• Views from Penobscot Mountain summit.


    National Park Maine

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  • Temporary Road Closure

    A section of the Western Mtn Road in Southwest Harbor will be closed until 8/18 while park crews replace a culvert with a new fish-friendly open bottom culvert. For more information and a map visit our Getting Around Page. More »

  • Trail Closure: Gorge Path weekdays, 7 am - 4 pm

    The section of the Gorge Path between the Hemlock Path intersection and the A. Murray Young Trail intersection is closed until rehabilitation work is completed. The closure will be in effect Mondays through Fridays only, from 7 am to 4 pm.

Field Guide to Marine Invertebrates - Mollusks

Periwinkle feeding on alga
Littorina littorea (gastropod)
Littorina littorea ("common periwinkle") is an introduced snail that is one of the most abundant and important herbivores in the intertidal zone. Littorinids are inactive in winter and become active when temperatures rise in spring.
Green-colored periwinkle feeding on alga
Littorina obtusata (gastropod)
Littorina obtusata ("smooth periwinkle") is often found in the mid-intertidal zone of Acadia National Park on Fucus vesiculosus and Ascophyllum nodosum. This herbivorous snail has a smooth shell but occurs in many colors (e.g., black, brown, yellow, and orange).

Nucella lapillus (gastropod)
The shell of Nucella lapillus ("Atlantic dogwinkle," "dog whelk") varies in color from white to dark yellow, brown, or orange. The Atlantic dogwinkle is abundant in the low intertidal zone. Nucella commonly feeds on barnacles and mussels.

Five mussels on rock
Mytilus edulis (bivalve)
Mytilus edulis ("blue mussel") is a bivalve that attaches to rock by byssal threads. Blue mussels are filter feeders. During red tides, blue mussels feed on dinoflagellate algae containing saxitoxin in the phytoplankton. This makes the mussels unsafe to eat and causes closures of mussel beds to harvesting. Sea stars and crabs prey on mussels, restricting them to the mid- and upper intertidal zones. Larvae settle onto shores of Acadia National Park in autumn, when masses of young mussels can be observed on the rocky shore.
Limpets on algal crust
Tectura testudinalis (gastropod)
This limpet is an herbivore that feeds on algal crusts, including those of calcified red algae. It is found in tide pools and the lower intertidal zone. Young individuals are typically brown, but the shell is often worn and white in older animals.
Photos by Sarah Hall.

Did You Know?

Cobblestone Bridge, faced with rounded cobblestones, has a stream running underneath.

The historic carriage road system at Acadia National Park features 17 stone-faced bridges spanning streams, waterfalls, cliffs, and roads. The design of each bridge, such as Cobblestone Bridge, is unique.