Lake carbon

Glob. Change Biol. http://doi.org/r85 (2014)

Credit: © ROBERT HARDING PICTURE LIBRARY LTD / ALAMY

Excess nutrient levels in many lowland lakes in Europe and North America have led to declines in water quality and, in some cases, fish stocks. However, an analysis of European lake sediments suggests there may be one positive consequence of lake eutrophication: an increase in carbon burial.

John Anderson, of Loughborough University, UK, and colleagues examined the relationship between lake phosphorus levels and organic carbon burial using sediment core data collected from more than 90 European lowland lakes. On average, lake carbon burial increased from around 17 g carbon m⁻² yr⁻¹ in the nineteenth century to around 40 g m⁻² yr⁻¹ in the first half of the twentieth century, and around 60 g m⁻² yr⁻¹ in the latter half. The carbon burial rate reached in the second half of the twentieth century was four to five times greater than the global average. This rise in lake carbon burial was associated with an increase in lake phosphorus levels and rising fertilizer use in Europe. The researchers argue that the positive correlation between lake carbon burial and phosphorus levels points to eutrophication as a principal driver of the increased burial.

If these burial rates apply to other lakes throughout the continent, European lakes may be sequestering three times more carbon than previously thought, the researchers suggest.