Effects of prolonged sedimentation from permafrost degradation on macroinvertebrate drift in Arctic streams

Abstract

Retrogressive thaw slumps are areas of unstable degraded permafrost that often drain into nearby watersheds, leading to increased sediment loads and changes in water quality. Thaw slumps are prevalent across the Arctic, including western Canada, Alaska, and Russia, and high‐altitude areas of western China. Over the past several decades, increased temperatures and precipitation in the Arctic have led to increases in the size and frequency of thaw slumps. Our study explored the effects of prolonged sedimentation from thaw slumps in the Peel Plateau, NWT, Canada on benthic macroinvertebrate drift, an important biological function of stream ecosystems. Though sedimentation is known to initiate a catastrophic drift response, studies have generally not considered the drift response to ongoing, long‐term perturbation. Drift densities and sediment loads were measured using drift nets and sediment traps at paired sites upstream and downstream of thaw slumps. We compared drift densities and sediment loads between sites and examined how drift differed over a fine‐sediment gradient. The amount of suspended and settling fine sediments increased significantly at downstream sites. Drift densities decreased at downstream sites; however, when drift was corrected for benthic abundance at each site, there was an increase in proportional drift density associated with increased fine sediments. These results indicate that prolonged impacts from thaw slumps result in lower macroinvertebrate abundance and higher proportional drift relative to undisturbed sites. Ultimately, increased sediment loads from thaw slumps represent a chronic stressor that will continue to prevent recovery of macroinvertebrate communities at impacted sites until these features stabilize.

Sentinel responses of Arctic freshwater systems to climate: linkages, evidence, and a roadmap for future research

“…Elevated concentrations of major ions in the form of significant increase in salinity (Cland Na + ) or changes in nutrient ions or metal contaminants (e.g., Hg and As) can have important implication for ecosystems. Also, because solute concentrations are conservative, easily monitored, and are good indicators of enhanced subsurface flows, or the exposure of permafrost soils through disturbance, dissolved ion loads can be important tracers of these geomorphological and hydrological changes that may have direct ecological effects (Chin et al 2016;Levenstein et al 2021). Electrical conductivity (EC) is an easily measured proxy of total ion concentration, that could be easily monitored in nearly any fluvial setting at very low cost with long-term stability (Gillman et al 2017).…”

Fisheries Volume 48 Number 7 July 2023

“…However, the effects of rising water temperature will alter a suite of changes within freshwater ecosystems and it is possible that warming could decrease the effi ciency of energy transfer between tropic levels (Barneche et al 2021 ). Additionally, in areas with prolonged sedimentation from retrogressive thaw slumps there is a potential for lower macroinvertebrate abundance until features stabilize (Levenstein et al 2021 ), which will offset some positive effects of warmer water temperatures. These changes will likely lead to larger size-at-age due to a combination of longer growing season and faster growth rates in many habitats (Fechhelm et al 1992 ;Carey and Zimmerman 2014 ).…”

Climate Change Risks to Freshwater Subsistence Fisheries in Arctic Alaska: Insights and Uncertainty from Broad Whitefish Coregonus nasus

“…However, the effects of rising water temperature will alter a suite of changes within freshwater ecosystems and it is possible that warming could decrease the efficiency of energy transfer between tropic levels (Barneche et al 2021). Additionally, in areas with prolonged sedimentation from retrogressive thaw slumps there is a potential for lower macroinvertebrate abundance until features stabilize (Levenstein et al 2021), which will offset some positive effects of warmer water temperatures. These changes will likely lead to larger size‐at‐age due to a combination of longer growing season and faster growth rates in many habitats (Fechhelm et al 1992; Carey and Zimmerman 2014).…”