The strongest El Niño event on record has now been declared officially ended. For the past year and a half or so El Niño and a separate oceanographic phenomenon known as ‘The Blob’ have been battling it out for supremacy over weather and productivity in the northeastern Pacific, particularly in the California Current Ecosystem. It seems that The Blob, an area of unusually warm water stretching across the north Pacific from Japan to North America, had been in effect since 2014, and the arrival of El Niño combined with it to further depress productivity along the west coast of North America.
I’ve been recording temperatures in my seawater table at the marine lab for many years now. It has been only in the last year or so that I’ve made a concerted effort to record the temperature every day, but in general I have temperature data for at least several days a month going back to 1994. This morning I thought it would be interesting to compare 2016 temperatures with last year’s elevated El Niño temperatures. These are the data from 1 January through 26 July of both years:
The data are discontinuous in both years, but there are a few things to note. In the winter and spring there isn’t much difference in temperature between 2015 and 2016. Things change in April, when the 2016 temperatures are higher than in 2015. The El Niño was still in effect this past spring, which is reflected in the water temperatures. In May things get interesting. Starting in about mid-May 2015, the water temperature rose up to 15°C and remained at least that high for the next few months, with a handful of recordings as high as 18-19°C (data not shown). So far in 2016, the temperature has not exceeded 16°C in my table, and since mid-May has been averaging in the 14-15°C range.
A difference of 2°C may not seem like a big deal at all. One of my goals this summer was to collect plankton samples periodically and see if I could detect any biological signs that El Niño was abating. Of course, those plans got waylaid by the accident; I haven’t looked at a plankton sample since 27 April 2016. On the other hand I did manage to get out into the intertidal a few times after the accident, and noticed some differences from last year:
Okenia rosacea, the pink slugs that were everywhere in the intertidal last year, were much less abundant and a lot smaller this year. Last year it seemed that everywhere I looked I saw what looked like blobs of pink bubble gum spattered all over the rocks, along with their egg masses. This year I’ve seen Okenia but they aren’t nearly as conspicuous as they were last year.
Same goes for the large sea hares, Aplysia californica. Last year they were big weighty animals, common enough to make it hard not to step on them, and their spaghetti-like egg masses were everywhere. Seriously, many of the sea hares last year were two or three times the volume of my cupped hands. I did see several of them at Franklin Point last week, but they were much smaller.
I don’t have any quantitative measures or species-specific observations, but the algae seem more lush this year. And judging by what has been washing up on the beaches, the diversity is up, too.
We’re in that time of the year when the good low tides disappear for a couple of months, so there won’t be any more tidepooling excursions for me until October. Given the non-functioning condition of my brain, it’s probably just as well. I hope that some time this fall I can do some real science again, as it would be very interesting to see first-hand how the biota responds to the end of El Niño. Brain health must come first, though. For the time being I will have to content myself with eavesdropping on science and doing the little bits that I can.
This week saw the last of the good morning low tides of 2016. By “good” I mean a minus tide that hits during daylight hours. There are two more minus tide series in August, with the lows occurring well before dawn. After that the next minus tides don’t happen until mid-October; these will be late in the afternoon so loss of daylight will be an issue. I wasn’t intemperate enough to risk the health of my concussed brain on this week’s low tides but did want to get out if possible. And I’m so glad I tried, because having been out on the past few days’ low tides I feel more myself than I have since the accident. My head hurts a little, but not nearly as much as it would have if I’d done any significant driving two weeks ago. And, I have pictures to share!
Wednesday 22 July 2016—Davenport Landing
I went up to the Landing to collect some animals that I’ll need for my Fall semester class. The full moon was still visible, as the sun hadn’t yet risen above the bluff.
A month after the summer solstice and the algae are still nice and lush. Here’s a nice combination of mostly reds and greens, with some brown kelp thrown into the mix. How many phyla can you spot?
One of the two local species of surfgrass, Phyllospadix torreyi, was blooming. A month ago I’d noticed the congeneric species P. scouleri blooming at Mitchell’s Cove. These surfgrasses are vascular plants rather than algae, and as such they reproduce the way the more familiar land plants do, by pollen transfer from male to female flowers.
In the case of these obligately marine surfgrasses, the pollen is carried by water rather than wind. Not having to attract the attention of animal pollinators, the flowers have not evolved elaborate morphology, color patterns, or nectar rewards. They actually don’t look like much more than swellings near the base of the leaves. Some day I’ll remember to take one of the flowers back to the lab and dissect it to see what it’s like on the inside.
Thursday 21 July 2016—Franklin Point
This was the day I was most worried about. The drive up to Franklin Point takes about 30 minutes, and I hadn’t driven that distance since the accident. To make things even scarier, I couldn’t find someone to go with me. In the end I decided to try getting up there and back on my own, figuring that if my head wasn’t happy with the driving I could always turn around and come home.
When I got there it was cold and very windy, and I was glad I’d worn an extra thermal layer. Up on the exposed coast it is often windy on the road but can be less windy below the bluff on the beach. Yesterday it was windy on the beach, too, more typical of an afternoon than a morning low tide. The wind rippled the surface of the tidepools, making visibility and picture-taking difficult. I tried and didn’t have much success.
Coming over the last dune down to the beach I noticed four or five gulls and a couple of turkey vultures milling about at the mid-tide line. Something must be dead, I figured. And yes, it was very dead.
