Having grown up on the Oregon coast, I have been fascinated by marine animals since I was a young girl. I spent many long summer days exploring the tide pool and estuarine habitats in my neighborhood.
A naturalist at heart, I have inundated myself in ecology and natural sciences ever since, completing the coursework to become an Oregon Coast Master Naturalist a few years ago. Today, I am delighted to take you on a guided tide pool “hike” to one of the hidden gems of the Oregon seashore.
Cape Arago State Park
The tide pools at Cape Arago are incomparable. Here, you’ll find easy access to both the North and South Coves of Cape Arago. Tucked away below the cliffs, a short walk along the steep trails will take you to a secluded cove where tide pools and fossils can be found.
The south trail leads to tide pools teaming with diverse sea life. The north trail lets visitors view offshore colonies of seals and sea lions (however, the trail is closed from March – June to protect the seal pups during birthing season). Visitors to the area can also enjoy whale watching, crabbing, fishing, and scuba diving.
Nearby, there are two additional state parks: Sunset Bay (a sandy beach protected by towering sea cliffs – perfect for sunbathing and swimming) and Shore Acres (a lushly planted garden perched on rugged sandstone cliffs high above the ocean – once the famed estate of Louis Simpson).
Let’s now begin our guided hike of the south cove at Cape Arago.
Guided Tide Pool Hike
Upon hiking down the south trail you will first come to a small sandy beach. There is often driftwood and marine debris along the high tide line, pushed up against the base of the cliff atop the rocks and small boulders.
Purple Olive Snails
As you walk nearer the shoreline to the waters edge, you may see tiny little bumps in the sand. Olivella biplicata, commonly known as purple dwarf olive snails, burrow themselves in sand, leaving a plowed trail behind it. The foot is wedge shaped to facilitate plowing.
While burrowing it raises its long siphon up through the sand as a snorkel. They can be found nearshore on fairly quiet, protected beaches and farther offshore on more exposed beaches. Their predators include the seastars, octopus, moon snails, and gulls. Most active at night, often move up and down the beach with the tide. Omnivorous, they eat kelp blades and both live and dead animal material.
Take a closer look, however. Some of these snails are not like the other.
The snail shell at the top is inhabited by a hermit crab. There are more than 1000 species of hermit crabs -decapod crustaceans that possess an asymmetrical abdomen that is concealed in a scavenged mollusc shell which it carries around. As the hermit crab grows, it will seek out a larger shell.
Hermits are not the only crabs you’ll observe in the tide pools. Crawling about between rock crevices and amongst the blades of kelp and marine algae are a diverse number of small crabs, each with its own distinguishing characteristics.
- Purple shore crabs – Hemigrapsis nudus (pictured above) reaches sizes of approximately 4.0–5.6 cm and is generally dark purple in color, although it may be olive green or red, with white or cream markings. The color of the legs matches the color of the carapace but the white-tipped claws are a lighter color with purple or red spots. These markings distinguish it from the similar…
- Lined shore crabs – Pachygrapsus crassipes, whose chelipeds lack spots.
- Oregon shore crab – Hemigrapsis oregonensis is a similar species with setae or small hairs on its legs, a distinguishing characteristic the other two lack
- Porcelain crabs – a flat, round body (perfectly adapted to life between rocks) with two large front claws, these delicate crabs readily lose limbs when attacked, and use their large claws for maintaining territories.
No matter the depth or the substrate, these spiny skinned invertebrates are among the most successful marine creatures inhabiting the coast. The abundance and number of stars found along the west coast of North America is without equal in the world. I highlight just one in my post today.
Henricia leviuscula, the Pacific blood star, feeds mainly on sponges. It is fairly stiff with only small papulae (skin gills) and tube feet. It seems to rely much more on seawater uptake through the madreporite (a series of seawater-filled ducts that function in locomotion, feeding, and respiration) than do other sea stars of comparable size.
The gumboot chiton, Cryptochiton stelleri, can be found clinging to rocks, moving slowly in search of its diet of algae which it scrapes off of rocks with its rasp-like retractable radula, covered with rows of magnetite-tipped teeth.
Unlike some other chiton species, C. stelleri has well-developed ctenidia (gills) in the groove beside the foot (pictured above). A commensal polychaete worm can sometimes be found here, as can the pea crab, Opisthopus transversus.
There are many anemones in the tide pools of the Pacific Northwest. One of the most common is the green anemone, Anthopleura xanthogrammica. Anthopleura is not just one species, however. Hidden within its tissues is an algae.
In this symbiotic relationship, the algae gain protection from snails and other grazers and don’t have to compete for living space, while the anemones gain extra nourishment from the algae in their guts. Contrary to popular opinion, this anemone’s green color is produced by the animal itself, not the algae that it eats.
Another fascinating anemone is the aggregating anemone (pictured in the embedded photo above), Anthopleura elegantissima, the most abundant anemone species found on rocky shores along the Pacific coast.
Aggregating anemones can rapidly clone themselves. If buried by shifting sands, they can survive for more than three months.
Tide Pool Guidebook
You may not have the opportunity to explore a tide pool with a naturalist when you visit the Pacific Northwest Coast. In this case, you will want to find a guidebook or two to help you identify the diverse wildlife you will encounter.
One of the books we have at the marine life center that our visitors enjoy perusing when they have questions is The Beachcomber’s Guide to Seashore Life in the Pacific Northwest by J. Duane Sept. It was revised in 2009, it is beautifully illustrated and is a great guide to identifying the most common intertidal animals and plants of British Columbia, Washington, and Oregon.
The size is perfect to toss into your day pack if you wish to look up a specimen on your trek. It is written with the beachcomber in mind so while it does not feature every species, it is an excellent starting point for the more general specimens you may encounter.
While here, you may also be interested in Oregon Coast Quests – fun, educational, and clue directed hunts specific to the Oregon Coast.
Welcome to the Nature Book Club Monthly Link Up. Devoted to connecting children to nature, the monthly link up will begin on the 20th day of each month. We welcome your nature book and activity related links. Read on for more details.
See all the great posts from The Nature Book Club’s co-hosts in June
The Nature Book Club is brought to you by these nature loving bloggers which are your co-hosts. Are you following them? If you don’t want to miss anything, be sure to follow each one.
5 Senses at Sunset Walk from Barbara at Handbook of Nature Study
Discovering Nature in the Garden Scavenger Hunt from Jenny at Faith & Good Works
Nature Walk Alphabet Hunt from Emily at Table Life Blog
Guided Tide Pool Hike from Eva at Eva Varga
Foraging & Feasting Unit Study & Lapbook from Tina at Tina’s Dynamic Homeschool Plus
Fairy Gardens and Online Book Club from Dachelle at Hide The Chocolate
Decoupage Art with Nature Walk Findings from Katrina at Rule This Roost
Summer Nature Hike from Thaleia from Something 2 Offer
Leaf Shape Hunt from Karyn at Teach Beside Me
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