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My baby urchins have become scum-eating machines! They are 88 days old now and I am beginning to wonder if I can generate scum fast enough to keep up with them. I did a head count this morning and have three bowls, each of which holds a population of ~100 urchins, and a bowl that contains another 33. The first three bowls are going through food very quickly, and I change their scum slide every 2-3 days. And, since eating results in pooping I change the water every day.

Hungry urchins looking for food:

Juvenile sea urchins (Strongylocentrotus purpuratus), 18 April 2015 © Allison J. Gong
Juvenile sea urchins (Strongylocentrotus purpuratus), 18 April 2015
© Allison J. Gong

After they eat through the food on the upper surface of the slide, the urchins migrate to the lower side and begin munching there. Once most of the food is gone they go on the prowl, and I'll find them on the sides of the bowl looking for something to eat. In the photo, can you tell which urchins are on the underside of the slide? Most of them are, actually. They're the ones where you see a darkish ring around the center; that ring is the peristomial membrane that surrounds the mouth. That's what "peristomial" means, by the way, but you didn't need me to tell you that, did you?

Changing the slide involves using a paintbrush to pick up each urchin and drop it into the new bowl. It's rather tedious but is also the most convenient time to count them. And they do seem happy every time they find themselves in a new bowl with plenty to eat.

Baby urchins with lots of food to eat now:

Juvenile sea urchins (Strongylocentrotus purpuratus), 18 April 2015 © Allison J. Gong
Juvenile sea urchins (Strongylocentrotus purpuratus), 18 April 2015
© Allison J. Gong

Using the clue I gave you up the page, can you find the single urchin on the underside of the slide?

Having pentaradial symmetry means that the urchins don't have forward-backward or left-right axes, and they can and do move in any direction on the horizontal plane. They do, however, have a strong oral-aboral axis, and they definitely have a preference for how their bodies should be oriented with respect to gravity. The normal position is to have the mouth (oral surface) facing downward, with the opposite side (aboral surface) facing up. And for this species, at least, even in the field you don't see them sticking upside-down on overhanging surfaces, unless they have a vertical surface to hang onto as well. These little guys can hang onto the underside of the slide because they're not very heavy yet. Once they get bigger, it'll be a lot more difficult for them.

Setting an urchin down on its aboral surface, with its mouth facing up, will keep it from crawling away very quickly, but sooner or later it will right itself and take off. Even my little babies don't like to be flipped upside-down. This guy was pretty stubborn at first and spent a minute waving its tube feet at me while I looked at it through the microscope, but then took another minute or so to get down to the business of turning over. Don't worry, I cut out the boring first minute so this clip shows only the action sequence.

Quite clearly, urchins don't care about forward-backward or left-right, but they do care about up-down. Like most animals that live in essentially two dimensions, adult urchins prioritize knowing the orientation of one's body with respect to gravity. But remember those bilateral larvae? They swim in any direction in their pelagic, three-dimensional world, although the body always moves through the water in a particular orientation (arm tips first). It seems this is another aspect of metamorphosis that gets overlooked: the transition from a bilateral body that swims in both the horizontal and vertical planes (three body axes, weak response to gravity), to a body with pentaradial symmetry that walks only in the horizontal plane (one body axis, strong response to gravity). Hmm. I'm going to have to think about that for a bit.

1

Everybody knows that climate change is a hot--pun intended!--topic in both science and politics these days. Here along the northern California coast it seems that sea surface temperature (SST) has been elevated for at least a year now. I remember a time, not too many years ago, when I would put my hands into my seawater table and they'd go numb after several minutes. This told me that the water temperature was in the 11-12 ºC range. But that hasn't happened for a while, and recently I'd put my hands in the water and it didn't even really feel cold. My trusty not-fancy thermometer has been telling me that the temps have been hovering at around 14ºC.

The other day it occurred to me that I have a 20-year record of water temperatures from my seawater table, which is a pretty fair proxy for SST in the area. The numbers may not jive exactly with SST data produced by oceanographic instruments, but the trends should be very similar. If you click on the figure you'll be able to see a larger version of it.

