Return from the dead: Great Lakes shift toward more pristine conditions due to phosphorus reduction and dreissenid mussels

Lake Erie, once declared (erroneously) dead by the media in the 1960s, has joined at least two other lakes (Huron and Michigan) in a shift toward more oligotrophic conditions due to the dual anthropogenic influences of phosphorus reductions and reductions/shifts in algal communities due from pervasive filtering activities of zebra and quagga mussels.   These reductions in nutrients have cascaded through food webs effecting declines in zooplankton and Diporeia, which feed on algae, reduced recruitment of many fishes, declines of major forage fishes, especially the alewife in Lake Huron, and severe drops in top predators, especially stocked salmon.  As Lake Huron has moved toward more pristine conditions, there has been a dramatic increase in walleye natural reproduction in Saginaw Bay, due to reduced predation on larval forms or competition for food by alewives.  There is also evidence of more recruitment of lake herring, which were almost extirpated from Lake Huron, resurgence of emerald shiners, and higher abundances of naturally produced lake trout.  Lake Michigan has lagged behind Lake Huron.  In Lake Erie, walleye have also expanded their abundances and Hexagenia, the burrowing mayfly, once almost extirpated from the lake, have returned as anoxia has abated, nutrient inputs decreased, and contaminants reduced.