The saga continues. When I checked on my ailing stars yesterday I saw, as expected, that most of what I had called Leptasterias #1 (the pink star that had ripped itself into pieces the day before) had disintegrated into small piles of mush. There was no sign of life in any of the small fragments so I threw them away. The largest piece, consisting of two adjacent arms attached to what looks like most of the central disc, was still walking around so I kept it. Today I was surprised to see that it hasn’t died yet. In fact, it looks a little better, with both of the arms active and the central disc appearing to be somewhat more contracted and less sloppy.
The two arms appear to be working together, rather than trying to walk away from each other. I think this is a good sign, although it’s too early tell how much longer this fragment of a star will survive.
The star I had designated Leptasterias #2, which had the very large lesion on Friday, had died and dissolved into a mass of amorphous tissue and skeletal ossicles when I looked at it yesterday.
On the other hand, Leptasterias #3, the larger of the two gray stars, seems to be holding its own, or at least not getting any worse. On Day 1 of the outbreak this star had a small fluffy lesion on its aboral surface. Today the wound appears to have grown a bit but its edges look a little cleaner:
This star was particularly active this morning. I didn’t want to disturb it or give it any incentive to autotomize its arms, so I left it in its screened container to take pictures and video. It was zooming around and acting, for all intents and purposes, like a normal healthy star.
Sometimes the only word that will do is a bad word. I generally try not to use a lot of bad language because on the occasions when I do swear I want my f-bombs to really mean something. Late this afternoon I was on my way out of the lab when I made a quick last trip through the wet lab just to make sure everybody would be okay for the night, when out of the corner of my eye I saw a few odd pink bits in one of my screened containers.
This container held three small six-armed stars of the genus Leptasterias. I had collected them earlier this summer with the goal of showing them to my students when we do the echinoderm diversity lab at the end of the semester. Stars in this genus are interesting because their normal arm number is six and they brood their babies instead of broadcasting gametes into the sea to meet, fertilize, and develop on their own. Plus, like all their echinoderm kin, they are pretty animals. Lastly, enamored as I am of oddballs and out-of-the-ordinary things, I am charmed by Leptasterias‘s six arms because most stars have only five.
So when I opened up the screened container and saw that one of my Leptasterias stars had torn itself into pieces, I let fly with a few f-bombs and other choice expletives. I removed the star pieces into a bowl for a better view.
Seeing a star that had ripped its own arms off is every bit as horrifying when the star has six arms as when it has five. This act of self-mutilation had probably occurred today, as the star looked fine when I checked on it yesterday. All of the pieces were still alive and crawling around:
Actually, if you examined each of the pieces independently and didn’t know that it was only part of a greater whole, you’d think that they were entirely viable. I put these pieces aside in a separate bowl, although honestly I don’t know why. I’m almost certain they’ll be dead when I check on things at the lab tomorrow morning, and even if they aren’t they’ll be decomposing while still sort of alive, which is even worse. I must be a glutton for punishment.
For a while I held out a teensy glimmer of hope that the other two stars might be okay, but that didn’t last long. It took only a glance to see a big aboral lesion on the center of one of them:
Examination under higher magnification shows just how deep and intrusive these lesions are. The body wall is entirely compromised, resulting in the exposure of internal organs to the outside environment.
Whether or not this third individual will survive is up for grabs, but I wouldn’t bet on it. From my experience with wasting syndrome in Pisaster and Pycnopodia, the disorder progresses extremely rapidly once the animal starts showing signs of illness. And all of these animals appeared just fine yesterday. The small pink star is essentially dead already, it just hasn’t realized it yet. The gray star with the large lesion may very well be dead tomorrow, too. The star with the small lesion might still be alive tomorrow, and this is the only one for which I have a bit of hope for survival.
About a week ago the seawater temperature dropped to 16°C for a few days, but then started creeping back up; today it topped out at 19°C. Correlation is not causation, but I do wonder if another spike in the 19-20° range, on top of stress caused by the ongoing period of warm water, is the proverbial straw that broke the camel’s back. These poor stars have gone through hell lately, and there’s no indication that the water will cool off any time soon. I’d throw up my hands and ask, “What’s next?” but I have a sneaking suspicion that I’ll find out soon enough.
