Starter cities in pink and cream

On a blade of old eelgrass, the hermits and snails and the sea urchin were busy. Watching them, I noticed specks on the eelgrass, pink and cream.

Two bryozoan colonies, and social tunicate starter homes.

The bryozoans were mostly eaten by the time I found them. Now, a couple of days later, there's not a trace of them. The hermits tear down their walls and eat the animals inside.

They won't eat the social ascidians, but the sea urchin will, so today most of the pink spots were gone.

10 years ago (how time flies!) I wrote about the social tunicates in my tank, probably the same species as this crop. They are a colonial animal; one settles in and buds off new individuals (zooids), arranged in a double row around an open centre, with a circle of blood vessels around the outside of the colony.

Zooming in on the lower group. Just a baby colony.

I looked at a few of these under my microscope.

Here you can see the central siphons of some of the zooids.

10 years ago, there was no sea urchin in my tank. The hermits left the tunicates, on sea lettuce, strictly alone, and the colonies grew. And grew.

Photo from 2010; two colonies, yellow and pink.

There's more information about the structure and lifestyle of these animals in that post. And if these survive the onslaught of a hungry, growing urchin, I'll try to get clearer photos.

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En una hoja de hierba Zostera en mi acuario, mientras observaba a los ermitaños y caracoles y el erizo de mar que allí buscaban su cena, vi unas manchas de color crema, y otras color de rosa. Las de color crema eran briozoos, ya casi todos muertos. Los ermitaños les rompen las paredes y comen los zooides que viven adentro. Ahora, unos dias más tarde, no queda ni un vestigio de las colonias.

Las manchitas de color de rosa son ascidios coloniales. Estos, se los come el erizo de mar, así que ahora solo hay unos puntitos de colonias nuevas.

 Hace diez años, crecieron unas colonias de urocordados, en mi tanque. No había quien las comiera, y llegaron a cubrir una gran cantidad de lechuga de mar. Escribí sobre ellos, describiendo su estructura y manera de vida, en aquel entonces. Aquí está el post.

Son animalitos que viven en colonia, aunque pueden sobrevivir y empezar nuevas colonias si quedan aislados. Uno se fija en su sitio, y empieza a brotar clones, arreglados en una fila doble con un espacio en el centro, y un círculo de venitas alrededor. En la foto que saqué con el microscopio se pueden ver, apenas, las bocas centrales de cada zooide.

La última foto es una que saqué de las colonias grandes hace diez años. Aquí se ven claramente los sifones de cada animal.

Si es que el erizo no se las come todas, trataré de sacar fotos más claras.

So small

I found a few more tinies among my forgotten photos.

A jellyfish and bubbles in fine, hair-like sea lettuce. In my tank.

On a blade of kelp, a white dot turns out to be a small colony.

Zooming in. It looks like a patch of bryozoans.

A baby grainy hand hermit, in my hand. Going by the lines on my palm, he's about 7 mm. long.

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Entre las fotos olvidadas, encontré estas criaturas miniaturas. Primero, una medusa entre algas marinas "Ulva', en hilos finos. Luego, en una hoja de kelp, vi un botoncito blanco, que visto de cerca resultó ser un grupo de briozoos, animales que se hacen una cajita donde viven y de donde extienden sus tentáculos para capturar su comida del agua. La última foto es un ermitaño "de mano granosa", en la palma de mi mano. Mide aproximadamente 7 mm. de largo.

Blobby bryozoans

Early winter storms tear and uproot the summer's crop of seaweeds. The mound along the high tide line, that in summer is mainly eelgrass with a sprinkling of sea lettuce and rockweed, in November becomes a full salad bar, multi-coloured, multi-textured.

In a short walk, I collected a bag of treats for my hermit crabs, with only one sample of each species, I ended up with a full grocery bag. Sea lettuce, of course. Two kinds of rockweed. Turkish washcloth, and a black, leathery, pimpled towel seaweed, four or five kinds of kelp, the invasive sargassum, several tiny blackish curly weeds, Pacific rose algae, red blades, rubbery threads, ... I didn't bother with eelgrass; the aquarium is planted with a fair crop from my last collecting trip.

