I had seen the sea lettuces (Ulva spp.) spawning in these high pools at Franklin Point before, and usually cursed the murkiness of the water. But today the water was dead calm, with the tide low enough that there were no waves to slosh into the pools. The result was a gorgeous marbled swirl in the water. The patterns were stunning.
What these photos show is the Ulva releasing either spores or gametes. Without microscopic examination it's impossible for me to know whether these tiny cells are spores or gametes. What I can say is that the spawn is released from the distal ends of the thallus, making the body of the alga look ragged.
The parts of the thallus that have already spawned are now clear. The tissue itself will soon disintegrate, leaving behind only the healthy green parts, which should be able to regrow.
All of these photos were taken in pools where the spawning itself had either completely or mostly stopped. Obviously when the tide comes back all of this yellow spooge will get mixed up. It's only when the water is perfectly still that these streams would form. It was hard stepping around the pools to take the photos, as the last thing I wanted to do was stomp my big booted foot into a pool and disrupt the beautiful patterns. Fortunately the sun angle was a little cooperative this morning, and I was able to find a pool where active spawning was happening.
What appears to be an act of destruction—the alga's brilliant green thallus being reduced to yellow streaks that drift away with the tide—is really an act of procreation. This is terminal reproduction, literally the last thing an organism does before it dies. Salmon do this, as do annual plants. The sheer amount of algal spawn in these tidepools is astounding. Imagine the number of 2-micron cells needed to color the water to this degree. But if reproducing is the last thing you're going to do in your life, you might as well go all in on your way out, right?
I've written before about the rocky intertidal as a habitat where livable space is in short supply. Even areas of apparently bare rock prove to be, upon closer inspection, "owned" by some inhabitant or inhabitants. That cleared area in the mussel bed? Look closely, and you'll likely find an owl limpet lurking on the edge of her farm.
And of course algae are often the dominant inhabitants in the intertidal.
When bare rock isn't available, intertidal creatures need other surfaces to live on. To many small organisms, another living thing may be the ideal surface on which to make a home. For example, the beautiful red alga Microcladia coulteri is an epiphyte that grows only on other algae. Smithora naiadum is another epiphytic red alga that grows on surfgrass leaves.
We describe algae that grow on other algae (or plants) as being epiphytic (Gk: epi "on" + phyte "plant"). Using the same logic, epizooic algae are those that live on animals. In the intertidal we see both epiphytic and epizooic algae. For many of them, the epizooic lifestyle is one of opportunism--the algae may not care which animal they live on, or even whether they live on an animal or a rock. Some of the epiphytes, such as Microcladia coulteri, grow on several species of algae; I've seen it on a variety of other reds as well as on a brown or two (feather boa kelp, Egregia menziesii, immediately comes to mind). Smithora naiadum, on the other hand, seems to live almost exclusively on the surfgrass Phyllospadix torreyi.
Animals can also live as epiphytes. The bryozoan that I mentioned last time is an epiphyte on giant kelp. Bryozoans, of course, cannot move once established. Other animals, such as snails, can be quite mobile. But even so, some of them are restricted to certain host organisms.
The aptly called kelp limpet (Discurria insessa), lives only on the stipe of E. menziesii, the feather boa kelp. Its shell is the exact same color as the kelp where it spends its entire post-larval life. Larvae looking for a place to take up a benthic lifestyle settle preferentially on Egregia where adult limpets already live. It's a classic case of "If my parents grew up there it's probably a good place for me."
The limpets cruise up and down the stipe, grazing on both the epiphytic diatoms and the kelp itself. They can make deep scars in the stipe and even cause breakage. Which makes me wonder: What happens to the limpet if it ends up on the wrong end of the break? Does it die as the broken piece of kelp gets washed away? Can it release its hold and find another bit of Egregia to live on? Somehow I doubt it.
The last time I was in the intertidal I encountered another epiphytic limpet. Like the red alga Smithora naiadum, this snail one lives on the narrow leaves of surfgrass. It's a tiny thing, about 6 mm long, and totally easy to overlook, given all the other stuff going on in the tidepools. But here it is, Tectura paleacea. Its common name is the surfgrass limpet, which actually makes sense.
Tecturapalacea feeds on the microalgae that grow on the leaves of the surfgrass, and on the outer tissue layer of the plant. They can obviously grow no larger than their home, so they are narrow, about 3 mm wide. But they are kind of tall, although not as tall as D. insessa.
Cute little thing, isn't it? Tectura palacea seems to have avoided being the focus of study, as there isn't much known about it. Ricketts, Calvin, and Hedgpeth write in Between Pacific Tides:
A variety of surfgrass (Phyllospadix) grows in this habitat on the protected outer coast; on its delicate stalks occurs a limpet, ill adapted as limpets would seem to be to such an attachment site. Even in the face of considerable surf, [Tectura] palacea, . . . , clings to its blade of surfgrass. Perhaps the feat is not as difficult as might be supposed, since the flexible grass streams out in the water, offering a minimum of resistance. . . The surfgrass provides not only a home but also food for this limpet, which feeds on the microalgae coating the blades and on the epithelial layers of the host plant. Indeed, some of the plant's unique chemicals find their way into the limpet's shell, where they may possibly serve to camouflage the limpet against predators such as the seastar Leptasterias hexactis, which frequents surfgrass beds and hunts by means of chemical senses.
