UC Davis math professor Abby Thompson has sent us a batch of lovely marine invertebrate photos from California. Abby’s captions and IDs are indented, and you can enlarge her photos by clicking on them.
The October low tides had some challenging features. There was a strong wind (which makes me cold and everything harder to photograph), but most importantly the tides were running about a foot over (astronomical) predictions.
The very highest tides here are usually about 6 feet above sea level, and the very lowest about 2 feet below (listed as +6 or -2). A “good” low tide, when lots of different species are visible, is below –1. This means that a 1-foot difference from predictions has a significant impact on where you can go and what you can see. The reason for the overage is apparently twofold; the warmer water from El Niño (thermal expansion of the water), and the mysterious “Kelvin waves” sweeping up the coast, which interact in a complicated way. While the physics of the Kelvin waves escapes me, I can attest that the low tides were about 1 foot higher than projected, and that the water is warmer than usual. While my personal frustration is with the too-high low tides, everyone else is understandably worried about the upcoming King tides in November, December and January, when the maximally high tides of the year occur. If those high tides run 1-2 feet higher than usual, and happen to coincide with a storm surge, there’s going to be a lot of coastal flooding.
Challenging or not, it’s always beautiful to be on the beach, so here are photos from late October.
Some species of gull (Genus Larus)—perhaps someone can tell species from this photo. The sand acted like a mirror in the late afternoon sun:
By-the-wind sailor (Velella velella). In the spring these can wash up by the thousands, but it’s unusual to find any alive at this time of year. It might be because of the warmth of the water. I found two very small ones:
By-the-wind sailor underside:
Urtibrina rimicola; this used to be (approximately last week) called a “stubby Pacific rose anemone”; then the taxonomists got to work on it, and it’s now stuck with just a scientific name:
A clutch of nudibranchs: the first two are common, but happened to pose nicely for the camera:
The second two are rarer where I am; I’ve found each of them only once or twice.
Apata pricei. Dillon Beach (where I am) was close to the northern edge of this species’ range on inaturalist until a few days ago, when someone posted one from much farther north, near Trinidad, CA. El Niño at work?:
Polycera atra. It’s a little hard to believe this coloration is adaptive, but they’re surprisingly hard to spot. The second photo gives a little better idea of how they might blend into their bryozoan prey. Kind-of like a zebra:
Polycera atra blending in?:
The path down to the beach:
Beach in the wind and waves just after sunset:
Thanks Abby. I particularly like the beach and surf photos- I can feel and smell the marine air! I always found the extreme low tides fascinating each year when we lived on the James River tidal estuary which was five miles across in front of our house. While normal low tides left a foot or more of water under our neighborhood boat docks and piers, the extreme lows would expose the mud flat river bottom even beyond the longest pier. It was eery walking out a thousand or more feet from shore on exposed river bottom and strolling our neighborhood from what felt like being in the middle of the river…with views we normally only had from a boat.
By-the-wind Sailors are very strange creatures. Great pictures. And the nudibranchs are spectacular. It’s interesting what snails can do when they shed their shells. Love those intertidal pictures. Thank you and keep ‘em coming!
These photos are a treasure. I am amazed by the various configurations of these creatures. Delightful post.
Thanks!
Maybe the colors on Polycera atra are useful in that they break up the animals outline. Reminded me of the “Dazzle Camouflage” I read about that was used on ships in WW2. That made it difficult to track them I believe.
The pictures and the animals are great.
Beautiful photos Abby! I particularly like the last one: Nice work! Thanks for sharing these.
A couple of questions:
1) What equipment are you using? Especially the wet photos.
2) Where is the beach? It looks like the Oregon coast.
Dillon Beach is in Marin County.
A Olympus (or now “OM system”, I guess) TG-6. I was using a TG-7 but fried it so I had to go backward to my old one. They are amazing, particularly for a point-and-shoot camera. They’re supposed to be indestructible (and are definitely waterproof) but I’ve managed to destroy several.
And it’s Dillon Beach, about 1/2 hour south of Bodega Bay.
I think the gull photo is spectacular (award worthy?). I don’t know anything about Polycera atra specifically but aren’t most nudibranchs distasteful, toxic or loaded with stolen nematocysts? Why can’t this just be warning coloration (aposematism)?
Jerry made this observation also- and it’s likely the correct explanation. I was just struck by how easily they disappeared into the bryozoan. I was taking photos of one for several minutes before I noticed there were in fact two on the same ~2 inch ball of stuff.
Fantastic photos of fantastic creatures.
Thanks for the kind comments everyone!