During last year’s El Niño we saw lots of sea hares in the intertidal up and down the coast. And they were big, heavy football-sized monsters. Yesterday I saw many sea hares, but none of then were larger than my open hand and most were quite a bit smaller. Nor were there any egg masses on the rocks. This guy/gal combo (they’re both, remember?) was about 15 cm long.
By far the most unusual thing I’ve seen in the intertidal this year was a swarm of shrimpy crustaceans. Last year at about this time I witnessed a huge population of small sand crabs (Emerita analoga) in tidepools at Franklin Point. Yesterday the swarmers were swimmers, not burrowers. I think they had gotten trapped in this large pool by the receding tide. Not having any better idea of what they were, I’m going to say they were mysids. Mysids are quite commonly encountered in local plankton tows but I’d never seen them in the intertidal before.
My first, rather idiotic, thought was that these were krill. They’re about the same size as the krill species most common in Monterey Bay, so perhaps the thought wasn’t quite that idiotic. (but krill in the intertidal? yeah, that’s idiotic. although stranger things have happened and the animals is always right even when it does something that seems idiotic) However, it didn’t take me long to realize that these critters didn’t actually look like krill. They didn’t have the feathery gills under the thorax that krill have. I also noticed that some of them were brooding eggs in a ventral pouch on the thorax, making them members of the Peracarida. Okay, then. Definitely not krill, so maybe . . . mysids? They look like mysids and so far nobody has told me that they’re not mysids, so I’m going to call them mysids.
The sun came out as I finished up in the tidepools. I hiked back up the very steep sand dune and looked back at where I had come from. Wow. Talk about stunning vistas!
View of Franklin Point from atop the last (and steepest) sand dune. 21 July 2016
Friday 22 July 2016—Natural Bridges
Today was by far the best day this week for picture taking in the intertidal. However this post is getting long so I’m going to showcase the crabs I saw this morning.
Pachygrapsus crassipes is the common shore crab, ubiquitous in the intertidal and at the harbor. It lives in the mid-tide zone and hangs out among the mussels. It is a shy beast, not aggressive and is more likely to drop into the nearest pool if it detects movement nearby. However, if you sit still for only a few minutes, you’ll find yourself noticing many small crabs coming out to bask in the sun.
Here’s a little tidbit about crab biology. All crustaceans breathe with gills. Any gas exchange structure, even your own lungs, functions by providing a surface across which oxygen can diffuse from the surrounding medium into the animal’s blood. Aquatic animals breathe with gills (if they have any specialized gas exchange structures at all, that is) and air-breathing animals breathe with lungs.
These crabs are often seen out of the water, in the sun. How then, you may reasonably ask, do they breathe with gills? The answer is, they foam. They produce bubbles that keep the gills moist, allowing oxygen first to dissolve into a thin layer of water and then to diffuse into the blood. I’m not entirely certain exactly how the crab forms the foam, but suspect it has to do with manipulating a thin layer of secreted mucus to capture small air bubbles. You do see the crabs massaging the foam over their sides, where the openings to the branchial chambers are.
Hermit crabs are the undisputed clowns of the tidepools. Around here we have four species that are commonly seen in the intertidal, all in the genus Pagurus. Many other species in different genera can be seen subtidally.
The most easily identified hermit crab in these parts is, in my opinion, Pagurus samuelis. They have bright red unbanded antennae, and often have bright blue markings on their legs. This species usually inhabits the shells of the turban snail Tegula funebralis.
The other species that I saw today was the much smaller P. hirsutiusculus. The common name for this animal is “hairy hermit crab” but they don’t seem all that hairy to me. They may be found in small Tegula shells, but I most often see them in shells of smaller snails such as Olivella biplicata.
There’s another P. hirsutiusculus in that other Olivella shell in the right-side of the photo, but it did not want to have its picture taken.
All told it has been a very satisfying week. I may have overtaxed my concussed brain a little bit. My plan for the weekend is to revert back to the rest-and-do-nothing routine to let my brain recover. Totally worth it!
A long time ago in a galaxy called the Milky Way, a great adventure took place. We don’t know exactly when it happened, but it must have been very shortly after the evolution of the first cells. Some small prokaryotic cell walled itself off from its surroundings. Then it learned how to replicate itself and as cells continued to divide they began interacting with clones of themselves. Sooner or later, however, our clone of cells encountered cells from a different genetic lineage. These foreign cells were “other” and were recognized as such because they had a different set of markers on their outer covering. Perhaps there was an antagonistic interaction between the two clones of cells. In any case, this ability to distinguish between “self” and “non-self” was a crucial step in the evolution of life on Planet Earth.
The entire immune system in vertebrates is based on self/non-self recognition. It is why, for example, transplanted organs can be rejected by their new host–the host’s immune system detects the transplanted tissue as “non-self” and attacks it. As a result, patients who receive donor organs usually take immune-suppressing drugs for some period of time after the transplant.
The vertebrate immune system is quite complex and very interesting. It has two main components: (1) cell-mediated immunity, in which the major players are T cells; and (2) humoral (i.e. blood-based) immunity, which is the part of the immune system that produces antibodies to a pathogen when you get a vaccination. However, even animals much less structurally complex than vertebrates have some ability to recognize self from non-self.