Temperature in my seawater table at Long Marine Lab, July 1994-March 2015. © Allison J. Gong
Temperature in my seawater table at Long Marine Lab, July 1994-March 2015.
© Allison J. Gong

There are a couple of notable trends in these data. I was pleased to see a strong signal for the 1997-1998 El Niño event, visible as a prolonged period of elevated temperatures in the fall and winter. This was followed by a La Niña in 1998-1999, when temperatures were lower than average for a few months. Aside from those events, SST fluctuates between about 16º in the summer-fall and 11-12º in the winter-spring.

One more thing. Take a look at the far right end of the graph. Notice what appears to be a cooling trend so far in the spring of 2015?

Here are the data from March and the first three days of April:

Temperature in my seawater table at Long Marine Lab, March-early April 2015. © Allison J. Gong
Temperature in my seawater table at Long Marine Lab, March-early April 2015.
© Allison J. Gong

So there's definitely a cooling trend in the past few days. The interesting question is:  Why is this happening now, when it hasn't happened for about two years?

The answer, in a nutshell, is the wind. For the past week or so, we've had screaming afternoon winds at the marine lab, coming from the northwest. Northwest winds blowing down the coast drive the process of coastal upwelling, which results in cold water rising to the surface; it usually takes 3-4 days of sustained winds to start upwelling. This upwelled water, in addition to being cold, also contains a lot of nutrients, which are used as fertilizers by the primary producers of the marine ecosystem, the phytoplankton. Most of the phytoplankton are photosynthetic unicellular algae (NOT plants) that harvest the energy from sunlight and use it to fix carbon dioxide into organic molecules. The fixed carbon in turn feeds grazers such as copepods, which are then eaten by small predators, which are eaten by larger predators and so on up the food chain.

What this all means is that we may, for the first spring in two years, be getting some productive upwelling. I don't think I'm the only marine biologist in the area who is looking forward to seeing whether this apparent upwelling continues. If it does, then we should see the biota respond accordingly. Mind you, a four-day streak does not indicate a long-term return to typical spring upwelling conditions, and it may be merely a blip in the warmer conditions that are the new normal for us, but it is a stronger signal than we've seen in a few years. In any case, I will be keeping an eye on both the water temperature and the critters living in it.

Until recently I hadn't closely observed what it looks like when a leather star (Dermasterias imbricata) succumbs to wasting syndrome. When I had the outbreak of plague in my table almost 18 months ago now, my only leather star was fine one day and decomposing the next, so I didn't get to see what actually happened as it was dying.

(Un)fortunately, one of the leather stars at the marine lab started wasting a bit more than two weeks ago, and this time I was able to catch it at the beginning. This animal wasn't in my care so I didn't check on it as frequently as I would if it had been living in one of my tables, but one of the aquarists pointed it out to me when it began getting sick.

The first symptom was a lesion on the aboral surface. I say "lesion" but it's more of an open wound.

Dermasterias imbricata with aboral lesion, 2 February 2015. ©Allison J. Gong
Dermasterias imbricata with aboral lesion, 2 February 2015.
© Allison J. Gong

You can see that the animal's insides are exposed to the external environment. In the photo above the whitish milky-looking stuff is gonad (I'm pretty sure this animal was a male) and the beige ribbon bits are pyloric caeca, essentially branches of the stomach that extend into the arms. What typically happens along with the development of lesions like this is an overall deflating of the star as the water vascular system and other coelomic systems become increasingly compromised, and the tendency for the animal to start tearing off its arms.

Which results in this, a week later:

Wasting Dermasterias imbricata, autotomizing its arm, 9 February 2015. ©Allison J. Gong
Wasting Dermasterias imbricata, autotomizing its arm, 9 February 2015.
© Allison J. Gong

This poor animal had torn its arm off, and continued to live for a while. I find it fascinating that the lack of a centralized nervous system means that this animal literally didn't know it was dead. It was finally declared officially dead two days later. Compared to how quickly wasting syndrome kills the forcipulates that I've seen (Pisaster, Pycnopodia, and Orthasterias), the leather stars take a long time to die--several days from start to finish, opposed to a matter of hours as I saw with my stars. The leathers didn't seem to be hit as hard by the first wave of the disease outbreak, either. Is Dermasterias somehow able to fight off the infection a bit longer? It would be interesting to know, wouldn't it?

