published thus far. Analyses of some of the data have shown that the 
benthos in some of the urban bays and waterways are severely impacted. 
These measures are listed in Table 6. Descriptive and qualitative 
observations made in the 1950s indicated that many parts of the urban bays 
such as Everett Harbor and the Tacoma Waterways were abiotic. Abiotic 
bottom samples are very rarely encountered in the 1980s. The benthos of 
much of the Central Basin appears to be rich in species, high in biomass 
and populated with species indicative of a health environment. Spatial 
and temporal trends in the benthos may be influenced by depth, sediment 
texture, salinity, and food availability as well as by sources of 
pollutants. 
Table 6. Synopsis of community changes measured in Puget Sound. 
Biological Group 
Types of Measurements 
Where Observed 
Soft-bottom 
benthos 
Reduced species diversity 
and richness, structural 
changes 
Tacoma Waterways, 
Everett Harbor, Eagle 
Harbor, Duwamish, inner 
Elliott Harbor 
Epibenthos 
Reduced 6-month recruit¬ 
ment on standard-sized 
artificial surfaces 
Tacoma Waterways, lower 
Duwamish 
Selected marine 
algae 
Reduced species richness 
and growth rates 
Near sewage treatment 
plants 
Epibenthic recruitment. Successional patterns 
and species richness in 
epibenthic assemblages colonizing artificial substrates indicate that 
conditions in the Duwamish and Commencement Bay Waterways are 
significantly different from those of outer Elliott Bay (Seacrest) and 
relatively rural areas (Port Washington Narrows, Manchester). Figure 5 
demonstrates the number of species colonizing these suspended substrates 
after 6 months exposure in seven areas. Though the salinity was similar 
at all sites, the freshwater flow in the Duwamish may have been partly 
responsible for the low number of species observed there. The numbers of 
species in the Commencement Bay Waterway sites were lower than those found 
in the other (reference) areas. 
Marine algae . Marine algal species comprise a very important component of 
intertidal and subtidal communities in the Sound. They provide food and 
shelter directly to certain animals. They provide detritus for many food 
webs that support important fish and invertebrates. Some of the large 
kelps are harvested and consumed by people. Some species are very 
sensitive to changes in wave exposure, water clarity, and concentrations 
of toxicants in the water. Alterations in the algal components of 
epibenthic communities thought to not be related to natural factors have 
been observed near the sewage treatment plants in the Sound. 
42 