Sponges, for example, exist as aggregations of cells rather than bodies with discrete tissues and organs. Most zoologists, myself included, consider sponges to be among the most ancient animal forms. They have different types of cells, many of which retain the ability to move around the body and change from one type to another; this totipotency is a feature that sponge cells share with the stem cells of vertebrates. There are sponges that you can push through a mesh and disarticulate into individual cells, and then watch as the cells re-aggregate into an intact, functioning body. As if that weren’t cool enough, if you take two different sponges and mush them into a common slurry, the cells from the distinct lineages re-aggregate with cells to which they are genetically identical. So even animals as primitive as sponges have some degree of self/non-self recognition.
If you’re lucky, you can see self/non-self recognition and aggression in the intertidal. Here in northern California we have four species of sea anemones in the genus Anthopleura:
Anthopleura xanthogrammica, the giant green anemone
Anthopleura sola, the sunburst anemone
Anthopleura elegantissima, the cloning anemone
Anthopleura artemisia, the moonglow anemone (and my favorite)
Of these species, only A. elegantissima clones. It does so by binary fission, which means that the animals rip themselves in half.
It looks painful, doesn’t it? As the two halves of the animal walk in opposite directions they pull apart until the tissue joining them stretches and eventually rips. Then each half heals the wound and carries on as if nothing had happened. Each anemone is now a physiologically and ecologically independent animal, and can go on to divide itself. And so on ad infinitum. The logical consequence of all this replication is a clone of genetically identical anemones spreading over a rocky surface. And that’s exactly what you get:
Okay, it’s hard to tell that these are sea anemones, but this is what they look like when the tide goes out and leaves them emersed. They pull in their tentacles, close off the oral disc, and cover themselves with sand grains. They look like sand but feel squishy and will squirt water if you step on them. In this photo, each anemone is probably 4-5 cm in diameter.
There are three patches of anemones in the photo above, separated by narrow strips of real estate where there are no anemones. Each patch is a clone, essentially a single genotype divided amongst many individual bodies. The anemones in each clone pack tightly together because they are all “self.” However, they recognize the anemones of an adjacent patch as “non-self” and they won’t tolerate the intrusion of neighbors onto their territory. Those strips of unoccupied (by anemones) rock are demilitarized zones. When the rock is submerged the anemones along the edges of the clones reach out their tentacles and sting their non-self neighbors. This mutual aggression maintains the DMZ and nobody gets to live there.
Because A. elegantissima lives relatively high in the intertidal the clonal patches are usually emersed when I go out to the tidepools. Its congener, A. sola, lives lower in the intertidal and is more often immersed at low tide. Anthopleura sola is larger than A. elegantissima and is aclonal, meaning that it does not divide. Anthopleura sola also displays quite dramatically what happens when anemones fight.
These two anemones, each about 12 cm in diameter, were living side-by-side in a tidepool. You can see that each animal has two kinds of tentacles: (1) the normal filiform feeding tentacles surrounding the oral disc; and (2) thicker, whitish club-shaped tentacles below the ring of feeding tentacles. These club-shaped tentacles are called acrorhagi, and are used only for fighting. The acrorhagi and the feeding tentacles may contain different types of stinging cells, reflecting their different functions. All tentacles are definitely not the same.
These animals, which represent different genotypes, are non-self to each other, so they fight. They inflate their acrorhagi, move their feeding tentacles out of the way, and reach across to sting each other. See how some of the acrorhagi on the animal on the right don’t have nice smooth tips? Those tips have been lost during battle with the animal on the left; the tips are torn off and remain behind to continue stinging the offender even after the tentacle itself has been withdrawn.
Here’s another picture of the same two anemones, taken from a different angle:
The goal of these fights is not to kill, but to drive the other away so that each anemone has its own space. Eventually one of them will retreat, and a more peaceful coexistence will be established. Fights like these have been going on for over half a billion years. Eat your heart out, George Lucas.
Every year, as early as Memorial Day or as late as Father’s Day, there’s about a week of really lovely low tides. This midsummer tide series usually includes the lowest low tides of the year, and we intertidal ecologists plan our field activities around them. Incidentally, there’s a corresponding low tide series in the midwinter, too. However, at that time of year the lows are in the afternoon, and because the low occurs about 50 minutes later each day you’re fighting darkness as you work the series. But in the summer, even if the first day of the tide series has a low tide before sunrise, that 50-minutes-later-each-day thing is really nice and you never have to worry about running out of daylight.
This year, the California Academy of Sciences sponsored several citizen science excursions called Bioblitzes to various locations on the California coast. The goal of these Bioblitzes was to document biodiversity in the intertidal in protected and non-protected areas of the coastline. Back in May I volunteered to lead a Bioblitz at one of the sites close to me, and planned to participate in a few others as well. In addition to actual organized Bioblitzes, citizens were invited to submit their own independent observations to the project.
Today is the three-week anniversary of the car accident that left me bruised and concussed. The bruises are pretty much healed at this point, and the soreness in my ribcage is also much improved. The medical advice I got for dealing with the concussion was, “Protect your brain from stimulation. Let it heal. And REST.” So for the past three weeks I haven’t been doing much of anything. I was worried that I wouldn’t be able to go out on any of the midsummer low tides, as it didn’t take much to overtax my injured brain and I didn’t want to risk overextending myself. I did end up skipping the first Bioblitz of the week and modified my original plans for the rest of the tide series to play it safe and stay closer to home.
I’m still trying not to spend too much time on the computer (electronic screens are very bad for injured brains) so I’m going to summarize my week’s activities in a single post. I’ll keep the stories short. But I did want to share some of the things I saw.
