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Yesterday I had the great fortune to visit a new intertidal site. It can be accessed only by crossing private property. The property owner is my next-door neighbor, and he said I can visit any time. As I said, lucky me! The site is a little north of Pigeon Point, and at first glance the terrain is not very different from Pigeon. But I could tell that it a site that is rarely, if ever, visited by humans. It just had that look of being mostly undisturbed. Yesterday's marine layer was low, making for dark skies and pretty lousy light for picture-taking, so I had to try something new.

This site has a lot of lovely pools and channels to explore, and at this time of year the water is very clear, which does make for good picture-taking. Halosaccion glandiforme, one of the charismatic red algae, is more abundant here than at other sites, and in the pools it grows quite a bit taller than it does on the rocks.

Here's what it looks like on the tops of the rocks. This is a cluster of young thalli. The tallest of these "bladders" is about 4 cm tall. Note that they are about 2/3 full of water, with a large air space at the top.

Many olive-green spherical and ovoid bladders, attached to rock.
Young Halosaccion glandiforme thalli along the San Mateo County coast
2022-08-14
© Allison J. Gong

The really cool thing is what happened when I stuck the camera in the water and took a shot. I got something like this:

Two elongate olive-green bladders, filled about 2/3 with water, submerged in a tidepool
Halosaccion glandiforme and other algae submerged in a tidepool
2022-08-14
© Allison J. Gong

I got a little carried away. But don't things look interesting from the turban snail's perspective?

Olive-green towers rising from a carpet of pink algae. A black snail is nestled between a trio of the towers.
Halosaccion glandiforme and a black turban snail (Tegula funebralis) in a tidepool
2022-08-14
© Allison J. Gong

I'm kind of enraptured by these towers of algae.

Olive-green towers rising from a carpet of pink algae.
Halosaccion glandiforme in a tidepool
2022-08-14
© Allison J. Gong

But the best part of these experiments was the reflections on the surface of the water. Check it out.

Olive-green towers rising from a carpet of pink algae.
Halosaccion glandiforme in a tidepool
2022-08-14
© Allison J. Gong

And this is the money shot! I just love how this turned out.

Olive-green towers rising from a carpet of pink algae in the bottom half of the image. The same tower are reflected in the top half of the image.
Halosaccion glandiforme in a tidepool
2022-08-14
© Allison J. Gong

This was a super fun morning. I'm looking forward to visiting this site again, when the light is better. When the daylight low tides return in a few months they will be in the afternoon. I anticipate some fantastic light shows in these pools and channels. I'll be teaching most afternoons by then, but will get out as often as I can.

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Some organisms, like some people, have a charisma that just can't be explained. For me, the sea palm (Postelsia palmiformis) has always been one such organism. Maybe part of its charm is the fact that it's not very common; it lives on rocky outcrops on exposed outer coasts, which aren't the easiest places to get to.

See? That's a clump of Postelsia way out there in the center of the photo.

Rocks covered with olive-green seaweeds in the foreground and ocean in the midground, under a cloudy sky
Algae-covered rocks in the intertidal at Pigeon Point
2022-08-13
© Allison J. Gong

The tide was pretty good (-0.9 feet) so I figured it was worth working my way out there. I had a wishlist of critters to collect, but they would be pretty easy to find, and I had time to spend in the low intertidal. The algae are still going strong, although I did see some signs of senescence in some of the reds. The Postelsia, on the other hand, were in great shape.

Group of palm tree-shaped olive-green seaweeds attached to a rock in the intertidal.
Small stand of sea palms (Postelsia palmiformis) at Pigeon Point
2022-08-13
© Allison J. Gong

Despite its beautiful olive-green colors, Postelsia is a brown alga in the phylum Ochrophyta. It is in the same order (Laminariales) as the large canopy-forming kelps Macrocystis pyrifera and Nereocystis luetkeana. However, Postelsia gets to be only about a half-meter tall. It has a thick, flexible stipe and a cluster of thin blades at the top of the stop, which give it the palm tree appearance. Postelsia's hapterous holdfast does what it says on the label—it hangs on tightly to the rock. In fact, the rock often fails before the holdfast does, and when Postelsia washes up onto the beach it often has bits of rock (or mussel or whatever) still in the grip of the holdfast.

And it turns out that Postelsia is one of the many photogenic seaweeds. This morning it was doing the '80s hair band thing. Especially when photographed from the vantage of a front-row groupie.

Postelsia palmiformis rocking the joint at Pigeon Point
2022-08-13
© Allison J. Gong

So that's the organism that captured and held my attention this morning. The algae don't get nearly the appreciation they deserve, even among fans of the rocky intertidal. Maybe shining a light on them once in a while is something I can do to fix that.

