labs_title

Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions

A.M. Michalak, E.J. Anderson, D. Beletsky, S. Boland, N.S. Bosch, T.B. Bridgeman, J.D. Chaffin, K. Cho, R. Confesor, I. Daloglu, J.V. DePinto, M.A. Evans, G.L. Fahnenstiel, L. He, J.C. Ho, L. Jenkins, T.H. Johengen, K.C. Kuo, E. LaPorte, X. Liu, M.R. McWilliams, M.R. Moore, D.J. Posselt, R.P. Richards, D. Scavia, A.L. Steiner, E. Verhamme, D.M. Wright and M.A. Zagorski

In 2011, Lake Erie experienced a record-setting algal bloom covering over 5000 km2 at its peak and having a variety of ecological, health, and economic impacts. In this study, we show that the bloom was caused by a combination of trends in agricultural management practices and extremes in meteorological conditions. All of the factors found to have contributed to this bloom are also consistent with ongoing trends in land use and climate, supporting the idea that the 2011 bloom may be a harbinger of future blooms.


Figure: MODIS satellite Image of Lake Erie on September 3, 2011, overlaid over map of Lake Erie tributaries. This image shows the bloom about 6 wk after its initiation in the western basin. On this date, it covers the entire western basin and is beginning to expand into the central basin, where it will continue to grow until October.

Abstract

In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with a peak intensity over three times greater than any previously observed bloom. Here we show that long-term trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with meteorological conditions in spring 2011, produced record-breaking nutrient loads. An extended period of weak lake circulation then led to abnormally long residence times that incubated the bloom, and warm and quiescent conditions after bloom onset allowed algae to remain near the top of the water column and prevented flushing of nutrients from the system. We further find that all of these factors are consistent with expected future conditions. If a scientifically guided management plan to mitigate these impacts is not implemented, we can therefore expect this bloom to be a harbinger of future blooms in Lake Erie.

Michalak, A.M., E.J. Anderson, D. Beletsky, S. Boland, N.S. Bosch, T.B. Bridgeman, J.D. Chaffin, K. Cho, R. Confesor, I. Dalo─člu, J.V. DePinto, M.A. Evans, G.L. Fahnenstiel., L. He, J.C. Ho, L. Jenkins, T.H. Johengen, K.C. Kuo, E. LaPorte, X. Liu, M.R. McWilliams, M.R. Moore, D.J. Posselt, R.P. Richards, D. Scavia, A.L. Steiner, E. Verhamme, D.M. Wright, M.A. Zagorski (2013) “Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions”, Proceedings of the National Academy of Sciences, 110:16, 6448-6452, 10.1073/pnas.1216006110.