I collected three pieces of a red algae that was coated with bryozoans. None of the algae were entire; they were stalked, and opened out into red blades, badly torn, rotting along the edges; I couldn't determine their shape or full size. But the bryozoans intrigued me.

At home, in a bowl. The stalks are encrusted with these hard blobs. The pink stub at the right seems to be a growing tip of the algae; there were several of these.

One of the blobs. Each little hole was the home of one zooid. If you look really closely (click for full size) you can see tiny pink pores on the body of each case.

Where the stalks met the blades, the structure changed; here they lie flat, one critter deep. Membranipora sp., maybe?

I don't think any were alive; they'd been lying out on the shore for a while. I looked while they were underwater, but saw no hint of movement.

I've been searching for an ID in my books and on the web, but can't find any that take these two forms on red algae. Blobs on rocks, yes. Single layers encrusting kelp, yes. Both together, no.

Membranipora membranacea is common on bull kelp on our shores; it makes circular, flat colonies on the blades. I could find no photos or record of it making these blobs.

And the crabs, hermit and "true" are happy, busy climbing and feasting.

Where the living is green

In the intertidal zone, worms and snails live happily in sand. Crabs and fish live under rocks; limpets live on top. Crabs and  isopods like a seaweed blanket. But under a layer cake of sand, rocks, weed, it's party time; everybody mingles.

Lower intertidal zone, Simms Creek area. 

Calcareous tubeworms, spiral tubeworms, orange-legged hermit, bryozoans, limpet, assorted seaweeds, two pecies of snails, encrusting sponge.

More bryozoans, snail, hermit.

Encrusting sponge, with snails.

Grainy-hand hermit, Pagurus granosimanus.

Green mottled star, spiral tubeworms, bryozoans and sea urchin

Leather star and bryozoan. With hermit, snails, tubeworms.

Hermit (hiding), limpet, sea urchin, two kinds of snails.

Clingfish.

Little boxes all the same

In the lower intertidal zone, there's a new treasure to be found under every rock. This one holds a community of bryozoans, sponges, and pink spiral tubeworms.

Orange encrusting bryozoan, Schizoporella unicornis

These bryozoan colonies grow outward from the center. The inner ones die off, leaving the calcified framework behind, hexagonal boxes towards the center, switching to rectangles farther out. Along the edges, live zooids are orange; the boxy structure is less obvious, but looking closely, tiny dots show where the feeding lophophores emerge.

The orange encrusting bryozoan is an invader from Japan, and has found our waters much to its liking. My encyclopedia says it is,

"now the dominant encrusting bryozoan in much of the Pacific Northwest. ... Long term effects? An unfolding mystery."

An example of bryozoan "boxes". This one was from a bryozoan I found on kelp, examined under a microscope I had in 2012.

View of S. unicornis remains, showing the openings for the lophophores. Photo: Yale Peabody Museum. YPM IZ 049667 

Zooming in on the rock face, I found what looks like a new colony, circular and dotted with feeding zooids.

The blobs on the lower centre left show the same basic structure, but they're piled on top of each other. The little grey doughnut is the egg ring of an unknown snail.

And on to the next rock ...

(Title taken from a line of the song, "Little Boxes". The photo on Wikipedia is reminiscent of bryozoan crusts.)

On staples and little boxes

Sea lettuce. Barnacles. And eelgrass. The staple foods for my aquarium critters. Barnacles for the leafy hornmouth snail, sea lettuce for the hermits, the crabs, and the bubble shells. And eelgrass, preferably decorated with hydroids, for the hermits and snails. Anything else is a special treat, but these three are essentials.

This week, the high tide brought in a truckload of fresh, bright green sea lettuce, which pleased the bubble shells; one ate so much of it that I could see the green in his stomach right through the shell and flesh.

But though I walked a long way, just at the edge of the incoming waves, I only found one small eelgrass plant. And it was a meagre, frayed one, mostly straggly stem and browning leaves. I would have left it there, except that it was the only one available. I and the hermits would have missed a treat.