One of the reasons I selected this particular Earthwatch expedition was that it involved studies of both forest and ocean, which are my two favorite ecosystems here at home. I wanted to compare what I'm familiar with to similar habitats on the opposite coast. Regarding the rocky intertidal, I had been warned not to expect the spectacular biodiversity I'm used to on the Pacific coast, and that warning turned out to be quite a propos.

Along the California coast the rocky intertidal is an explosion of colors and textures, especially during the growing season. See this at Pigeon Point:

Ocean and seaweed-covered rocks
Rocky intertidal at Pigeon Point, San Mateo County, California
2022-06-01
© Allison J. Gong

and this at Asilomar:

Ocean and seaweed-covered rocks
Rocky intertidal at Asilomar, Monterey County, California
2022-06-03
© Allison J. Gong

And this is what you see when you walk—or in the case at Pigeon Point, climb down—to the site. It just is this varied, with several algae that are easily recognizable as being different even if you don't know what their scientific names are.

Contrast that with the rocky intertidal at Frazer Point on the Schoodic Peninsula:

Coastline with small rocks covered with golden-brown seaweed
Mounds of Ascophyllum nodosum at Frazer Point on the Schoodic Peninsula
2022-06-17
© Allison J. Gong

All of the algae covering these rocks are rockweeds, and most of it is Ascophyllum nodosum. One of the projects we worked on was a study measuring the biomass of Ascophyllum on the coast of the Schoodic Peninsula. To do so we sampled along 30-meter transects in the intertidal, counting the number of Ascophyllum thalli in half-meter quadrats, looking for other algae and some key invertebrates, and weighing the Ascophyllum. This last part was new to me, and a lot of fun. It involved dividing the masses of Ascophyllum into as many as three bundles, wrapping it all up in a net like a burrito, and weighing the burrito using a hand-held metric scale.

Three people wearing yellow high-visibility vests kneeling among algae in the intertidal
Left to right: Sally, Alex, and Valerie weighing Ascophyllum at Frazer Point in Acadia National Park
2022-06-17
© Allison J. Gong

Clearly, Ascophyllum nodosum makes up the vast majority of biomass along this coastline. There are some other rockweeds in the genus Fucus, a bit of sea lettuce (Ulva sp.), and that's about it. But the lack of diversity doesn't mean the intertidal doesn't have its own sort of spartan beauty. The lead for this project, Maya, described Ascophyllum as having a Van Gogh effect in the landscape. It didn't take long to see what she meant. Check it out:

Ascophyllum nodosum at Frazer Point in Acadia National Park
2022-06-17
© Allison J. Gong

and

Ascophyllum nodosum at Frazer Point in Acadia National Park
2022-06-17
© Allison J. Gong

There are, of course, many types of beauty in the natural world. What I saw in the intertidal at Acadia wasn't at all like what I'm used to seeing on the Pacific coast, but I wouldn't say it is any less beautiful. The variation in color between new growth and the older parts of the Ascophyllum thalli makes for gorgeous patterns as the thalli drape over cobbles.

Besides, any morning in the intertidal is a good morning! I certainly wasn't going to complain.

One of the many delightful animals in the rocky intertidal is the vermetid snail, Thylacodes squamigerus. Unlike their more typical gastropod relations, the vermetids don't live in a shell, per se. Instead, they live in a calcareous tube, which forms a loose coil draped over the surface of a rock. The tubes can be up to about 12 mm in diameter, and, if straightened out, about 15 cm long. In some locations, Thylacodes can be very abundant. In a recent visit to Point Pinos in Pacific Grove, I saw many of them in the low intertidal. I occasionally see them on the northern end of Monterey Bay and points farther north, but at nowhere near the abundance I see in Pacific Grove. At a larger scale, iNaturalist shows observations of T. squamigerus from northern British Columbia down to southern Mexico.

Three coiled white tubes and one spherical snail on a rock amid greenish seaweed
Trio of vermetid snails (Thylacodes squamigerus) with their more conventional cousin, the black turban snail (Tegula funebralis)
2022-06-03
© Allison J. Gong
Loosely coiled whitish tube on a rock
Thylacodes squamigerus
2022-06-03
© Allison J. Gong

Most snails are either grazers (e.g., abalones, limpets, turban snails) or predators (e.g., whelks, conchs, cone snails). Thylacodes is a bit of an outlier with regards to feeding as well as housing, for it is a suspension feeder. Being entirely sessile, it cannot go out and forage. And unlike its doppelganger, the tubeworms Serpula columbiana and S. vermicularis, Thylacodes does not create a water current to catch food on ciliated tentacles. Instead, it spins threads of sticky mucus that thrash around in the current and capture suspended detritus. When the tide is out the snail hunkers down in its tube, same as any worm. It cannot feed unless it is immersed. Where the worms live in the low intertidal on exposed rocky coasts, the water is moving constantly, and it requires relatively little energy for Thylacodes to feed the way it does. As a bonus, even the calories expended in producing the mucus are recouped, as the snail ingests the mucus strands as well as the food particles they capture.

