Constantine, JA, GB Pasternack, JH Viers, JB Feliciano. 2001. A Multi-Proxy Approach to Examining Land-Use Change Effects on Steelhead Trout and Coho Salmon in NW California. EOS Trans. AGU 82(20):B41B-06

Historically, juvenile and spawning adult steelhead trout and coho salmon were found in abundance in the Navarro Basin of NW California. However, the numbers of juvenile steelhead and spawning adults have declined greatly over the past 100 years, while coho salmon rearing and spawning is now limited to only one sub-drainage. Steelhead and coho population data taken by the DFG along with GIS images of recent land-use change are being used in conjunction with sediment core data to determine specific land-use effects on watershed geomorphology and in-stream habitat quality. The study uses historical information on land use, fish populations, and river flow along with a multi-proxy analysis of cores taken from the Navarro floodplain to reconstruct geomorphic effects of land-use change and includes geochemical, palynological, grain size, LOI, and radiocarbon analyses. An historical analysis of logging operations within the watershed indicates three periods of increased mill operations peaking in 1952 with 32 mills. Digitized aerials from 1936 show the distribution of land-uses, including large swaths of clear-cut land. When these data are combined with a 100-yr record of fish distribution and a 50 yr record of discharge, a timeline of cumulative impacts is available for comparing against the multi-proxy record. For example, results from geochemical analyses may indicate anthropogenic effects on watershed sediment transport. A spike in Hg concentration at a depth of ~5 m occurs in all cores and an increase in concentrations of Hg, Cu, Co, Ba, Cr, and Ni begins at 3 m in most. Geochemical ternary diagrams of different core locations and depths show that sediment depositing in the floodplain of sub-drainages differ from main stem sediment, indicating spatio-temporal changes in sediment source areas. A palynological investigation is being conducted which will provide data of changes in ecosystem structure through time and will aid estimates of recent sedimentation rates.