What it is
The spiny water flea, Bythotrephes longimanus, is considered one of the most ecologically and economically destructive invaders of North American freshwaters, and it was believed to have reached the Laurentian Great Lakes in ballast water from trans-Atlantic ships in the 1980s. Combining microfossils from lead-210-dated lake sediments, radiocarbon dating of its chitinous remains and sediment DNA, the authors show that it was present at low densities in inland lakes in Ontario, Canada, at least 100 years earlier than initially reported.
Why it matters
For decades, management has focused on limiting the species' spread from the Great Lakes on the premise of a 1980s introduction. A presence a century older challenges that accepted history, and the authors consider how the species' recent proliferation coincided with widespread environmental change and with shifts in other processes that influence its establishment and population growth.
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Filed underMarine Ecology and Invasive Species, Marine Invertebrate Physiology and Ecology, Environmental DNA in Biodiversity Studies