And that seems to sum up what is known about Tectura palacea. There has been some work on its genetic population structure, but very little about the limpet's natural history. The intertidal is full of organisms like this, which are noticed and generally known about, but not well studied. Perhaps this is where naturalists can contribute valuable information. I would be interested in knowing how closely the populations of T. palacea and Phyllospadix are linked. Does the limpet occur throughout the surfgrass's range? Does the limpet live on both species of surfgrass on our coast? In the meantime, I've now got something else to keep my eye on when I get stranded on a surfgrass bed.
A few weeks ago I was contacted by a woman named Kathleen, who reads this blog and is herself a student of the seaweeds. She said that she studies a site up at Pescadero, about an hour up the coast from me. We decided to meet up during the series of low tides around the Fourth of July so we could explore the area together, and she could help me with my algal IDs. My friend and former student, Lisa, joined us for the fun.
The most prominent landmark along the coastline in this region is Bird Island, which is accessible only at minus tides, when it is revealed to be a peninsula. It smells pretty much as you probably imagine, especially if you happen to be downwind. Given the prevailing wind direction, that means that the closer you get to Bird Island from the south, the stronger the smell. Kathleen's site is the south side of Pescadero Point, fortunately far enough south of Bird Island that the smell isn't noticeable from that distance. She has a permanent transect that she surveys regularly, taking note of algal abundances and distributions.
One of the notable things we all noticed was the conspicuous presence of big, healthy ochre stars (Pisaster ochraceus)--many hand-sized or larger. I also saw many smaller stars, in the 2 cm size range, but these were hidden in crevices or under algae. The big guys and gals, were out there in plain sight.
However, not all was perfect for the sea stars at Pescadero Point. One of the ochre stars showed symptoms of sea star wasting syndrome (SSWS). It had autotomized two of its arms and had a sloppy, goopy open wound that extended into the oral disc. It was also mushy when I touched it and didn't firm up the way healthy stars do. This star is a goner, even though it doesn't know it yet. That's the beauty (and in this case, tragedy) of an entirely decentralized nervous system.
After I mentioned having seen a sick sea star we compared notes on the current status of SSWS. What more do we know about the syndrome, and any recovery of stars? We came to the consensus that the oubreak was probably caused by a perfect storm of ecological conditions--an opportunistically pathogenic virus that is ubiquitous in the environment, environmental stresses, and high population densities both intertidally and subtidally. Kathleen asked me what I had been seeing recently. I told her that Pisaster ochraceus, one of the species that melted away in spectacular fashion, seems to be making a strong comeback in the places where I used to see it in large numbers. Even though every once in a while i see a sick star, places like Natural Bridges and Davenport Landing are again populated by lots of hand-sized-or-bigger ochre stars. Which of course brings up the question of where these large stars suddenly came from. I think they were tiny stars when the outbreak occurred, hiding in the mussel beds. Many of them died, but as with any plague there are always some survivors. Those lucky few managed to hang on and creep into the niches that opened up when so many adults died. But would little juveniles only a few millimeters in diameter be able to grow to the sizes that we're seeing now, in ~5 years? I suppose that's not out of the question, and we know that when fed well in the lab they grow very quickly, but individual growth rates in the field are difficult to measure.
Another animal goody that we saw were clusters of the bryozoan, Flustrellidra corniculata. Unlike most bryozoans, which are calcified and crunchy, Flustrellidra colonies are soft and flexible. They look more like strange, thick pieces of brown algae than anything recognizable as a bryozoan.
We were there to do some basic marine botany, and although I kept getting distracted by the invertebrates I did also pay attention to the floral aspect of Kathleen's site. She pointed out that Laminaria sinclairii, one of the small low-intertidal kelps, was always abundant. It's true, there were rocks that were entirely covered with L. sinclairii, like this one:
Laminaria sinclairii and L. setchellii are the most common intertidal species of the genus on our coast. They are easily distinguishable because L. sinclairii has a single undivided blade arising from the stipe, and L. setchellii has a blade that is subdivided into fingerlike sections; in fact, the former species epithet for L. setchellii was dentigera, referring to 'finger'.
See the difference?
There is a third species of Laminaria on our coast, that I knew only by reputation. What I'd heard is that Laminaria ephemera resembles L. sinclairii except for the morphology of the holdfast: L. ephemera has a discoid, suction-cup holdfast while L. sinclairii has the more typical hapterous holdfast (made of intertwined cylindrical projections). I think I might have seen a few L. ephemera at Pescadero. These thalli appear to have suction-cup holdfasts, don't they?
We didn't spend much time on the south side of the point, but scrambled over the rocks to the north side, where there are stretches of sandy beach between rocky outcrops. Bird Island is that peninsula in the top of the picture. As I mentioned above, it is connected to the beach only at low tide, so while I think of it as a peninsula, it really is an island most of the time.
