Lake Erie just can’t catch a break. The lake has experienced harmful algal blooms and severe oxygen-depleted “dead zones” for years, but now a team of researchers led by Carnegie’s Anna Michalak and Yuntao Zhou has shown that the widespread drought in 2012 was associated with the largest dead zone since at least the mid-1980s.
Until now, the size of the dead zone each summer and the factors explaining the variability from year to year have been elusive. Using 28 years of data collected in and around the lake, the team was able to “measure” the size of the dead zone each summer and identify factors that explain the year-to-year variability for the first time. They found that the 2012 drought, with extremely low water inflow from tributaries, was associated with a record-breaking dead zone in the lake, and that meteorological factors together with agricultural practices explain why these events vary annually. Previous studies have focused on phosphorous from agricultural runoff as the primary driver of the lake’s dead zones, but this analysis shows that the inflow of water from tributaries is actually the largest explanatory factor. The results are published in Environmental Science & Technology.