Water Resources Research Act Program

Details for Project ID 2019VT262B

Response of phytoplankton communities to recovery from acidification in Vermont lakes

Institute: Vermont
Year Established: 2019 Start Date: 2019-06-18 End Date: 2020-06-17
Total Federal Funds: $9,999 Total Non-Federal Funds: $20,146

Principal Investigators: Ana M. Morales-Williams

Abstract: Problem: Surface waters in the Northeastern United States are currently recovering from acidification that occurred prior to 1970. Many lakes in the state of Vermont impacted by acid deposition have been slow to recover due to a low buffering capacity pre-acidification, making them less resilient to pH change. Twelve lakes in the state are recognized as acid-impaired and have been monitored monthly for chemical and physical parameters by the Vermont Department of Environmental Conservation (VT DEC) since 1980. While these data demonstrate that lake chemistry is improving, little is known about the biological response of aquatic communities because biological data have not been collected as part of the long-term monitoring program. Over the past 40 years, spring phosphorus concentrations have doubled in all oligotrophic lakes in Vermont monitored by the VT DEC (n equaling 22). Coupled with warming surface waters and an increase in intense storm events, acid recovery has the potential to support an increase in primary production, but it is unclear if acid-impaired lakes are at risk of developing harmful cyanobacteria blooms as has occurred in other low-nutrient lakes in the Northeast. Methods and Objectives: Because phytoplankton community data has not been collected in Vermont’s 12 acid-impaired lakes since initial sampling in 1980, the goal of the proposed research is to characterize water column phytoplankton communities (diatoms and soft algae) and the presence or absence of cyanobacteria resting cells (akinetes) in shallow sediments. Together with comprehensive long-term physical and chemical data collected by the VT DEC, these data will inform the presence or absence and potential for emergence of bloom-forming cyanobacteria. We will identify indicator species of planktonic diatoms to further inform trophic status of these rapidly changing ecosystems. In addition to observational data, we will conduct microcosm experiments in four of twelve lakes in which we manipulate nutrient concentrations along an experimental gradient of predicted pH and temperature increase. Results of these experiments will inform threshold ecological conditions for community shifts to bloom-forming cyanobacteria. The primary objective of this study is to assess the risk of Vermont’s acid-impaired lakes to harmful cyanobacteria blooms. As these sensitive ecosystems recover, increasing pH, warming surface waters, and increased nutrient concentrations may collectively pose a new danger to water quality. Because cyanobacteria blooms are increasing in frequency and intensity globally, it is critical to assess this risk early and inform mitigation strategies before ecological state shifts occur..