Having read multiple news accounts of domoic acid (DA) events up and down the Pacific coast of the U.S., I decided to do my own informal survey of the culprit that makes DA. Domoic acid is a naturally occurring toxin that is produced by some (but not all) species of the diatom Pseudo-nitzschia during a plankton bloom. It is ingested by filter-feeding animals such as mussels and anchovies and gets passed to higher trophic levels as these animals are themselves preyed upon. The filter feeders are thought to be unaffected by the DA they ingest, but due to bioaccumulation the toxin occurs in higher concentrations in the tissues of the predators. Humans can be affected by DA also, when they eat contaminated shellfish, for example. This is why coastal states advise seafood foragers not to collect and eat bivalves (clams, mussels, oysters) when DA is detected in the water. When humans are sickened by domoic acid, the affliction is called Amnesic Shellfish Poisoning (ASP).
I had originally hoped to collect a sample from a boat over deeper water, but when those plans failed to materialize I did the best I could on my own: I went out to the end of the Santa Cruz Municipal Wharf and threw the net from there. As soon as I hauled the net back up I could smell the diatoms. Yes, diatoms have a smell, as does just about anything when you concentrate it enough. The diatom smell is rich and organic, but not at all unpleasant.
This is what the sample looked like:
All those clear needle-like things are chains of Pseudo-nitzschia cells. When they are reproducing quickly (a.k.a. “blooming”) the cells remain connected by their tips (see below). Longer chains indicate favorable conditions for asexual reproduction in diatoms; I saw some chains that were 12+ cells long. The small whitish things zooming around are barnacle nauplii. Obviously barnacles are having lots of sex right now.
Pseudo-nitzschia is a pennate diatom, which simply means that the cells are pen- or boat-shaped. Some of the pennate diatoms have a raphe, or slit-like opening on the frustule through which a tiny bit of protoplasm can be extruded. These diatoms, of which Pseudo-nitzschia is one, don’t swim but can actually scoot around on surfaces. Don’t believe me? Then watch this long chain of Pseudos move back and forth like a train on tracks.
See how the individual cells remain connected to each other by their overlapping tips? Each of the cells is about 75 µm long and contains two roughly rectangular chloroplasts that are golden brown in color.
Pseudo-nitzschia wasn’t the only diatom in the sample, either. I saw surprising numbers of Coscinodiscus, a genus of centric diatoms, ranging in size from 160-250 µm in diameter. Coscinodiscus frustules are beautifully sculptured, making the cells look like fancy buttons.
That little bleb at about 10:00 on the larger diatom is a dinoflagellate, Peridinium or Protoperidinium, that came along for the ride. There is also a chain of Pseudos making a cameo appearance in the bottom of the photo.
The other unusual diatom in the sample was Chaetoceros. This diatom has a name that hints at the morphology of the cells: “chaet-” is Greek for “spine” or “bristle”. Indeed, the cells of Chaetoceros are box-shaped and have four long spines that link adjacent cells together to form chains.
The intriguing question that came to my mind was “Why now?” Around here I’ve grown accustomed to a typical succession of phytoplankton in Monterey Bay, with diatoms (especially Chaetoceros) blooming in the spring and early summer, corresponding to our usual upwelling season, then giving way to dinoflagellates in the late summer and fall when upwelling abates. And yes, we did have a major Pseudo-nitzschia bloom back in April and May. Diatoms bloom in response to high levels of nutrients, especially nitrate, that occur when upwelling returns nutrients to surface waters. We did have a few weeks of decent upwelling in the spring. Then El Niño started to build and we went through several weeks of warm, clear water when diatoms were pretty much absent and we saw phytoplankters such as silicoflagellates and coccolithophores, which can thrive in waters that are too nutrient-depleted for diatoms.
And now the diatoms are back. Chlorophyll levels in nearshore waters are high right now all along the central California coast. These data are from CeNCOOS, an ocean observing system:
Assuming that the chlorophyll being measured is in the cells of Pseudo-nitzschia and other diatoms, it appears that we’re having a return to springtime conditions. Bait fish are back in the Bay, and following them are dolphins and birds. I would dearly love to do some whale watching this fall; we may have another spectacular season for humpback whales. Whatever the cause for this apparent late-season rebirth, this autumn is shaping up to be interesting.
