Spatial and temporal variation in Arctic freshwater chemistry—Reflecting climate‐induced landscape alterations and a changing template for biodiversity

• Published in: Freshwater Biology
• Main Authors: Huser, Brian J., Futter, Martyn N., Bogan, Daniel, Brittain, John E., Culp, Joseph M., Goedkoop, Willem, Gribovskaya, Iliada, Karlsson, Jan, Lau, Danny C. P., Rühland, Kathleen M., Schartau, Ann Kristin, Shaftel, Rebecca, Smol, John P., Vrede, Tobias, Lento, Jennifer
• Other Authors: Environment and Climate Change Canada
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: Arctic; permafrost
• Online Access: http://dx.doi.org/10.1111/fwb.13645; https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.13645; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/fwb.13645

Abstract Freshwater chemistry across the circumpolar region was characterised using a pan‐Arctic data set from 1,032 lake and 482 river stations. Temporal trends were estimated for Early (1970–1985), Middle (1986–2000), and Late (2001–2015) periods. Spatial patterns were assessed using data collected since 2001. Alkalinity, pH, conductivity, sulfate, chloride, sodium, calcium, and magnesium (major ions) were generally higher in the northern‐most Arctic regions than in the Near Arctic (southern‐most) region. In particular, spatial patterns in pH, alkalinity, calcium, and magnesium appeared to reflect underlying geology, with more alkaline waters in the High Arctic and Sub Arctic, where sedimentary bedrock dominated. Carbon and nutrients displayed latitudinal trends, with lower levels of dissolved organic carbon (DOC), total nitrogen, and (to a lesser extent) total phosphorus (TP) in the High and Low Arctic than at lower latitudes. Significantly higher nutrient levels were observed in systems impacted by permafrost thaw slumps. Bulk temporal trends indicated that TP was higher during the Late period in the High Arctic, whereas it was lower in the Near Arctic. In contrast, DOC and total nitrogen were both lower during the Late period in the High Arctic sites. Major ion concentrations were higher in the Near, Sub, and Low Arctic during the Late period, but the opposite bulk trend was found in the High Arctic. Significant pan‐Arctic temporal trends were detected for all variables, with the most prevalent being negative TP trends in the Near and Sub Arctic, and positive trends in the High and Low Arctic (mean trends ranged from +0.57%/year in the High/Low Arctic to −2.2%/year in the Near Arctic), indicating widespread nutrient enrichment at higher latitudes and oligotrophication at lower latitudes. The divergent P trends across regions may be explained by changes in deposition and climate, causing decreased catchment transport of P in the south (e.g. increased soil binding and trapping in terrestrial vegetation) and ...