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Marine Ecosystems Sunset Bay SP Tidepools Oregon Department of Biological Sciences, Fort Hays State University Instructor: Mark Eberle Course Homepage One coastal ecosystem we visit in Oregon is the rocky tidepool. We camp at Sunset Bay State Park, located near Coos Bay on the Cape Arago Highway, so named because it terminates at Cape Arago. Exploring the Tidepools at Cape Arago State Park, Oregon (with Mary Schmidt, Niki Lambrecht, and Mark Eberle) Photograph by William Cook, August 2000 Within the tidepools at Cape Arago and Sunset Bay, we see several species of green algae (Chlorophyta), brown algae (Phaeophyta), and red algae (Rhodophyta). We also see individuals from several phyla of marine animals, including sponges (Porifera); sea anemones (Cnidaria); mussels, limpets, snails, and chitons (Mollusca); barnacles, crabs, and shrimps (Arthropoda); sea stars, sea urchins, and sea cucumbers (Echinodermata); and tunicates and sculpins (Chordata). Several are included in the photographs on the next page. Marine Algae and Animals, Sunset Bay Tidepools, Oregon Can you identify any? Photographs by Jennifer Matiasek, August 1997 (top left) and Curtis Wolf, July 2005 Many intertidal organisms attach to the firm, rock substrate to hold themselves in place when exposed to waves and currents. Because they are sessile, attached organisms depend on these same currents to bring them food in the form of small organisms that swim or drift in the water. Others, such as chitons, limpets, and sea urchins, are grazers on the various types of algae attached to the rock surfaces. For protection against predators, many of these organisms have hard protective shells or plates. Carnivores, such as sea stars and whelks, have developed interesting methods to overcome the protective shells of the mussels and barnacles that they eat. Sea stars pull the shells of the mussel apart and invert their stomach inside the bivalve to digest the soft tissues (photograph next page). Whelks (gastropods) use an enzyme and their rasp-like radula to bore holes through the shells. In addition to protection from predators, shells of mollusks and barnacles also help them limit desiccation while the tide is out and they are exposed to the sun and wind. Ochre Sea Star Wrapped around Mussel, Cape Arago SP, Oregon Photograph by Mark Eberle, July 2002 As in the mountains, communities of rocky tidal areas exhibit vertical zonation. In this case, the zones are related to the height of the tides rather than precipitation and temperature gradients. Generally, tolerance to desiccation sets the upper limits of species distributions, and lower limits are set by competition and predation (summary by Schultz, 1990:108‒115). These zones are easiest to discern on sloping rock faces (notice the different bands across the photograph below); however, some mixing of species from different zones occurs around cavities that retain water during low tides—the tidepools. North Cove Tidepool Area, Cape Arago State Park, Oregon Photograph by Mark Eberle, August 2000 The high intertidal zone is covered only during the highest tides. Animals commonly inhabiting this zone include the Acorn Barnacle (Balarus glandula) and limpets that are well adapted to tolerate desiccation. The mid intertidal zone is regularly covered and uncovered by the tides, usually twice each day. The upper portion of this zone often can be recognized by the presence of beds of the California Mussel (Mytilus californianus) and Goose Barnacle (Pollicipes plymerus) (dark band in the photograph above). Ochre Sea Stars (Pisaster ochraceus) and Green Sea Anemones (Anthopleura anthogrammica) are common in the lower portion of the mid intertidal zone (central pinkish band in the photograph above). The presence of the Ochre Sea Star in the lower portion of the mid intertidal zone is a primary reason that mussels are generally restricted to the upper portion of this zone. Sea stars, whelks, and other predators susceptible to desiccation have difficulty feeding during the limited time high tides inundate the upper portion of the mid intertidal zone. The low intertidal zone is only exposed during the lowest tides (dark band closest to the water in the photograph on the previous page). It is the home to the Purple Sea Urchin (Strongylocentrotus purpuratus), which grazes on macrophytic algae. Because the low intertidal zone is covered by water most of the time, it has the greatest diversity of organisms in the tidal area. Simpson Reef (photograph below) extends north from Cape Arago. Even though the reef can be reached at low tide from the tidepools at the North Cove of Cape Arago, it is part of the Oregon Islands National Wildlife Refuge and is closed to all public use. However, a viewing area along the Cape Arago Highway provides a good vantage point from which to watch marine mammals and birds with binoculars or a spotting scope. We have regularly observed the Harbor Seal (Phoca vitulina), Elephant Seal (Mirounga angustirostris), California Sea Lion (Zalophus californianus), Stellar (Northern) Sea Lion (Eumatopias jubatus), Pigeon Guillemot (Cepphus columba), and Black Oystercatcher (Haematopus bachmani) on our trips (photographs below). Simpson Reef (Shell Island in the center), Cape Arago State Park, Oregon Photograph by Mark Eberle, July 2005 Shell Island, Simpson Reef, Cape Arago State Park, Oregon Photograph by Eric Hoch, July 2002 In addition to organisms among the rocky tidepools, there are animals that make their homes on or within the sandy beaches of the coast. Among the more brightly colored animals is the Ghost Shrimp (Neotrypaea californiensis), which can live 10 years in a U-shaped burrow that is also home to several other species (Sept, 1999:112). Ghost Shrimp, Sunset Bay State Park, Oregon Photograph by Eric Hoch, July 2002 Sunset Bay is the mid-point of our trip, and we spend 2 nights camping here. Although our mornings are filled with class activities, we spend the afternoon and evenings enjoying the scenery, revisiting tidepools, dining on seafood, and doing laundry. Sunset Bay, Oregon (10-minute walk from our campsite in the coastal forest) Photograph by Mark Eberle, August 2000 Included in this “down time” is an afternoon visit to Shore Acres State Park, located between Sunset Bay and Cape Arago. Shore Acres is a botanical garden situated on rocky bluffs above the ocean. It features English and Japanese gardens, as well as colorful beds of award-winning hybrid roses. Rough-skinned Newts (Taricha granulosa) live in the pond in the Japanese garden. During the early 1900s, Louis Simpson, West Coast lumberman and shipbuilder, had a mansion and gardens on this spot. During the Great Depression and World War II, the tracts of land that now comprise Sunset Bay, Cape Arago, and Shore Acres state parks were given or sold to the state of Oregon. Bluffs and Japanese Garden Pond, Shore Acres State Park, Oregon Photographs by Mark Eberle, August 1998 Literature Cited Schultz, S. T. 1990. The Northwest Coast: A Natural History. Timber Press, Portland, Oregon. Sept, J. D. 1999. The Beachcomber’s Guide to Seashore Life in the Pacific Northwest. Harbour Publishing, Madeira Park, British Columbia, Canada. Next Stop: South Slough Estuary | Species Checklists | Return to Trip Summary Homepage