The Great Lakes now have a total of 180 documented foreign species now that scientists have observed two new exotic species, both about the size of a flea. They both have been found in low abundance, and scientists have no evidence so far of serious negative side-effects on native zooplankton species. For that reason, they are not yet being referred to as “invasive,” a term which is typically reserved for species with negative impact. These are the third and fourth non-native zooplankton species discovered in the Great Lakes in the past three years.
Plankton serve as the base of the food chain and are a staple in several small fish species’ diets. Over the last few decades, native zooplankton populations in the Great Lakes have plummeted thanks to the highly-efficient filtering of invasive zebra and quagga mussels. It’s unclear what, if any, effect these two new species will have on Great Lakes ecosystems. Scientists’ next job is figuring out how they arrived, but an early suspicion is the ballast water ships carry from foreign ports.