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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.

Round Top Mountain, viewed from meadow above Carson Pass
25 July 2017
© Allison J. Gong
Snow field in the high Sierra
25 July 2017
© Allison J. Gong

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.

Watermelon snow
25 July 2017
© Allison J. Gong

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.

 


1 California Department of Water Resources

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 at Whaler's Cove at Pigeon Point
28 June 2017
© Allison J. Gong
Mazzaella flaccida at Natural Bridges
9 July 2017
© Allison J. Gong

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.

Thalli of Mazzaella flaccida at Natural Bridges
9 July 2017
© Allison J. Gong

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:

Life cycle of some red algae, showing alternation of three generations
© McGraw-Hill

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.

Carpospores of Mazzaella flaccida
12 July 2017
© Allison J. Gong

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?

As spring arrives in full force, the algae are starting to come back in the intertidal. The past two mornings I went out on the low tides to look for something very specific (which I did find--more on that later) and noticed the resurrection of the more common red algae. So early in the season the algal thalli are nice and clean, not yet having been fouled or munched. And, like all babies, they're pretty dang cute.

Here's a little clump of Endocladia muricata, a red alga with the common name 'scouring pad alga.' I've also heard it referred to as 'pubic hair alga,' by a former instructor of marine botany who shall remain nameless.

Endocladia muricata growing on the test of the large barnacle Tetraclita rubescens, at Natural Bridges
1 April 2017
© Allison J. Gong

What I tried, and failed, to capture in this photo is that the strands have little thornlike extensions that give them the texture of . . . a scouring pad. Here's a better picture of a larger clump, and if you squint you might be able to see what I'm talking about.

Endocladia muricata
1 April 2017
© Allison J. Gong

And here's another baby red, this gorgeous little piece of Plocamium. When they're young like this the branching structure is easier to see. And isn't that color splendid? Especially with the green of the fresh young surfgrass.

A baby Plocamium, growing among the surfgrass Phyllospadix scouleri
1 April 2017
© Allison J. Gong

What I was really thinking about this morning were the morphological similarities that can make it very difficult to distinguish between different species. For example, there are three species of rockweeds that are common around here: Fucus distichus, Silvetia compressa, and Pelvetiopsis limitata. Rockweeds are brown algae but are usually olive-green in color, and live in the high mid-intertidal above the mussel zone. In some places all three species occur together. Fucus (see below) is easy to recognize because its blades are wider and somewhat straplike, with prominent midribs. When Fucus is reproductive the tips of the blades become swollen and full of a gooey mucilage, which contains the gametes. There are other interesting things about sex in Fucus, and at some point I may address those in a later post.

Fucus distichus, a rockweed, at Franklin Point
17 July 2017
© Allison J. Gong

The other rockweeds, Silvetia and Pelvetiopsis, are a lot more difficult to distinguish. They both have less straplike blades. They share a generalized dichotomous branching pattern, but in neither is it as consistent as it is in Fucus.

Pelvetiopsis limitata at Mitchell's Cove
2 April 2017
© Allison J. Gong
Silvetia compressa at Mitchell's Cove
2 April 2017
© Allison J. Gong

 

 

 

 

 

 

 

 

 

This morning these two specimens were growing side by side. In terms of scale the overall length of Silvetia is about twice that of Pelvetiopsis. Keeping that in mind, what you can't tell from these photos is that Silvetia is also coarser and stiffer, like pasta that is about a minute short of being cooked al dente--not hard, but still more firm that you'd probably like it to be. Pelvetiopsis, on the other hand, is rather soft and much more flexible.

If I were to ask you to contrast these organisms based solely on the photos above, you might say that Silvetia looks somewhat less orderly than Pelvetiopsis. And you would be right! The almost-but-not-quite-dichotomous branching in Silvetia doesn't always occur in the same plane, resulting in a thallus that doesn't lie flat. Look at this:

Silvetia compressa at Mitchell's Cove
2 April 2017
© Allison J. Gong

See how those branches, especially the terminal branches, don't all come off in the same direction? That's what I mean. A cross-section of Silvetia's blades would be somewhere between flat and cylindrical, also contributing to the tendency of this thallus not to lie flat. This means that when you press it it does get a little mashed looking.

Pelvetiopsis, on the other hand, is a much more regular beast. The blades are distinctly linear in cross-section and generally branch in one plane. One other thing to note is that in Pelvetiopsis the terminal branch tips are very short relative to the overall thallus length compared to those of Silvetia.

Blade tips of Pelvetiopsis limitata
2 April 2017
© Allison J. Gong

A fair question to ask is: How can you tell the difference between a baby Silvetia and a full-grown Pelvetiopsis? Absolute size might not be a useful characteristic, but the other morphological traits are. The branching orientations and overall blade shapes are fairly consistent throughout the size range for each species. Consistent enough, at least, to make a good gut-level first ID guess.