Once on the north side of the point we slowed down and made some more attentive observations of the flora. It turns out that this portion of our intertidal visit was sponsored by the letter 'P'. One of the things we all noticed was the prevalence of Pyropia, the filmy red alga that is common in the high-mid intertidal. The thallus of Pyropia consists of a single layer of cells connected to form a very thin elastic tissue. It dries to a crisp in the sun, but rehydrates when the tide returns. You've probably encountered Pyropia before without realizing it: nori is made of Pyropia that has been shredded and processed into paper-like sheets, used for things like sushi rolls.
Although it looks uniformly blackish-green when packaged for human consumption, Pyropia's color in life is a glorious iridescent mixture of greens, olives, and purples. It is another of those easily overlooked denizens of the intertidal that deserves a much closer look than it usually gets.
Another common red alga at Pescadero Point is the delicate and lacy Plocamium cartilagineum. This is one of the hobbyist phycologist's favorite species because it presses like a dream and makes great gifts or wall decorations. As I wrote about here, Plocamium has a doppelganger: Microcladia coulteri. These algae share a similar morphology, but as I mentioned in the previous post, natural history makes it easy to distinguish between the two in the field. Microcladia is epiphytic, growing on other algae, and Plocamium is not.
Plocamium grows on rock surfaces in the mid-to-low tide regions. It sometimes gets surrounded or even buried in sand, but if you dig down far enough you'll always find the holdfast attached to a rock (or shell or other hard object).
Last month I wrote about Postelsia palmaeformis, the sea palm. We found a most handsome specimen washed up on the beach. Note that, as per usual, it wasn't the holdfast of the kelp that failed. The holdfast did its job perfectly well, and it was the mussel it was attached to that broke free of the rock.
The sad thing about finding great specimens like this on the beach is the realization that it will soon be dead. In fact, so will the mussel. Such is the price organisms pay for failing to hang onto their substrate (or for their substrate's failure to hang on). The rocky intertidal is a harsh place to live, and can be unforgiving of mistakes and bad decisions.
That's part of the reason I find it so fascinating. Most wild organisms live on the knife-edge of survival, with only the thinnest margin between life and death. Every organism has its predators, pathogens, and parasites to deal with on a daily basis, in addition to the physical stresses of its habitat. All of the organisms that I study in the intertidal are marine--not freshwater or even brackish, although some can tolerate reduced salinity (and on the other extreme, some tolerate very high salinity). They evolved to live in the ocean, in a habitat where the ocean abandons them for a few hours twice a day. Yet as improbable as that sounds, the diversity in the intertidal is astonishingly high. Obviously, for those that can live there, the trade-off between stability and safety is worthwhile. Nature will always find a way.
The annual Snapshot Cal Coast period is scheduled to coincide with the best midsummer low tides, to maximize opportunities for people to get out and blitz the intertidal. The whole idea of Snapshot Cal Coast is to document as much biodiversity as possible, to render a comprehensive account of what our coastal and nearshore biota look like at this moment in time. For someone like me, participating in the various bioblitzes that occur during Snapshot is a good excuse to get up early and play in some of my favorite intertidal sites.
We're in the high summer growing season now, and the algae are taking off. Pigeon Point has always been a great spot for seaweed diversity, and I anticipated having a lot much phycological fun when I went there last week. And, very happily, I was not disappointed. There were many animal finds as well, including some nudibranchs that I brought back to the Seymour Center, but the algae were definitely the stars of the show. So I thought I'd show off how beautiful and diverse they are.
The red algae
The vast majority of macroalgae at Pigeon Point are red algae, in the phylum Rhodophyta. Everywhere you look is a sea of rosy pinks, dark purples, and bright or brownish reds, punctuated now and then by a brilliant splash of green which is due to the surfgrass (not an alga!), Phyllospadix. The algae cover all surfaces. They drape into and drift with the water currents. They provide shelter and food for the animals of the intertidal. They make walking a treacherous undertaking--a large part of exploring the intertidal safely is knowing which algae will support your weight and which will dump you on your butt without a moment's hesitation.
At first look, the eye is bombarded with a confounding mélange of reds, dark greens, pinks, and purples. Knowing that they are all in the Rhodophyta doesn't help you make sense of what you are seeing. As usual, what helps is an ability to flip between what I call 'forest' and 'tree' observing: you can spend some time zeroing in on individual specimens and learning or remembering their names, but every once in a while you need to step back and take note of the larger environment where and with whom these species live.
Here's a small forest view to study. How many different red algae can you see?
It's kind of a trick question. A knowledgeable person can probably pick out seven or eight different species. I can distinguish six but can identify only five with any real certainty.
Here's the same photo, with some of the algae labeled for identification:
Species A: Prionitis lanceolata
Species B: Erythrophyllum delesserioides (my favorite alga!)
