Runoff from farming operations and other sources has resulted in an excess of phosphorus in Great Lakes waters.
This nutrient stimulates algal blooms, which degrade freshwaters by stripping out essential oxygen and killing fish and aquatic insects.
Meanwhile, in the 20th Century alone, more than 80 invasive species were intentionally or accidentally introduced into the Great Lakes. Some of these invaders, such as the zebra mussel and Goby consume or displace resources normally eaten by native fish.
The dual pressures of invasives and pollution led to Lake Erie being deemed “dead” in the 1950s and 60s. Policy changes allowed the lake to rebound – until now. This summer, Lake Erie suffered its worst algal bloom in decades
A recent report from the National Wildlife Federation says nutrient quality has been declining in the lakes for the past decade. Julie Mida Hinderer, an author on the report, says the way we look at the Great Lakes has to change.
“Both of these problems are largely driven by invasive zebra and quagga mussels, but they’re also exacerbated by direct human impacts such as land use, so we have this new, unprecedented ecosystem regime that means we can’t continue to study and manage the lakes as we did in the past.”
Invasive mussels have displaced a small shrimp that is an essential food for sport fish. This has lead to a decline in salmon and walleye populations and dealt a major hit to the fishing industry in the Great Lakes.
The report was submitted to Congress this fall, but no specific action has come yet.