Publication Summary

The Marine Water Column Monitoring Program was initiated in 1967 to monitor ambient water quality in Puget Sound, Grays Harbor, and Willapa Bay. Data are currently collected monthly as part of an ongoing, long-term monitoring component to the program. During Wateryear 1993 (WY 1993 = October 1992 through September 1993), the Washington State Department of Ecology monitored water quality monthly at 23 stations in Puget Sound, five stations in Grays Harbor, and five stations in Willapa Bay. Of the 48 scheduled surveys for long-term monitoring, 43 were completed. Incomplete surveys resulted from inclement weather conditions (i.e., low visibility and rough sea surface) that prevented sampling.

The Marine Water Column Monitoring Program was initiated in 1967 to monitor ambient water quality in Puget Sound, Grays Harbor, and Willapa Bay. Data are currently collected monthly as part of an ongoing, long-term monitoring component to the program. During Wateryear 1993 (WY 1993 = October 1992 through September 1993), the Washington State Department of Ecology monitored water quality monthly at 23 stations in Puget Sound, five stations in Grays Harbor, and five stations in Willapa Bay. Of the 48 scheduled surveys for long-term monitoring, 43 were completed. Incomplete surveys resulted from inclement weather conditions (i.e., low visibility and rough sea surface) that prevented sampling.

Climatic conditions of WY 1993 were characterized by lower than normal precipitation in the fall and winter and higher than normal in spring and early summer. Precipitation and air temperature anomalies show some correlation with anomalies in sea-surface temperature and salinity, particularly in May. The presumed effect of the 1992 El Nio is seen as a preponderance of higher sea temperatures in WY 1992, as compared to WY 1993. A slight increase in surface salinities may reflect two years of below normal precipitation.

The stratification characteristics of the water column were classified as persistent, seasonal, episodic, and weak. The majority of the Puget Sound monitoring stations were either persistently (9 out of 23 stations) or seasonally (8 out of 23 stations) stratified. The degree of stratification has implications for water column dissolved oxygen concentrations. Dissolved oxygen (D.O.) concentrations < 5.0 mg/L were measured at six stations located in northern Puget Sound and in Hood Canal during WY 1993. At two of these stations D.O. concentrations were < 3.0 mg/L. Observations of low D.O. primarily occurred in late summer, and early fall. Similar D.O. conditions have been exhibited at these stations during the same seasons in previous wateryears. However, in WY 1993, two of the northern Puget Sound stations developed depressed D.O. levels during mid-summer (July) as well.

The seasonal cycle of increased chlorophyll a (chl a), decreased nutrients, and reduced euphotic zone depth was clearly seen for many of the stations in Puget Sound. The contribution of phytoplankton versus non-chl a containing particles (e.g., sediments) was assessed from examining linear regressions of the light extinction coefficient versus surface chl a concentration. High runoff months were identified as outliers to the regression. Some estuaries showed that chl a was not the major determinant of light extinction, presumably due to more constant suspended particle loads.

Fecal coliform bacteria counts > 14 organisms/100 mL were found at seven Puget Sound stations and three coastal stations during WY 1993. Most of these stations have shown these high counts in previous wateryears. Five of the Puget Sound stations differed from the usual pattern of high counts in winter with the addition of high counts in June or July. Both coastal estuaries showed fecal coliform bacteria counts that were more persistent than those at stations in Puget Sound with high counts. The highest and most persistent counts were in Grays Harbor.