When the tide came back, I got to watch Thylacodes in action. At Point Pinos there are some areas that form lovely tidepools, deep enough for animals to react to the return of the water and clear enough to make photography and videography possible. So standing knee-deep in a pool I stuck the camera underwater and hoped for the best. And I got lucky—you can see the mucus threads!

See here:

Thylacodes squamigerus
2022-06-03
© Allison J. Gong

and here:

Thylacodes squamigerus
2022-06-03
© Allison J. Gong

And not only that, but I captured some video footage. I use a point-and-shoot for these underwater shots, and usually don't know what or whether I've shot anything good until I download images and video at home. Color me happy to have seen these clips!

Despite the unusual aspects of its biology, Thylacodes is indeed a snail. It has a conventional snail's radula, and uses it the way, say, an owl limpet (Lottia gigantea) uses hers to scrape algae off rocks at Natural Bridges. Only instead of scraping the radula against rocks, Thylacodes uses its radula to reel in the detritus-laden mucus threads. That's what's going on in the second video clip above.

So there you have it, another of my favorite animals. Thylacodes is one of those animals that doesn't look like much when you see it just sitting there. But we get to see it only during the tiny fraction of its life that it spends emersed. As with most inhabitants of the rocky intertidal, much of Thylacodes' life occurs out of sight for human eyes. This makes the occasional sighting of Thylacodes under water especially enlightening. And delightful!

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Last week we had some of the best low tides of the season, and I was grateful to spend three consecutive mornings in the intertidal. The picture-taking conditions were fantastic when I went to Natural Bridges, and I snapped away like a madwoman. Unfortunately, last week was also finals week, and it wasn't until I got all of the grading done and actual grades submitted that I let myself look at the photos. And there were a lot of good ones!

There are many wonderful things about the early morning low tides. One of the best is that most people prefer to remain in bed rather than get up before the sun and splash around in cold water. The past several weeks had been very busy, with little time for solitude, and I badly needed some time by myself in nature.

Usually when I post an entry here I have a story to tell. This time I don't, unless the photos themselves tell the story. Let me know what you think.

Rocks covered in green surfgrass and brown seaweed, surrounded by water. Wave breaking in the background. Clouds in the sky.
Low intertidal at Natural Bridges
2022-05-17
© Allison J. Gong

Act I

At this time of year the algae are the stars of the show. They are at their most lush and glorious for the next several weeks.

Brown and dark iridescent seaweeds on rocks
Assemblage of mid-intertidal organisms
2022-05-17
© Allison J. Gong

Even in the sand, the algae were abundant and conspicuous. In the low intertidal the most prominent algae are the kelps. Here the feather boa kelp (Egregia menziesii) and the various Laminaria species are doing really well. Egregia also occurs higher in the intertidal, but Laminaria and Macrocystis (just visible along the right edge) are low intertidal and subtidal species.

Kelps (Egregia menziesii, Laminaria setchellii, and Macrocystis pyrifera) in the low intertidal
2022-05-17
© Allison J. Gong

My absolute favorite sighting of the morning was this group of algae on top of the sand. I love the way that the algae are splayed out. They are just so pretty!

Assemblage of algae in the sand
2022-05-17
© Allison J. Gong

Macrocystis pyrifera is justifiably well known as the major canopy-forming kelp along our coast. But it does occur in the low intertidal, as mentioned above.

Long strands of golden-brown seaweed
Giant kelp (Macrocystis pyrifera)
2022-05-17
© Allison J. Gong

Intermission

Act II

And now to focus on some individual organisms. Starting with my favorites, the anemones. This time it was the giant green anemone, Anthopleura xanthogrammica, that was the star of the show.

Large bright green sea anemone
Green anemone (Anthopleura xanthogrammica)
2022-05-17
© Allison J. Gong

I experimented with close-up shots, too!

There was a clingfish (Gobiesox meandricus), in its usual under-rock habitat. Don't worry, I made sure to carefully replace the rock as I found it. This fish was about 10cm long. It may be the first clingfish I've ever seen at Natural Bridges. Clearly, I need to do more rock flipping.