Yesterday I drove up the coast to Pigeon Point to do a little poking around. I had originally planned to search for little stars, survivors that had made it through the most recent outbreak of wasting syndrome. But I got distracted by other things and gave up on the stars, for now. I need to do some thinking about the best way to find tiny animals in a very complex 3-dimensional habitat.

I did spend quite a bit of time turning over rocks in tidepools. The most common critters I found were the usual suspects--porcelain crabs, limpets, snails, the odd sculpin or two, and chitons. One rock yielded a gold mine: five chitons of a species I didn't recognize (which doesn't mean I haven't seen it before, just that I didn't immediately know its name) that demonstrated a most interesting behavior.

Stenoplax heathiana, on underside of rock, 31 January 2015. Photo credit:  Allison J. Gong
Stenoplax heathiana, on underside of rock, 31 January 2015.
© Allison J. Gong

I turned the rock over and watched as the chitons ran away from the exposed surface onto the other side. Yes, RAN. I've never seen a chiton do anything this fast. Chitons, for the most part, lead apparently inactive lives. When we do get to see them in their natural setting, at low tide, they are usually scrunched down hard on the rock waiting for the water to come back. Obviously they are much more active when covered with water, but we don't get to see them then. In the lab, where they can be immersed all the time unless they crawl up the walls, they do wander around a bit; however, to see a chiton do much of anything requires time-lapse photography.

Don't believe that a chiton can run? Well, get a load of this:

This is in real-time, not sped up. Watch the chiton push a limpet and the snail out of the way. Okay, I'll grant that a limpet and a snail are not the strongest obstacles one could face when trying to flee from the light. But you can't deny that this chiton seems to be feeling a sense of urgency.

This species, Stenoplax heathiana, spends its days buried in sand on the underside of rocks. It comes out to feed at night, not on algal scums as most chitons do, but on bits of algae that drift by and get caught between rocks. Apparently the chiton can be found exposed in the very early morning. I'm going to have to try finding some this spring when we get our morning low tides back.  Anybody want to come with me?

 

Every winter northern elephant seals (Mirounga angustirostris) return to their breeding rookeries in central and northern California. These animals spend the majority of their time foraging at sea, but as with all pinnipeds they must return to land to birth their pups. The breeding site in central California is Piedras Blancas, a few miles north of San Simeon. In the northern part of the state the elephant seals breed at Ano Nuevo, about 20 miles north of Santa Cruz. While elephant seals do occasionally haul out along other beaches, the best places to see them are at the rookeries during the breeding season.

The adult males typically show up first, in late November and early December. They arrive early to set up and defend territories. Adult females arrive mid-December and are herded into harems by the alpha males, who meanwhile continue to fight over territory and dominance. Since the seals' food is found at sea, all adults and subadults fast while at the rookery. They loll about in the sun, flip sand over themselves, and doze.

Elephant seals at Piedras Blancas, 3 January 2015. Photo credit:  Allison J. Gong
Elephant seals at Piedras Blancas, 3 January 2015. © Allison J. Gong

For female elephant seals, the first order of business is to give birth to their pups. The pregnant females arrive carrying a pup that was conceived during the previous year's haul-out. A given female will give birth about a week after her arrival, and pupping season lasts until around mid-January. Pups are born with very dark fur and loose, wrinkly skin, until they fill out and take on the e-seal look of fat sausages. On my visit I saw pups that still had their umbilical cords attached, as well as pups that had been nursing for a while and gotten fat.

Despite the apparent laziness of the seals themselves, a rookery can be a noisy place. Pups and mothers squawk to each other, and males bellow a sort of low-pitched rumble as part of their dominance displays. Listen to the various e-seal vocalizations in this video:

In the right side of this video clip a female e-seal is being forcibly mounted by a male. I say "forcibly" because she does seem to be protesting and trying to get away. Of course, this is all just sexual selection in action--it is in the female's best interest, in terms of the quality of next year's pup, to be mated by the strongest male on the beach. Thus if she makes it difficult for him to copulate with her and he still manages to succeed, she can be reasonably certain that the father of her pup is healthy and vigorous.

