Sea Star Loss From Our Coast Might Be Mussels Gain

By Jay T. Cullen

Note that the video above was shot on May 8, 2015, set to Debussy’s Clair de Lune, by the YouTube user NorthOlbo who makes wonderful pieces about the British Columbian coast. Check him out.

The purpose of this more visual post is to report on a recent trip my students and I took to a local beach and what we saw there. Botanical Beach is renowned for its tide pools and part of the Juan de Fuca Provincial Park here on the southwest coast of Vancouver Island, British Columbia Canada. There are strange conditions currently in the northeast Pacific from the “blob” of warm water related to anomalous winter mixing in 2013-2014 to the widespread disappearance of sea stars owing to wasting disease after infection by virus. Some link these changes in the marine ecosystem to the very low levels of Fukushima derived radioisotope contamination present offshore and recently detected at the shoreline although there is little evidence to support such views nor are such impacts very likely. There is indeed life abundant at Botanical Beach but it is changing. The sea star is a keystone predator whose removal has consequences. The most obvious of these on visiting the beach again was the predominance of California mussels to be found. More about our adventure below the fold.

A recent article in the Hakai Magazine documents the efforts of University of California Santa Cruz graduate student Monica Moritsch to study the population dynamics of sea stars in response to the wasting disease outbreak and to look at the impact of removing this important predator from the intertidal zone. Sea stars eat California mussels and the complete decimation of the sea star population would likely have consequences for the success of mussel populations. Indeed, it is likely that the intertidal would likely see significant numbers of mussels given the lack of mortality from sea star predation.

On May 18, 2015 (the 35th anniversary of both the passing of Joy Division singer Ian Curtis and the eruption of Mt. Saint Helens in Washington State) my laboratory group headed down to Botanical Beach to have a look and otherwise poke around at low tide. The sun came out breaking through cloud for a short period only to be obscured by fog as the morning wore on. The photos below document our trip. It is quite clear that California mussels are doing quite well there. We saw chitons, limpets, green anemones, goose neck barnacles, barnacles, sea urchins, snails, branching coralline algae, coralline algae, sculpin, crabs, bald eagles and various species of kelp. Some juvenile sea stars were present. It will be interesting to see if infection with the virus causing wasting syndrome returns as local water temperatures rise this summer. Marine ecologists will be busy studying how the species composition and abundance changes as, hopefully, the sea stars reestablish themselves in the future. The current imbalance and its impacts will require careful research by the scientific community.

Information sign at the trail above the beach showing species that are predominant in the tide pools at Botanical Beach.

California mussels exposed at low tide May 18, 2015.

Mussels showing their dominance in the intertidal.

Looking roughly east down the beach toward the rising sun.

Mussels bordering one of the tide pools scoured by rock and wave action at Botanical Beach, Port Renfrew BC Canada.

Green anemones in a tide pool at Botanical Beach.

Purple urchin in the pool with a small boot for scale.

Wave energy shapes the physical and biological environment at the beach.

Talented graduated students on the beach…and they spot a black bear foraging not too far away.

I shot these rather unsatisfactory movies of the bear as it moved along toward us. The fog started coming in rather quickly and signaled that, with less visibility of our bear friend, we should beat a retreat for the trail.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s