Mottled brown fish with large head, on a rock
Northern clingfish (Gobiesox meandricus)
2022-05-17
© Allison J. Gong

A clingfish's pelvic fins are fused together and modified to form a suction cup on the ventral surface. Clingfish can hop around a bit and are super cute when they eat. They sort of dart forward and land on the food, then shuffle around as they ingest it.

The coralline algae were both abundant and flourishing. They are looking fantastic this season. Someday I'll study up on the coralline algae and write about them. For now, here are some happy snaps of Bossiella.

Pink, stiff, seaweed. Body of repeated sections.
Bossiella sp., one of the erect coralline algae
2022-05-17
© Allison J. Gong

Such a beautiful organism!

Sticking with the pink theme, another oft-overlooked organism is the barnacle Tetraclita rubescens. It has a few common names, including pink volcano barnacle and thatched barnacle. It is the largest of the intertidal barnacles along the California coast, and can be fairly abundant in some places. It is never as abundant as the smaller white (Balanus glandula) and gray/brown (Chthamalus dalli/fissus) barnacles, though.

Large pink barnacles on a rock
Tetraclita rubescens, the large pink barnacle
2022-05-17
© Allison J. Gong

Which brings us to my favorite color, purple. The tentacles of the sandcastle worm, Phragmatopoma californica, are a beautiful shade of purple. You don't get to see the tentacles unless the worm is under water, and with the tide as low as it was when I was there this past week, it wasn't easy finding any Phragmatopoma that were submerged. I've written about Phragmatopoma before, so won't go into details here. But look at all those fecal pellets!

Tentacles of the sandcastle worm, Phragmatopoma californica
2022-05-17
© Allison J. Gong

And last but not least, here are a couple of the many purple urchins (Strongylocentrotus purpuratus) out there. At Natural Bridges there's a large pool fairly high in the mid-intertidal that is called the Urchin Pool because it contains dozens (hundreds?) of urchins. Most of them are burrowed into the soft rock. Those are sort of easy pickings. I like finding urchins in less-obvious places, like these.

Purple urchins (Strongylocentrotus purpuratus) tucked into burrows
2022-05-17
© Allison J. Gong

Urchins in the intertidal often cover themselves with bits of shell, small pebbles, and algae. This helps them retain water as the tide recedes. At a location where the rock is soft, such as Natural Bridges, many of the urchins have grown larger than the opening to their burrow and cannot leave to forage; these imprisoned urchins have to wait for pieces of algae to drift nearby, which they can grab with their tube feet and then transport to the mouth on the underside. So long as they don't get pried out by otters, the urchins seem to do just fine.

I think that's enough for now. I hope these photos give you some idea of what it was like out there a week and a half ago. The next excellent low tide series is in mid-June. Snapshot Cal Coast will be in full swing then, so get out there if you can!

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Big waves breaking on beach, with cliffs on the right side

One of the things that I've been doing with my Ecology class since almost the very beginning is LiMPETS monitoring in the rocky intertidal. Usually we have a classroom training session before meeting in the field to do the actual work. This year we are teaching the class in a hybrid mode, with lecture material being delivered remotely, so we don't have class meetings except for our field trips. The LiMPETS coordinator for the Monterey Bay region, Hannah, and I arranged to meet at our sampling site, where she would do a training session on the beach before we herded everyone out into the intertidal. It truly was a great plan! But the weather intervened and a spring storm blew through, bringing in a big swell. There was a high surf warning for our area the day of our scheduled LiMPETS work. Hannah and I conferred via email and decided that we'd still give it a shot, and at least the students would have an opportunity to learn about the LiMPETS program and practice with the datasheets and gear.

I arrived early to see how the surf was looking, and it was impressive. The waves were regularly covering our sampling location with whitewash, even as the tide was going out. When my co-instructor arrived and I showed him where the transect would lie, it was an easy decision to make to cancel the monitoring. But we would still be able to do the practice stuff, so we convened with Hannah on the bluff and she went into teacher mode.

College students standing in a circle, listening to instructor
Hannah (right) explaining the LiMPETS program
2022-04-22
© Allison J. Gong

We didn't bother with the transect, but had groups of students work through some quadrats out on the intertidal bench, which you can just see in the background of the photo above. Hannah kept everyone out of the danger zone and we stressed the importance of having one member of each group keep an eye on the ocean at all times. We stayed mostly in the high zone, venturing down into the upper mid zone only when the tide was at its lowest. Even then, the big swells would surge up the channels and splash up onto the benches. Nobody got swept off, though, or even more than a teensy bit damp.

