Some of the freshwater species found along the Colorado River and its perennial tributaries include coyote willow, arrowweed, seep willow, cottonwood seedlings and exotic tamarisk. Cladophora , a filamentous green algae, is abundant in the cool, clear river water. This algae is an important food source for aquatic invertebrates such as amphipods. Hanging gardens, seeps and springs often contain rare plants such as the white-flowering redbud tree, haplopappus and flavaria. Other freshwater species such as monkeyflower, watercress, columbine, sedges, horsetail and rushes are associated with seeps and springs. Sedges are the predominant freshwater species in stock tanks and ponds on the North Rim.
Maine ocean islands provide the only nesting sites for Atlantic puffins in the United States. Eastern Egg Rock in the midcoast region, Seal Island and Matinicus Rock at the mouth of Penobscot Bay, and Machias Seal Island and Petit Manan Island off the downeast coast provide habitat for more than 4,000 puffins each summer.