Species C: either Cryptopleura or Callophyllis
Species D: Neogastroclonium subarticulatum
Species E: Mazzaella splendens
Just because it's my favorite, and is undeniably beautiful, here's another photo of Erythrophyllum:
To give you some idea of the color and morphological variety in the reds, here's a quartet:
Some of the red algae are epiphytic, living on other algae or plants. Epiphytes are not parasitic and obtain their nutrients from the surrounding water. Although they do not drain nutrients from the alga or plant on which they live, epiphytic algae can occur so densely that they shade their host and deprive it of sunlight. In the intertidal, algae in the genus Microcladia grow as epiphytes. I've seen them most often on other reds, but they'll also live on some of the browns. A while back I wrote about how Microcladia closely resembles another red alga, Plocamium, and how one of the ways to tell them apart is to examine the habitat of each. Microcladia is an epiphyte, and Plocamium grows attached to rocks.
This is Microcladia:
You can see the morphology of M. coulteri a little better here, where it is an epiphyte on host with a smoother texture:
The coralline algae are a subset of the red algae. They have a different texture from the other reds, because they deposit calcium carbonate within their cell walls. Corallines can grow as encrusting sheets over surfaces, or have upright branching forms. They are often epizoic (living on animals) or epiphytic.
The brown algae
The brown algae (Phylum Ochrophyta) are not as diverse as the reds, but can be locally abundant. The browns come into their own in the subtidal, where they form the physical structure of California's famous kelp forests. Even in the intertidal they can be among the most conspicuous of the algal flora.
Egregia menziesii, the so-called feather boa kelp, is very common on our coast. It has tough, strap-like stipes that can be 3-4 meters long and a large conical holdfast, so it is pretty conspicuous. Egregia is the most desiccation-tolerant of the kelps around here; it grows as high as the mid-intertidal. The specimen in the photo below looks a little ragged at the ends, which makes me think it might be a holdover from last year.
I've seen Egregia at every rocky intertidal site so far. Other brown algae are more particular about where they live. Dictyoneurum californicum, for example, is a brown alga that lives only in areas that get a lot of water movement. It is seasonally abundant at Pigeon Point, where it is a low intertidal resident, but I don't see it at more sheltered locations such as Davenport or Natural Bridges. This year D. californicum is at Pigeon Point, although not in large patches as it was a few years ago. As the blades mature, they develop a split in the basal region just distal to the short stipe. The blades themselves feel crunchy and brittle.
All that said, the most remarkable brown alga at Pigeon Point has got to be Postelsia palmaeformis, the sea palm.
Postelsia is restricted to the most exposed rocky outcrops, where they bear the full force of the bashing waves as the tide rises and falls. They stick up defiantly above the surrounding topography, as if daring the waves to do their worst.
Sea palms grow to a height of about half a meter, and are usually the tallest things where they live. They typically occur in small clusters. They do resemble miniature palm trees, don't they? It's the thick, very flexible stipe that allows them to live where they do. When the waves come crashing down, the stipe simply bends with the force of the water, and then pops back up after the wave recedes. This hardiness doesn't make the thalli invincible, though. After winter storms blow through, you can often see Postelsia washed up on the beach.
You might think that Postelsia gets ripped off rocks by strong waves, but you'd be wrong. The holdfast for these algae is surprisingly tough and good at doing its job. When you see Postelsia stranded on the beach, you'll usually find that it wasn't the holdfast that gave way--most likely the rock or mussel it was attached to will have been torn off along with the sea palm. That's pretty impressive! Of course, any sea palm washed up on the beach is a dead sea palm, so in that sense it doesn't matter whether it was the alga or the substrate that failed. But given the forces that these algae withstand on a daily basis, it's remarkable how well they manage to hang on in the high energy environment where they thrive.
Algae don't get a lot of love, even among marine biologists. If I think there are not many people who study the invertebrates, there are even fewer who study seaweeds. Some organisms have an easier time attracting the attention of human beings, and among macroscopic organisms the invertebrates and algae are probably tied for the bottom ranking. It amazes me that visitors to the seashore can look over a place like Pigeon Point and not see anything. I suppose it's a matter of getting lost in the forest and forgetting that it is made up of trees, or not even recognizing that it is a forest. In the intertidal the 'trees' are at foot level so it does take some work to figure out what's going on. Like most worthy endeavors, though, the effort is well rewarded.
Professor Emeritus John Pearse has been monitoring intertidal areas in the Monterey Bay region since the early 1970s. Here on the north end of Monterey Bay, he set up two research sites: Opal Cliffs in 1972 and Soquel Point in 1970. These sites are separated by about 975 meters (3200 feet) as the gull flies. My understanding is that the original motivation for studying these sites was to compare the biota at Soquel Point, which had a sewage outfall at the time, with that at Opal Cliffs, which did not. The sewer discharge was relocated in 1976, and the project has now morphed into a study of long-term recovery at the two sites. In the decades since, John has led students, former students, and community members to conduct Critter Counts at these sites during one of the mid-year low tides. Soquel Point is visited on the first day, and Opal Cliffs is visited the following day. When John founded the LiMPETS rocky intertidal monitoring program for teachers and students in the 1990s, the Soquel Point and Opal Cliffs locations were incorporated into the LiMPETS regime.