Day 1 – Natural Bridges, Monday 6 June 2016, low tide -1.6 ft at 06:25
My first venture out by myself was to Natural Bridges. It’s very close to my house and I figured that if I needed to bail I could walk out and be home within 15 minutes. It was cold and foggy and I felt energized just to be out there again.
Turns out this trip was about all my brain could cope with that early in the week. I skipped a Bioblitz up at Pigeon Point on Tuesday so I could stay home and rest, which ended up being a good call. A whole day of doing nothing was exactly what my concussed brain needed.
Day 2 – Mitchell’s Cove, Wednesday 8 June 2016, low tide -1.1 ft at 08:02
The day of rest was enough to get me back out there on Wednesday. My friend Brenna met me at Mitchell’s Cove for a morning of tidepooling. Mitchell’s Cove is a popular, dog-friendly beach in Santa Cruz, particularly busy in the mornings and evenings. Last September it was visited by a juvenile humpback whale, which came right into the Cove and hung out there for several days. I didn’t see any whales this week, but there was a surprising diversity of life in a relatively small area of rocky intertidal.
Phyllospadix scouleri, the species that has flatter, more ribbon-like leaves, was blooming. Its congener, P. torreyi, growing in almost exactly the same place, has narrow leaves that are more cylindrical in cross-section, and was not in bloom. Phyllospadix is a true marine plant; the flowers are inconspicuous swellings near the bottom of the leaves and the pollen is carried by water, rather than wind, to nearby plants.
And I saw two species of hydroids! This one is easy to ID to the genus Aglaophenia, but I would need to examine it under a microscope to determine the species. I wasn’t collecting anything on Wednesday so I don’t know which species it is.
And I saw an octopus! We know that they’re in the intertidal, but they are so cryptic and clever at hiding that we don’t see them very frequently. This one was definitely smarter than I was. Instead of scooping it out and placing it on dry ground so I could photograph it more easily, I chased it around a tidepool with my camera. Thus, this is the best picture I could get:
Day 3 – Davenport Landing, Thursday 9 June 2016, low tide -0.7 ft at 08:52
This was the day of my “official” Bioblitz. I had four participants–Brenna, Alice, Martha, and Andy. As of right now (Brenna hasn’t yet uploaded her observations) the other four of us have made 120 observations, documenting 50 species. Here are some of mine:
There are kelps, such as Egregia menziesii (feather boa kelp) whose habitat is the rocky intertidal. Most kelps, though, live subtidally, often in kelp forests. Nereocystis luetkeana, the bullwhip kelp, is one of the subtidal canopy-forming kelps. This one recruited to the intertidal. It is quite small and extremely cute; the float is only 2 cm in diameter.
Algae look their best when immersed. Out of the water they usually collapse into stringy or gooey masses, making it difficult to appreciate their structural beauty. This piece of Microcladia borealis was submerged in a tidepool, and fortunately there was enough light that I could take this picture.
Day 4 – Natural Bridges, Friday 10 June 2016, low tide -0.2 ft at 09:42
Yesterday I returned with a former student, Daniel, to Natural Bridges. It was sunny and warm, completely different from how it had been on Monday. There were many boaters out on the bay, taking advantage of the glassy flat sea.
I’ve seen a lot of shore crabs running around on the rocks this year. On cool, damp days they just scurry about, but on warm sunny days they often sit still and literally foam at the mouth. The bubbles they produce keep their gills moist so they can still breathe even while emersed. This biggish shore crab was working up quite a froth.
Nuttallina californica is one of the most common chitons seen around here. They often hunker down into small crevices where water will collect even at low tide. This individual was nestled among a clump of Phragmatopoma tubes; being closely surrounded by other animals will help keep its own body moist.
Unlike the hard granite that you’d find at the southern end of Monterey Bay, the rock at Natural Bridges is a soft, easily eroded mudstone. You can scratch it with your fingernail. Limpets take advantage of this soft rock by digging themselves little home scars, which conform perfectly to the contours of their shells and make a snug, water-tight fit. The limpet leaves its home scar to forage when the tide is in and returns to it as the tide recedes. The owner/occupant of this scar has likely died, as it wouldn’t have abandoned its home scar when we were there at low tide.
And speaking of limpets, Daniel and I spent a lot of time observing the owl limpet, Lottia gigantea. This limpet is noteworthy not only for its large size, but for its territorial behaviors. They are indeed large–the biggest ones I’ve ever seen are about the size of the palm of my hand–and the big ones are all females. Lottia gigantea is a protandrous hermaphrodite: individuals begin sexual maturity first as males, and then the lucky few turn into females.
The truly remarkable thing about L. gigantea is its ability to modify the environment. The large females maintain an area called a farm, from which they diligently remove interlopers. They will scrape off settling larvae of barnacles and mussels, and will push off other limpets. Lottia farms are very common at Natural Bridges; if you are here and see a suspiciously empty patch of rock amid the mussel bed, look for a big limpet hanging out on the edge of the empty spot.
The owl limpet has a good reason for keeping other animals off her territory. It provides her food. This animal is indeed a farmer. See the pale zig-zag markings in the Lottia farm? Those are marks made by the limpet’s radula as she grazes over the rock. All limpets are grazers, but L. gigantea actively manages her farm so that she feeds on one area while allowing the algal film to grow on other areas, then rotates to a new feeding spot as the old one becomes depleted. Pretty clever for a snail, isn’t it?
