Zebra Muscles....

....are alien to the Great Lakes, and yet they've spread across all five of them. They were first discovered some 30 years ago in Lake St. Clair (which connects with Lake Huron to the north and Lake Erie to the south), the mussels likely coming from the ballast water of freighters that had traveled through eastern Europe. The zebra muscles reproduce quickly, so crowd out the native clam species, disrupt the base of the aquatic food chain, and attach to everything, causing, among other damage, the clogging up of the water intake pipes. There are areas of the beaches along Lake Michigan that are full of the empty Zebra Muscle shells, most of which are about the size of a dime. 
Hope you're all having a great start to the week, and a big
thanks to Nickimags888 for hosting MonoMondays, & for her theme of "alien". :))