Searching for Alien Invaders

WHOI Research Associate Mary Carman scans the tidepools near Sandwich Town Beach on Cape Cod to find sea squirts, an invasive, filter-feeding species (genus Didemnum) that has been crowding out other life in coastal waters. This species spreads up from the bottom of rocks as it grows, covering everything in its path, including vegetation and shellfish. “Anyone who likes to eat seafood should worry about this,” Carman said. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)