I have participated in the annual Critter Counts off and on through the years--around here, one takes any chance one gets to venture into the intertidal with John Pearse! I usually have my own plans for this series of low tides, but try to make at least one of the Critter Count mornings. This year (2019) the first 16 days of June have been designated the official time frame for Snapshot Cal Coast, giving marine biologists and marine aficionados an excuse to go to the ocean and make observations for iNaturalist. I had set myself the goal of submitting observations for every day of Snapshot Cal Coast, knowing that every day this week would be devoted to morning low tides. That's the easy part. Next week, when we lose the minus tides, I'll do other things, like look at plankton or photograph seabirds. My plans for this week included a trip to Franklin Point on Wednesday and doing the Critter Count at Opal Cliffs on Thursday. John asked me if I could also do the Wednesday Critter Count. As I alluded above, I'm not going to say "No" to an invitation like that! So I didn't make it out to Franklin Point to document the staurozoans for Snapshot Cal Coast, but that's okay. Some plans are meant to be changed.
Day 1- Soquel Point
Both the Soquel Point and Opal Cliffs sites are flat benches with little vertical topography. The benches are separated by channels that retain water as the tide recedes. The Soquel Point site has deeper channels that make the benches more like islands than connected platforms.
The benches are pretty easy to get around on, as long as you remember that surfgrass (Phyllospadix spp.) is treacherous stuff. The long leaves are slippery and tend to cover pitfalls like unexpected deepish holes. The difficulty at this site is that it takes very little rise in the tide for water in the channels to get deep. You can be working along for a while, then get up to leave and realize that you're surrounded by water. Keeping that caveat in mind, we worked fast.
For the Critter Count we keep tabs on only a subset of the organisms in the intertidal. The quadrat defines our sample; we put it down at randomly determined coordinates within a permanent study area. Some animals, such as anemones, turban snails, and hermit crabs, are counted individually. For other organisms (surfgrass, algae, Phragmatopoma) we count how many of the 25 small squares they appear in. Some quadrats are pretty easy and take little time; others, such as ones that are placed over channels or pools, are more difficult and take much longer.
Because of the rising tide I didn't have a lot of time to look around and take photos of the critters we were counting. Linda and I were worried about finishing our quadrats before the channels got deep enough to flood our boots. But here are two of the things that caught my eye:
Day 2 - Opal Cliffs
The next day we met a half hour later and a few blocks down the road. The Opal Cliffs site is a popular spot with surfers: If you've ever heard of the surf spot Pleasure Point or seen the movie Chasing Mavericks, you know about this location. As far as the intertidal goes, it's an easy site to study. The channels aren't as deep as those at Soquel Point so we could work at a more leisurely pace. As the rest of the group hauled up all the gear and left to get on with their day, I stayed behind to take pictures for my iNaturalist observations. The sky was overcast, making for good picture-taking conditions. I'll just add a gallery of photos to share with you.
There is one critter that deserve more attention here, because I'd never seen one in the intertidal before. Two of the guys finished their quadrats early and started flipping over rocks to look for an octopus. To my knowledge they didn't find any octopuses, but they did find a bizarre fish. At first it didn't look like much:
Hannah, the LiMPETS coordinator for Monterey and Santa Cruz Counties, recognized the fish right away and grabbed it by the body. She held it up so we could see the ventral surface.
This is a plainfin midshipman. These are nearshore fish found in the Eastern Pacific from Alaska to southern Baja. Clearly, I need to spend more time flipping over big rocks! The midshipman is a noctural fish, resting in the sand during the day and venturing out to feed at night. Like many nocturnal animals, it is bioluminescent--those white dots on the fish's belly in the photo above are photophores. Midshipmen are heavily decorated with photophores all over the body. This bioluminescence is used both for predator avoidance and mate choice.
The lives of plainfin midshipmen and human beings intersect in the wee hours of the morning. During breeding season these fish sing or grunt. They breed in intertidal areas, where females lay eggs in nests that are subsequently guarded by males. Both sexes make noise, but it's the breeding males that are the noisiest. They grunt and growl at each other when fighting for territory, but hum when courting females. Females typically grunt only when in conflict with others. People who live in houseboats on the water in Sausalito have reported strange sounds emanating from the water beneath them, only to learn that what they hear are the love and fight songs of fish!
I've always been a fan of the intertidal fishes. They seem to have a lot of personality. Plus, any aquatic animal that lives where the water could dry up once or twice a day deserves my admiration. Of course, all of the invertebrates also fall into this category, which may explain why I find them so fascinating.
After we admired the midshipman's photophores and impressive teeth, we put it back in the sand and replaced the rock on top of it. It was probably happy to get back to snoozing away the next few hours before the tide returned. I don't know how I never realized the midshipmen were in the intertidal. I think I just assumed that they were in deeper water. Now that I know where to find them, I will spend more time flipping over rocks. And who knows, maybe I'll even find an octopus!
All semester I've been taking my Ecology students out in the field every Friday. We've visited rivers, forests, natural reserves, endemic habitats, and fish hatcheries--none of which fall into my area of expertise. This year I have several students interested in various aspects of food production, natural/holistic health practices (which sometimes conflict with actual science!), mycology, as well as some who haven't yet decided in which direction to take their academic endeavors. Until very recently I haven't been able to share with my students much of what I really know, which is marine biology. I did have them learn the organisms that live on docks at the harbor, but that was to study the process of ecological succession rather than natural history.
