DOI: 10.5061/dryad.0gb5mkm96
title: Environmental and food web determinants of Lake Trout mercury concentrations in Ontario Lakes

description: Prey composition and availability are considered a primary predictor of
 Lake Trout (Salvelinus namaycush) mercury (Hg) concentrations. Evidence
 from other freshwater fishes suggests that environmental and landscape
 factors likely also contribute to fish Hg dynamics, yet comprehensive,
 contemporary assessments for Lake Trout from boreal and north-temperate
 lakes are lacking. Here, we reassess the importance of prey
 characteristics using both previously published and contemporary data,
 incorporating additional variables and model complexity to better
 understand factors influencing Hg dynamics of Ontario Lake Trout. Our
 analyses indicate that 1) Lake Trout Hg concentrations are primarily
 associated with individual body size, 2) high dissolved organic carbon
 (DOC) concentrations elevate Hg for fish of a given size, and 3) a coarse
 categorization of food chain length, specifically the presence of Mysis
 diluviana, informs Hg biomagnification slopes. The inclusion of DOC was
 vital for assessing human consumption risk, as Lake Trout in high DOC
 lakes were more likely to exceed Hg guidelines at sizes often harvested by
 anglers. Drivers of Lake Trout Hg levels in boreal and north-temperate
 lakes closely match those reported to affect other fishes in the region,
 regardless of feeding, thermal, and habitat strategies.
description: # Environmental and food web determinants of Lake Trout mercury
 concentrations in Ontario lakes
 [https://doi.org/10.5061/dryad.0gb5mkm96](https://doi.org/10.5061/dryad.0gb5mkm96) Raw data associated with two Lake Trout Hg datasets. ### Cabana.et.al(1994)\_cjfasMercuryData.csv 1\) Cabana et al. (1994) summary data. These data were transposed from the tables published within the main publication [Cabana.et.al(1994)_cjfasMercuryData.csv] *ColumnID; Column Info; Unit; Notes* * SPC; Species name; n/a; lt = Lake Trout, Sm = Smallmouth Bass * Lk_Nm; Lake name; n/a; n/a * LATD; Latitude; degrees; n/a * LATM; Latitude; minutes; n/a * LONGD; Longitude; degrees; n/a * LONGM; Longitude; minutes; n/a * Region; Region; units; All cells intentionally left blank though initial manuscript has northern and southern region distinction * Lat_DD; Latitude, decimal degrees; n/a * Long_DD; Longitude, decimal degrees; n/a * AREA_ha; Lake surface area; hectares; n/a * ZMax_m; Max lake depth; m; n/a * pH; Lake pH; unitless; n/a * Cond_us_cm; Specific conductivity; micro Seimans per centimeter; n/a * Secchi_m; Secchi depth; meter; n/a * Mysis; Mysis presence/absence; 0 = absent, 1 = present * Foragefish; Cisco, Lake Whitefish, and/or Rainbow Smelt presence/absence; 0 = absent, 1 = present * Weight_g; Mean fish round weight per lake; grams; n/a * Hg_ug_g; Mean fish mercury concentration wet/weight per lake; microgram mercury per gram fish tissue; n/a * n; Sample size; whole integer; n/a For ColumnIDs Area_ha to Secchi_m, the presence of a period (i.e., ".") indicates a missing value, as was reported in the initial Cabana et al. (1994) manuscript ### allMercAndPredictorData\_20250320.csv 2\) Fish Hg data summarized from the Ontario Ministry of Environment, Conservation and Parks as well as from the IISD-ELA, as well as environmental covariates taken from IISD-ELA and Ontario Ministry of Natural Resources databases [allMercAndPredictorData_20250320.csv] *ColumnID; Column Info; Unit; Notes* * lakeName; Lake name; n/a; n/a * waterbodyID; Waterbody code ID; n/a; n/a * biopsyID; Muscle biopsyID; n/a; NA indicates no biopsy was taken on the fish * pit; Pit tag ID; n/a; NA indicates no pit tag implanted or recovered * speciesName; Fish species; n/a; n/a * yearSample; Sample year; n/a; n/a * dateSample; Calendar sample date; n/a; n/a * length_mm; Total fish length; millimeter; NA indicates missing data * weight_g; Round weight; grams; NA indicates missing data * Hg_Wet_ugG; Fish mercury concentration wet/weight per individual; microgram mercury per gram fish tissue; n/a * comments; Individual specific comments; n/a; No comments indicated by both NA or blank cells * sex; Sex of fish; n/a; 1 = male, 2 = female, 9 = sex could not be determined, NA = no information provided * age; Fish age; years; NA = no age assigned * forkLength; Individual fork length; millimeter; n/a * totalLength; Individual total length; millimeter; n/a * lakeClass; Categorical Prey Lake Class; n/a; 1 = no Mysis or pelagic prey fish, 1.5 = Mysis present but not pelagic prey fish, 2 = no Mysis but pelagic prey fish present, 3 = both Mysis and pelagic prey fish present * lat; Latitude; decimal degrees; taken from lake centroid * long; Longitude; decimal degrees; taken from lake centroid * surfaceArea; Lake surface area; hectares; NA indicates no information was available * lakeVolume; Lake volume; cubic meters; NA indicates no information was available * maxDepth; Maximum lake depth; meter; NA indicates no information was available * meanDepth; Mean lake depth; meter; NA indicates no information was available * Ca; Lake calcium concentration; mg/L; NA indicates no information was available * DIC; Lake dissolved inorganic carbon; mg/L; NA indicates no information was available * DOC; Lake dissolved organic carbon; mg/L; NA indicates no information was available * Na; Lake sodium concentration; mg/L; NA indicates no information was available * TDP; Lake total dissolved phosphours; ug/L; NA indicates no information was available * alk; Lake alkalinity; meq/L; NA indicates no information was available * cond; conductivity; us/cm; NA indicates no information was available * pH; Lake acidity pH; unitless; NA indicates no information was available * ChlA; Lake chlorophyll-a concentration; ug/L; NA indicates no information was available * NO2; Lake nitrite concentration; mg/L; NA indicates no information was available * NO3; Lake nitrate concentration; mg/L; NA indicates no information was available * PARTP; Lake particulate phosphorus; ug/L; NA indicates no information was available * TDN; Lake total dissolved nitrogen concentrations; ug/L; NA indicates no information was available * gdd5c_30yrNorm; 30-year norm of cumulative growing degree days above 5 degrees Celsius for a given lake; degrees Celsius; NA indicates no information was available In addition to data, R code is provided to create all data summaries, statistics, and visualizations ## Code/Software All Code was run in R, version 4.4 Packages and version numbers include: * merTools: v. 0.6.2 * tidyVerse: v. 2.0 * here: v. 1.0.1 * lme4: v. 1.1-35.3 * lmerTest: v. 3.1-3 * MuMin: v. 1.47.5 * patchwork: v. 1.2.0 * vegan: v. 2.6-4 * randomForestSRC: v. 3.2.3 * ggRandomForests: v. 2.2.1 * gt: v. 0.10.1 * gtExtras: v. 0.5.0 * readxl: v. 1.4.3