From Great Lakes Wiki
This animal is forms underwater colonies and filter feeds like sponges would. Only 50 of the 1,500 known species of Bryozoan lives in freshwater, the rest inhabit saltwater marine ecosystems. Good or bad for The Great Lakes? These answers are unclear, but other scientists have noticed cleaner water when these species arrive and speculate some connection. On the negative side, the saltwater species has been known to produce a skin irritant called Dogger Bank Itch, which fisherman often get when they hall up this moss animal in their nets.
Image from:www.duke.edu/~jsr6/otherpics.html
