Here is my take on last night’s wonderful outing at Miracle Beach
Thirteen naturalists caught a break in the weather to survey the sand flats of Miracle Beach Provincial Park. Under the light of a full moon, the group lamped up to catch the 10:30 pm low tide. Some of the highlights from the outing included
Moonsnails (Neverita lewisii)
· Pipefish (Syngnathus leptorhynchus)
· Leather Stars (Dermasterias imbricata)
· Purple Sea Star (Pisaster ochreus)
· Kelp Crabs (Pugettia sp.)
· Decorator crabs (Oregonia gracillis)
· Aeloid Nudibranch (Hematina trophina ?)
· Sand anemone (species uncertain)
· Eccentric Sand Dollars (Dendraster eccentric)
· Large hermit crabs (Pagarus sp.)
· Horse Clams/Gapers (Tresus sp.)
· Nuttall’s Cockle (Clinocardium nuttallii)
· Whelk shells (occupied by hermit crabs)
· Tube worm casings galore
There were a few remarkable things we saw in the throughs between sand bars. There was a remarkable density of oblique-to-vertically-oriented sand dollars. I counted more than 100 in a 1 m2 at my feet and then got tired of counting. This video from the California Academy of Sciences gets into the physics of their orientation and morphology as it related to feeding and currents and might be of interest to those who were taken with their orientation & form.
Ian pointed out that he has noticed pipefish around pilings and amongst eelgrass beds whilst kayaking. We found them in groups loitering casually in sandy depressions. What were they doing just hanging out here? These relatives of the seahorse feed on crustaceans (maybe the small translucent-brown shrimp or copepods?). Like the seahorses, the males hold the eggs during development. We didn’t notice any brood pouches. Maybe we caught them just being pipefish, living around the eelgrass and feeding on little shrimp.
We saw one unhappy moonsnail with a semi-retracted foot, while Diane found a vigorous specimen cruising the low-tide line looking for some mollusk to murder. Ian and Betty clarified that the moonsnails are vicious predators, using their muscular foot and abrasive radular to drill holes through the shells of bivalves and gastropods so that they may feed on the soft tissues within. This website by Tom Carefoot digs into the research about the mechanics and efficacy of moonsnail feeding.
A seaslug of uncertain affinities
Forgive the lack of photographs, but it was dark. Near the end, we saw a translucent white nudibranch with reddish-pink cerata (fleshy/hairy outgrowths along the back) that terminated in a creamy yellow bulb. If anyone has a confident ID of this, let us know. The keys pointed towards Hematina (Flabellina) trophina, but at that point they were using the flange of the vas deferens as an identifying character. Never the less, the broader group “Aeolids” in this environment have an interesting feeding feature. All over the beach were tubeworm sheaths. It turns out species in this group feed on hydroids (like Obelia) that grow on the outer surface of these tubeworm casings.
It was informally resolved that we try a late summer evening outing to catch bioluminescence in action. Another winter low tide outing will be planned for next year.
Betty Brooks has invited botany and shoreline group members over in February to look into a demonstration of seaweed pressing and survey the tatters of seaweeds onshore in the late winter. Exact details will be mailed out soon.