Next week classes for the Fall semester begin, and this will be my fourth term teaching a marine invertebrate zoology class at this particular institution. I have built this class on a foundation of comparative anatomy and functional morphology; lab activities include dissections (to observe how bodies are put together) and diversity labs (to examine the morphological diversity within major taxa). This year I wanted to include a lab with a broader ecological context. So back in April I hung a box of glass slides from one of the boat slips at the harbor. The idea is that the students in the invert zoo class will examine the slides after they’d been marinating in the ocean for several months and have to figure out what’s growing on them.
The organisms that have and will continue to colonize the slides are members of what is rather disparagingly referred to as a “fouling community.” To be fair, they can be nuisances, fouling docks and pilings, boat hulls, water intake and outflow pipes, and pretty much anything that is left in the water for any significant amount of time. In fact, my friend Adam has a job scraping fouling organisms off the bottoms of boats at the harbor; boat owners either pay to have this done or do it themselves every so often. But to me, these animals and algae form a fascinating ecological community that illustrates many of the principles I teach to my students.
Harbors are some of the places where exotic (i.e., non-native) species are first detected. It is not uncommon for many of the species in a fouling community to have evolved elsewhere and been transported (usually, but not always, unintentionally) to a new location, where they grow swiftly and often out-compete the native species. Obviously, not all species introductions “take” and it’s anybody’s guess how many species were dumped in a new site and failed to stick around. The ones that do take, though, tend to become very prominent.
So, back to my slide box. It was still there, hanging from a string about 2.5 meters below the bottom of the dock. As I pulled it up, I was relieved to see different colors and textures:
Even without knowing what all the differently colored blotches are, you can tell that there’s a lot of stuff growing. I’m not going to dismantle the box until we use it in lab in early November, but I thought it might be worth a closer look. It just so happened that I had both a clean bucket in my car and the foresight to bring it with me onto the dock. This photo shows that the slides themselves are covered with growth:
The red encrusting sheet is the bryozoan Watersipora, probable species subtorquata, an invasive species that is found in harbors all along the California coast. The pale orange blobs are colonies of sea squirts; it is difficult to identify them to species without examination under a microscope. There is also quite a bit of a brown upright branching bryozoan that I think belongs to the genus Bugula.
As an unabashed aficionado of all things hydroid, I’m always very pleased to see certain species of ‘droids at the harbor. They are simply so beautiful that I love looking at them. This is the hydroid Ectopleura crocea. It is common but sporadic and patchy at the harbor, and usually isn’t one of the first species to colonize an area. Its congener, E. marina, occurs in the intertidal; I can find it fairly reliably in a particular pool at Davenport Landing and have occasionally seen it elsewhere.
Having reassured myself that my slide box was doing well I took some time to check out other bits of real estate in that area of the dock. I played around with the super-macro setting on my camera, with mixed results. I do now know, though, that it works underwater:
I found a cooperative barnacle and took some video footage of feeding behavior. Barnacles are strange crustaceans that lie on their backs and kick their modified thoracic appendages through the water to capture small particles. What a weird way to make a living. But the animal is always right, and barnacles can be quite efficient at clearing water.
And, finally, does anybody know the source for the title of this post? Answer in the comments section, please!
In defiance of post-nasal drip and an ominous tickle at the back of my throat, I got up early again this morning and went out on the low tide. I skipped yesterday’s low tide in favor of getting a little more sleep, thinking that it would help me fight off this incipient summer cold, but I didn’t want to miss two of the three intertidal trips I had planned for this weekend. So I made the quick drive up to Davenport Landing, where low tide was at 06:4o.
The first thing I noticed when I got down to the beach was that the algae have started piling up. There were drifts that I sank into almost knee-deep. Fortunately they hadn’t really started decomposing yet, so the smell wasn’t too bad. That will change if it stays warm and the high tides don’t wash any of the algal detritus back out to sea.
