Dreissena in the Great Lakes: what have we learned in 30 years of invasion

We summarized over 30 years of research on zebra and quagga mussels in the Laurentian Great Lakes and compared with data from European and North American inland lakes. Invasion dynamics, growth, and reproduction of dreissenids in the Great Lakes are governed by lake morphometry. At < 30 m mussels overshot their carrying capacity and declined within 13–15 years after first detection. At 30–90 m their densities increased more slowly and declined to a lesser extent, while at > 90 m populations continue to increase even after 30 years of invasion. After the proliferation of quagga mussels, benthic wet biomass (including molluscs shells) increased about two orders of magnitude and currently exceeds zooplankton biomass > 40-fold. Strong benthic/pelagic coupling redirects food and energy from the water column to the bottom causing an increase in Secchi depth, decline in phosphorus, chlorophyll, phytoplankton and zooplankton biomass. The abundance of commercially important fishes declined as a result of the dramatic decrease in their main food deep water amphipods Diporeia , which has been outcompeted by exotic mussels. However, the introduction of round goby into the Great Lakes in the 1990s provided an important link between dreissenids and commercially and recreationally valuable fish species, increasing their productivity.