With tidal fluctuations as large as 25 vertical feet, Glacier Bay exhibits some of the largest tidal extremes in the world. Visitors to the park will notice dramatic difference between high and low tides. One minute you can be gazing out over 100 yards of mud flats and six hours later the waves can be lapping at your toes.
That area between high and low tides – known as the intertidal zone – is an extremely complex and important biological community and a fun place to explore. Lower portions of the intertidal zone are dominated by marine organisms such as algae and kelp, invertebrates and fishes. Grazers like sea urchins, predators like sea stars and dogwinkles, and space dominators like rockweed, barnacles, and mussels are some of the dominant members that strongly influence this community's structure.
The Intertidal Life of Bartlett Cove
A guide to the wonders of Glacier Bay's Intertidal Zone
Organisms that live in this area need to be able to move or they need to be able to survive long periods of time out of the water when the tide is low. During such times they are exposed to heat from the sun and risk being eaten hungry animals.
Grasses and sedges colonize the area immediately above the intertidal zone in areas where they find enough stable soil to grow. Because they contain highly nutritious plants, flowers, and berries, these meadows are important food sources for animals. In fact, sedge meadows are perhaps THE most important single habitat type in the park for bears. The absence of large trees and tangled underbrush makes beach meadows ideal for travel, and they serve as important thoroughfares for everything from mink to bears to people.
Steep headlands and exposed rocky shores tend to host intertidal species that attach themselves to rocks, such as barnacles, anemones and tubeworms, as well as a variety of marine algae and kelps. Embayments where the waters are calmer accumulate sediments that are home to many burrowing creatures, such as clams and worms. These rocky and sedimentary communities each provide important foraging habitat for terrestrial and marine animals. Virtually every animal that lives in Glacier Bay has been seen feeding in the intertidal zone – even mountain goats and shrews!