| To determine the influence of drawdown on littoral sediments and benthic communities, I compared temporal and spatial changes in sediment physical and biogeochemical properties, benthic macroinvertebrate communities, and chironomid communities of a drinking water reservoir that experiences more than six meters of seasonal drawdown (Sooke Lake Reservoir) to a nearby, morphometrically and trophically similar lake that experiences less than one meter of water level change (Shawnigan Lake). Drawdown impacted sediment physical and biogeochemical characteristics and the density, biomass, composition, and distribution of benthic macroinvertebrate communities. The benthic macroinvertebrate community in Sooke had unique structural and functional attributes compared to Shawnigan, especially with respect to the chironomid community. Similarities in zoobenthic biomass between Sooke and Shawnigan suggest that littoral benthic fauna may be more resilient to repeated drawdown than previously thought and the drawdown adapted benthic macroinvertebrates are as abundant and diverse in reservoirs as natural lakes of similar morphometry and productivity. |
