Washington had both S. alterniflora and Z. japonica. No nonindigenous species were 
observed at California sites. 
Quadrat Emergent Macrophyte Height and Seagrass Maximum Length 
For most emergent species, maximum plant height/length were recorded at fewer 
than 5 sites throughout the study area, making this a problematic variable to evaluate as 
a potential indicator (Appendix Table 6). Maximum height of S. virginica was recorded 
at 29 sites throughout the West (not including San Francisco Bay), ranging between 6 
and 76 cm. Maximum length of this species was recorded at 15 sites in San Francisco 
Bay. The mean value at these sites was 49 cm. Maximum blade length of seagrass 
was recorded at most sites when present. For the West overall, blade lengths of Z. 
marina (range 14-122 cm) were longer than those of Z. japonica (range 7-38 cm). 
Quadrat Biomass 
Total biomass in the vegetation quadrat throughout the study ranged between 0 
and 800 g/m 2 dry weight. Total biomass was greatest for sites in San Francisco Bay 
(mean = 350 g/m 2 ) and California (mean = 193 g/m 2 ; Figure 3.3.14). This can be 
attributed to the fact that these sites had greater cover by vegetation of all types while 
Oregon and Washington sites had more bare cover (Figure 3.3.7). For the West overall 
(not including San Francisco Bay), algae contributed the most to quadrat biomass 
(mean = 44%; Figure 3.3.14), followed by emergent macrophytes (mean = 38%) and 
seagrass (18%). This finding can be attributed to the fact that for many sites in Oregon 
and Washington, only macroalgae were present in the vegetation quadrats. In contrast, 
emergent macrophytes were the major contributor to quadrat biomass in San Francisco 
Bay and California sites. Emergent macrophytes contributed 99% on average to 
quadrat biomass in San Francisco Bay sites and 67% to quadrat biomass in California 
sites. The geographic patterns in relative contribution of different plant types to total 
quadrat biomass may again be attributed to differences in habitat types, and 
subsequently vegetation groups, among states. Tidal wetland habitat in California and 
San Francisco Bay is dominated by marsh habitat and emergent macrophyte 
vegetation. Oregon sites were a mixture of habitat types and thus different vegetation 
types contributed to quadrat biomass at different sites. Washington sites are classified 
primarily as tidal flat. Subsequently, seagrass and macroalgae are the major 
contributors to quadrat biomass. 
Mean biomass of emergent macrophytes varied among the states, attributable to 
geographic differences in macrophyte taxa encountered. For example, the only 
emergent macrophyte observed in the quadrats of Washington sites was S. alterniflora, 
a relatively large, perennial grass. In contrast, sites in California, San Francisco Bay 
and Oregon had a mix of macrophyte taxa of different growth forms. Most emergent 
macrophyte taxa were only found at a few sites (and weights recorded at even fewer), 
making it difficult to evaluate geographic trends in biomass. Biomass of most emergent 
macrophyte taxa was greater than that of seagrass species or macroalgal taxa 
(Appendix Table 7). Mean biomass of Z. marina and Z. japonica in the West were 
45 