Most of the students left after what little work we had for them to do, and that gave me the freedom to poke around on my own and take pictures. I hadn't had a chance to do this in a long time, and intended to make the most of a decent low tide that was almost wiped out by huge swell.

So here we go!

First up, the high-intertidal seaweeds:

Olive-green seaweed on rock, with mussels surrounding
Silvetia compressa
2022-04-22
© Allison J. Gong

And here's a typical high intertidal community at Davenport Landing. Inhabitants include:

  • Several large clumps of rockweed (Silvetia compressa and Fucus distichus)
  • Several smaller bunches of tufty reds (Endocladia muricata)
  • Mussels (Mytilus californianus)
  • Many blotches of "tar spot alga" which is the encrusting tetrasporophyte phase of Mastocarpus papillatus
Clumps of olive-green seaweeds, dark red seaweeds, and mussels on rock
High intertidal community at Davenport Landing
2022-04-22
© Allison J. Gong

The water was pretty murky, so not great for underwater photography. Some of the shots turned out pretty well, though. The soft pale purple structures that you see in the photo below are papullae, used for gas exchange. You can see these only when the star is immersed.

Clumps of pale purple transparent tubes interspersed with white blotches
Aboral surface of the ochre star Pisaster ochraceus, showing papullae and spines
2022-04-22
© Allison J. Gong

The anemones were, as always, happy to be photographed. In this shot, the anemone was being photobombed by a turban snail.

Large green sea anemone and small purple snail in a tidepool
Green anemone (Anthopleura xanthogrammica) and black turban snail (Tegula funebralis)
2022-04-22
© Allison J. Gong

Here's another typical intertidal assemblage:

Clump of sandy tubes with mussels, barnacles, and greenish-purple seaweed
Sandcastle worm (Phragmatopoma californica), iridescent alga (Mazzaella flaccida), gooseneck barnacles (Pollicipes polymerus), and mussels (Mytilus californianus)
2022-04-22
© Allison J. Gong
Gooseneck barnacles (Pollicipes polymerus)
2022-04-22
© Allison J. Gong

A couple of students stayed after the rest of the class had left. They were happy to see the nice fat ochre stars, and so many of them in one small area.

It's always good to see so many big ochre stars. For this species, in the intertidal areas that I visit, sea star wasting syndrome (SSWS) no longer seems to be a problem. Fingers crossed! We'll have to see what unfolds in the next months and years.

On this winter solstice, as we anticipate the return of light, I thought I'd write about a different kind of light.

Merriam-Webster defines fluorescence as "luminescence that is caused by the absorption of radiation at one wavelength followed by nearly immediate reradiation usually at a different wavelength and that ceases almost at once when the incident radiation stops". It is a type of luminescence that occurs in both biological and non-biological objects. For example, mushrooms and scorpions are notably fluorescent, as are several minerals. Technically, to qualify as "fluorescent" an object can absorb any wavelength of radiation and re-radiate any other, although the re-radiated wavelength is usually longer than the absorbed wavelength.

We humans, with our three (and occasionally four) color photoreceptor types, can see only the tiny fraction of the electromagnetic spectrum that we call visible light. The visible light range (approximately 400-700nm) is bounded by UV on the short end and infrared on the long end. Other organisms have very different light perception capabilities. We know, for example, that insects can see in UV and pit vipers can see in infrared. And as for mantis shrimps, which have as many as 12 types of photoreceptors, we don't yet understand how they see the world, but you can bet it's nothing like the way we do. For practical purposes, fluorescence is most easily seen when an object absorbs UV light and re-radiates light of a longer wavelength that falls into the visible light range.

When you shine a UV light on one of these fluorescent objects, you see an apparent color change from whatever it looked like under visible light. This color change is most striking in the dark, because the fluorescent object will appear to glow. The same thing happens in daylight, but is obviously more difficult to see.

Here, let me show you. A few weeks ago I went to Natural Bridges to photograph the anemones, first under normal daylight conditions and then under UV light. I have a pretty wimpy UV flashlight, it turns out, but you can still see the fluorescence.

Here's Anemone #1, under daylight:

Sea anemone in daylight
Sunburst anemone #1 (Anthopleura sola) at Natural Bridges
2021-12-07
© Allison J. Gong

And here's Anemone #1 under UV light:

Sea anemone under UV light
Sunburst anemone #1 (Anthopleura sola) at Natural Bridges, under weak UV light
2021-12-07
© Allison J. Gong

Striking difference, isn't it?

This is Anemone #2. It was getting dark by then, but this photo was also taken without flash and I did not increase exposure of the image.

