Novel zooplankton community compositions in lakes that have recovered from acidification in Sudbury, Ontario

Abstract

Biomonitoring has repeatedly been proven to be an effective tool in assessing aquatic ecosystems and is especially useful in historically stressed environments like Sudbury area lakes, that are on an acid-recovery trajectory while facing contemporary changes including urbanization, calcium declines, climate change and lake brownification. Due to the varied ranges of sensitivities among different species, zooplankton are important bioindicator taxa of pelagic waters often used in biomonitoring. Their crucial link between primary producers and fish communities also make them important taxa for monitoring. After decades of water chemistry improvements in Sudbury, crustacean zooplankton communities have sometimes lagged in recovery that may be attributable to factors such as dispersal, residual metal toxicity, biotic resistance, and incomplete food webs. I conducted a broad spatial survey of 58 historically acidified lakes and 24 reference lakes in the Sudbury acid deposition zone and 5 remote reference lakes to understand the current variation in pelagic zooplankton community compositions in lakes along numerous gradients of change to and to determine the recovery status of zooplankton communities. My results show that zooplankton communities in lakes that have chemically recovered from historical acidification do not resemble reference compositions after over four decades since emission reductions, suggesting a shift to alternate community compositions due to changing contemporary environmental factors.