Settling it into the tank, I noticed a small patch of bryozoans on one thin blade of grass, just below the water surface. A live patch, too; I could even see, with a lens, movement on its surface.

I rarely get to see these; out of the water, they shut down instantly. Underwater, the turbidity and the depth make them into a faint blur. Too much light, and they're asleep. And the individual animals are so very tiny; millimetre-high, transparent funnels.

Encrusting bryozoan colony, Membranipora membranacea, awake and feeding.

This is a small colony, about 8 to 10 animals from edge to edge. Each individual zooid lives inside a little box; seen from above, they look like walls, but there is a top, as well. The animal lies horizontally inside, and when the situation looks right, extends its feeding funnel up into the water. At the slightest disturbance, the funnels disappear and all that can be seen are the walls.

Hydroids and anemones have stinging tentacles, to subdue their prey; these bryozoans do not, but are filter feeders like the barnacles, relying on water currents to deliver their groceries. They will eat diatoms and bacteria, as well as other planktonic swimmers, like my newly-hatched crab zoea.

The little spines at the corners of their boxes (difficult to see here, but we really need a microscope for a better view, like this one) help to make the colony an uncomfortable base for a hungry Doridella nudibranch. I found several of these a few years back, on kelp, eating bryozoans, spines or no spines. There were none on this little eelgrass; not enough prey to keep them here.

...

That was the beginning. I kept finding more and more interesting things on that eelgrass. Unidentified "thingies", tomorrow. And a thingie mimic.

In the latest style

Eelgrass isopods are shy creatures, usually hidden in the shadows, sometimes so firmly attached to the underside of an eelgrass blade as it waves in the current, that they become effectively invisible. This one broke precedent and climbed to the surface to say, "Hello!"

"And look at my cute cap!"

As far as I can tell, he's wearing a patch of bryozoans, rakishly tilted over one eye. Cool, eh?

Birthday candle bryozoan

In my last load of seaweed from Boundary Bay, I brought home a rotting piece of green stuff, about 4 inches long. Just "stuff", because it was so well rotted that I couldn't identify it. It was a once-sturdy blade, of the texture of bull kelp, but a bright green, whereas bull kelp rots to a sickly yellow-brown colour.

And it was covered, both sides, edge to edge, with an encrusting bryozoan.

I put it in the aquarium while I was busy with other things, and the hermits picked at it, emptying out the bryozoan cases. The next day, I collected it, and examined it with a microscope. All that was left were the white walls of each animal.

All lined up in alternating rows, like a brick wall.

Zooming in.

The individual cases are not quite rectangular; they're often more the shape of a first birthday candle, with the fat base and the overhang at the top. (On the candle; I don't know which end is the lophophore or mouth end of the bryozoans.)

Compare them to the kelp bryozoans we usually find.

Kelp bryozoan colony, 2009. They form circles on the kelp, radiating out from a central point.

Zooming in. The cases are less regular, slightly rounded. The walls are thinner.

I looked at hundreds of photos of encrusting bryozoans.  Some of the Membranipora membranacea, the kelp-encrusting bryozoans, stretch out on giant kelp, not limited to the narrower blade of bull kelp. The outer edges of these colonies become more rectangular and orderly, much more similar to the "birthday candle bryozoan" (my name).

In the Wikipedia article on M. membranacea, I found this:

Zooids within a colony can communicate via pores in their interconnecting walls, through which coelomic fluid can be exchanged.

It may be that the discontinuities in the walls are the pores. Hard to tell. I really wish I had examined them before the hermits finished them off. I just might have found some still alive.

Living encrusting bryozoans. Feeding zooids in their individual boxes. Image from U of Washington. 

Basic description of bryozoan anatomy and "weird stuff".

