Cyanobacterial blooms in remote lakes of the U.S. Upper Midwest during past climate variability

The ecological factors that promote or impede formation of cyanobacterial harmful algal blooms (cyanoHABs) are poorly understood, and large uncertainty remains about how climate interacts with other drivers to shape cyanoHABs. While much research has focused on cyanoHAB development in eutrophic systems, there are increasingly more observations of cyanobacterial blooms in low to moderate productivity lakes, raising questions about specific climate drivers involved. We examined the history of cyanobacterial blooms in three remote lakes on Isle Royale National Park in the Upper Midwest of the U.S. Contemporary observations reveal that two of these lakes experience frequent cyanobacterial blooms in the summer; it was unclear whether this was a recent phenomenon and to what extent climate played a role. Paleolimnological records capturing the past 2,000 years of algal community structure revealed that the recent blooms in these two lakes began in the 1970s. Prior to that, all three lakes demonstrated cyanobacterial blooms during the Roman Warm Period (RWP; 1-300 CE), a warm and dry period in this region, whereas only moderate changes in algal blooms occurred during the Medieval Climate Anomaly (800-1300 CE), a warm but hydrologically variable period. These results from remote lakes demonstrate the ongoing importance of both temperature and hydrologic variability in driving cyanobacterial blooms.

Presentation Preference: Oral

Primary Presenter: Jasmine Saros, University of Maine (jasmine.saros@maine.edu)

Authors:

Jasmine Saros, Climate Change Institute, University of Maine  (jasmine.saros@maine.edu)

Rachel Fowler, University of Maine  (rachel.a.fowler@maine.edu)

Mark Edlund, St. Croix Watershed Research Station, Science Museum of Minnesota  (medlund@smm.org)

Adam Heathcote, St. Croix Watershed Research Station, Science Museum of Minnesota  (aheathcote@smm.org)

Daniel Engstrom, St. Croix Watershed Research Station, Science Museum of Minnesota  (001dre@gmail.com)

Charles Umbanhowar, Departments of Biology & Environmental Studies, St. Olaf College  (ceumb@stolaf.edu)

Jeffery Stone, Department of Earth & Environmental Systems, Indiana State University  (jeffery.stone@indstate.edu)

Kristin Strock, Department of Environmental Science, Dickinson College  (strockk@dickinson.edu)

David VanderMeulen, Great Lakes Inventory & Monitoring Network, U.S. National Park Service  (David_VanderMeulen@nps.gov)

Mark Romanski, Isle Royale National Park, U.S. National Park Service  (Mark_Romanski@nps.gov)