I wanted to write about this because I saw the organisms, checked them off in my head, and then backed up a bit. I found myself second-guessing my instincts when it came to identifying these specimens. I mean, I know these organisms. Or, I think I do. It's frustrating to look at the creatures I see regularly in the intertidal, organisms whose names I learned many years ago (even through the inevitable taxonomic name changes), and say to myself, "Wait a minute; is that right?" This led me to seriously consider these two rockweed species and evaluate what I really know about each of them. How do I know that one specimen is Pelvetiopsis, when it looks a hell of a lot like a baby Silvetia? I think this unusual self-doubt has to do with post-concussion syndrome. For the past several months I've known that words fly out of my mind as I'm trying to recall them. Why not names as well? At this stage in my recovery I'm supposed to be slowly challenging my brain as well as continuing to rest it. Finding that balance has been tricky. In a few weeks I will have my early morning low tides back. It will be easier for me to drive to intertidal sites then, and I'm going to use tidepooling as therapy. It has been good for my soul in the past, and I hope that it will also be good for my brain in the near future.

A few days ago I was in the intertidal with my friend Brenna. This most recent low tide series followed on the heels of some magnificently large swells and it was iffy whether or not we'd be able to get out to where we wanted to do some collecting. Our first day we went up to Pistachio Beach, just north of Pigeon Point, where the rocky intertidal is bouldery and protected by some large rock outcrops.

Pigeon Point lighthouse, viewed from Pistachio Beach.
27 January 2017
© Allison J. Gong
27 January 2017
© Allison J. Gong

So while the swell was indeed really big, we were pretty well protected in the intertidal. The Seymour Center has a standing order for slugs, hermit crabs, and algae. I was easily able to grab my limit (35) of hermit crabs over the course of the afternoon, and while it's too early in the season for the algae to do much I had my sluggy friend with me to take care of finding nudibranchs, which left me free to let my attention wander as it would.

Codium setchellii at Pistachio Beach.
27 January 2017
© Allison J. Gong

The very first thing to catch my eye as we go out there was the coenocytic green alga Codium setchellii, which I wrote about last time. I've seen and collected C. setchellii from this site before, but don't remember seeing it in such large conspicuous patches. I need to review what I learned about the phenology of various intertidal algae, but here's a thought. Maybe Codium is an early-season species that gets outcompeted by the plethora of fast-growing red algae later in the spring. Red algae were present at Pistachio Beach but not in the lush (and slippery!) abundance that I'll see in, say, June. I'm willing to bet that Codium will be less abundant in the next few months.

Leptasterias sp. at Pigeon Point.
24 April 2016
© Allison J. Gong

In my experience, the six-armed stars of the genus Leptasterias have always been the most abundant sea stars on the stretch of coastline between Franklin Point and Pescadero. Even though they are small--a monstrously ginormous one would be as large as the palm of my hand--they are very numerous in the low-mid intertidal. I've seen them in all sorts of pinks and grays with varying amounts of mottling. Alas, I don't know of any really reliable marks for identifying them to species in the field.

Unlike other familiar stars, such as the various Pisaster species and the common Patiria miniata (bat stars), which reproduce by broadcast spawning their gametes into the water, Leptasterias is a brooder. Males release sperm that is somehow acquired by neighboring females and used to fertilize their eggs. There isn't any space inside a star's body to brood developing embryos, so a Leptasterias female tucks her babies underneath her oral surface and then humps up over them. Leptasterias also humps up when preying on small snails and such, so that particular posture could indicate either feeding or brooding.

Here's a Leptasterias humped up on a rock, photographed last spring:

Leptasterias sp. at Pigeon Point.
5 May 2016
© Allison J. Gong

The only way to tell if a Leptasterias star is feeding or brooding is to pick it up and look at the underside. I did that the other day and saw this:

Brooding Leptasterias sp. star at Pistachio Beach.
27 January 2017
© Allison J. Gong

Those little orange roundish things are developing embryos. While the mother is brooding she cannot feed, and can use only the tips of her arms to hang onto rocks. Don't worry, I replaced this star where I found her and made sure she had attached herself as firmly as possible before I left her. In a few weeks her babies will be big enough to crawl away and she'll be able to feed again.

Looks like the reproductive season for Leptasterias has begun.


The next day Brenna and I went to Davenport, again hoping to get lucky despite another not-so-low tide and big swell.

Davenport Landing Beach and adjacent rocky areas.
© Google Earth

Davenport Landing Beach is a popular sandy beach, with rocky areas to the north and south. The topography of the north end is quite variable, with some large shallow pools and lots of vertical real estate to make the biota very diverse and interesting. The big rocks also provide shelter from the wind, a big plus for the intrepid marine biologist who insists on going out even when it's crazy windy. The southern rocky area is very different, consisting of flat benches that slope gently towards the ocean, with comparatively little vertical terrain. The southern end of the beach is always more easily accessible, which is why I almost always go to the north. But this day the north wasn't going to happen. The winter storms had washed away at least a vertical meter of sand between the rock outcrops. That and the not-so-low tide combined for conditions that made even getting out to the intended collecting site a pretty dodgy affair. So Brenna and I trudged across the beach to the south.

