Changes in lake sediment carbon accumulation rates in southwestern Canada since the mid-1800s.

Abstract

Carbon (C) storage in lakes is an increasingly recognized component of the global C cycle. Yet, rates of C accumulation in lake sediments remain poorly quantified in some regions such as in Canada. This study assessed C stocks and C accumulation rates (CARs) in sediments from 18 lakes across four provinces and seven national parks in southwestern Canada. We analyzed temporal and spatial variability in CARs and examined their relationship with landscape characteristics (e.g., land use and lake morphology) and climate variables (e.g., temperature and precipitation). Fourteen lakes showed increasing trends in CAR between 1830 and 2009. The average CAR during the modern period (1980–2009) was 42.8 ± 2.6 g/m²/year, representing a 14% increase compared to the historical period (1920–1949). Variability in CARs was primarily explained by temperature-related factors, including mean annual temperature, degree-days under 0 °C, and seasonal temperatures, particularly in spring and summer. Land use also played a significant role as the percentage of catchment area dedicated to agriculture and development was a strong predictor of CAR increases. These findings indicate that rising temperatures and intensified land use are key drivers of enhanced C accumulation in southwestern Canadian lakes, trends likely to continue under ongoing climate change.