Green, fading to black

One of the pleasures of summer along our shores is to wade at the low, low tides, knee-deep in the eelgrass beds, watching the swirl of the deep green blades reaching up to the surface and floating there. We watch our step carefully; among the stalks, good-sized, maybe toe-pinching crabs scuttle. On the long leaves, if we look closely, we can see large green isopods and small snails. Sculpins and other small fish dart away at our approach, no matter how stealthily we tiptoe.

Most of what lives in these green forests, though, we don't see. Kozloff, in his chapter on sandy beaches, lists, among the inhabitants:

• On the leaves: the tinies; diatoms and other microscopic plants, invisible alone, but in mass, forming a brownish "fur" or long threads; bacteria, protozoa, algae, microscopic worms, crustaceans, copepods.
• The small critters: amphipods, including skeleton shrimp, hydroids, flatworms, ribbon worms, jellyfish, anemones, chink snails, sea slugs, including Melibe leonina, two species of isopods.
• On the mud, sand, roots: bubble shell snail, clams, sea stars, sea cucumbers, five crabs; Dungeness, red, two spider crabs, and helmet crabs.

Another list adds sponges, bryozoans, spiral tube worms. I would add the limpets and their cargo. There are many more, and we must not forget the fish.

So important is Zostera's role in this food cycle that estimates reveal that more than 20 species of commercially valuable fish species feed in these eelgrass meadows at some point in their lives. (R.I. Sea Grant Fact Sheet)

 That's the summer.

Summer eelgrass, waiting for the return of the tide.

In the fall, the eelgrass begins to die back. Stormy seas rip up the plants by their roots, and propel them toward the shore. The waves, coming and going, roll them up in dense masses, metre-long tough leaves wound and knotted around each other, and push them onto the beaches. There, they gradually die and blacken, always pushed further up the beach by the next tide's eelgrass roll-up, until they form great mounds of black, sharp-smelling gunk.

Drying eelgrass, caught on driftwood log. Boundary Bay.

But their useful life isn't over yet! First, while they are drifting ashore, Canada geese congregate to eat the green stems that they usually can't reach.

Geese and gulls, watching the eelgrass come in. White Rock.

I collect handfuls for my aquarium critters from the fresh rolls, disentangling the greenest, the ones with bits of root still attached. In the winter, the low tides usually fall well after dark; I can't wade out to what's left of the eel-grass beds. I'm glad it comes to me, instead.

In summer, any eelgrass I harvest is well checked over for other life. I always find limpets, usually quite a few snails, occasionally an eel-grass isopod or two. There may be amphipods along the leaves, often polychaete worms in the roots, and always the fuzzy diatom communities.

In the fall and winter, the eelgrass looks bare until I run a finger down a leaf; then I notice the hard, raspy bryozoan communities, the thickening where a cryptic limpet is attached, and maybe an isopod will transfer his clingy feet to my finger. All of these go into the aquarium where I plant the eelgrass.

I don't bring home the black stuff. Some people do; I have seen gardeners with wheelbarrows and big barrels on the shores of Crescent Beach and Boundary Bay, filling their containers (once a pickup truck bed!) with nutritious mulch for the winter garden.

But I do roll it over, to watch hundreds of beach-hoppers leap every which way. (I remember, back when Laurie didn't know me quite so well, I called him over to see. "Look!" I said, and turned over a heap of dead eelgrass. He wasn't prepared; the hoppers ended up on his legs, and he jumped back, annoyed. He got over it, and now is as enthusiastic as I am. Sometimes more.)

Inside that rotting mass, worms, fungi and bacteria work at reducing it to fine dust, which will sift slowly out to sea, returning the nutrients to their source for another round. In the meantime, tiny black flies swarm over the surface, feeding and breeding in the relative warmth from the decomposing grass. Nothing ever gets wasted.

Bryozoan colony on dying eelgrass.

In my aquarium, fall eelgrass only lasts a couple of weeks before it dies and turns black. I doesn't look good, and eventually will disintegrate and clog the filters, so I remove it. But first, I make sure I'm not removing live animals. Most of the limpets have moved on to greener pastures; so have the isopods and amphipods. But there are still patches of bryozoans and hydroids.

