Snow avalanche‐induced disturbances can resurrect extinct zooplankton and alter paleolimnological records

We present a detailed observational study of the effects of the impulse wave caused by a snow‐avalanche on an alpine lake (Lake Peñalara, Sierra de Guadarrama, Spain). The avalanche broke the lake's ice cover (> 50 cm thick) and caused the lake to overflow. The impulse wave altered the lake water column stratification and physicochemical properties (dissolved oxygen, conductivity) in the short (hours) and mid‐term (days and weeks). It also caused the mobilization of hundreds of cubic meters of sediment, changing the lake morphometry. The sediment reconfiguration is likely the cause of the observed increased sedimentation rate and changes in the zooplankton density and composition in the following 4 yr after the avalanche, including the resurrection of a cladoceran species (Daphnia pulicaria) that had disappeared from the lake decades ago. Events such as the one we present can have significant paleolimnological implications: in this case, 75 cm of the sediment sequence were lost. Given these results, we propose that past avalanches could be the explanation to the almost complete removal of sediment from the deepest part of the lake around 260 yr cal BCE.