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LOCAL TIDEPOOLS
by Ari Kornfeld

The summer seashore provides endless opportunities for even the most casual naturalist.You can spend hours simply contemplating the vast power in the pounding surf, the rise and fall of tides, or the clouds and fog that roll inland and keep us so cool. The beach also harbors an incredible diversity of life. Few activities are more enjoyable than looking for unusual creatures in colorful tidepools.

The rocky beaches north and south of Trinidad boast many excellent tidepools, particularly during full and new moons when tides are at their most extreme -- both low and high. Tide tables and moon phases are published in the local paper as well as on the web (Humguide, for example). Average low tides are listed as 0 feet, so look for negative-number tides and try to arrive around an hour ahead of time. Local tides range from -2 feet to a high of 8 feet.

Because of these fluctuations, tidepool creatures have adapted to extreme changes of temperature, moisture and salinity; many must survive part of each day entirely out of the water, fully exposed to the sun. It is not surprising, then, how strange and wonderful many of these little plants and animals appear to our terrestrial sensibilities.

Sea stars are among the most common inhabitants of tidepools. Ochre stars (Pisaster ochraceus), can be found in most locations. Large numbers of them often cluster near the base of Camel Rock at Houda point. Ochre stars have five rays and, despite their name, can be orange, red, or purple. A colony of beautiful pink short-spined stars (Pisaster brevispinus) might be found near the Trinidad boat ramp. Among the rocks at Trinidad State Beach, tidepoolers might find a brilliant orange or even a blue sunflower star (Pycnopodia helianthoides) and watch its many rays flow in and out of rocky crevices as it searches for food. Sunflower stars may have over 20 rays! The tiny six-rayed star (Leptasterias hexactis) or the spidery-looking brittle stars (Ophiuroidea) are harder to find, but equally delightful.

Sea stars have no front and back: they can move in any direction without turning around and do so by means of hundreds of tiny tube feet which operate hydraulically (look carefully at the top of the sea star and you will find the intake valve: the madreporite). Hydraulic muscles give them the strength and stamina needed to cling to rocks or pry open mussels when it is time for lunch. And speaking of eating, sea stars squeeze their stomachs through their mouths and digest food outside their bodies before swallowing! The mouth is in the center of the underside.

But the tidepools are home to many other fascinating creatures as well. During a typical visit you may find a wide variety of molluscs (clams, oysters, snails, abalones). The familiar black and brown turban snails (Tegula funebralis or Tegula brunnea, respectively), whose shells are often appropriated by hermit crabs, are almost everywhere. If you look closely you will find other slow-moving molluscs such as the black chiton (Katherina tunicata) or the giant gumboot chiton (Chryptochiton stelleri), as well as brightly colored nudibranchs (sea slugs, photo to the right). Mobile molluscs are typically grazers; the sedentary ones, such as California mussels (Mytilus californianus) clinging to the rocks by means of bissel threads, are filter feeders.

Goose barnacles (Pollicipes polymerus), tightly packed among the mussels, may seem like kindred molluscs but they are actually arthropods (jointed limbs). Crabs, shrimp, and isopods are more obviously arthropods. Rock crabs (Cancer antennarius), with their brick red carapaces and black-tipped claws, are among the largest shore crabs. Dozens, if not hundreds of them may be found burrowed in the sand or crowded into shallow pools around Camel Rock alongside other predators such as sea stars and giant green sea anemones (Anthopleura xanthogrammica, of the Phylum Cnidaria -- which means 'nettle' because of the stinging hairs they shoot out to capture prey). Anemones, with their iridescent green tentacles, are sometimes mistaken for plants, but they are actually animals.

Diligent explorers may even find feather duster worms, sea cucumbers, tiny orange corals, and other exotic creatures at Indian Point beach or along Mattole Road near McNutt Creek.

If all these names make your head swim, come visit our live exhibits at the museum, check out the various guide books available there and in other bookstores, or just go out and enjoy yourself!