It’s treacherous stuff, that algal duff. It covers up deep holes and slippery rocks, so each footstep becomes an adventure. Because it has been so warm I had considered going out in shorts and surf booties, but more than once this morning I was glad to be wearing my hip boots.
It was a busy day for nemertean worms. Nemerteans are unsegmented, slimy, predatory worms that feed by shooting out a proboscis and wrapping it around prey. In some nemerteans the proboscis is armed with a stylet that injects toxins to help immobilize prey, which are often small polychaete (segmented) worms. Nemerteans are not uncommon, but are often inconspicuous and easily overlooked. None of the ones that I saw today were actively hunting.
As you can see, the body of this worm is not segmented. However, it has the same body wall musculature that you’d find in the polychaetes, which are the segmented marine worms. It uses the muscles to alternately contract and elongate the body and move forward. In most nemerteans neither the head nor the tail end is particularly distinguishable, but in worms you can usually tell the anterior (head) end by the direction of locomotion. Here’s a video:
Continuing to play with the ‘microscope’ setting on my camera, I took this picture of a chiton (Mopalia muscosa):
I’m still learning how to make that compromise between super-macro and depth of field on this setting. The chiton in the above photo is about 4 cm long so I wasn’t zoomed in terribly far, and I like how it is in focus but some of the other critters are as well.
On the reef to the north of Davenport Landing beach there’s a large pool that gets to a bit more than knee deep on me, and is cut off from the ocean during low tide. This pool has proven to be a great place to practice my underwater picture taking. The past couple of times I’ve come out here I’ve seen schools of surfperches swimming in this pool. The school contains large individuals (about as long as my hand) and smaller ones that I think are the babies of the big ones. I haven’t been able to catch one–for some reason I’ve never included a dipnet in my collecting gear, preferring to catch sculpins with my hands–but I think they are shiner surfperches (Cymatogaster aggregata).
Before trying to photograph the fishes underwater, I shot some video from above:
It turns out that photographing fish underwater isn’t as easy as I thought it might be. Surfperches are pretty skittish and I couldn’t get as close to them as I wanted. However if I stood still for a minute or so they forgot about me and would resume their normal behavior. In the meantime I did sort-of-accidentally take some cool pictures of the pool from below the surface.
Last, but certainly not least, in this same large pool I found several anemones. The most brightly colored are the Anthopleura artemisia. I love how their tentacles can be such a vibrant translucent orange or purple, or the oral disc can have that deep saturated red color.
Hard to believe that these animals are the same species, isn’t it? Then again, to an alien scientist studying humans it might be hard to believe that a Viking, an Australian aboriginal and I (an Asian-American) are the same species. It’s all simply a matter of perspective.
This morning I collected another plankton sample from the end of the Santa Cruz Municipal Wharf, equipped this time with a 53-µm net used to collect phytoplankton. Phytos, as we refer to them, are the (mostly) unicellular photosynthetic organisms that make up the bottom of the pelagic trophic web. In a nutshell, they are the food that sustains all other organisms in the pelagic realm; i.e., every creature that lives away from the sea floor. Without phytoplankton, we would essentially have zero life in the sea. Think about that the next time you see a “Save the Whales” sign: To save the whales, maybe we should work harder at saving the phytoplankton.
The water is still that pretty shade of aquamarine, but to the naked eye it seemed a little less opaque than it was a week ago. One thing I did see immediately was a huge school of bait fish, and a gaggle of teenage boys trying to catch them with their fishing poles. The school was pretty impressive; the teenage boys, not so much. But they get props for trying.
I find schooling behavior fascinating. I love how the amorphous blob moves through the water, avoiding predators and obstacles (including my plankton net) alike with apparently little effort. Even the sea lions swimming around the pilings didn’t generate much of a response from the fish except a lazy move out of the way.
The arrival of bait fish makes me wonder if whales will follow.
Back in the lab I looked at what I had caught. As expected there were very few large animals, but quite a lot of interesting phytoplankters and small zooplankters. Here’s a sort of representative sample:
The coolest thing I found in today’s sample was a silicoflagellate. I think in all my years of observing local marine plankton I’ve seen silicoflagellates only once before today, when I was in graduate school. Not much is known about their biology, but their siliceous fossils have been pretty well studied.
