3.2.3 Sediment Nutrients 
Sediments perform the function of removal of nitrogen and phosphorus from the 
water column through the process of sequestration of these nutrients in organic matter 
into the sediments. Nitrogen and phosphorus sequestered in sediments can also be a 
source of dissolved nutrients exported to the water column, where they are essential for 
phytoplankton growth, but in excess may lead to undesirable phytoplankton blooms. 
Average percent sediment concentrations of both total nitrogen and total 
phosphorus were lowest in Washington and highest in California (Figs. 3.2.3, 3.2.4; 
Appendix Table 3). West wide (excluding high marsh in San Francisco Bay), the mean 
value of sediment total nitrogen was less than 0.5 percent in 96% of intertidal area, and 
sediment total phosphorus was less than 0.1 percent in 95% of intertidal area. The 
mean value of sediment total nitrogen was < 0.3 percent in 100% of Washington 
sediments but 0.5 percent or more in 13% of area in Oregon, 18% of San Francisco Bay 
area, and 23% of area in the rest of California. The mean value of sediment total 
phosphorus was 0.1 percent or less in 99% of area in Washington, 98% of area in 
Oregon, 77% of San Francisco Bay area, and 80% of area in the rest of California. The 
five highest values for sediment concentrations of both total nitrogen and total 
phosphorus occurred in sediments from estuary sites within the Southern California 
Bight and from San Francisco Bay (Appendix Table 3). 
Figure 3.2.3. Average percent sediment total nitrogen for intertidal samples obtained in 
2002 for the West Coast region, individual states, and San Francisco Bay (mean 
± 1 sd). 
28 
