Tag: Pescadero Marsh

Diversity

Because I’m currently taking the California Certified Naturalist class, I’m spending more time than usual looking at and photographing various organisms. I’m astonished at the diversity of organisms that I saw this week within a 45 minute drive of our house. I managed to see organisms from four kingdoms — plants, animals, fungi, and Chromista (which includes brown algae). Going down one taxonomic level, I saw organisms from over a dozen different phyla (for animals) or divisions (for the other three kingdoms).

This represents an astonishing evolutionary diversity: green algae, red algae, vascular plants; sac fungi and allies, mushrooms and allies; brown algae; sea anemones and allies, molluscs, sea stars and allies, arthropods, ringed worms, flatworms, chordates. And I saw eight of these taxonomic groupings within a five minute walk from my desk.

I have a tendency to focus on flowering plants and vertebrates, while ignoring other organisms. Sometimes it’s good to remind myself how much biological diversity is in my own back yard.

Ochre Sea Star (sea stars and allies), Sea Lettuce (green algae), Surf Grass (vascular plant), and unidentified red algae at Pescadero State Beach on Friday — that’s four phyla/divisions in one photograph.

Cnidarians

Carol and I went to Pescadero Natural Preserve today. It was delightfully cool (about 70 degrees) with high fog blocking much of the sun. The tide was quite low when we arrived, so I wandered around looking at the variety of organisms in tide pools: sea anemones, crustaceans, molluscs, seaweeds, etc. Then we decided to walk to the mouth of Pescadero Creek and head up into the marsh.

As we followed the creek upstream under the Highway 1 overpass, Carol noticed that there were dozens of jellyfish washed up along the high tide line, translucent organisms looking a little like plastic bags filled with water. Most of the organisms were damaged; some had obviously been stepped on, some appeared to have broken in pieces, some no longer had a definable shape. I walked closer to the water, and began to find a few organisms that looked less damaged; one in particular, shown in the photograph below, retained a good deal of its structure:

When we got home, I did some online research to find out what kind of Cnidarian this was. I concluded it was a Moon Jellyfish, the common name of Aurelia species; most likely Aurelia labiata, which the authorities I consulted online agreed was the Aurelia species found along the San Mateo County coast. More specifically, what I saw was most likely the central morph of Aurelia labiata, the type specimen of which came from Monterey Bay (M. N. Dawson, Macro-morphological variation among cryptic species of the moon jellyfish, Aurelia [Cnidaria: Scyphozoa], Marine Biology [2003] 143:369-379).

Based on this tentative identification, I made two drawings of some of the structures that might be seen in the photograph. The first is based on Dawson (2003), and shows the organism from the underside; this approximates what you see when the jellyfish is lying flattened out on the sand, as in the photograph. The second drawing, based on a drawing by Richard Fox of Lander Univ., shows the organism as if it were alive and floating in the water.

The gonads are clearly visible in the photograph (note that the gonads and gastric pouch are right next to one another, so the gastric pouches are also visible). The manubrium and stomach in the center show fairly clearly. I did not see any tentacles when I looked at the organism, and none are visible in the photograph; this is not surprising as they would be quite small. Some of the radial canals are visible, enough to give the sense that the organism has radial symmetry. But the organism in the photo appears to have disintegrated somewhat.

The organism I photographed, and most of the Moon Jellyfish I saw stranded along the creek, were clear to translucent. One of them, though, was amber-colored; others had dark red or purple structures. The Encyclopedia of Life Web page on Moon Jellyfish, citing an article by the Monterey Bay Aquarium, states that Aurelia labiata are translucent when young, turning “milky white, sometimes with a pink, purple, peach, or blue tint” at maturity. So most of the individuals I saw were, apparently, young jellyfish.

Carol and I walked around the marsh for a couple of hours, and came back to the creek as the tide was beginning to flood again. I watched the tide pick up some of the stranded jellyfish, hoping to see some signs of life. One or two of the jellyfish floated away, looking intact, with their bells extended; perhaps they survived their exposure. But most of them sank beneath the water, or crumpled up, or seemed to be coming apart; it seems very unlikely these individuals survived.

Drawings revised, July 20.

More info: Article on Aurelia labiata on the Animal Diversity Web provides links to several academic references.

Note on my drawings: In making the drawings, I began with the cited sources, then consulted various online photos identified as Aurelia labiata. I saw significant variation in online photos, especially as regards tentacle length; since my drawings are not made from living specimens, they should be taken as schematic drawings, not accurate representations of live individuals.

Fast food for gulls

I spent the afternoon and early evening hiking around Pescadero Marsh. At the beach near the end of Pescadero Creek, I saw many of the same animals I saw during my last trip here: Harbor Seals (Phoca vitulina): shells of the California Mussel (Mytilus californianus): the remains of Red Crabs (Cancer productus), Pacific Sand Crabs (Emerita analoga), and Eccentric Sand Dollar (Dendraster exentricus); Black Oystercatchers (Haematopus bachmani), etc.

