Treasures from Coastal Middens:
Sea Otter mtDNA and Oxygen Isotopes in Sea Mussels

Coastal middens are treasure troves of historical and cultural information that also preserve ecological information of inestimable value. Shell middens contribute alkalinity to acid-rich soils, and thus promote preservation of bone. By identifying bird, mammal and mollusk species in shell middens, archaeologists can portray the environment of the past. This pilot project is exploring the usefulness of the prehistoric record to reconstruct specific climatic details about that paleoenvironment.

Sea otters (Enhydra lutris) once were numerous on the Oregon coast where they filled an important role in the ecosystem. Historic records of the late 1700's and early 1800's attest to this and prehistoric middens, stretching back for millennia, confirm it. Although sea otters were extirpated from the Oregon coast, having been hunted for the high price of their fur, evidence of past sea otters and their value to native people is preserved in middens. Native people, archaeologists and biologists have teamed together to learn more about the prehistoric sea otters, in the hope that if re-introduction of the sea otter is attempted, it will be done with an understanding of the prehistoric population of sea otters in Oregon. Currently, two sub-species of sea otter are recognized, a southern and a northern branch. By analyzing the mitochondrial DNA recorded in sea otter skeletons, this pilot project will determine genetic features of Oregon’s prehistoric sea otters; on the possibility that sea otter populations at different times varied with climatic cycles, we are studying the sea surface temperature by using midden-preserved remnants of the sea (or California) mussel, Mytilus californianus. The shell of this mussel, which lives only along the sea coast and which requires relatively high salinity, “records” the Oxygen 18 isotope ratio from which sea surface temperature during its period of growth can be estimated. Funded by Oregon Sea Grant, this project is in an exploratory phase. We are using midden materials from the Bandon Nah-so-Mah village (35-CS-43) site, the Seal Rock site (35-LNC-14), the Whale Cove site (35-LNC-60), Tseriadun (near Port Orford), the Neptune site (35-LNC-3), Umpqua Eden (35-DO-83), and Bullards (35-CS-3). To learn more about sea mussel isotopes we studied recent shells from the south and central coast and for comparison studied sea mussels from a site excavated by Loren Davis on the Baja coast. If the pilot study provides useful insights, we hope to study material from a larger range of sites. We believe that these midden data will help us to foster a healthier ecosystem along the coast.

Researchers: Dave Hatch, organizer of the Elakha (sea otter) Alliance and a member of the Confederated Tribes of Siletz Indians; Debbie Duffield, Portland State University biologist; Virginia Butler, Portland State University archaeologist; Roberta Hall, Oregon State University anthropologist; Diana Roy, pharmacy graduate student, OSU; Lorelei Patrick, biology graduate student, PSU. Isotope samples are prepared at the OSU faunal lab and processed in the OSU Stable Isotopic Facility directed by Alan Mix and staffed by Bill Rugh, Oceanography. Scott Byram, archaeologist; Mike Graybill, manager of the South Slough Estuarine Reserve; and Loren Davis, OSU archaeologist, graciously provided samples in addition to those excavated by OSU staff and curated at OSU. Ann Rogers, forest service archaeologist, provided valuable insights about the Whale Cove otter and mussel samples. Sharon Keen, heritage resource consultant, Victoria, British Columbia, and Sylvia Yamada, OSU ecologist, are consultants; Alan Mix and Bill Rugh provided background and technical advice. Barbara Butler and Aleta Carte of the Oregon Institute of Marine Biology shared data on the temperature and salinity of seawater samples taken daily at OIMB for two decades. Doug Kennett and Tobin Bottman, University of Oregon Department of Anthropology, shared their experience with sea mussel isotopic analysis.

Reports and talks:
Duffield D. and V. Butler. 2003. Use of ancient DNA to determine the affiliation of Oregon sea otters. Report to OSU Sea Grant Program on Development Grant.

Duffield, D., K. Valentine and V. Butler. 2003. Pre-fur trade Oregon sea otters. Sea Otter Conservation Workshop III. Talk given at Seattle Aquarium. Seattle, WA. Mar 14-16.

Duffield, D., K. Valentine and V. Butler. 2002. Use of midden-retrieved ancient DNA to study the historic distribution of sea otters in Oregon. Talk given at symposium, Secondary Adaptation to Life in Water, University of Otago, Dunedin, NZ. Dec 9-14.

Hall, Roberta, Virginia Butler, Debbie Duffield, Dave Hatch, and Kim Valentine. 2004. Applying archaeology and genetics to understand the once and future sea otter. Journal of Northwest Anthropology 38(2): 230.

Background on sea mammals in Oregon prehistory:
Hall, Roberta L. 2002. Resource Traditions. In: Changing Landscapes, edited by Don Ivy and Scott Byram, Coquille Indian Tribe, North Bend, Oregon, pp. 99-120.

Hall, Roberta . 2001. Nah-so-mah Village, Viewed Through Its Fauna. Report to OSU Sea Grant and the Coquille Indian Tribe. 59 pp.

Hatch, Dave. http://www.tidepool.org/features/elakha5.cfm

Lyman, R. Lee.1991 Prehistory of the Oregon Coast. Academic Press, San Diego.

June 1, 2005