Dissolved organic carbon in eastern Canadian lakes: Novel patterns and relationships with regional and global factors

Md Noim Imtiazy; Andrew M Paterson; Scott N Higgins; Huaxia Yao; Suzanne Couture; Jeff J Hudson

doi:10.1016/j.scitotenv.2020.138400

Dissolved organic carbon in eastern Canadian lakes: Novel patterns and relationships with regional and global factors

Sci Total Environ. 2020 Jul 15:726:138400. doi: 10.1016/j.scitotenv.2020.138400. Epub 2020 Apr 8.

Authors

Md Noim Imtiazy¹, Andrew M Paterson², Scott N Higgins³, Huaxia Yao⁴, Suzanne Couture⁵, Jeff J Hudson⁶

Affiliations

¹ Department of Biology, University of Saskatchewan, Collaborative Science Research Building, 112 Science Place, Saskatoon, SK S7N 5E2, Canada. Electronic address: noim.imtiazy@usask.ca.
² Ontario Ministry of the Environment, Conservation and Parks, Dorset Environmental Science Centre, 1026 Bellwood Acres Road, Dorset, ON P0A 1E0, Canada. Electronic address: Andrew.Paterson@ontario.ca.
³ IISD - Experimental Lakes Area Inc., 111 Lombard Ave. Suite 325, Winnipeg, MB R3B 0T4, Canada. Electronic address: shiggins@iisd-ela.org.
⁴ Ontario Ministry of the Environment, Conservation and Parks, Dorset Environmental Science Centre, 1026 Bellwood Acres Road, Dorset, ON P0A 1E0, Canada. Electronic address: Huaxia.Yao@ontario.ca.
⁵ Environment and Climate Change Canada, Water Science and Technology, 105 McGill Street, Montreal, QC H2Y 2E7, Canada. Electronic address: suzanne.couture2@canada.ca.
⁶ Department of Biology, University of Saskatchewan, Collaborative Science Research Building, 112 Science Place, Saskatoon, SK S7N 5E2, Canada. Electronic address: jeff.hudson@usask.ca.

PMID: 32315845
DOI: 10.1016/j.scitotenv.2020.138400

Abstract

Long-term patterns in dissolved organic carbon (DOC) concentrations in 49 eastern Canadian lakes from four sites were re-examined with a ~ 35-year (~1980-2015) dataset. The study sites were Dorset (number of lakes, n = 8), Experimental Lakes Area (ELA, n = 4), Kejimkujik (n = 26) and Yarmouth (n = 11). Lake DOC patterns were synchronous within each site. However, comparisons of DOC patterns across sites showed that they were synchronous only between the Kejimkujik and Yarmouth locations. Hence, these two sites were pooled into a single Nova Scotia site (NS). Increases in DOC concentration were evident in Dorset, Ontario from 1988 (r² = 0.78, p < 0.001) and NS from 2000 (r² = 0.43, p = 0.006). DOC at the ELA in northwestern Ontario had a different pattern compared to the other sites, i.e., DOC had increased earlier (1983-2000), and then, unlike Dorset and NS, neither an increase nor decrease was detected between 2001 and 2015 (p = 0.78). Precipitation and sulfur deposition explained the greatest variance in DOC patterns at the Dorset and NS sites (i.e., precipitation: 21-49% and sulfur deposition: 24-54%). Precipitation was the most important driver of DOC at the ELA. Our results indicate that all the sites have gone through a process of increasing DOC, but at different times. The stabilizing pattern at the ELA since 2001 may suggest that DOC concentrations in ELA lakes have reached, or are approaching a new equilibrium, a phenomenon that was not observed at the other sites. Also, the increase in DOC was not always associated with declining sulfur deposition (e.g., ELA). Therefore, we conclude that there was considerable variation in DOC patterns across this large geographic region of Canada and potential drivers of these patterns were not consistent across these diverse sites.

Keywords: Global variables; Long-term DOC pattern; Precipitation; Stabilized DOC; Sulfur deposition; Temporal coherence.