Yesterday, finally, I took the class into my real field, the rocky intertidal. This year it happened that the best Friday to do our annual LiMPETS monitoring was at the end of the semester. We welcomed the new regional LiMPETS coordinator, Hannah, to our classroom on Thursday for some training. Students learned about the history of the LiMPETS program, some natural history of the rocky intertidal in California, and got to practice some organism IDs with photo quadrats of actual intertidal areas.
The real fun, of course, occurs in the field where the organisms live. So we went here:
We didn't have a very good student turnout, unfortunately, but the ones who did show up were diligent workers and we got everything finished that Hannah needed. Most of the time was spent sampling along the permanent vertical transect line. This line is sampled at 3-meter increments along a line that runs from the high intertidal into the low. The same quadrats are sampled every time, and the data collected are used to determine how specific sites change over time. The most difficult part of the monitoring is finding the eye bolts that mark where the transects begin!
I admit, I was a little bummed at the low turnout and late arrival of my students. But the intertidal is the intertidal, and it didn't take long for me to adjust my attitude. I worked up a handful of quadrats with Hannah, then let the students do the bulk of the heavy lifting. This was their field trip, after all. So I wandered around a bit, remaining within hearing distance in case I was needed. I needed to find some stuff!
I just want to show some of the animals and algae in the intertidal yesterday. I didn't realize how much I missed this basic natural history stuff until I got to spend some time simply looking at things.
Such rich life to see! One of the students was astounded when she learned that we could visit sites like this only a few days each month. "At dinnertime today the spot where you're standing will be under several feet of water!" I told her. Mind blown.
Looking more closely, there were, as usual, interesting zonation patterns to observe. One was the restriction of large brown algae to the vertical faces of rocky outcroppings.
In the mid-intertidal, mussels (Mytilus californianus) rule the roost. They are often (but not always) accompanied by gooseneck barnacles (Pollicipes polymerus). The barnacles, for reasons discussed in this earlier post, always live in clumps and are most abundant in the lower half of the mid-intertidal mussel beds.
During the training session on Thursday, Hannah told the students that Pollicipes is easily identifiable because the barnacles look like dragon toes. I think I can sort of see that. They are scaly and strange enough to be dragon toes.
The algae are taking off now, and the site is starting to look very lush.
Even algae start as babies! These balloon-shaped things are young Halosaccion glandiforme thalli, surrounded by other red algae. The large blades belong to Mazzaella flaccida, which makes up a large portion of algal biomass in the mid-intertidal zone.
The tidepools at Davenport Landing are good places to see fish, if you have the patience to sit still for a while and watch. This woolly sculpin (Clinocottus analis) posed nicely in the perfect pool for photography--deep enough to submerge the camera, with clear, still water.
And I was finally able to take a good underwater shot of a turban snail carrying some slipper shells. I've already written about the story of this gastropod trio in case you need a refresher. I'm still waiting to see a taller stack of slipper shells some day.
It was impossible not to feel satisfied after spending some time looking at these creatures. My attitude was mercifully adjusted, and we all departed feeling that we'd done a good morning's work. Our small group of students was able to collect a full set of data for Hannah. That ended up being a very important accomplishment, as Hannah doesn't have any other groups monitoring at Davenport this spring. This means that our data will probably be the only data collected this year at this site. I'm glad the tide and weather conditions allowed us to stay out there as long as we did.
The marine macroalgae, or seaweeds, are classified into three phyla: Ochrophyta (brown algae), Rhodophyta (red algae), and Chlorophyta (green algae). Along the California coast the reds are the most diverse, with several hundred species. The browns have the largest thalli (the phycologists' term for the bodies of algae), including the very large subtidal kelps as well as the smaller intertidal rockweeds. The green algae are small in both thallus size/complexity and species diversity; many of the greens are filamentous and look like nothing more than slime growing on rocks or other surfaces.
On the other hand, what appears to be simple at first glance can turn out to be delightfully complicated and puzzling upon closer examination. Take, for example, the two species of green algae in the genus Codium that occur intertidally in northern California: Codium setchellii and C. fragile. Codium setchellii is a native species here. It grows as a thick rugose mat over rocks in the mid-intertidal. Its color is a very deep olive green, but when dry it looks almost black.
Codium setchellii has a smooth texture and feels like very thick velvet. It grows on vertical faces of rocks, rarely on exposed horizontal surfaces--at least, I've not often seen it on top of a rock. Patches of C. setchellii are usually about the size of my outstretched hand, although some can be a little larger than that. When you see C. setchellii in the field, it's hard to imagine what type of structure would result in a thallus like this. To figure out what's going on, you need to look at small pieces under a microscope. It's this level of observation that reveals the filamentous nature of C. setchellii.
Phycologists have a few tricks for observing the internal structure of algae. The firm-bodied algae can be examined via cross-section, which can be more or less difficult to make depending on the species. Many simpler thalli, however, can be examined by making a squash, which is exactly what it sounds like: You take a piece of the alga, place it in a drop of water in a slide, and squash it with a cover slip.
