Our Marine Environment
The Intertidal Environment
What is the intertidal zone? Sometimes called the littoral zone, the intertidal region is a zone of transition extending from areas of high tide, that are routinely exposed to air and sunlight, to areas of low tide that are rarely exposed. Plants and animals that inhabit this area have adapted to the extreme variability of conditions in and out of the water.
Marine vegetation in the intertidal zone serves multiple functions for the animals that live in the area. Marine vegetation is used as habitat and refuge for many species and is a food source or birthing areas for other species. Crabs creep along the bottom, fish hide in the thick beds of grass and kelp, and snails slide their way up and down the vegetation that grows on the ocean's floor. A complexity of organisms rely on vegetation in the intertidal zone to live, feed and reproduce.
Shellfish harvesting is a popular recreational activity here in the Pacific Northwest. Manila clams, butter clams, littlenecks, geoducks, horse clams, and oysters are all popular seafood fare and can be found at or below the surface of a mud flat at low tide. These species of shellfish are also important to the economy of the Northwest Straits as many are harvested for commercial profit.
In recent years, the state of salmon populations has become an important issue in the Northwest Straits. The public attention given to the needs of salmon, can sometimes overshadow the needs of other species of fish which are equally important to the Northwest marine ecosystem. Such species of fish are generally grouped into two categories, baitfish, sometimes called forage fish, and groundfish or bottomfish. These species of fish are important members of the marine food web.
Marine mammals are often a favorite for people visiting the shoreline. Local marine mammals include seals, sea lions, porpoises, dolphins and whales. Such large animal species are easy to recognize and can be quite entertaining to watch!
Over 100 species of marine birds make Puget Sound their home during some portion of the year. Waterfowl, seagulls, shorebirds, wading birds and raptors are just a few of the types of birds we find near our local waters.
Shrimp and Crab
Marine crustaceans like shrimp and crab are common organisms in Puget Sound. Dungeness crabs are the popular choice for recreational and commercial harvesters in Puget Sound.
Substrate in the intertidal region provides a bed of sediment for marine vegetation to grow in. It also provides a home for many marine invertebrates including clams, oysters, crustaceans and marine worms that live within the sediment or among the rocks.
Invasive Species in Puget Sound
Organisms that are not native to an area can become invasive species. Non-native species may be intentionally or accidentally introduced to an area. These species do not always survive in their new environments, but those that do survive and reproduce may change the ecosystem in a number of deleterious ways including:
- Introduction of new diseases
- Competition with native species for food, light, and living space
- Predation on native species
- Hybridization with native species
For more information about marine nuisance species visit these Washington Department of Fish and Wildlife (WDFW) links to:
Species of Concern
- European Green Crab
- Eurasian Water Milfoil
- Purple Loosestrife
- New Zealand Mudsnail
- Rusty Crayfish
- Red Swamp Crayfish
- Chinese Mitten Crab
- Zebra Mussel
- Purple Varnish Clam