within samples. See "Macroinvertebrate_data_raw.csv" for this data. Taxonomic diversity was calculated using Hill numbers (q = 0, 1, 2: corresponding to species richness, Hill-Shannon and Hill-Simpson) from abundance data using the “hillR” package (Li, 2018) R (v. 4.3.3; R Core Team, 2024). Abundance counts were summed by site, then were used to derive three Hill diversity values per site. Three biotic indices were calculated to assess water quality using the “biotic” R package (Briers, 2016): the British Monitoring Working Party score (BMWP) and Average Score Per Taxon (ASPT) were calculated using the [biotic::calcBMWP] fuction, then the Walley Hawkes Paisley Trigg score ASPT (WHPT-ASPT) index using [biotic::calcWHPT]. The Enchytraeidae and Lumbriculidae families were merged into an Oligochaetes subclass to allow for these counts to be included in the indices. See "Hill_diversity_and_biotic_indices_scores_per_site.csv" for this data. Funding No funding was recieved for this research, which was initially conducted at Liverpool Hope University for CBR's Masters of Science dissertation in summer 2022.