Low Tide Beach Walk – April

Sound Water Stewards are trained volunteers working in and around Island County for a healthy, sustainable marine environment through education, science and stewardship.

Steward Stacey Thompson, SWS Class of 2011, wrote a series of articles about exploring the low tide beaches of Camano and Whidbey Islands, alone, in the fresh air, during the long days of Covid restrictions, January through May. Her exploration prompts all of us to get out onto a beach and see what we can find!

January 2021 – A Winter Beach Walk
February 2021 – Zones 2 and 3: Midlittoral Zones: The Beachcombing Zone
April 2021 – Rocky Beach Intertidal Zone 4
May 2021 – Minus Tide at Keystone Jetty & at Bush Point

This drawing (above) by Jan Holmes is found in Beach Watchers/Sound Water Stewards training materials including Stacey Thompson’s Monitoring Manual.

This is the third in a series by Stacey Thompson. During the pandemic, Stacey’s articles have kept Stewards in touch with the Intertidal Zones.

April 2021 –  Rocky Beach Intertidal Zone 4
By Stacey Thompson, SWS Class of 2011

Whether you call it Puget Sound or Salish Sea, we all recognize what a beautiful area we live in. When the sun shines it surpasses most areas of the world in beauty and abundant life. With miles of shore to explore, you’ll soon discover something new to you. Let’s keep becoming more aware and determined to protect and preserve natural resources.

It’s time for another walk on the rocky beach. Did you check the tide tables for when the tide will be at its lowest in your location? Get your jacket and pull on your rubber boots to see what we can find on the rocky shores of our beautiful islands. Grab your loupe or magnifying lens, your EZ-ID guides, Getting to the Water’s Edge book and welcome the fresh air. Maybe binoculars too for spotting whales?

It’s especially important for your safety and that of the organisms, as in all zones, to watch your footing so you don’t step on creatures or slippery rocks or seaweed. You don’t want to injure what you came to discover.

Last summer on a beach monitoring trip, Elaine Chan and I noticed many missing barnacles. Have you seen those round white markings on rocks? That’s the footprint of where a white barnacle, Balanus glandula once was. Then we found barnacles that were disintegrating in our hands. This is very unusual and made us wonder about the cause. Is it part of the life cycle, ocean acidification or another cause? (If you know, please let us know.)

While strolling along, search for agates and other pretty rocks, too. Agates are a variety of chalcedony, also known as quartz, that are translucent and considered a semi-precious stone. They come in different colors, banding, shapes and sizes.

Agate. Photo by Kelly Zupich

We make our way down to Zone Four, also known as the Infralittoral Fringe, or subtidal waters, the lowermost intertidal region. It is only exposed during extremely low tides in the range of 0.0 to minus 3.5 feet. Here is the most abundant life of all the zones; there is more food and shelter and less exposure to the sun. When we are beach monitoring, this is where we will set up our quadrats after surveying the upper parts of the beach.

We soon find aggregating anemones, Anthopleura elegantissima, colonial creatures with just their mouths showing. They are dark green, attached to a rock and surrounded by sand, and found in Zones Four and Three (Three is the lower mid-intertidal zone). They look like a gritty blob grouped with others. If you accidently step on them, they will squirt water at you. When underwater, each one will stand 4 to 5 cm high on a columnar trunk with pink tentacles spread. A. elegantissima, aggregating anemones reproduces through cloning asexual multiplication. When this polyp colony happens to encroach on another colony of the same, a warfare ensues over territory and they fire stinging capsules aggressively at each other. The capsules are found at the base of their tentacles. Aggressive aggregating anemones, the underwater flowers named elegantissima, engaging in battles against others of its kind? Oh my! This is documented in Eugene Kozloff‘s 1993 book, Seashore Life of the Northern Pacific Coast, a book I highly recommend.

Anthopleura xanthogrammica, bright green sea anemones have a broad flat oral disc (mouth) with pale emerald green tentacles around the center. Underwater, the tentacles can expand to reach 15 cm in length. These carnivores usually eat mussels. If you touch it, it will send out microscopic threads and discharge nematocysts, a specialized cell in the tentacle. The tentacles will retract and are used to trap prey and pull it into the mouth. Remember to use the “one wet finger” technique to have the least human impact on the life form.

Giant green sea anemone, Anthopleura xanthogrammica. Photo by Kelly Zupich

Twenty different kinds of surf grass and seaweeds are listed in Zone Four in Kozloff’s book. Looking at our EZ ID cards, we can see fourteen brown seaweeds, and nine green seaweed common to Island County beaches. While monitoring we see many of them. There is usually an abundance of bright green sea lettuce, Ulva, the sheets of algae that cover large areas. Seaweeds must be attached (that is, not free floating) to some structure, such as a rocks, to be counted for our records.

There are two main kinds of eelgrass found here, Zostera marina (native) and Zostera japonica (a more recent arrival). Both are narrow-leaved grass usually located where there is less wave action. Japonica is smaller and blades are shorter. Eelgrasses are vital to the marine environment as they provide habitat for young fish to grow, shade organisms in the hot sun, and are home to a large number of species.

Eelgrass, Zostera marina. Photo by Pat Vivolo

Rosario Beach at Deception Pass State Park has one of the most extensive lists of species found in Zone Four. There, the cumulative list of creatures in 2017-2018 the rocky shore habitat, including erratic boulders and tide pools, is home to purple stone crab, hairy shore crab, hermit crab and graceful decorator crabs to name a few species. (Today, access to Rosario Beach’s tide pools on low tides is restricted to allow restoration after it has been “loved to death.” Despite limited access, with naturalist guides you can view a wide variety of life forms.)

Sea urchins can live to be 75 years old! They are Echinoderms, meaning spiny skin, a group that includes sea stars and the sea cucumber, Cucumaria miniata which can grow to 20 cm long and are distinguished by a crown of bright orange oral tentacles. Found in crevices or between rocks, most of the body is reddish brown or pinkish brown. A sea cucumber’s tentacles are branched and trap small bits of particles floating in the water. It then moves the food to the mouth by pushing the tentacle there and cleaning it off. They help recycle nutrients, breaking down detritus and playing a role in the degradation process. Sea cucumbers have been found as deep as 5.5 miles deep. They form large herds to hunt for food in the depths of the ocean floor.

Sea cucumber, Cucumaria miniate (underwater). Photo by Nancy Neudecker at Rosario Tide Pools

Rosario Beach’s list of species found in quadrats is wide-ranging. Nudibranchs, snails, round worms, barnacles, sea squirts and crab, as well as rock scallops, oysters, mussels, chitons, limpets, isopods, amphipods, and the red velvet mite are all present in this lower intertidal Zone Four, the subtidal zone.

How does this compare to the rocky beach you are monitoring or a beach you visit frequently? Are there erratics and tidepools? What kind of life can you find on the docks and floats made accessible by the low tide?

I encourage all of you to participate in the monitoring opportunities this summer to see what organisms you find on your beach. Or just enjoy the beach and see what and who you can find.