I wondered, the other day, whether the bryozoan colonies were still alive, so I brought them out to a tray of shallow water and examined them under a microscope. All the tiny, glassy barrel shells were empty; the makers were gone.

Each little tube was the home of one zooid.

If you were seeing these photos live, you would also see tiny specks of light moving between the shells, barely visible transparent threads weaving back and forth, white dots that seem to have legs scuttling across the green spaces. The bryozoans have died, but the colony is still very much alive. And the spiral tube worms are still busy catching the specks and threads for supper.

Bryozoan colony with feeding tubeworm.

I replaced the eelgrass in the aquarium. These industrious hunters and gatherers deserve their full life span.

One rock makes an entire habitat

I came home to a long note on my kitchen table, and my trusty encyclopedia full of purple sticky notes. My granddaughter had come over to water the plants, and had taken the time to mark all (or most, she says) of the "neat stuff" she saw scuba diving off Whytecliff (Horseshoe Bay) on the weekend.

"There are probably hundreds more, but ... lots of stuff is so small I probably didn't even know I was looking at it."

She's right, except that there are probably thousands more. Here's one rock I found on the beach near Stories Creek on Vancouver Island, for proof:

Looks like a painter's drop cloth.

That's too much to see, in one photo. I'll break it down a bit:

Green. red. white, orange ...

The red patches are some sort of encrusting sponge*. The green is a bryozoan. The white circles are possibly the same bryozoan, except that the green one is tinted with algae. On the right, the orange and cream stuff is a scramble of bryozoans. The curly red ribbon is the tube of a calcareous tubeworm, probably red trumpet, Serpula columbiana. The rock is sprinkled with tiny barnacles, and smeared underneath all with a deep wine-coloured encrustation, possibly encrusting coral.

Another section of the rock:

A scrambled mess.

Lots of stuff, but hard to see. The central yellowish stuff is a sponge; the large holes are exit holes (osculae) for the water it filters. The tiny pores are intake holes.

For the rest, let's break the photo up a bit:

A fan or leaf-shaped bryozoan, in bright orange.  Compare the regular pattern of holes (lophopores) to the randomized arrangement of the sponge next door.

A "feather duster" organism. I don't know what it is, yet.

And further along the rock:

Red/pink/green bryozoan, encrusting the rock, itself, and barnacles. The limpet has escaped. For now. The bright green stuff is sea lettuce, masked by red algae fronds.

This one's difficult.

Examining this photo carefully, I find a variety of bryozoan colonies, a few barnacles, a limpet with red encrustations on the shell, a couple of calcareous worms, at least half a dozen tiny coiled tubeworms, and a smear of yellow sponge. And I think that white thing towards the left bottom looks suspiciously like a white nudibranch. I wish I'd noticed it at the time I took the photo.

(I loaded these photos in the usual format, 1024 x 768), but you may want to check the full size ones over on Flickr.)

One more:

A few nice, neat bryozoan colonies, in a warm brown, on a substrate of assorted purple and bluish encrustations. With barnacles and pink "somethings".

And I wonder what I've missed here. I could have spent an entire afternoon on the beach with this rock and a portable microscope. (Which I forgot to pack; I won't next year. I promise.)

*The encyclopedia observes,

"Sponge classification and recognition is a most problematic and frustrating subject for a naturalist. Indeed, academic professionals who spend their careers studying the group are likewise challenged -- a fact that leads to much uncertainty in scientifically oriented sponge publications."

I'll just stick to "yellow sponge, red sponge, etc."

High tide sampler

I've been working late tonight, and I'm so sleepy I can't type straight. But before I head off to bed, I can maybe post a few of the small critters we saw on Crescent Beach the other day:

Periwinkle with a red band

Bryozoan colony on red seaweed

A tiny piece of "coral".

Pacific plate limpet, possibly

Melibe leonina, the hooded nudibranch.

We found four of these tangled in washed-up eelgrass on Boundary Bay Beach. One was dead; the other three died later that night. This one was still moving gently, but had lost several of its cerata.

And now, goodnight!