Haematopus bachmani

Above: Black Oystercatchers on the rocks at Pescadero Beach

dead Emerita analoga being eaten by unidentified organisms

Above: The remains of a Pacific Sand Crab being eaten by unidentified smaller organisms

Walking around the marsh, I saw an even greater diversity of animals: warblers hiding in willow thickets, butterflies cruising in amongst the coastal scrub, raptors hunting over the marsh, huge nests made by wood rats. This is an area of ecotones, where several different plant communities meet one another: ocean comes up against beach; sandy beach comes up against coastal scrub; coastal scrub comes up against saltwater marsh; freshwater riparian corridor and marsh flows into saltwater marsh. I’m amazed by how many biomes, and organisms adapted to live specifically in those biomes, can be found within a short walk: I saw Arroyo Willow (Salix hinsiana) growing next to an ephemeral freshwater stream; fifteen minutes of slow walking brought me to Snowy Plovers (Charadrius alexandrius) who live and breed on sandy beaches above the high tide line.

And then there are the organisms who happily move from one biological community to another, exploiting the resources of all of them. Like gulls (Larus spp.) who fly everywhere, and eat everything. Everywhere I went, I saw gulls. As I walked north on the beach, I cam across two Western Gulls (Larus occidentalis), in beautiful fresh plumage, snacking on what remained of a Harbor Seal:

Larus occidentalis eating a dead Phoca vitulina; Larus delawarensis in the distance

I walked up to the dead Harbor Seal to have a look; the gulls, looking grumpy, gave way to my intrusion, watching me from a safe distance. The corpse didn’t stink, but there was no longer a head, and it looked like it had been lying there for a while. I guess gulls will eat just about anything.

Web of relationships

Today I was at Pescadero Marsh to look at live birds, but the dead things proved more interesting. It was just after low tide, and I saw two empty crab shells (prob. Red Crabs, Cancer productus), looking as though they had been eaten by gulls; interesting, but a pretty common sight, and it’s more interesting to actually see a gull eating a crab. Then I found the empty shells of two small crustaceans, organisms I’d never seen before. Here’s one of them:

BlogMar1215a

I have no idea what species this is, though I suspect it’s a fairly common organism.

Later, I walked along the dike near Butano Creek, and came across a dead mole (the notebook next to the mole is marked in inches):

BlogMar1215b

Given the size of those front feet and the short tail, I’d say it was a Broad-footed Mole (Scapanus latimanus). This is the third dead mole I’ve found in six months.

What interests me when i see dead things in the field is trying to figure out how they died, and how they are tied in to the ecosystem. The Red Crabs were easy to figure out — probably eaten by gulls. But why did that little crustacean die? it didn’t look as though another organism had tried to eat it, so was it simply left high and dry at low tide? As for the Broad-footed Mole, there was a definite hole in the other side of the animal, which could have been made by a bird’s bill; I saw Red-tailed Hawks and Northern Harriers hunting in the marsh; perhaps a raptor killed the mole, then got scared away before it could eat.

These are just possible scenarios; I’ll never know what really happened; but what I do know is that somehow these dead creatures reveal something about the web of relationships between organisms.

Pescadero Marsh

Pescadero Marsh

I went for a walk in Pescadero Marsh for the first time today. It’s a pretty remarkable place. It encompasses a variety of habitats, including pickleweed salt marsh, freshwater marsh, riparian corridor, sandy beach, old sand dunes, etc. Birdlife ranged from birds typical of beaches, like Sanderlings and Black Turnstones; to birds typical of freshwater marshes, like Marsh Wrens and Common Yellowthroats.

There were signs of other resident animals as well. Along the edge of Pescadero Creek, you pass by what look like big piles of sticks, but they’re actually houses built by Dusky-footed Wood Rats (Neotoma fuscipes). In the photo below, the tape measure at lower left is extended to 12 inches (300 cm); so this particular wood rat house is about four feet high (1.3 m).

house of Neotoma fuscipes

From a little further down the same trail, you can see a Great Blue Heron rookery. Their nests look like big piles of sticks, piles that may be three or more feet from bottom to top, that somehow got stuck high up in the branches of dead trees. I counted at least eight herons sitting on nests — four foot high birds roosting on three foot high piles of sticks thirty or forty feet above the ground.

immature Phalacrocorax auritus

On a secluded part of the beach on the other side of Highway 1, an immature Double-crested Cormorant (Phalacrocorax auritus) was too stupid, or too dazed, to move away when I walked past it. It stood quite still while I took its photo (above). The other birds and animals I saw were far less trusting than this cormorant: as soon as humans came into view, they flew or scuttled away out of danger. Except for the fifty or so Elephant Seals I saw lying on the rocks out beyond the beach: they did not seem to pay any attention to the humans walking on the beach; but then, they were well out of reach of any meddling humans, protected by a couple hundred feet of surf and slippery rocks.