The Puget Sound Basin in the State of Washington is one of 15 water-quality study units started in 1994 under the National Water-Quality Assessment Program. As part of the initial phase of the study, current (1995) and historical aquatic biological conditions of the streams of the study basin were summarized, and the natural and anthropogenic factors affecting aquatic organisms within the basin were evaluated to provide a framework for developing study plans and evaluating current and future water- quality trends.
The Puget Sound Basin encompasses a 35,224- square-kilometer area that drains into Puget Sound and adjacent waters. It is dominated by forest (75 percent of basin), urban (11 percent of basin) and agricultural (6 percent of basin) land uses. Each of these land uses have had an effect on aquatic biological resources within the basin. Within the basin, cold-water species of fish represent a significant economic and cultural resource. Of the 46 species and subspecies of fish found in the basin, 11 are migratory (anadromous), 33 are native and 5 are candidates for listing as threatened or endangered. Seven species or sub-species of native migratory salmon and trout are found in the basin and have exhibited declines in their populations. Much less is known about the remaining species of fish found in the basin. Aquatic invertebrates can also be used to evaluate water-quality conditions. More than 165 genera or species of aquatic invertebrates have been identified in the basin. One of these species, the Fender's soliperlan stonefly (Soliperla fenderi) is a Washington species of special concern and a federal candidate for listing under the Endangered Species Act. To date, a limited number of studies have used aquatic invertebrates to evaluate water- quality conditions within the basin. One such study identified the negative effects of urbanization on stream health.
Aquatic habitat conditions within the basin have been altered by current and historical land uses. Channelization, sedimentation, and alterations in vegetation along channel margins have all affected water-quality and biological resources. While many habitat studies have been done, few basin-wide summaries of these data exist. An evaluation of a number of habitat surveys indicates that the abundance of in-stream large, woody debris is limited throughout the basin when compared with streams draining old-growth forests, and the number of pools in the streams draining U.S. Forest Service lands are well below historical levels.
The availability of data on freshwater fish or invertebrate tissue samples analyzed for trace elements and synthetic organic compounds is limited in the Puget Sound Basin. Only 11 freshwater sites were identified in which fish tissue samples were collected between 1980 and 1996. The fish sampled included game fish and bottom fish. Generally, cadmium, copper, and lead concentrations in fish tissue were above the national geometric mean concentrations for samples collected as part of the U.S. Fish and Wildlife Service's National Contaminant Biomonitoring Program. At a few sites, cadmium, copper, lead, and mercury concentrations exceeded maximum levels observed in the U.S. Fish and Wildlife Service national study. At one site, levels of mercury in fish tissue exceeded the levels thought to affect fish-eating birds. Levels of synthetic organic compounds found in fish tissues within the basin were generally below the geometric means found in the U.S. Fish and Wildlife Service's national study. However, at a few sites, levels of BHC, PCB's, DDT and its breakdown products, and nonachlor were above the national geometric mean. At one location, levels of BHC and PCB were above the guidelines for protection of predatory fish and wildlife.