With no zooplankton to eat them, there was no natural control for the
populations of phytoplankton in the lakes. At the same time, we humans – who
until now had little reason to treat our sanitary or industrial waste – were
fertilizing the rivers and lakes with nutrients. With all the nutrients they could
consume and few natural predators, phytoplankton populations exploded –
causing the now infamous death of Lake Erie, robbing Lake Michigan of oxygen,
thereby killing millions of alewifes near Chicago, and strangling Green Bay.
None of this was done with malice and forethought. The men who spent
winters in lumber camps did not set out to cause the collapse of the Great Lakes
fishery. The commercial fishermen who stacked lake sturgeon like cordwood
did not intend to drive the species close to extinction. The steel industry greatly
expanded its operations in the basin to win the Second World War, not poison
the lakes. Cities built sewers to protect their populations, not to over-enrich
Lake Erie.