Know your beach—this week from the beach

#5 in the 2017 series of guest blog posts by Seattle Aquarium beach naturalists Bobby Arispe and Jen Strongin.

Did you make it out to the last series of minus tides on our local beaches? If not, don’t despair! We have another set of some of the lowest tides of the summer coming up July 21–25. I had the great pleasure of working during the past two low tides at several beaches: Lincoln, South Alki and Seahurst.

Each beach has its own flavor. If you want to spot an octopus, Lincoln is your best bet. If you want to see sea stars, crabs, moon snails and nudibranchs, South Alki won’t disappoint. If you want to see living sand dollars, huge clams and maybe an unusual find or two, Seahurst is your place.

All three beaches are marine preserves. This means the habitat is protected and collecting or harvesting of any kind is not allowed—what you see on the beach, stays on the beach (bring your camera to document what you find)! I love that we live in a city that values the conservation of our very special marine habitats.

Every visit to the beach is an adventure with new discoveries. At South Alki this past week, along with all of my favorite animals, I saw a couple of unexpected surprises. The first was a juvenile salmon that swam into the collapsible forest of eelgrass right next to me. It was the first time I had seen a salmon during low tide at my home beach. Our forests of eelgrass provide an important habitat for young fish like salmon and sand lance. It gives them shelter and a place to hide from predators. I would have loved to take a photo of that beautiful salmon but it was so fast and the eelgrass did its job of hiding it!

Beach etiquette tip of the week: Eelgrass is the “unwelcome mat” for us humans. Walk around it when you can to avoid trampling juvenile fish, eggs and other animals hiding there!

I do have some photos of the second surprise. At the north end of South Alki, my friend and fellow beach naturalist, Preston, showed me some ten-tentacled anemones. Super small, maybe an inch in diameter at the most, these beautiful anemones are worth seeking out. They burrow into the sand and quickly withdraw their tentacles and disappear if disturbed.

At Seahurst Beach, I was convinced I had found a crazy, tentacle-headed worm! A young visitor, exploring the many holes left behind by clams on the beach, had found a couple of these interesting-looking animals. After taking lots of photos and video and observing it for a while, I went home determined to find out what it was we’d been looking at. It turns out, it was a species of burrowing sea cucumber, Leptosynapta clarki. This beautiful, worm-like sea cucumber feeds on bits of organic material in the sand. You can see its feeding tentacles at work in the video above. It also lacks respiratory structures and instead, absorbs oxygen through its skin.

At Lincoln Beach, my favorite discovery was a striped nudibranch, Armina californica. One of the larger nudibranchs, this species can reach six inches in length. You’re likely to find it part buried in the sand, hunting for its favorite food: sea pens.

I admit to being a bit disappointed that my burrowing sea cucumber at Seahurst wasn’t a cool worm. We have so many beautiful and interesting marine worms here in the Salish Sea. Take, for example, the basket-top spaghetti tube worm, pictured above. You might overlook it, thinking it’s some algae or detritus, but it’s really a spectacular structure. The worm builds a tube-shaped home and then adorns the top of it with this intricate, fibrous basket. The basket may serve as protection, camouflage or even a filter for food.

The red-banded commensal scale worm is often found living on a host of another species, like this striped sun star. It is very territorial, and has been known to bite attackers of its host or other commensal worms hoping to join the party!

Although its common name is bat star worm because of its commensal relationship with bat stars, this striking polychaete worm is often found living on its own here in Puget Sound. Muddy sand, pilings and floats are good places to find one.

The northern feather duster worms are my favorites. They look like flowers in bloom when they are under the water. Their fringy tentacles are used for both feeding and respiration (and for wowing us land dwellers!). They build their tube homes out of mucus and sediment.

Look on and under rocks and you’re sure to see evidence of calcareous tube worms. Their maze-like, calcium carbonate homes give their soft bodies protection from predators. Like the northern feather duster, the various species of calcareous tube worms use fringy tentacles to feed and breathe.

We look forward to seeing you out on the beach! Don’t forget to tag photos of all of your beach finds with #beachnaturalist #knowyourbeach #beachnaturalists #seattleaquarium. Happy tide pooling!