Sea anemone
Sunburst anemone #2 (Anthopleura sola) at Natural Bridges
2021-12-07
© Allison J. Gong

And, under UV light:

Sea anemone under UV light
Sunburst anemone #2 (Anthopleura sola) at Natural Bridges, under weak UV light
2021-12-07
© Allison J. Gong

Here's what's going on. Pigment molecules in the anemones' tissues are absorbing the UV radiation and re-radiating light in the visible range. It's easier to see the fluorescence in Anemone #2 because it was much darker when I took that set of photos. Fluorescence still occurs during the day, but we can't see it as well in the daylight. This is why our local bowling alley does their Atomic Bowling at night! They can dim the overhead lights, crank up the black lights, and let the tunes roll.

Incidentally, if you've ever wondered why so-called black lights are purple, there's a reason for it. A true black light emits only UV light. UV light is invisible to us, hence the term "black", as in pure darkness. UV lights that ordinary folks like us can buy are tinged purple so that we can see it. The purple isn't UV, of course, but seeing the purple light keeps people from looking into the beam and frying their retinas from the actual UV radiation.

Sea anemones, of course, do not celebrate the solstice, but they do perceive it. They, and just about every other living thing, can sense the cyclical changes in day length as the year progresses. After tonight the days will start getting longer as we move through winter and towards spring. Personally, I cannot wait until we get the early morning low tides in the spring.

In the meantime, happy solstice, everyone!

Yesterday I had some time to kill before getting a COVID test, and, as usual, wandered down to the ocean. This time I was at Seacliff State Beach. It was pretty crowded, so I walked onto the pier to see if the fishermen were having any luck. They weren't, really. One man kept catching jack silversides (Atherinopsis californiensis) that were too small to keep. There was a lot of banter about sharks and bait and crabs, but what I witnessed yesterday confirms my hypothesis that a lot of what people call "fishing" is merely an excuse to get outside for a few hours. And there is absolutely nothing wrong with that.

As for me, I have nowhere near enough patience to make a decent fisherman. I did, however keep myself amused by eavesdropping on their conversations and writing snippets in my nature journal. I did also find myself mesmerized by the anchovies. Watch for yourself.

Northern anchovies (Engraulis mordax) at Seacliff State Beach
2021-11-23
© Allison J. Gong

Like sardines, anchovies are planktivorous filter feeders. If you watch the video again and can focus on an individual fish for a while, you'll see that as it swims forward, the front end becomes white and bulbous for a few seconds. That's sunlight reflecting off the fish's jaws. Anchovies have metallic silver coloring, which is a defense against predators. For fish that live in surface waters that are brightly lit, all of those glinting flashes of light make it difficult for a predator to zero in on a single fish to pursue. There is safety in numbers, and for anchovies the silvery coloring combined with schooling behavior means that if a predator manages to catch some of the fish in the baitball, most will avoid being eaten. This works against predators such as larger fish, squid, and birds, which generally capture one or a few fish at a time. But if the predator happens to be a humpback whale, which is capable of engulfing the entire school, then the anchovies are SOL. Think about it, though. For any anchovy, the probability of encountering a larger fish, squid, or bird is much higher than encountering a humpback or blue whale. Thus the selective advantage of schooling!

Okay, now back to the feeding. Anchovies have really long jaws for their size and can, like snakes, open their mouths very wide. This allows them to filter as much water as possible as they swim. Food, mostly plankton, is caught on the gill rakers, which are bony or cartilaginous structures projecting forward (i.e., towards the mouth) from the gill arches. Some fishes' gill rakers are nothing more than short nubs. Filter feeding fishes such as anchovies have long thin gill rakers. Water enters the mouth as the fish swims forward, and plankton is caught on the array of gill rakers. The water then passes over the gill filaments, where respiratory exchange occurs, and then out from underneath the operculum. Anchovies cannot suck water into their mouths, and thus can feed only while swimming forward, or ramming water into the mouth. This is a type of feeding called ram feeding.

These anchovies were very close to shore. They were feeding, so obviously there was plankton in the water. I haven't done a plankton tow in a while, as I generally assume that fall/winter plankton isn't as interesting as spring/summer plankton. However, given the presence of feeding anchovies inshore, it might be time to test that assumption.

4

For some reason, many of the sunburst anemones (Anthopleura sola) in a certain area at Davenport Landing were geared up for a fight. I don't know what was going on before I got there yesterday morning, but something got these flowers all riled up. We think of them as being placid animals, but that's only because they operate at different time scales than we are used to. A paradox about cnidarians is that they don't do anything quickly except fire off their stinging cells; that, however, they do with the fastest known cellular mechanism in the animal kingdom. Go figure.