It felt really good to spend some quality time with Mother Nature again. I’m still taking it very easy, careful not to get overtired and to continue letting my brain heal. Getting outside for even short periods definitely seems to help.
Well, we can’t—at least, not very well. I suppose we can eat it in small amounts, but sand itself is one of the most nutrient-poor substances imaginable. Sand is, after all, ground up bits of rock. It would provide certain minerals, depending on the type of rock, but none of the essential macronutrients—carbohydrates, proteins, and lipids—that animals need to survive.
When I was a kid I thought that sand dollars were called sand dollars because I’d find their broken tests on sandy beaches. I knew they lived in sand, hence the name. As I started studying marine invertebrates in college I learned that sand dollars don’t just live in the sand; they also eat sand. In addition to organic matter, usually in the form of detritus, sand dollars eat sand to create ballast. This makes them heavy and keeps them from being picked up and carried away by waves. It is also why, if you come across an intact sand dollars test and break it open, sand will fall out of it.
I have a batch of recently settled Dendraster excentricus, the common sand dollar in northern California. They began metamorphosing only 30 days post-fertilization. As the larvae settled and transformed into tiny sand dollars, I decided to try to figure out what to feed them. These animals aren’t grown commercially and there doesn’t seem to be a definitive answer on how to raise them. One of the suggestions I got was “Well, we know they eat sand, so feed them sand.”
Which is what I did. The first time I just sprinkled a bit of sand in the dish with the juvenile sand dollars. Then I looked under the microscope to see that the sand grains were about 10 times the size of the animals. Oops. But the sand dollars didn’t look unhappy so I let them be. I decided that they also needed something organic to eat so I ground up a small piece of Ulva and dropped some of the resulting slurry on them.
The second time I offered sand to the sand dollars I ground it up in a mortar and pestle that I scrounged from the lab next door. Let me tell you, grinding sand makes a sound that is every bit as horrible as you imagine. At least it produced smaller particles that the sand dollars might be able to eat. I continued to offer Ulva mush in addition to the fine sand. If they end up eating either sand or Ulva, I can provide that pretty easily. The question is, how do I know whether or not they’re eating?
How many sand dollars can you find in the above photo? They are exactly the same color as the sand. I don’t have real proof that these little guys are eating sand; even their poops would look like the sand. The animals do tend to clear the space in their immediate vicinity, but I think that might be due to the action of the tube feet and spines rather than consumption of either sand or Ulva. In this video clip you will see that the sand dollars are very active, even though all the motion doesn’t seem directed the way it does in urchins at this stage.
They do a lot of waving around, but don’t actually walk. They do, however, seem to like being tilted up a bit, similar to the way adult sand dollars position themselves when in calm water:
By Chan siuman at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=23041434
I do have circumstantial evidence that my sand dollars are eating something. The first ones metamorphosed at 30 days post-fertilization. Today is day 51 post-fertilization, which means some of the animals have been post-larvae almost as long as they were larvae. I know it takes about a week for newly metamorphosed sea urchins to form their new guts and begin feeding, and I assume it’s the same for sand dollars. In fact, because these sand dollars raced through larval development so quickly I expected their juvenile mouths to break through quickly as well. If this were the case, then these animals should have had complete and functional guts for almost two weeks now. The fact that they’re not dead or dying makes me think that they have to be eating.
Call it a hunch, call it intuition, call it wishful thinking. I’m not sure how they’re doing it, but I think they’re fine. Next week I hope I can find time to measure them.
I’ve already written several times about seastar wasting syndrome (SSWS) and you’ve probably seen your share of photos of wasted, melting, self-mutilating stars. However, you may also be wondering about the current state of affairs regarding SSWS, and whether or not sea star populations have recovered at all since the outbreak began three years ago now. The question “How does SSWS affect the stars?” can be addressed on two different levels: the level of an individual star, and the level of the population of stars. In this post I discuss the first aspect, and in a subsequent post I’ll share my observations of sea star populations in the field.
Level 1: SSWS as it affects individual stars
I remember very vividly the feeling I had when I opened the door to the wet lab and glanced into my table to see this:
And after that it only got worse, until (almost) every star was dead. It was interesting to watch how the disease manifests in different species of stars, though. The forcipulates–genera Pisaster (ochre stars), Pycnopodia (the huge sunflower star), Orthasterias (rainbow star)–succumbed quickly and violently. These were the animals that ripped their own arms off, often without showing any prior signs of distress, and then melted away.
On the other hand, other species seemed to be more resistant to SSWS. At least, they didn’t succumb right away. Perhaps the disease (if it is indeed a disease) progresses more slowly in some groups of species compared to others. These stars, including the bat stars (Patiria miniata) and leather stars (Dermasterias imbricata), didn’t rip their arms off. The only leather star in my care died about a week after the forcipulates bit the dust, and the bat stars seemed fine for months. And when these species got sick they showed different symptoms.
Instead of self-mutilation, the leather and bat stars developed lesions on their skin. The lesions could be very deep, exposing the animal’s internal organs (guts and gonads) to the external environment.
The white objects inside the yellow circle are the star’s skeletal ossicles, which have fallen away because the tissue holding them in place has been severely eroded. I haven’t seen a leather star survive longer than a week once the lesions appear. Bat stars, on the other hand, can and do live for months with lesions. For example, this star of mine first developed lesions back in September 2015:
The lesions were small and superficial, and for a long time the animal didn’t actually seem sick. It wandered around its table, remained sticky, and even ate. Now, seven months later, the star is still hanging in there. I took this photo of it yesterday:
The lesion is bigger and deeper and now the innards are exposed. The star is also a little deflated, which might be a bad sign. From what I’ve observed, once an animal can no longer maintain its internal turgor pressure, it probably can’t recover. However, this one isn’t totally deflated yet, so I still have hope for it. Heck, this animal has been sick for over half a year now and hasn’t died yet. It obviously has some ability to resist the illness, or perhaps it’s just dying very slowly.
