Effects of the White River Ash Event on Aquatic Environments, Southwest Yukon, Canada

Abstract

Chironomid and sedimentary records from four lakes in the southwest Yukon reveal that the effects of the White River Ash event on aquatic environments varied with distance from the source vent, with sites closer to the source experiencing a greater impact. Upper Fly and Jenny Lakes, located ~200 km away from the volcano, had the thinnest ash layers. The Upper Fly site showed no response to the fallout of the ash, but at Jenny Lake the ash event affected the lake environment for almost 20 years. Donjek Kettle and Lake WP02, which were closer to the source (~100 km), had considerably thicker ash layers that substantially affected the aquatic ecosystems. Initial impacts of the tephra on the aquatic environments at these sites lasted about 60 years; however, the chronic effects of the tephra deposition on the chironomid community continued for up to 40 years longer. Chironomid community abundance declined in the lake environments affected by White River Ash fallout following the event. However, species composition remained the same after recovery of the aquatic ecosystem as in the pre-deposition chironomid community.