concentrations were higher in WA and OR waters than in CA, and higher in the OC 
NMS than in the CA sanctuaries. An estimated 94.3% of the area had bottom-water DO 
concentrations < 4.8 mg/L and 6.6% had concentrations < 2.3 mg/L. The high 
prevalence of DO from 2.3 to 4.8 mg/L (85% of survey area) is believed to be 
associated with the upwelling of naturally low DO water across the West Coast shelf. 
Mean TSS and transmissivity in surface waters (excluding OR due to sample 
problems) were slightly higher and lower, respectively, for stations in WA than for those 
in CA. There was little difference in mean TSS or transmissivity between NMS and non- 
NMS locations. Mean transmissivity in bottom waters, though higher in comparison to 
surface waters, showed little difference among geographic regions or between NMS 
and non-NMS locations. 
Concentrations of nitrate + nitrite, ammonium, total dissolved inorganic nitrogen 
(DIN) and orthophosphate (P) in surface waters tended to be highest in CA compared to 
WA and OR, and higher in the CA NMS stations compared to CA non-sanctuary 
stations. Measurements of silicate in surface waters were limited to WA and CA 
(exclusive of the SCB) and showed that concentrations were similar between the two 
states and approximately twice as high in CA sanctuaries compared to OCNMS or non¬ 
sanctuary locations in either state. The elevated nutrient concentrations observed at 
CA NMS stations are consistent with the presence of strong upwelling at these sites at 
the time of sampling. Approximately 93% of the area had DIN/P values < 16, indicative 
of nitrogen limitation. Mean DIN/P ratios were similar among the three states, although 
the mean for the OCNMS was less than half that of the CA sanctuaries or non¬ 
sanctuary locations. Concentrations of chlorophyll a in surface waters ranged from 0 to 
28 pg L" 1 , with 50% of the area having values < 3.9 pg L' 1 and 10% having values > 
14.5 pg L' 1 . The mean concentration of chlorophyll a for CA was less than half that of 
WA and OR locations, and concentrations were lowest in non-sanctuary sites in CA and 
highest at the OCNMS. 
Shelf sediments throughout the survey area were relatively uncontaminated with 
the exception of a group of stations within the SCB. Overall, about 99% of the total 
survey area was rated in good condition (<5 chemicals measured above corresponding 
effect range low (ERL) concentrations). Only the pesticides 4,4-DDE and total DDT 
exceeded corresponding effect range-median (ERM) values, all at stations in CA near 
Los Angeles. Ten other contaminants including seven metals (As, Cd, Cr, Cu, Hg, Ag, 
Zn), 2-methylnaphthalene, low molecular weight PAHs, and total PCBs exceeded 
corresponding ERLs. The most prevalent in terms of area were chromium (31%), 
arsenic (8%), 2-methylnaphthalene (6%), cadmium (5%), and mercury (4%). The 
chromium contamination may be related to natural background sources common to the 
region. The 2-methylnaphthalene exceedances were conspicuously grouped around 
the CINMS. The mercury exceedances were all at non-sanctuary sites in CA, 
particularly in the Los Angeles area. 
XXI 
