3.2.5 Total Suspended Solids 
The surface values for Total Suspended Solids (TSS) in waters of the 
West Coast shelf ranged from 0 to 10 mg/L for the 137 stations with data. 
Because the TSS samples from Oregon were not properly processed, these data 
were not included in the present analysis. The 50 th percentile of the survey area 
had a TSS concentration of 4.0 mg/L, and the 90 th percentile of area 
corresponded to a TSS concentration of 7.4 mg/L. Mean TSS in surface waters 
was slightly higher for stations in Washington than for those in California (Figure 
3.2.11 A). There was little difference in mean TSS between NMS and non-NMS 
locations (Figure 3.2.1 IB). 
3.2.6 Transmissivity 
Transmissivity in the surface waters of the West Coast shelf ranged from 
13.7% to 98.9% across the 140 stations with acceptable data. The 50 th 
percentile of the survey area had transmissivity of 74.3%, and the 90 th percentile 
of area had a transmissivity of 86.8%. Mean transmissivity in surface waters was 
higher for stations in California than for those in Oregon and Washington and 
showed little difference between stations inside vs. outside NMSs (Figure 
3.2.12). 
Transmissivity in the bottom waters of the West Coast shelf ranged from 
5.0% to 95.2% across the 175 stations with acceptable data. The 50 th percentile 
of the survey area had transmissivity of 85.6% and the 90 th percentile of area had 
a transmissivity of 91.6%. Mean transmissivity in bottom waters showed little 
difference among geographic regions or between NMS and non-NMS locations 
Figure 3.2.13). Across the West Coast shelf, bottom waters had relatively higher 
mean transmissivity than surface waters (Figures 3.2.12; 3.2.13). 
3.2.7 Nutrients 
The surface-water concentration of nitrate + nitrite in waters of the West 
Coast shelf ranged from 0 to 546.6 pg/L at the 188 stations with data. The 50 th 
percentile of area of the surface waters of the West Coast shelf sampled had a 
nitrate + nitrite concentration of 26.2 pg/L, with the 90 th percentile of area 
characterized by a nitrate + nitrite concentration of 354 pg/L. The mean value of 
nitrate + nitrite concentration in surface waters was highest in California as 
compared to Washington and Oregon and three times higher in the CA NMS 
stations as compared to the CA non-NMS stations (Figure 3.2.14). The elevated 
nitrate + nitrite observed at the CA NMS stations is consistent with the presence 
of strong upwelling at these sites at the time of sampling. 
42 
