Northeast Pacific being developed by the EPA and USGS (Lee and Reusser, 2007). Of 
the 420 taxa, there were 170 native species, 42 nonindigenous species (NIS), 32 
cryptogenic species, 1 cosmopolitan pelagic copepod, 3 unclassified species, and 172 
indeterminate taxa. In terms of relative abundance, polychaetes and oligochaetes were 
the dominant taxa, composing over 40% and 20% of the individuals, respectively 
(Figure 3.3.2). The only other taxa to comprise more than 5% of the individuals were the 
amphipods and bivalves (Table 3.3.1). 
The oligochaetes were not identified to species, but are a reasonably diverse 
taxon with almost 200 species reported from marine, estuarine, and tidal fresh habitats 
in the Northeast Pacific (Lee and Reusser, 2007). Oligochaetes are a numerically 
dominant taxa in a number of Pacific Coast assemblages, including Spartina beds in 
San Francisco (Neira et al., 2005), “fresh-brackish sandy” and “estuarine margin” 
subtidal benthic assemblages in San Francisco Bay (Lee et al., 2003), and Zostera, 
Upogebia, and Spartina habitats in Willapa Bay (Ferraro and Cole, 2007). In the 
present study, oligochaetes were abundant along the entire coast and constituted the 
most abundant or second most abundant taxon in California, San Francisco, Oregon, 
and Washington (Table 3.3.1). The highest oligochaete densities tended to be 
associated with the presence of macroalgae, Zostera marina or Z. japonica beds, or 
marsh habitat including Spartina though moderately high densities also occurred in 
unvegetated flats. Given the number of species on the West Coast, it is likely that 
species composition varied among the habitat types and/or geographically. Because 
certain families of oligochaetes, in particular tubificids, are associated with polluted 
conditions (Engle et al., 1994; Llanso et al., 2002) and because they constitute a major 
proportion of the total individuals in many intertidal assemblages (Figure 3.3.2) we 
recommend that future studies identify oligochaetes at least to the family level. 
The high abundance of polychaetes in these assemblages is fairly typical of other 
soft-bottom assemblages (e.g., Nelson et al., 2004). Less expected was that the single 
most abundant polychaete in the West was the nonindigenous Manayunkia aestuarina , 
a sabellid introduced from the Northeast Atlantic. Manayunkia aestuarina was 
particularly dense in Oregon, much less so in Washington, and not recorded from 
California (Table 3.3.1) though a congener ( Manayunkia speciosa) is abundant in lower 
salinity regions of the San Francisco Bay (Cohen and Carlton, 1995; Lee et al., 2003). 
In Willapa Bay, M. aestuarina has been reported as a numerical dominant primarily 
limited to Spartina alterniflora beds (Ferraro and Cole, 2007). In the present 
probabilistic survey, the greatest abundance of M. aestuarina (148,178/m 2 ) occurred in 
an unvegetated sand flat in Coos Bay, Oregon though high densities were also found in 
Spartina alterniflora in Washington and in Carex lyngbyei , a common shoreline sedge, 
in Oregon. Other abundant polychaetes (average > 20 individuals per 0.09 m 2 sample) 
included two capitellids ( Capitella capitata, Mediomastus califbrniensis), several 
spionids ( Streblospio benedicti, Pygospio elegans, Pseudopolydora paucibranchiata, 
Pseudopolydora kempi, and Polydora cornuta), and a cirratulid (Tharyxparvus). Of 
these, four of the spionids (S. benedicti, P. paucibranchiata, P. kempi, and P. cornuta) 
are nonindigenous and Capitella capitata and Pygospio elegans are cryptogenic. All of 
these species are frequently found in subtidal and intertidal assemblages in the 
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