Pale green sea anemone with slender feeding tentacles surrounding the oral disc. Below the ring of feeding tentacles there is a ring of thick club-shaped tentacles used for fighting.
Sunburst anemone (Anthopleura sola) with inflated acrorhagi
2021-06-27
© Allison J. Gong

What looks like an anemone wearing a tutu is actually an anemone ready to fight. The normal filiform feeding tentacles are easily recognized. But those club-shaped white tentacles below the ring of feeding tentacles are called acrorhagi. They are all about fighting. The tips are loaded with potent cnidocytes that usually aren't used to catch food. They are used to fight off other anemones, and possibly predators.

Here's another shot of the same animal, which shows how the feeding tentacles and acrorhagi are arranged in concentric rings:

Pale green sea anemone with slender feeding tentacles surrounding the oral disc. Below the ring of feeding tentacles there is a ring of thick club-shaped tentacles used for fighting.
Sunburst anemone (Anthopleura sola) with inflated acrorhagi
2021-06-27
© Allison J. Gong

So who would this anemone be fighting? This individual was the only one of its kind in the pool where it lives. I don't know why its acrorhagi are inflated. I suppose they could be used to fend off a would-be predator, but I didn't see any other animal in the pool that seemed a likely candidate.

But look at this duo:

Two pale green sea anemones with slender feeding tentacles surrounding the oral disc.The anemone on the right has inflated fighting tentacles. The animal on the left has fewer inflated fighting tentacles.
Sunburst anemones (Anthopleura sola) with inflated acrorhagi
2021-06-27
© Allison J. Gong

Now, clearly there is (or had been) something going on between these individuals. They both have their acrorhagi inflated. I've been looking at this photo for a while and can't decide which is the aggressor. At first I assumed that the anemone on the right had initiated an attack on the other. But now I wonder if that is a defensive posture rather than an offensive one. That animal does seem to be more bent out of shape than the one on the left.

I've seen anemone fights before, and I've also seen anemones living side by side, tentacles touching, in apparently perfect amity. It's very clear that they can coexist peacefully. Why, then, do they sometimes choose to fight? It's important to point out that Anthopleura sola is an aclonal species. Unlike its congener A. elegantissima, whose primary mode of growth is cloning, each A. sola represents a unique genotype. With these anemones, whether or not two individuals fight is not determined by relatedness.

In a different pool these two anemones are sharing the carcass of a rock crab.

Sunburst anemones (Anthopleura sola)
2021-06-27
© Allison J. Gong

Maybe that third anemone at the top had also taken part in the feast, but at this point it seemed to be minding its own business. Given the demonstrated aggression of some A. sola, it would be interesting to know whether or not this trio ever fight amongst themselves. When we 'ooh' and 'aah' over them in the tidepools they look like passive flowers, and we forget that they are active predators. But we humans have access to the anemones' home for only a few hours every month, and I have no doubt that they get up to all sorts of shenanigans when we're not looking.

2

Sometimes things just work out, through no fault of my own. In terms of good minus tides occurring in daylight hours, this weekend's tides are the best we will have all season. Today (Saturday 29 May) is the third of five intertidal excursions I have planned. This morning I went up to Pistachio Beach to collect some things for the Seymour Center. I always feel a teensy bit apprehensive agreeing to collect for anybody but myself, because it is quite likely that I will get skunked and not be able to bring back what is needed. So usually I just agree to keep my eyes open for things that are on the wish list and make no promises.

The current wish list for the Seymour Center includes fishes. I've already brought them some sculpins and a clingfish, but small pricklebacks are also welcome. Pistachio is a popular place for people who fish for large pricklebacks. Apparently they (the pricklebacks) put up a good fight and make tasty eating. The usual way of fishing for them is poke-poling. I am not entirely sure how that works, but it involves a long pole and baited hooks. I think the idea is to lure a prickleback out from its hiding place at low tide, when it is sort of stranded away from open water. Adults get up to 70-80 cm long, and are as big around as my forearm.

Unlike the fishermen, I was fishing for young pricklebacks, hoping to find some that were about the length of my hand. Possessing the ideal set of characteristics for avoiding capture—a long eel-like body, small head, slimy coating, and the ability to augur really quickly into even the tiniest crack amongst the cobbles—these small fish led me on a merry chase for quite a while. However, the advantages that I have over even a wily prickleback are an enlarged cerebral cortex, opposable thumbs, and the dexterity to use both a dip net and a zip-loc baggie. When all was said and done I had two appropriately sized pricklebacks in my baggie, and two others had gotten away from me. Oh, and I did also bag another clingfish!

