Saturday, April 13, 2024 was a perfect day to explore the seaweeds in the sandy and rocky intertidal area off the Empress of Japan Figurehead in Stanley Park. The unpredictable rainy weather dissipated providing us with a bright day for our intertidal exploration.

The spring tides are in their extreme ranges now, meaning that the lower low spring tide level (LLW) at 16:11 PDT had an elevation of a mere 0.7 m. The meet-up time at the Spray Park was at 14:00, allowing us lots of time to explore the expansive intertidal habitats. Even this early in the season, there was lots to discover.

MBS was delighted to have Dr. Bridgette Clarkston join us again this year to focus on seaweeds. In her position at UBC as the Associate Professor of Teaching in the Botany Department, Bridgette was excited to enhance participant’s learning and understanding of the common species. She took the time to develop a handy laminated guide – The Stanley Park Seaweeds – that includes 37 species expected to be found intertidally in the area ranging around the rocky point of the Empress of Japan Figurehead to the Girl-in-Wetsuit rock.

Bridgette included interesting tidbits about the seaweeds in terms of the three major seaweed groups, pronunciation of scientific names, common names, key characteristics to identify, size range, attachment substrate, time of year generally seen or prevalent, and the tidal elevation where the species most often occur. Physiological adaptations in the intertidal are important for any organism when it comes to their preferred habitat based on abiotic factors like oxygen, temperature, exposure tolerance and salinity.

One beautiful dainty specimen, found by Bridgette’s former student Isaak, stirred up some excitement such that it required dissection and microscope examination for accurate identification. It was either the red sea fan (Callophyllis sp.) or the delicate northern sea fan Euthora timburtonii. Had it been identified as the northern sea fan, it would be the first record of this genus in Greater Vancouver. But another red seaweed, the winged rib (Cumathamnion decipiens), was a surprise to find because it tends to be most abundant at Stanley Park in February. The winged rib was reported on iNaturalist by Wilfred Jones, one of Bridgette’s undergraduate students, and was selected to be iNaturalist’s Observation of the Day! You can see more of the winged rib here: https://www.inaturalist.org/observations/207077507

In the lower tidal zone, I always find the draping effect of the green rope on the boulders, a lovely seaweed to see and feel. As Bridgette noted, each seaweed (in fact even animal species) have their own unique look and feel.

The following list provides the common names for examples of the three main colour groups of seaweeds observed, organized by group evolutionary age:

acid-weeds (3 species), bull kelp, five-ribbed or seersucker kelp, rockweed, sausage weed or soda straws, sugar kelp, winged or ribbon kelp;

nori, red eyelet silk, red opunita, red sea fan, splendid iridescent seaweed, Turkish towel, Turkish washcloth and winged rib;

green rope and sea lettuce.

Bridgette has generously shared the link to her Seaweed Teaching Resources where the Stanley Park Seaweeds guide can be downloaded. NOTE: these seaweed teaching resources are all Creative Commons By-NC-SA (attribution-non commercial-share alike). They are free to use, modify and share as long as credit is given to whomever created the resource. They cannot be used for making money without the author’s permission, and anything made new from our materials should also be shareable with a Creative Commons license.

Of course, no field trip to the Figurehead Point rocky shore is possible without finding some surprises! As with the several unusual seaweeds found by Bridgette and her team there were also some interesting finds with the invertebrates. For example, several normally 5-armed leather stars were observed with 6 arms!?!? That was a new surprise to most of us but according to Andy Lamb, he has been observing this oddity more recently and frequently around Thetis Island. What this means conjures up a few things in my mind, but nothing that I can justifiably confirm.

Seeing the giant California sea cucumber exposed in the lower intertidal was literally another BIG surprise! Several were seen though not very active, with their soft leathery skin showing definite signs of drying out. As with a number of the seaweeds observed that were likely dislodged and washed up into the intertidal area by waves or tides, the habitat of this cucumber species is generally subtidal. It probably was trapped by the fast-receding spring tide before it had a chance to escape exposure by crawling into deeper waters. We placed a large moist piece of seaweed over the cucumber to help keep it moist until covered again by the incoming tide.

Later, an unusual green egg mass was found near the low tide edge that quite possibly could be the egg mass of the banner sea-nymph (also clam worm, or rag worm), Nereis vexillosa. This is the time of year when these benthic worms swarm near the surface of the ocean to perform their nuptial dance before shedding their eggs and sperm. The banner sea-nymph is commonly found at Figurehead Point so it would not surprise me that this mass is a result of the spawning activity undertaken in April or May, depending on the environmental conditions. According to descriptions, this is my best guess at what laid this egg mass, although I am not overly familiar with fish egg mass identifications. Thanks to the keen eyes of observers like student Aly Lalani, it is the first time I have seen with my own eyes evidence and result of the banner sea-nymph nuptial dance off Figurehead Point.

Speaking of worms, although not new to the area, several observers found a very long and brilliant orange ribbon worm, a scaleworm and several feather duster worms, all near the low tide level.

The photographs in this report are by Sheila Byers but many more photos by other participants have been uploaded to two sites, thanks to Denis Laplante and Teresa Gagné. Those uploaded to iNaturalist can be found at this link (which uses Custom Boundary and date filter – the otter sighting at 5am is included because it matches location and date). As well, Denis has created a Google Photo album for the April 13 field trip. If any other participant would like to post their photos to these sites, please contact denis@NatureVancouver.ca.

Our trip to the Figurehead Point location at Stanley Park is always fun and provides new and interesting observations, regardless of what time of the year. Thanks to Bridgette and her compilation of the common seaweed field guide, we can visit the area on a low tide during the other seasons when we may find other seaweed species that we did not see at this time of year.

A special thank-you to Bridgette for sharing her knowledge and love of seaweeds with us and thank you to all who participated in the field trip. We will no doubt want to do this again!!

Sheila Byers

April 23, 28, 2024