The toughest neighbourhood on Earth, rearranged twice a day.

Look at a Fundy rock face at low tide and you will see zones. Periwinkles and lichens can occupy the higher, drier surfaces, followed by barnacles, rockweed, mussels, and other algae closer to the low-water line.

The upper limit of each zone is strongly influenced by how much drying and temperature stress an animal can survive. Lower down, competition, predators, food, and wave exposure become increasingly important.

The tide draws the map.

Periwinkles seal themselves inside their shells with a trapdoor called an operculum, helping them retain moisture while the tide is out. They can also seek shelter in crevices and among seaweed.

Barnacles are crustaceans that cement themselves permanently to rock and other hard surfaces. When submerged, they extend feathery appendages to capture tiny particles from the water. When the tide falls, they close their plates and wait.

Blue mussels anchor themselves with byssal threads — strong protein fibres they produce themselves. The attachment can be adjusted, allowing mussels to respond to changing conditions and reposition when necessary.

The brown seaweed draped over the shore is not decoration.

Rockweed helps hold moisture and provide shade during low tide. The spaces beneath it shelter small crabs, snails, amphipods, and juvenile animals from drying and extreme temperatures.

Remove the rockweed and you can remove the shelter too.