Long-term carbon burial in European lakes: Analysis and estimate

Sediment accumulation in lakes provides a small but permanent carbon sink. To date, global estimates of the C cycle have barely considered variations in lake carbon burial. To improve the understanding of carbon storage in lakes this study analyzed the sedimentary record of 228 European lakes concerning long-term carbon burial and its correlation to lake and catchment properties. The results suggest that carbon mass accumulations in small lakes are significantly lower than those used for global estimates so far. On the other hand, the total surface area of small lakes has been severely underestimated. Results from calculations based on a Pareto distribution show that total lake surface is 240,000 km2 in Europe. We estimate total C burial in European lakes at 1.25 Mt yr−1. Half this storage takes place in boreal lakes of northern Europe, although they contribute up to 65% to the European lake surface. This is due to generally lower carbon burial rates in this region. Carbon mass accumulation rates increased in many lakes between 5000 to 2000 years BP. This coincides with increased clastic inputs due to land use change, i.e., increasing cropland coverage and soil erosion. On average, carbon accumulation rates are twice as high in younger sediments at 20 cm depth when compared to the long-term mean