A squash of C. setchellii revealed this mishmash of filaments:
This particular squash shows the utricles, which are the pigmented ends of the filaments. It didn't really help me understand how the filaments are organized within the thallus, though. I even tried making a cross-section of the little piece of C. setchellii I have, but it turned to mush. I did at least get one squash that showed the filaments to be arranged in approximately parallel fashion at the outer edge of the thallus.
So, seeing the internal structure of Codium setchellii allows me to understand how its closely packed filaments produce the velvety cushion of the thallus that I see in the field. The way that the filaments are aligned allows them to be tightly packed together, resulting in a cushion that is surprisingly firm rather than squishy.
The second species of Codium that we see in northern California is C. fragile, commonly called 'dead man's fingers'. It is a non-native species here, originating in the western Pacific near Japan, and has spread into the Atlantic. In California it has a patchy distribution and, in my experience at least, isn't as common as C. setchellii. I have never seen the two species together at the same site, but according to iNaturalist they do co-occur in some locations.
Like its congeneric species, C. fragile is a dark greenish color and lives in the mid- to low-intertidal. But otherwise it looks entirely different. The thallus morphology must be what gave rise to the common name. I remember learning years ago about a seaweed called 'dead man's fingers' and being disappointed when I saw it for the first time. It didn't look like dead man's anything!
This thallus resembles a clump of approximately dichotomously branching tubes. It is spongy in texture and is often colonized by bits of a filamentous red alga.
In this case, the red alga (Ceramium sp.) is in turn colonized by the benthic diatom Isthmia nervosa:
You might expect Codium fragile, having a tubular morphology, to be more amenable to being examined in cross-section. I can tell you that that isn't the case. It's easy enough to make the first transverse slice of one of those 'fingers', but the second slice, even made with a brand new razor or scalpel blade, results in a pile of mush. I made and looked at several such piles, hoping that at least one would show an approximation of the cross-sectional anatomy of this thallus. The best I could get was this:
At least it shows the radiating arrangement of the filaments. I think this is really interesting. The utricles (pigmented tips of the filaments) are a bit thicker than the unpigmented section of the filaments that make up the interior of the cylinder, but there's still space between them at their distal tips. It is this arrangement that gives Codium fragile a squishiness that C. setchellii lacks.
So there you have it. One genus, two species with radically different gross morphology but similar internal morphology. They're made of the same types of cells, at least. Like I said, I've not seen them in the same place in the field, but here in my blog you can see them side by side.
The Sierra snowpack is California's largest single reservoir of fresh water, accounting for 1/3 of the state's water supply1. A state with a mediterranean climate, such as California, receives precipitation only during the short rain/snow season. During years of drought, when the average Californian frets about how little rain is falling, state water managers are keeping a worried eye on the amount of snow falling in the Sierra. Snow surveyors use remote sensing and field measurements to estimate the water content of the snowpack. The snow water equivalent on 1 April is used to compare snowpack water content across years.
The 2016-2017 snow year was a productive one, dumping near-record amounts of 'Sierra cement' on the mountains. (Skiers accustomed to the powder snows of Utah and Colorado often disparage the heavy snow in the Sierra, but Sierra cement carries a lot more water than powder so is much more beneficial to the state's water supply). Most of that snow eventually melts, births streams and rivers, and flows from the mountains to lower elevations. After a good snow year, though, snow fields remain at high altitudes even during high summer. That definitely is the case around Lake Tahoe.
A few days ago my husband and I hiked from Carson Pass to Big Meadow, a through hike about 8 miles long. The hike goes through some gorgeous alpine meadow, with an absolutely stunning display of wildflowers. Even in late July we had to cross several streams and saw lots of snow.
If you look closely at the bottom photo, you may notice some faint pink streaks on the face of the snow field. This pink snow is called 'watermelon snow' because of the color. It is a phenomenon that occurs only at high altitudes or polar regions in the summer. Here's a closer look, taken with a 70-200 mm lens that I rented for the week.
Given the color of those streaks, you'd think the organism producing it would be a red alga of some sort, wouldn't you? I did, too, until I did some research and learned that it is a green alga! Chlamydomonas is a genus of unicellular green algae, most of which are indeed green in color because the only photosynthetic pigments they contain are chlorophylls. However, Chlamydomonas nivalis also contains reddish carotenoid pigments that serve to shield the cell's photosynthetic pigments from excess radiation, which is intense at the high altitudes where the algae live. The pigments absorb heat, which increases the melting of snow in the immediate vicinity and provides liquid water that the algae require. Watermelon snow is found in alpine regions across the globe, although it isn't known whether or not the same species of alga is responsible in all cases.
Cross-country skiers and snowshoers pass through these areas in the winter, and never report seeing watermelon snow. What happens to the cells in the winter? Do they die?