28 January 2017
© Allison J. Gong

Along the way we saw lots of these thumb-sized objects on the beach. At first glance they look like pieces of plastic, but after you see a few of them you realize that they are clearly (ha!) gelatinous things of biological origin. They are slipper-shaped and you can stick them over the ends of your fingers. They have a bumpy texture on the outside and are smooth on the inside.

Any guesses as to what they are?

Pseudoconch of Corolla spectabilis, washed up on Davenport Landing Beach.
28 January 2017
© Allison J. Gong

These funny little things are the pseudoconchs of a pelagic gastropod named Corolla spectabilis. What is a pseudoconch, you ask? If we break down the word into its Greek roots we have 'pseudo-' which means 'false' and 'conch' which means shell. Thus a pseudoconch is a false shell. In this case, 'false' refers to the fact that this shell is both internal (as opposed to external) and uncalcified.

The animal that made these pseudoconchs, Corolla spectabilis, is a type of gastropod called a pteropod (Gk: 'wing-foot'). Pteropods are pelagic relatives of nudibranchs, sea hares, and other marine slugs. They are indeed entirely pelagic, swimming with the elongated lateral edges of their foot. Like almost all pelagic animals, Corolla has a transparent gelatinous body. Even their shell is gelatinous, rather flimsier than most shells, but it serves to provide support for the animal's body as it swims.

You can read more about Corolla spectabilis and see pictures and video here.

Why, you may be wondering, do the pseudoconchs of C. spectabilis end up on the beach, and where is the rest of the animal? The body of Corolla and other pteropods is soft and fragile. When strong storms and heavy swells seep through the area, the water gets churned up and pteropods (and other pelagic animals) get tossed about and shredded. This leaves their pseudoconchs to float on currents until they are either themselves demolished by turbulence or cast upon the beach. Corolla is commonly seen in Monterey Bay, and it is not unusual to find their pseudoconchs on the beaches after a series of severe storms.

Brenna and I were wondering if we could preserve the pseudoconchs somehow. I took several back to the lab and tried to dry them, thinking that they might behave like Velella velella does when dried. Unfortunately, the next day they had shriveled into unrecognizable little blobs of dried snot, and the day after that they had disintegrated completely into piles of dust. Maybe drying them more slowly would work. Something to consider the next time I run across pseudoconchs in the sand.

1

A few days ago I told my friend Brenna that I'd hunt around in the marine lab for a bit of a green alga that she wants to press. I had a pretty good idea of where to look, only the animals I'd seen it on had been removed from the exhibit hall. I asked for and got permission to examine the animals behind the scenes. And fortunately I had remembered correctly, and I was able to pick off some nice clumps of dark green stuff.

Bryopsis corticulans is a filamentous green alga. It grows to about 10 cm in length and is a dark olive color. When emersed it sometimes looks almost black. I've seen it in the intertidal in a few places, where at low tide it resembles nothing so much as a shapeless slime. It's very difficult to see the beauty of organisms when they're out of their natural element, which in this case is water.

B. corticulans emersed during low tide at Mitchell's Cove.
8 June 2016
© Allison J. Gong

But see how pretty it is when submerged?

Bryopsis corticulans
23 January 2017
© Allison J. Gong

One of the reasons I love the algae is their very inscrutability. I enjoy discovering the beauty of organisms that, at first glance, don't look like much. Many of the filamentous algae, both the greens and the reds, have a delicate structure that requires close examination to be appreciated. Fortunately, I have access to microscopes, so close examination is very easy.

The thallus of B. corticulans is relatively simple, consisting of a bipectinate arrangement of filaments.

Apical tip of Bryopsis corticulans.
23 January 2017
© Allison J. Gong

Here's a closer view:

Thallus of Bryopsis corticulans.
23 January 2017
© Allison J. Gong

This is a shot of the main axis and side filaments. The small green blobs are chloroplasts. One thing to notice is that there are no crosswalls separating any of the filaments. That's because the thallus is coenocytic, essentially one large cell with a continuous cytoplasm. Coenocytic cells are common in fungi, the red and green filamentous algae, and a few animals. In animals, coenocytic cells are often referred to as syncytial. They can arise in one of two ways: (1) adjacent cells fuse together; or (2) nuclear replication occurs as usual during normal mitosis but cytokinesis (division of the cytoplasm) does not. However the syncytium arises, it can result in very large cells. Even though B. corticulans itself is a small organism, some algae in the Bryopsidales consist of single cells that can be over 1 meter long!

Sometimes things that appear simple at first glance conceal a deeper complexity when you look more closely.

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