About Rocky Shores in Oregon

More than 1400 rocks and islands are sprinkled along nearshore zone of the Oregon coast, usually in association with cliffs and other resistant rocky features of the shoreline. These rocky remnants are dramatic and picturesque, but the are also valuable habitat that supports a diverse coastal ocean ecosystem. Most of these rocks and islands are in the Oregon Islands National Wildlife Refuge and are home to major colonies of seabirds, such as the common murre and marine mammals, including the threatened Steller sea lion.

Rocky intertidal areas, or tidepools, are unique marine environments that offer a glimpse into the marine realm. These areas are biologically rich and have evolved to take advantage of, as well as withstand, the environmental rigors of the edge of the sea. Submerged rocky reefs are also scattered along the coast. These areas are critical habitat for a wide variety of marine species, from encrusting corals and sponges to invertebrates, fish, and marine mammals and seabirds. In waters less than 80 feet deep, Bull kelp [Nereocystis luetkeana], a large marine algae, is associated with these rocky reef structures. The presence of kelp adds a third dimension to the reef and creates additional habitat.

Oregon Rocky Shores North to South

Oregon's rocky shores are artifacts of dynamic geologic processes; for thousands of years the Pacific Ocean has worked against the rocks of the land, exploiting variations of hardness and orientation in the rocks, seeking out the zones of weakness caused by fractures and faults, eroding deeper into the coastal mountains.  Because of this variety of geologic origins and processes, Oregon's rocky shores are mixtures of kinds, types and conditions. While there are some similarities among sites, each is unique.

Volcanic basalt, a resistant rock, forms the cliffs and rocks along the north coast at Cape Lookout, Seal Rocks, Haystack Rocks [there is a Haystack Rock at Cannon Beach, a Haystack Rock at Pacific City, and a Haystack Rock at Bandon], and Otter Rock. South of Coos Bay, the reefs and rocks of Cape Arago are tilted layers of hardened sedimentary rocks that once formed on the ocean floor. Further south, remnants of ancient metamorphic rocks form the cliffs, offshore rocks and reefs such as Coquille Point, Cape Blanco, Cape Sebastian, and Cape Ferrelo.

The rise of sea level after Earth's most recent ice age accelerated erosion against the land and drowned remnant rocks and islands before they could be completely worn away. Rogue, Orford, and Blanco reefs are the largest of these drowned remnant rocky landscapes covering thousands of acres with only the tips of rocky spires now visible above water. Because of this variety of geologic origins and processes, Oregon's rocky shores are mixtures of kinds, types and conditions. While there are some similarities among sites, each is unique. 

Intertidal Zones

The physical environment of intertidal areas changes dramatically as the tide rises and falls, either covered by salt water or exposed to air, fresh water (rain), and the sun. You may notice bands or zones of plant and animal life based on the amount of time the habitat is covered by water or exposed to the air. At some sites, such as vertical cliffs or steep slopes, zones are very distinct, while at other sites they are barely detectable. The effects of drying, temperature changes, and wave exposure help determine which plants and animals live in each zone. The tidal height of each zone also varies depending on wave exposure, shoreline slope, and a number of other factors. Because conditions in the intertidal environment vary so dramatically, species have adapted a variety of ways to survive. Some move to follow the level of the water as the tide rises and falls. Others retain water in their shells and bodies; still others seek shelter in shaded nooks and crannies, under seaweeds, and in tidepools to avoid drying out. 

Spray Zone

Only the highest waves, ocean spray, and rainwater wet the spray zone. Animals and plants living in this zone
must be able to retain moisture, tolerate salinity changes due to evaporation and rain, and survive extremes in temperature. The spray zone supports fewer species than other zones; however, there can be large numbers of individuals. Look for finger limpets, checkered periwinkles, the rock louse, and lichens.

High Intertidal Zone

This zone is only covered during the high tides. It experiences changes in temperature, salinity, and availability of water that are almost as extreme as in the spray zone. However, the high intertidal zone has more wave action, so the plants and animals must attach themselves securely to the rocks. Look for Endoclodia, the nail brush seaweed, and Mastocarpus, a scruffy, blackish red alga. Rockweed, little rockweed, sea moss, and acorn barnacles also grow in the high intertidal zone. Hermit crabs and the black turban snail travel in and out of this zone with the tide.

Mid Intertidal Zone

Tides cover and uncover the mid intertidal zone about twice a day. Changes in temperature and salinity are less severe than in zones above it. Many animals living in this zone depend on the waves to carry food to them. Higher in this zone, look for California mussels, goose barnacles, thatched barnacles, buckshot barnacles, and acorn barnacles growing very close together. Among them you will find their predator, the emarginate whelk. Also look for shore crabs and mossy chitons, which will seek out shady hiding places. You may also find sea palms among the mussel beds. If you are near sea palms, watch out for large waves; they only grow where surf pounds the rocks. The presence of ochre sea stars, aggregating anemones, giant green anemones, shield lim¬pets, black Katy chitons, and sea cabbage will tell you that you are in the lower part of the mid intertidal zone. Other plants to look for are sea lettuce, iridescent seaweed, and feather boa kelp.

Low Intertidal Zone

Water covers the low intertidal zone except for a limited time during the lowest tides. Temperature and salinity changes are much less severe. Most plants and animals in the low intertidal zone can only survive short periods out of the water. More species are found here than in any other zone exposed by the tide. You may see sculpins, purple sea urchins, kelp crabs, sunflower stars, hydroids, tunicates, sponges, and bryozoans. You will see many kinds of red algae, such as the mermaid's cup and the larger brown kelps such as winged kelp and oar weed. This is also where the surfgrass beds are located. From the lower intertidal zone you will be able to get a glimpse of the vast undersea garden that surrounds the rocky shore. On the surface of the water you will see the tops of the tree-like algae, such as bull kelp and bladder chain. In a clear pool, you may see schools of surf perch and young rockfish gliding in and out among the seaweeds.