It turns out that the alga persists year-round, although in different life history stages. Given the inhospitality of their habitat, most of the life cycle involves waiting in a dormant stage, with a short burst of activity in the spring. The red form that we see in the summer is a dormant resting stage, having lost the pair of flagella possessed by swimming unicellular green algae. These spores, former zygotes resulting from fertilization, are non-motile and cannot escape to deeper snow to avoid UV radiation, so they use carotenoids to serve as sunscreens. They are not dead, though, and continue to photosynthesize all summer. They rest through the winter and germinate in the spring, stimulated into activity by increased light and nutrients, and flowing water. Germination involves the release of biflagellated cells that swim to the surface of the snow, where at least some of them function as gametes. Fertilization occurs, with the resulting zygotes soon after forming the resting spores that result in watermelon snow.
It may seem strange that this organism spends most of its time in a dormant stage, but this is not at all uncommon for things that live in hostile habitats. When conditions for life are difficult, the best strategy can be to hang out and wait until things get better. Chlamydomonas nivalis does this on a yearly basis, as do many of the marine unicellular algae. And some animals, namely tardigrades, can dry out and live for decades or perhaps even centuries in a state of suspended animation, returning to life when returned to water. As with many natural phenomena, this kind of lifestyle seems bizarre to us because it is so unlike how we do things. But if C. nivalis could observe and think about how we live, it would no doubt consider us inconceivably wasteful, expending enormous amounts of energy to remain active at times when, clearly, it would much more sensible (from C. nivalis's point of view) to sleep until better conditions return.
The marine macroalgae are, as a group, the most conspicuous organisms in the intertidal. Yet, most tidepool explorers dismiss them as "seaweeds" and move on to the next thing, which they hope is somehow more interesting. This is akin to visiting the jungles of Brazil and not paying attention to the lush foliage that defines that particular biome. I will admit that, as a zoologist whose primary interest is the marine invertebrates, I have been guilty of this offense. I've also felt guilty about the oversight and thought to myself, "I really should know the algae better." I have no formal training in phycology beyond auditing marine botany labs after I finished graduate school, but I've got the basics down and really have no excuse for the continuation of this gap in my knowledge.
So a couple of years ago I decided to start filling in that gap. I dragged out my marine botany notebook and have slowly been adding to it, building up my herbarium collection at the same time.
The red algae (Rhodophyta) are the arguably the most beautiful of the seaweeds, and inarguably are the most diverse on our coast. Some of them are easy to identify because nothing else looks like them, but many share enough morphological similarity that field IDs can be tricky if not downright impossible. For example, to ID a specimen and distinguish it from a close relative you may need to examine the number, size, and arrangement of cells in a cross-section of a blade. Some species are impossible to identify beyond genus (or even family, in some cases) unless you can look at their reproductive structures, which they might not have at the time they're collected.
One of the most ubiquitous red seaweeds, and one that is easily identified to genus, is Mazzaella. The genus name for this group of species used to be Iridea, which gives a hint as to the appearance of the thalli--many of them are iridescent, especially when wet. The species that I see most often are M. flaccida in the mid intertidal and M. splendens lower down. These species are usually not difficult to tell apart once you get used to looking at them and their respective habitats.
Mazzaella splendens is generally a solid brown with sometimes a green or purple cast. It is soft and floppy, and the blades are long (up to 50 cm) and taper to a point. The Marine Algae of California, which we call the MAC, uses the term "lanceolate" to describe this shape. Mazzaella flaccida is green or greenish-purple, sometimes more brownish along the edges; its blades are flexible but a teensy bit crisper than those of M. splendens, and its blades are described as cordate (heart-shaped) or broadly lanceolate.
Got it. That's not too bad, right?
But then you see something like this, and a whole other set of questions comes to mind.
Based on habitat alone these are both M. flaccida. The greenish thallus on top looks like textbook M. flaccida, but the lower thallus looks more ambiguous. It has the right size and shape but is the wrong color, and what's up with all those bumps? I brought these thalli back to the lab to examine them more closely. Here are the entries from my lab notebook:
Now is the time to bring up the subject of life cycles in red algae. Algae such as Mazzaella alternate through three generations: male and female gametophytes, both of which are haploid; a diploid sporophyte; and a diploid carposporophyte. Here's a diagram that shows how this alternation of three generations works:
It was easy to see that the bumpy thallus I collected was sexy, while the smooth green thallus was probably not reproductive. Having both thalli in hand, along with the MAC and phycology texts in the lab, I was able to determine that the bumpy brown thallus is actually two generations in one body. So cool! But how does this work? The bumps on the thallus are called cystocarps. In Mazzaella a cystocarp contains the diploid tissue of the carposporophyte surrounded by the haploid tissue of the female gametophyte. Et voilà! Two generations in a single thallus.
Now, what's inside the cystocarp? What does the carposporophyte tissue actually look like? To find out I had to do some microsurgery, first to remove a carpospore (1-1.5 mm in diameter) from the female gametophyte and then to cut it open to see what's inside. What's inside were microscopic diploid carpospores, which grow into the macroscopic sporophyte generation. Forcibly dissected out as they were, they don't look like much, just tiny round cells about 2 µm in diameter.
The next logical step would be to isolate some of the carpospores and try to grow them up. I wasn't thinking about that at the time and pressed both thalli. However, I do have another female gametophyte with cystocarps that I can investigate further tomorrow. It's probably a fool's errand, as I am not going to bother with sterile media and whatnot. Oh well. Nothing ventured, nothing gained, right?