Tuesday, April 20, 2010

The eelgrass dwellers

The tide was coming in.

(I remember how, when I was growing up on Vancouver Island's west coast, how our stories always began with the tide. It was high tide, it was low tide, the tide was going out ... For weather, we had seasons; rain every day, or fire season. What defined the state of our surroundings at the moment was the eternal tide.)

Last week on Boundary Bay, off Centennial Park, the tide was coming in. It was still far enough out that we could barely see the water beyond a great expanse of empty sand, so we didn't know that. I hurried straight out to the edge, hoping to get to where the seaweeds and crabs start. Too late; knee-deep in the water, I could see ahead where the green showed through the waves. Behind me, I could see that the crab shell I had placed just above the water line as a marker was now floating away. Time to head back.

All that first half-mile of the beach is lugworm and sea snail territory; we don't see much else, beyond an occasional crab molt or shattered clam.

The invasive Batillaria snails, and snail trails.

In the shallow pools near the edge, we noticed some strange brown blobs, floating like furry balloons on six-inch strings.

This one has several blobs. The dark patches are the shadows of the bubbles floating on the surface.

They were soft and mushy to touch, but held together when I pulled at them. They didn't break away from the stem. I dug a few up; they were on a strand of tiny eelgrass, and the roots went deep into the sand. But what were the blobs? Eelgrass is a flowering plant, were they flower heads? I thought they were supposed to be inconspicuous.

Blob, bubbles, and a barely visible eelgrass stem.

I dropped a few into my plastic bag to investigate at home. While I was at it, I collected a tangle of eelgrass roots from the dry sand.

The snails feed around these. There's one of the blobs in this knot, too.

Back home, I looked over my harvest. The blobs, spread out in water, turned out to be made of fine, brown hairs, baby-hair soft.

I had imagined that they would be populated by small critters; amphipods or snails, maybe. But there was nothing but the hair to be seen.

There was nothing like this in the Encyclopedia; I finally found it in Kozloff. The eelgrass is dwarf eelgrass, Zostera japonica, a small, introduced eelgrass, growing to about 8 inches tall; the leaves are half the width of native eelgrass blades. And the blobs ... I'll quote from Kozloff:
In certain places, especially during the summer months, the leaves of eelgrass become colonized by a variety of essentially microscopic plant organisms. Most obvious among these are the diatoms, which, if present in large numbers, constitute a furry, olive brown coating. If some of the diatoms present are of the chain-forming type, a good deal of the coating will seem to consist of fine filaments. Bacteria will also be plentiful, and once the biological ball starts to roll, detritus tends to become incorporated into the film.
The diatoms, bacteria, and detritus, as well as the decaying tissue of eelgrass leaves themselves, feed the mouths of many protozoa, microscopic worms ... and small crustacea.
It is still early in the season; the colonies were still free of detritus. Any other organisms were microscopic.

I turned my attention to the eelgrass roots. This is the larger, native eelgrass; the leaves are long, up to the length of my arm and more. The leaves grow out of a thick, brown rhizome that anchors it in the sand; small roots grow from the rhizome.

This rhizome, at least as it deteriorates, provides hollow tubes where small organisms can hide. Once, while I was nursing a broken flatworm back to health in a little bowl, I provided it with an inch of eelgrass rhizome for shelter. After a few days, it disappeared. I looked for it several times a day for three days, then it crawled out of the rhizome. So I put the eelgrass, roots and all, in water, and watched carefully.

There were amphipods, of course; there are always amphipods. And a couple of tiny snails. And a whole collection of worms:

Polychaete, (pronounced "Polly Keet"), after I'd liberated it into a tub of water and sand.

A ribbon worm. This is the head. It was blood-red under the light.

The ribbon worm entertained us for quite a while; it slid up to the surface along the rim of the bowl and spent the evening going round and round, occasionally lifting its head about an inch above the water line. Round and round and round; it only stopped when I dumped it in the tub outside. It was about 4 inches long, very red, very smooth, and featureless, except for the little triangular head.

Tube worm.

There were a couple of these tubes; this smaller one was about a inch long. I wouldn't have noticed it, except that it twitched occasionally.

The tube is decorated with sand grains cemented on.

The larger worm, about 3 inches long, kept extending its head (or maybe proboscis) and waving it around, in a searching pattern.

I looked it up in the Encyclopedia and on the web, but couldn't identify it.

And there was one more, not exactly worm-like, but I think it's a polychaete, going by the tufted "feet" along the sides:

Tiny worm, under the microscope. About 5 mm. long.

There are four appendages visible on the head end; two pale antenna-like things, and these two with a black spot at the tip, like a snail's eyes. My first photos didn't turn out, and when I went back to try again, I couldn't find it. It's somewhere in the tub; maybe someday I'll find it again, grown up a bit.


  1. How interesting. You always look below the surface to see the world in all of its glory. - Margy

  2. Fascinating. How much I appreciate your posts - the research you do, and the presentations you make. I love how you look beneath the surface to see the real life, the tiny life, below. You inspire me!

  3. Quite fascinating. Most of us never see these little things. ~karen


If your comment is on a post older than a week, it will be held for moderation. Sorry about that, but spammers seem to love old posts!

Also, I have word verification on, because I found out that not only do I get spam without it, but it gets passed on to anyone commenting in that thread. Not cool!