Silicoflagellates are flat unicellular phytoplankters with two flagella that they use to swim. You can sort of see one flagellum sticking out at about 10:30 on the cell perimeter. You can see it better in this video clip (apologies for the background music). Watch as the flagellum wiggles and pushes the cell around.
Did you see the flagellum? How cool is that? Pretty fancy for a simple unicell, isn’t it?
I’m sorry. I had to go there. You didn’t really expect me not to, did you?
The reason, of course, is that today we got our first settled and metamorphosed Pisaster stars! We were doing our normal Monday water change when I noticed a teensy orange speck on the bottom of one of the jars. I used my beat-up old paintbrush to remove the tiny dot to a dish, put it under the dissecting scope, and saw this:
From this picture it’s a little hard to see what’s going on. The entire body has contracted a lot, from a 2.5-mm larva to about 1/4 of the original size as a 600-µm juvenile, and become much more opaque. There are tube feet and spines as well as some remnants of larval body (the soft bits at the bottom of the animal) at this in-between larvenile stage.
Here’s a picture of a fully metamorphosed little star:
I expect we’ll be seeing more tiny orange dots on the bottoms and sides of the jars in the next several weeks. At some point we will have to figure out what they eat and provide it for them. But at least we know we’re able to get them through the larval phase.
Just for kicks, here are some pictures of where we grow the larvae and how we do the twice-weekly water changes.
Today is the six-month birthday of my baby urchins! Six months ago to the day these little guys were zygotes, and six-months-plus-one-day ago their parents were roaming the intertidal. They grow up so fast!
And lastly, that little shmoo-type thing that I found in the plankton yesterday has revealed itself to be. . . an anemone!
One of the things I like best about cnidarians is the beautiful transparency of their bodies. I love how you can see fluid circulating through the tentacles. Gorgeous, isn’t it?
California is being slammed by a very intense El Niño event, and the effects are being felt up and down the coast. Seawater temperatures here in Santa Cruz have been in the 15-16°C since late May, and in the past week have shot up to 18.5°C. While Californians have their fingers crossed that El Niño will bring drought-relieving rain this winter, I’m also concerned about how it is affecting marine life.
On a whim, I decided this morning to take a look at what’s going on in the local marine plankton. I grabbed a plankton net with a mesh size of 165 µm (we call a net with this mesh size a “zooplankton net”) and headed out to the end of the wharf. The water is a milky greenish aqua color, which the Monterey Bay Aquarium says is due to a bloom of a type of phytoplankton called coccolithophores. I’ve never seen living coccolithophores before, as they are usually not common in Monterey Bay. Besides, they are really small and don’t often get caught in the type of plankton net that I deploy. So while I didn’t really think I’d catch any coccolithophores, it is always fun looking at plankton. Given the warm water and lack of productive upwelling this season, I didn’t know what to expect.
When the water around here is this color, it usually means that phytoplankton are not very abundant. And sure enough, when I pulled up the net it wasn’t very brown and didn’t have that certain smell of diatoms, which were extremely thick earlier in the season. In fact, earlier this month the Central and Northern California Ocean Observing System (CeNCOOS) detected high levels of both the toxin domoic acid and the diatom, Pseudo-nitzschia, that produces it. But in today’s sample I didn’t see a single diatom and only a few dinoflagellates. It’s conditions like this–warm, nutrient-depleted water–that the coccolithophores like.
One of the best things about examining a plankton sample is that you never know what you’ll find. Despite the lack of phytoplankton in the water, my sample was chock full of interesting zooplankters. In addition to the usual copepods (probably the most abundant animals in the world) and their larvae, there were larval polychaete worms and molluscs, medusae of multiple species, and assorted other goodies.
In the video clip below you can see the familiar baby-urchin-learning-how-to-walk, as well as a better view of the polychaete. Note the conspicuous segmentation and chaetae (bristles) that the animal splays out when disturbed or, in this case, gently squashed under a cover slip.
The little worm looks like it’s dancing! Sometimes you can see its four eyes.
