From carbon sequestration to algae blooms: remote lakes as sentinels of global change

Dr. Adam Heathcote

Senior Director of the Department of Water and Climate Change and the St. Croix Watershed Research Station at the Science Museum of Minnesota

Abstract

Lakes are integrators of their surrounding environment and sentinels for global change.  They are among the fastest warming ecosystems on the planet, often exhibiting rates of warming that outpace coincident increases in air temperature. This effect is especially pronounced in our most northern biomes, where the impact of climate change on lake ice has been shown to compound this effect and may have indirect effects on nutrient cycling in these sensitive ecosystems.  I will present results from two studies looking at how global change drivers, including warming, have impacted ecosystem functioning in lakes.  The first study will look at a set of lakes in one of the most protected environments in North America, the Boundary Waters Canoe Area Wilderness, with the purpose of documenting and diagnosing a recent wave of observed harmful algal blooms which have alarmed local resource managers and stakeholders.  The second study is pan-Arctic synthesis of carbon sequestration in lakes. We have assembled the largest dataset of radiosotopically dated sediment cores from the Arctic and quantified the trajectory and magnitude of carbon burial over the last 100 years.  Using this dataset, we also produced a predictive model to upscale our estimates to lakes across the entire Arctic and predict future contributions of Arctic lakes to the global carbon cycle on a progressively warming planet. Together, these studies demonstrate the sensitivity of northern ecosystems to global change and quantify the already significant impacts warming is having on these systems.