Just for kicks I zoomed in on the lesion under the dissecting scope, and it actually looks sort of cool. It isn’t every day that you can see the internal structures of an animal without cutting it open.
Sea stars don’t have a lot of space in the central disc of the body, so they keep their gonads and guts in their arms. Each arm contains a pair of pyloric caeca (extensions of the gut) and a pair of gonads. In the photo above, the whitish ribbons are the pyloric caeca and the tan bits are gonad. Just for kicks I snipped off a piece of the gonad and looked at it under the compound scope. And lo and behold, it’s a girl!
Those large round-ish blobs are oocytes in varying stages of maturity. I’m a little surprised to see any developing oocytes at all, given that this poor star has been sick for so long. Maybe this is a good sign. The internal fluid of the animal’s main body cavity is essentially seawater, so having the gonads and guts exposed to the outside might not be the direct avenue to infection that it would be for us. From what I can tell the tissue itself looks healthy: it doesn’t appear to be decomposing, the oocytes are full and more or less round, and there aren’t a lot of ciliates swarming all over it. So I think there’s hope for this animal, which has already survived so much, to pull through.
Another bat star that I’ve been keeping an eye on is a beautiful 8-armed star that was collected by Prof. John Pearse. Somehow I never managed to take a picture of this animal until it got sick about two weeks ago. One of the lab assistants noticed that it looked a little off on a Saturday, and two days later it had some nasty lesions.
Because this bat star went from zero symptoms to ulcerated lesions in two days, we didn’t think it would last much longer. The lab assistants isolated it in a tub filled with 0.2-µm filtered seawater and have been changing its water daily. Just as it didn’t take long for symptoms to appear, it didn’t take long for this individual to show signs of recovery. About five days after first being isolated the star was sticking to the side of its tub, indicating that its water vascular system was still functioning. A week after that, I looked at it again and saw that the lesions seemed to be healing!
The surface of the lesion appears to be more solid, as if the epidermis had been knitted back together. There’s still a bit of gonad exposed, though. Is this significant? At this point I’m not sure. The animal will remain in ICU, separated from all other echinoderms, until we are absolutely certain that it has recovered. And of course I may be jumping the gun to say that the animal is recovering at all. Only time will tell. It is, however, extremely refreshing even to think about SSWS without despair, for which I am grateful.
In recent years, citizen science has become a very important provider of biological data. This movement relies on the participation of people who have an interest in science but may not themselves be scientists. There is some training involved, as data must be collected in consistent ways if they are to be useful, but generally no scientific expertise is required. The beauty of citizen science is that it allows scientists and science educators to share the experience of discovery with people who might not otherwise know what it’s like to really examine the world around them. I think it is a great step towards creating a less science-phobic society, one in which science informs policy on scientific matters.
LiMPETS stands for “Long-term Monitoring Program and Experiential Training for Students.” The program seeks both to give students experience doing real science and to establish baseline and long-term ecological data for California’s sandy shores and rocky intertidal areas. As an intertidal ecologist myself, I naturally wanted my students to participate in the rocky intertidal monitoring.
The LiMPETS coordinator for Santa Cruz and Monterey Counties is a woman named Emily Gottlieb. She and I decided to have my class monitor the site at Davenport Landing. Emily came to class two weeks ago to train the students in identifying the relevant organisms and recording the data.
Tidepooling is easy and comfortable when you do it inside a classroom seated at a table. But today was all about the real thing. It was overcast and breezy when we met up with Emily at 09:30 and headed out to the site. At first the students seemed to be a little skeptical about the whole thing.
We were extremely fortunate to be joined this morning by Dr. John Pearse, Professor Emeritus of Biology at UC Santa Cruz, one of my graduate advisors, and the founder of LiMPETS. Dr. Pearse has been monitoring some sites, including this one at Davenport Landing, since the 1970s. He is THE person to talk to about intertidal changes in California over the past 40 years.
Years ago John set up permanent transect lines and plots at Davenport Landing, marking the origin of each transect with a bolt. The first thing we had to do when we got to the site was find the bolt. Then John ran out the transect line to the lowest point that students could work safely, given the conditions of tide and swell; this happened to be about 15 meters.
For the vertical transect, 1/2-meter square quadrats were placed at each meter. Some organisms were counted as individuals and others were marked as either present or absent in each of the 25 small squares within each quadrat. Emily gave the students their assignments and data sheets, and they spread out along the transect line.
Aside from the experience of learning how to do this kind of data collection, I hope the students understand what a privilege it is to have been in the field with John Pearse. He has such a thorough understanding of the intertidal that he is a treasure vault of knowledge. Here he is explaining what owl limpets are all about:
Interestingly, we didn’t find many owl limpets. And certainly not any of the big ones that I see all the time at Natural Bridges. John said that this is one of the differences between a protected area (Natural Bridges) and an unprotected one (Davenport Landing). Collecting is not allowed at Natural Bridges, and the owl limpets are left unmolested–by humans, at least–to grow large (10+ cm long is not uncommon). On the other hand, people do collect at Davenport and I’ve heard it said that owl limpets are good to eat; today we saw fewer than a dozen owl limpets and they were all small, none larger than 3 cm long.
