Warner Pacific College Boiler Bay Intertidal Trip - Dwight J. Kimberly

This is a summary of things to look for on the field trip and a few suggestions to make the trip more enjoyable for you. Be careful where you step because the intertidal floor is the home of many . No animals will be collected without a permit. When close to the surf, watch the at all times. Take your time climbing around the rocks. They are slick and a fall could break a bone or remove skin. Use the accompanying checklist to key the phyla that you have learned in the course The following discussion is based upon Ricketts and Calvin, Between the Pacific . Three factors modify the intertidal marine fauna: 1) wave shock, 2) tidal exposure and 3) type of bottom. You will see an example of the protected rocky coast in which the shock of the waves is reduced by the influence of a long sloping shelf. Other possible modifications which produce the same result are offshore reefs, headlands, islands or large kelp beds. The bottom is typically rocky and affords a firm substrate for attachment to plants and animals. By turning over rocks you will uncover a myriad of animals, but at the same time expose them to the fatal effects of the sun. Therefore, replace the rocks as you found them to assure the survival of these animals. The zonation of the animal life as a result of the tides is apparent. Familiarize yourself with the zones and their characteristics. ZONE 1. Spray zone (highest high to mean high water) This area is wetted primarily by the ocean spray. One of the most common indicator is the periwinkle, Littorina planaxis. These animals are nearly adapted to a terrestrial existence and if placed in sea water for long periods, may drown. The limpet, Acmaea digitalis is also common to this zone. The pillbug, Ligida, the sand flea or beach hopper, Orchestia, and the barnacle, Balanus, are still other common inhabitants of this area. ZONE 2. High tide zone (Mean lower high water) The indicator species here are another species of periwinkle, Littorina scutulata, and the turban shell, funebralis. Another limpet, Acmaea, the hermit , Pagurus, and the purple shore crab, Hemigrapsus, are commonly found in this area. ZONE 3. Mid tide (Mean low water to mean high water) Three species which often occur together in this zone are the sea mussel, Mytilus californianus, the seastar, Pisaster, and the goose-neck barnacle, Mitella. Mytilus establishes large mussel beds which serve as homes for large numbers of animals such as the crab, Petrolisthes, the clam worm, Nereis, and the sipunculid and nemertean worms to name a few. These animals depend on the shelter of the beds. The chitons such as Katharina and the snail Thais emarginata may be observed on rocks and in crevices. In the tide pool one can observe many kinds of animals such as the , Pagurus, the green sea anemone, Anthopleura zanthogrammica, tube worms such as the sabellids, purple sea urchins, Strongylocentrotus purpuratus, the key hole limpet, Diadora, the turban shell Tegula, and the isopod, Idothea. Fish, mostly blennies, are fairly common. ZONE 4. Low tide (Lowest low to mean lower water) Careful investigation of rock ledges and over-hangs may disclose the presence of colonial hydroids. Most of these do not produce swimming medusae as does Obelia since they would be destroyed by the surf. Encrusting sponges (red and yellow blobs on rocks) are present but often over-looked by the casual observer. In addition, nudibranchs, (Pugettia and Cancer antennarius), brittle stars (under rocks) erpulid worms, snails, anemones, purple sea urchins and the gum boot chiton, Cryptochiton (with symbiont, Arctonoe), in grass and rocks.