TRACE-METALS (CD, CU, NI, AND ZN) AND NUTRIENTS IN COASTAL WATERS ADJACENT TO SAN-FRANCISCO BAY, CALIFORNIA

Samples collected in December 1990 and July 1991 show that dissolved C d, Cu, Ni, and Zn distributions in the Gulf of the Farallones are domi nated by mixing of two end-members: (1) metal-enriched San Francisco B ay water and (2) offshore California Current water. The range of disso lved metal concentrations observed is 0.2-0.9 nmol kg(-1) for Cd, 1-20 nmol kg(-1) for Cu, 4-16 nmol kg(-1) for Ni, and 0.2-20 nmol kg(-1) f or Zn. Effective concentrations in fresh water discharged into San Fra ncisco Bay during 1990-1991 (estimated by extrapolation to zero salini ty) are 740-860 mu mol kg(-1) for silicate, 21-44 pmol kg(-1) for phos phate, 10-15 nmol kg(-1) for Cd, 210-450 nmol kg(-1) for Cu, 210-270 n mol kg(-1) for Ni, and 190-390 nmol kg(-1) for Zn. Comparison with eff ective trace metal and nutrient concentrations for freshwater discharg e reported by Flegal et al. (1991) shows that input of these constitue nts to the northern reaches of San Francisco Bay accounts for only a f raction of the input to Gulf of the Farallones from the estuary system as a whole. The nutrient and trace metal composition of shelf water o utside a 30-km radius from the mouth of the estuary closely resembles that of California Current water further offshore. In contrast to coas tal waters elsewhere, there is little evidence of Cd, Cu, Ni, and Zn i nput by sediment diagenesis in continental shelf waters of California.