The sun came out after a while, but the wind also picked up. The tide came up as well, and some of the students got more than a little wet. Overall they were real troopers, though, and I didn’t hear much complaining. Next week is the last lab of the semester, and we’ll be participating in another citizen science project. But that’s a tale for another day.
I did take advantage of the beautiful setting to have one of Emily’s LiMPETS volunteers (and a former student of mine!) take our class photo. Here we are, the Bio 11C class of 2016!
This week it has been very windy on the coast. As in hope-the-next-gust-doesn’t-arrive-while-I-am-still-holding-onto-the-door windy. Seriously, the other day I almost wrenched my shoulder when the wind caught a door I was walking through just as I opened it. I should have braced myself before opening that door. The wind also blows around dust and pollen, exacerbating everybody’s spring allergies.
Despite all that, the wind is a good thing because it is the driving force behind coastal upwelling, the oceanographic phenomenon that brings cold, nutrient-rich water from depth to the surface. Upwelled water provides the nutrients that primary producers such as phytoplankton require for photosynthesis. The simple equation is: Sunlight + nutrients = photosynthesis. With the days getting longer as we head toward the summer solstice, this is the perfect time of year to be a phytoplankter. (Note: a phyto- or zooplankter is any creature that lives as plankton)
It takes several days of sustained winds from the north to start upwelling along the coast. I record the temperature in one of my seawater tables every day and keep an eye out for decreases that might indicate upwelling. Given that it’s been crazy windy since Sunday (today is Wednesday) I thought today would be a good day to collect a plankton sample and see what’s going on.
What did I find? Lots of phytoplankton, right on schedule!
Most of these critters are diatoms, of which there were several different types. Diatoms are unicellular algae whose cells are encased in a fancy silica shell called a frustule. More on that later. In Monterey Bay, the first phytoplankters to bloom in the spring are usually diatoms; they can take advantage of upwelled nutrients to fuel rapid asexual division so their populations grow quickly. Photosynthetic creatures from diatoms to redwood trees can perform the biochemical magic of capturing light energy and converting it to chemical energy held in molecules containing fixed carbon (e.g., glucose). Diatom blooms provide food for grazing zooplankters such as copepods and krill. These small animals become food for any number of larger animals, and so on up the food chain, so in every sense possible the phytoplankton are the foundation upon which the entire marine food web is based. Interested in saving the whales? Then you should focus your energies on saving the phytoplankton. Seriously.
The largest object in the photo above is a large protozoan ciliate called a tintinnid. They also live in glass shells, only theirs is called a lorica (L: “body armor”). The tintinnids I see most frequently in tows from the Wharf have a clear goblet-shaped lorica that is entirely transparent. These tintinnids are big, for single-celled creatures, up to over 1 mm in length. That’s a lot bigger than some multicellular animals!
Tintinnids are frantic little swimmers. They are heavily ciliated, which means they can swim really fast. The one in the photo was tangled up in the phytoplankton and squashed under a cover slip, which conveniently retarded its motion, but in this video you can see its little cilia beating. I added a few seconds of a different tintinnid swimming solo to the end of the video clip, which will give you a better idea of how they swim.
Here are some other plankters from today’s sample:
Photo #1 – Diatoms. The large cell with the spines on both ends is Ditylum brightwellii, one of my favorite scientific names. Chaetoceros cells each have long spines at the corners of the cells. The spines link adjacent cells together, forming chains.
Photo #4 – Assorted phytoplankton. In this photo the five roundish cells are the dinoflagellate Protoperidinium. They have two flagella, one in a groove that wraps around the cell and one that trails free. The two button-like cells near the center of the picture are (I think) the diatom Thalassiosira. There are two chains of Chaetoceros debilis and several other chain diatoms. That big opaque vaguely bullet-shaped object to the right of center? That’s a fecal pellet, probably from a copepod.
Speaking of copepods, as usual they were very abundant, both as adults and as larvae. In terms of numbers of individuals, copepods are likely the most abundant animals in the sea. Copepods are small crustaceans that feed on phytoplankton and are in turn eaten by many larger animals. In life they have beautifully transparent bodies, allowing us to see the beating heart. See for yourself:
And, finally, about those diatom frustules. As I mentioned above, a diatom’s frustule is a sculpted shell made of silica (SiO2). It comes in two parts, an epitheca and a hypotheca, that fit together like the two halves of a petri dish. In fact, I use a petri dish as a frustule model for my marine biology students; it is made of roughly the same substance and demonstrates the size relationship between the epitheca and hypotheca.
The large round centric diatoms best show the structure of the frustule. Here’s the best photo I was able to take today of one of the very large centrics, Coscinodiscus:
I hope that later in the season I can take some better photos of these diatoms. They are so beautiful that I really to do them justice. So much diversity early in the season makes me hope for a good productive season. We’ll see!
This morning I drove up the coast to Pigeon Point. It was cold and very windy, and I was grateful to have decided to wear all of my layers. I don’t remember any cold mornings from last year’s low tides, which made me think that perhaps we’re returning to a more normal non-El Niño weather pattern. The wind was screaming down the coast from the north, and if it keeps up we should get some upwelling in a few days. Fingers crossed!
