Sediment delivery from thermo-erosional gullies alters macroinvertebrate community dynamics in headwater streams on the North Slope, Alaska

Recent research has highlighted increased permafrost degradation and formation of thermo-erosional thaw-features across the Arctic landscape as a consequence of a warming climate. These thaw-features, or thermokarst, influence sediment and nutrient delivery to adjacent streams. Data collected in summers 2010 and 2011 near Toolik Lake, Alaska revealed a near doubling of total sediment deposited in downstream areas (~250m) impacted by thermokarst features relative to unaffected upstream reference reaches. Early summer samples in both years indicated an increase in macroinvertebrate abundance with a decrease in diversity, but trends were opposite later in the season. A significant decrease in grazer abundance late in the season may support the hypothesis that sediment decreases the quality of epilithic food sources. The effects of thermokarst features may be relatively local and short lived, but this study showed that some impacts on ecosystem function can last beyond the initial disturbance.