This week saw the last of the good morning low tides of 2016. By “good” I mean a minus tide that hits during daylight hours. There are two more minus tide series in August, with the lows occurring well before dawn. After that the next minus tides don’t happen until mid-October; these will be late in the afternoon so loss of daylight will be an issue. I wasn’t intemperate enough to risk the health of my concussed brain on this week’s low tides but did want to get out if possible. And I’m so glad I tried, because having been out on the past few days’ low tides I feel more myself than I have since the accident. My head hurts a little, but not nearly as much as it would have if I’d done any significant driving two weeks ago. And, I have pictures to share!
Wednesday 22 July 2016—Davenport Landing
I went up to the Landing to collect some animals that I’ll need for my Fall semester class. The full moon was still visible, as the sun hadn’t yet risen above the bluff.
A month after the summer solstice and the algae are still nice and lush. Here’s a nice combination of mostly reds and greens, with some brown kelp thrown into the mix. How many phyla can you spot?
One of the two local species of surfgrass, Phyllospadix torreyi, was blooming. A month ago I’d noticed the congeneric species P. scouleri blooming at Mitchell’s Cove. These surfgrasses are vascular plants rather than algae, and as such they reproduce the way the more familiar land plants do, by pollen transfer from male to female flowers.
In the case of these obligately marine surfgrasses, the pollen is carried by water rather than wind. Not having to attract the attention of animal pollinators, the flowers have not evolved elaborate morphology, color patterns, or nectar rewards. They actually don’t look like much more than swellings near the base of the leaves. Some day I’ll remember to take one of the flowers back to the lab and dissect it to see what it’s like on the inside.
Thursday 21 July 2016—Franklin Point
This was the day I was most worried about. The drive up to Franklin Point takes about 30 minutes, and I hadn’t driven that distance since the accident. To make things even scarier, I couldn’t find someone to go with me. In the end I decided to try getting up there and back on my own, figuring that if my head wasn’t happy with the driving I could always turn around and come home.
When I got there it was cold and very windy, and I was glad I’d worn an extra thermal layer. Up on the exposed coast it is often windy on the road but can be less windy below the bluff on the beach. Yesterday it was windy on the beach, too, more typical of an afternoon than a morning low tide. The wind rippled the surface of the tidepools, making visibility and picture-taking difficult. I tried and didn’t have much success.
Coming over the last dune down to the beach I noticed four or five gulls and a couple of turkey vultures milling about at the mid-tide line. Something must be dead, I figured. And yes, it was very dead.
During last year’s El Niño we saw lots of sea hares in the intertidal up and down the coast. And they were big, heavy football-sized monsters. Yesterday I saw many sea hares, but none of then were larger than my open hand and most were quite a bit smaller. Nor were there any egg masses on the rocks. This guy/gal combo (they’re both, remember?) was about 15 cm long.
By far the most unusual thing I’ve seen in the intertidal this year was a swarm of shrimpy crustaceans. Last year at about this time I witnessed a huge population of small sand crabs (Emerita analoga) in tidepools at Franklin Point. Yesterday the swarmers were swimmers, not burrowers. I think they had gotten trapped in this large pool by the receding tide. Not having any better idea of what they were, I’m going to say they were mysids. Mysids are quite commonly encountered in local plankton tows but I’d never seen them in the intertidal before.
All those brown, orange, and white streaks are mysids. They are about 2 cm long, zooming around super fast. See for yourself:
My first, rather idiotic, thought was that these were krill. They’re about the same size as the krill species most common in Monterey Bay, so perhaps the thought wasn’t quite that idiotic. (but krill in the intertidal? yeah, that’s idiotic. although stranger things have happened and the animals is always right even when it does something that seems idiotic) However, it didn’t take me long to realize that these critters didn’t actually look like krill. They didn’t have the feathery gills under the thorax that krill have. I also noticed that some of them were brooding eggs in a ventral pouch on the thorax, making them members of the Peracarida. Okay, then. Definitely not krill, so maybe . . . mysids? They look like mysids and so far nobody has told me that they’re not mysids, so I’m going to call them mysids.
The sun came out as I finished up in the tidepools. I hiked back up the very steep sand dune and looked back at where I had come from. Wow. Talk about stunning vistas!
Friday 22 July 2016—Natural Bridges
Today was by far the best day this week for picture taking in the intertidal. However this post is getting long so I’m going to showcase the crabs I saw this morning.
Pachygrapsus crassipes is the common shore crab, ubiquitous in the intertidal and at the harbor. It lives in the mid-tide zone and hangs out among the mussels. It is a shy beast, not aggressive and is more likely to drop into the nearest pool if it detects movement nearby. However, if you sit still for only a few minutes, you’ll find yourself noticing many small crabs coming out to bask in the sun.
Here’s a little tidbit about crab biology. All crustaceans breathe with gills. Any gas exchange structure, even your own lungs, functions by providing a surface across which oxygen can diffuse from the surrounding medium into the animal’s blood. Aquatic animals breathe with gills (if they have any specialized gas exchange structures at all, that is) and air-breathing animals breathe with lungs.
These crabs are often seen out of the water, in the sun. How then, you may reasonably ask, do they breathe with gills? The answer is, they foam. They produce bubbles that keep the gills moist, allowing oxygen first to dissolve into a thin layer of water and then to diffuse into the blood. I’m not entirely certain exactly how the crab forms the foam, but suspect it has to do with manipulating a thin layer of secreted mucus to capture small air bubbles. You do see the crabs massaging the foam over their sides, where the openings to the branchial chambers are.
Hermit crabs are the undisputed clowns of the tidepools. Around here we have four species that are commonly seen in the intertidal, all in the genus Pagurus. Many other species in different genera can be seen subtidally.
The most easily identified hermit crab in these parts is, in my opinion, Pagurus samuelis. They have bright red unbanded antennae, and often have bright blue markings on their legs. This species usually inhabits the shells of the turban snail Tegula funebralis.
The other species that I saw today was the much smaller P. hirsutiusculus. The common name for this animal is “hairy hermit crab” but they don’t seem all that hairy to me. They may be found in small Tegula shells, but I most often see them in shells of smaller snails such as Olivella biplicata.
There’s another P. hirsutiusculus in that other Olivella shell in the right-side of the photo, but it did not want to have its picture taken.
All told it has been a very satisfying week. I may have overtaxed my concussed brain a little bit. My plan for the weekend is to revert back to the rest-and-do-nothing routine to let my brain recover. Totally worth it!