Even the pelicans, which can fly through strong winter storms, were having a bit of trouble with the wind:
My favorite kelp grows in the intertidal, and it wasn’t having any difficulty at all with the strong surf. It’s not large and doesn’t form the magestic kelp forests that divers flock to, but it is very charming in its own way. The sea palm Postelsia palmaeformis is a small (1/3-1/2 meter tall) kelp that lives only on exposed rocks sticking out into the brunt of the waves. It requires the full force of the crashing waves, where other algae would get broken off. They have a thick flexible stipe that bends with the waves and then pops back up. Postelsia is a protected organism and I can’t collect it even with my scientific collecting permit, which is fine with me.
This is the kind of environment in which Postelsia thrives:
You can tell how windy it was by the sound of the wind and my inability to hold the camera steady. As the tide comes in the pounding from the waves will only get worse. These little algae are pretty damn impressive!
Pigeon Point has always been a good place to see the 6-armed stars of the genus Leptasterias. Unlike the five arms that most of the local asteroids have, Leptasterias has six. And unfortunately for us naturalists, the taxonomy of the genus is incompletely understood. All that is agreed upon is that there are several species in the genus. This is referred to as a species complex, acknowledging that the genus contains more than one species but that the species have yet to be definitively described.
As you can see, these stars vary quite a bit in terms of arm thickness and color pattern. Most of the time they are blotchy but the blotches can be pink, gray, orange, or cream-colored. Some of the stars have slender arms with very little taper, while others have thicker arms that taper strongly to the tips. For the time being, until the sea star systematists come to consensus about the species in this genus, I’ll refer to all of them as Leptasterias sp.
Most of the Leptasterias that I see in the field are in the size range of 1-4 cm in diameter, usually no longer than my thumb. Today I saw a big one, which would have been about the size of the palm of my hand.
The reason this star doesn’t look quite as big as that in the above photo is that it was eating when I disturbed it. The star was humped up over its breakfast!
The unfortunate breakfast item, the turban snail Tegula funebralis, was about 2 cm in diameter. It seems like a very large and well-protected prey item for a star this size, doesn’t it? And yet, there it is. The animal is always right, and Leptasterias certainly knows what it should be eating.
And lastly, because they were just so beautiful and I can’t help myself, I’m going to close with photos of anemones.
So. Last week when I looked at my sand dollar larvae I wasn’t at all sure what to make of them. I thought that all of the offspring from one of the matings (F2xM1) were going south and didn’t know how much longer they would survive. The offspring from the other two matings seemed to be doing much better.
Fast forward a week and a half and my, how things have changed. I have some juvenile sand dollars now! And so far they are all from the F2xM1 mating, the ones that had started looking strange and that I thought might die. I’m surprised that any of the larvae metamorphosed, as my general understanding of sand dollars was that competent larvae settle among adults of their species, so that when they finish metamorphosis they would be in a suitable location to grow up. However, the animals is always right, and in this case I was happy to learn that my understanding was wrong.
This larva is almost competent. The main part of its body is almost completely filled by the juvenile rudiment (the tannish structure on the left side of the more reddish stomach) and the arms are shorter.
And here is a video of a trio of competent larvae.
Their bodies are almost entirely opaque now but they are unquestionably pluteus larvae.
As metamorphosis begins, the tube feet in the juvenile rudiment rupture through the body wall and the animal starts sticking to a hard surface, in this case a glass slide. For a while the animal is suspended between the larval and juvenile forms, in a state I call a larvenile. Hopefully the time spent in the larvenile stage is short, as to be neither larva nor juvenile is a bad thing. I’ve seen both sea urchins and sea stars get stuck in the larvenile stage, and they all died.
Larveniles are strange things. See for yourself.
In this video the right side of the animal (not the anatomical right but the right side of the image as it is presented on the screen) is the juvenile, and the left side is the larva. The larva half still has its fenestrated arm rods, which will eventually be dropped and left behind. It also retains for the time being the ciliated band which it used both to swim and to capture food. Another weird feature of the larvenile is the transition between the bilateral symmetry of the larva and the pentaradial symmetry of the juvenile. The bilateral symmetry has been more or less obliterated by the process of metamorphosis, but there isn’t enough of the juvenile to have complete pentaradial symmetry yet.
And, finally, metamorphosis is complete and a little sand dollar walks around on tube feet.
Yesterday this animal was a larva, and today it’s a juvenile. The sea urchins do the same thing. But these sand dollars have done everything faster than the urchins, and that includes development immediately after metamorphosis. You may recall that the purple urchins have only five tube feet when they metamorphose, and they struggle to coordinate them to walk. From what I can see these sand dollars have at least twice that many tube feet very shortly after metamorphosis, and they can walk much more quickly.
The tube feet themselves are different, too. Urchins’ tube feet are suckered and look like little plungers. Sand dollars’ tube feet have those pincher-looking tips (although I haven’t seen them open up and grab things yet). Adult sand dollars live partly buried in sand and don’t use their tube feet to cling to surfaces; they do use their tube feet to grab food, though.
Speaking of food, I don’t know what these juvenile sand dollars will be able to eat. Fortunately I have a while to figure out what to try feeding them, as their mouths won’t open up for at least a week (I hope). While it’s easy to observe what happens on the surface of the animal as it metamorphoses, it’s impossible to see what’s going on with the internal reorganization of the body. I do know that an entire new gut will have to be formed before the animal can eat. In the meantime it will have to survive on energy stores stashed in all that opaque part of the body.