This creature is called a cyphonautes larva. It is the sexually produced pelagic propagule of a benthic bryozoan colony, most likely Membranipora membranacea. If it looks like a swimming triangle, well, that’s exactly what it is.
Goodie #4:
This living lava lamp is very enigmatic. I called it a shmoo-type thing and was so intrigued that I isolated it into a separate dish for further observation. I was delighted to see that, a few minutes later, it had settled and metamorphosed into this:
It has eight stubby little tentacles and an obvious cnidarian appearance. I think it is a little anemone, but only time will tell.
This beautiful object is a radiolarian, a type of marine amoeba. The main part of the cell is concentrated towards the center and pseudopodia are extended along the skeletal spines, which, in addition to making the cell an unpleasant mouthful, also aid in buoyancy. This one was rather large, measuring about 2 mm across. I saw many of these in today’s sample.
All in all I spent a very enjoyable morning collecting and looking at plankton. I didn’t see any coccolithophores, but I’m thinking that I probably should go out again with a finer-meshed net to see if I can catch them. And to see what will happen with the zooplankton if the phytoplankton remain scarce for the rest of the season.
Huzzah again for natural history! I love it when natural history provides the answer to a taxonomic or identification question. Sometimes you need to see the organism where it lives in order to understand what it’s all about. Quite a lot of modern biology has to do with grinding up organisms and examining their DNA; while I do appreciate the evolutionary and ecological insights these data provide, it’s really not my cup of tea. I’d rather spend my time looking at intact organisms than their molecules, and getting outdoors to see them in nature instead of running gels and staring at computer algorithms. As in most other walks of life, it takes many kinds of work to get at the whole picture in ecology, and I am grateful to be able to contribute a little piece to the puzzle.
If you visit the California rocky intertidal in the spring or summer, one of the first things you notice will be the macroalgae, or seaweeds. They are incredibly abundant and diverse this time of year, covering just about every bit of rock. In fact, in a landscape sense the only visible organisms are macroalgae and surfgrass:
Of the three major divisions of algae (the greens, browns, and reds), the red algae are the most diverse. We have several hundred species along the California coast, and while they don’t get as big as the kelps (which are brown algae) they display an astonishing assortment of morphologies, colors, and life history complexities. Almost all of the algae in the photo above are reds. The olive-greenish stuff? Yep, those are reds; multiple genera of reds, in fact. The dark brown things? Those are also reds, again representing more than one genus.
Within the incredible diversity of red algae, today I want to focus on two species: Microcladia coulteri and Plocamium pacificum. Both of these algae have delicate branching forms that make beautiful pressings. But despite their apparently similar morphologies, they represent different taxonomic orders and have completely different lifestyles. Let’s take a look at how similar they actually are:
Pretty tough to distinguish, aren’t they? The specimen on the left is a bit more robust in comparison, but if you had only one of these in front of you and nothing to compare it to you’d probably be hard-pressed to determine which species it is.
This is where an understanding of natural history becomes invaluable. Since these species are morphologically so similar to each other, an extremely helpful piece of information is where (and how) each one lives. In terms of habitat, these species can be found pretty much right next to each other, so that doesn’t help much. However, the surface on which each species grows tells you exactly what you need to know.
The specimen on the left in the photo above is Plocamium pacificum, a member of the taxonomic order Plocamiales. It lives from the mid-low intertidal to the shallow subtidal and is always attached to rocks, as you can see below:
The specimen on the left was taken from a thallus that was growing on a rock. This means that it is Plocamium pacificum. Now we can label our photograph with one name.
The specimen on the right was growing as an epiphyte (“on plant”) on a large blade of another red alga. This epiphytic lifestyle tells me that it is not Plocamium, but a species in the genus Microcladia in the taxonomic order Ceramiales. When I brought it into the lab to key it out I was able to identify it as Microcladia coulteri. Three cheers for natural history!
Here’s a picture of M. coulteri growing on blades of another red alga, Mazzaella sp. See how green the Mazzaella looks? Color isn’t the only factor that determines which major group an alga belongs to, and can in fact be quite deceiving!
Which is all well and good when you have two specimens in hand that you can compare directly to each other. But what if all you have is this little bit?