However, notice that large male on the left. He doesn't like seeing "his" female being approached by another male. We kept waiting to see if a full-blown altercation would develop, but when all is said and done the animals are pretty lazy and won't waste energy on fights that aren't absolutely necessary. That big male on the left made a couple of feints towards the interloper but it didn't seem that his heart was in it.

All in all it was a fairly peaceful late afternoon at the rookery. We watched a spectacular sunset and then left the e-seals to their own devices on the beach.

Sunset at Piedras Blancas, 3 January 2015.  Photo credit:  Allison J. Gong
Sunset at Piedras Blancas, 3 January 2015. © Allison J. Gong

 

At last, a publication on the causative agent for sea star wasting syndrome! Several co-authors have written a paper that was published in the Proceedings of the National Academy of Sciences (PNAS), in which the culprit was identified as a densovirus.

The Smithsonian wrote up a nice article summarizing the findings here.

While it remains to be seen why the virus caused such widespread disease this time, at least now researchers have something to focus their work on.

4

Today is Monday.

Last Friday morning I was at the marine lab doing my usual feeding and cleaning stuff, and everything was fine. I was back at the lab Friday afternoon to return some animals that we had borrowed for one of the classes I'm teaching, and as soon as I got out of the car I knew something was wrong. I could smell it. Plankton bloom.

When I opened the door to one of the wet labs, it felt like walking into a wall of stench. It is a peculiar smell of excessive fecundity, which we occasionally see at the lab this time of year, due to a rapid population increase, or "bloom," of one or a few phytoplankton species. I'm not sure if the smell is actually bad or if it just seems bad because of all the negative things I associate with it. Negative things such as:  Sludge accumulating and decomposing on any horizontal surface in a table, including the surfaces of animals; said animals being fouled and dying because their respiratory surfaces are gunked up; seeing water straight from the tap coming in brown.

But whenever we get a nasty bloom like this, I am always curious about which critter it actually is. Back in the summer of 2010 there was a phytoplankton bloom in Santa Cruz that was at least partially caused by a dinoflagellate in the genus Alexandrium, some of which are known to produce toxins that work their way up the food chain and cause paralytic shellfish poisoning in people.

I took a sample from some build-up from this current bloom and looked at cells under the microscope (fun!). I was able to identify a couple of dinoflagellates right off the bat.

This is Ceratium.  I saw a lot of cells that look like these:

Ceratium cells.
Ceratium cells.
© Kudela lab, UCSC

Various species of Ceratium are present in plankton tows most of the year and as far as I know are pretty innocuous.

I also saw lots of these cells, too. This is Prorocentrum, a dinoflagellate that is pretty easy to recognize because of the little spine at one end of the cell. I don't think these guys are toxic, either.

Prorocentrum cells. ©2013 Allison J. Gong
Prorocentrum cells.
© 2013 Allison J. Gong

Lastly, there were a lot of these cells. I wasn't able to get a very good look at them and don't know for sure who they are, but they may be a species of Cochlodinium polykrikoides. I saw single cells and chains of two cells. C. polykrikoides is not nearly as harmless as the other two algae I saw. It has been responsible for fish kills in Asia.

These cells in a short chain might be Cochlodinium polykrikoides. ©2013 Allison J. Gong
These cells in a short chain might be Cochlodinium polykrikoides.
© 2013 Allison J. Gong

On my way out of the marine lab yesterday I stopped by the overlook to see what the surf looked like. I could see that the water was discolored with a brownish tinge. Look at the water as it recedes from the rocky bench. It would normally be white, but here it is kind of a dirty gray-brown color.

The good news is that today, Monday, the bloom seems to have abated quite a bit. I cleaned all of my tables and tanks on Saturday (extremely gross) and Sunday (not nearly as gross) and this morning there wasn't very much sludge at all. And the smell was nothing like it had been on Friday afternoon. So maybe we're getting a reprieve and won't have to deal with weeks and weeks of this stuff. That would be nice. My poor animals need a break from environmental conditions that are trying to kill them.

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