Having had that bit of success and not wanting to press my luck, I started poking around just for the hell of it, without any clear objective in mind. As I've said before, what we gain from a super low tide like this (-1.6 ft) is not only access to more real estate in the low intertidal, but more time to spend there before the tide returns. I took lots of photos, which I will present in chronological order. These will give you an idea of what it was like out there this morning.

Even the hike across the beach yielded something nice—this small stand of Postelsia palmaeformis, the sea palm. These poor junior kelps will be taking a beating with these spring tides rushing up and down. That's the price they pay for living out there on those exposed rocky points.

Group of 6 sea palms on the beach
06:53 Postelsia palmaeformis
2021-05-29
© Allison J. Gong

The leather star Dermasterias imbricata isn't one of the most common stars in the intertidal around here. It was one of the species that was hit pretty hard by the most recent outbreak of Sea Star Wasting Syndrome. We see one every so often, but they are nowhere as abundant as the ochre stars or bat stars.

07:10 Dermasterias imbricata
2021-05-29
© Allison J. Gong

Pistachio Beach isn't the best place for large anemones, but of course there are some. This is one of the few big Anthopleura anemones that I saw today. There are many of the small cloning anemones, A. elegantissima, in the high intertidal, as well as the moonglow anemones, A. artemisia, in the mid and low sandy areas.

07:12 Anthopleura xanthogrammica
2021-05-29
© Allison J. Gong

I was so pleased to see my favorite red alga doing really well in the low zone! It is so pretty.

Red seaweed
07:29 Erythrophyllum delesserioides
2021-05-29
© Allison J. Gong

And at the same time I accidentally discovered a pretty big rock crab, which was tucked under a rock. For its species, this one was pretty calm and didn't come at me with big claws up. It could be that this crab is a male, and is clasping a female beneath him. I didn't check.

Dorsal view of a rock crab
07:29 Romaleon antennarium
2021-05-29
© Allison J. Gong

One of the things I found while turning over rocks to look for fish is this purple urchin:

Sea urchin with purple and green coloration
08:02 Strongylocentrotus purpuratus
2021-05-29
© Allison J. Gong

And a bit later, a nice healthy group of Dictyoneurum californicum. As these thalli age, they will develop longitudinal splits at the base of the blades. Right now they are young and crispy.

Blades of a brown seaweed with a waffle-like texture
08:15 Dictyoneurum californicum
2021-05-29
© Allison J. Gong

And who can resist such an exuberantly decorated limpet? Certainly not I! Reminds me of the fancy hats that ladies used to wear for Easter. Or Beach Blanket Babylon.

Limpet heavily fouled with encrusting and upright coralline algae
08:28 Limpet, probably Lottia sp.
2021-05-29
© Allison J. Gong

Chitons, the overlooked molluscs that reach peak abundance and diversity in the intertidal, can be very common along the coast. Species composition varies from site to site, though. Here at Pistachio Beach, the two species of Tonicella are very common. I found several of them on the undersides of rocks. This one is T. lokii.

Chiton with dark wavy lines on the shell plates and alternating pink and beige patches on the girdle
08:52 Tonicella lokii
2021-05-29
© Allison J. Gong

After two hours of catching fish and looking around, I was getting cold. Time to head back up and out. That took an additional half-hour or so, because I kept getting distracted by the algae. For example, look at how beautiful this Fucus is. And note the swollen tips, which mean this thallus is getting sexy. 'Tis the season, after all.

Olive-green seaweed with wide dichotomous branches and swollen branch tips
09:15 Fucus distichus
2021-05-29
© Allison J. Gong

One of the other rockweeds, Pelvetiopsis limitata, was also very thick and abundant.

Olive-green seaweed with narrow dichotomous branches
09:19 Pelvetiopsis limitata
2021-05-29
© Allison J. Gong

The rockweeds share the high intertidal with a few species of red algae. The most common reds in this zone are the two (or however many there are) species of Mastocarpus, and Endocladia muricata.

Reddish-brown seaweed with wavy blades, covered with tiny bumps
09:21 Mastocarpus papillatus
2021-05-29
© Allison J. Gong

I always want to stop and look around in the high zone on my way down. Because when I walk past sights like this, it's hard not to stay and study more closely. Then I remember that I can take as much time as I want in the high zone on the way out. This morning I took lots of photos of these reds and rockweeds.

How many different types of seaweed can you see?

09:24 High intertidal algal assemblage
2021-05-29
© Allison J. Gong

So there you have it, my morning summarized in about a dozen photos. I hope your Saturday was as enjoyable as mine was!

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