You are here:
CONDITION OF ESTUARIES OF THE WESTERN UNITED STATES FOR 1999: A STATISTICAL SUMMARY
Citation:
NELSON, W. G., H. LEE, II, J. O. LAMBERSON, V. D. ENGLE, L. C. HARWELL, AND LISA M. SMITH. CONDITION OF ESTUARIES OF THE WESTERN UNITED STATES FOR 1999: A STATISTICAL SUMMARY. U.S. Environmental Protection Agency, Washington, DC, EPA/620/R-04/200 (NTIS PB2007-107908), 2005.
Description:
As a part of the National Coastal Assessment, the Environmental Monitoring and Assessment Program (EMAP) initiated a five-year Western Coastal component in 1999. The objectives of the program were: to assess the condition of estuarine resources of Washington, Oregon and California based on a range of indicators of environmental quality using an integrated survey design; to establish a baseline for evaluating how the conditions of the estuarine resources of these states change with time; to develop and validate improved methods for use in future coastal monitoring and assessment efforts in the western coastal states; and to transfer the technical approaches and methods for designing, conducting and analyzing data from probability based environmental assessments to the states and tribes. The focus of the study during 1999 was the small estuaries of Washington, Oregon, and California, excluding Puget Sound, the main channel of the Columbia River, and San Francisco Bay, which were sampled in 2000 during the second year of the program. The environmental condition indicators used in this study included measures of: 1) general habitat condition (depth, salinity, temperature, pH, total suspended solids, sediment characteristics), 2) water quality indicators (chlorophyll a, nutrients), 3) pollutant exposure indicators (dissolved oxygen concentration, sediment contaminants, fish tissue contaminants, sediment toxicity), and 4) benthic condition indicators (diversity and abundance of benthic infaunal and demersal fish species, fish pathological anomalies). The study utilized a stratified random sampling design, with the base study consisting of 150 sites equally divided among the three states. Additionally, intensification studies were conducted that consisted of 30 sites located in Tillamook Bay, Oregon, and 30 sites distributed among the mouths of river dominated estuaries in northern California. All sites were combined for statistical analysis. Cumulative distribution functions (CDFs) were produced using appropriate sampling area weightings to represent the areal extent associated with given values of an indicator variable for the small estuaries of the West Coast. Reflecting the fact that the sampling effort spanned both the Columbian and Californian Biogeographic Provinces, the indicators of general habitat condition showed wide ranges of values, e.g., bottom water temperatures from 8.5 to 32.1 °C. Approximately 54% of the area of the small West Coast estuaries would be classified as euhaline (≥30 psu) based on the EMAP sampling. Approximately 65% of the estuarine area had sandy sediments (<20% silt clay), 29% had intermediate muddy sands (20-80% silt clay), and 6 % had mud sediments (>80% silt clay). The TOC content of sediments was ≤ 1% in approximately 84% of the area of the small West Coast estuaries. The pH of bottom waters for the small estuaries of West Coast states had the surprisingly wide range of from 5.1 to 10.2, with extreme values associated with low salinity locations. There was no geographic pattern to high values of chlorophyll a. Most water quality indicators showed similar CDF patterns, with high values being observed in a very small percentage of estuarine area, thus generating extensive right hand tails to CDF distributions. For example, the average water column concentration of nitrate/nitrite of small West Coast estuaries ranged from 0 to 3472 μg L-1, but only 2.7 % of estuarine area had nitrate/nitrite values that exceeded concentrations of 300 μgL-1. Approximately 75% of estuarine area had molar ratios of average water column total nitrogen to total phosphorus (N/P) values ≤ 16, suggesting nitrogen limitation. While total suspended solids (TSS) ranged from 0 to 276.2 mg L-1, approximately 95% of estuarine area had TSS ≤ 19.1 mg L-1. Only about 12 % of estuarine area showed an indication of strong water column stratification as indicated by the difference in surface and bottom salinities, suggesting the estuarine areas sampled are generally well mixed. Among pollution exposure indicators, less than four percent of estuarine area had dissolved oxygen concentrations in bottom waters below 5 mg/L. High values of potentially toxic metals generally occurred in a very small percentage of the estuarine area sampled, with maximum values of many of the metals being observed in the highly urbanized Los Angeles Harbor (cadmium, copper, lead, selenium, silver, tin, zinc). DDT and other pesticides were detected in a relatively small percentage of estuarine area. Seventy- three percent of estuarine area had non-detectable levels of total PCBs. Highest levels of organic contaminants (pesticides, PAHs) generally were associated with urbanized estuaries of southern California. Sediment toxicity tests with the amphipod Ampelisca abdita had control-corrected survivorship ≤ 80 % in only about 9 % of estuarine area. Using sediment pore water bioassays, the control corrected, percent fertilization of eggs of the sea urchin Arbacia punctulata was ≤ 91 % in only about 10.5 % of estuarine area for the 100% of the water quality adjusted (WQA) porewater treatment. Survivorship was higher for both 50% and 25% WQA porewater treatments. For a similar test using percent successful development of Arbacia punctulata embryos, the control-corrected normal development of embryos was ≤ 91 % in about 49 % of area of small West Coast estuaries for the 100% of the WQA porewater treatment. Normal embryo development was higher for both 50% and 25% WQA porewater treatments. There was a total of 144 successful trawls across the three states, but due to the number of stations without successful trawls, the analysis of the fish trawl data is limited to summary statistics and species composition, and no CDFs are presented. The number of individuals per trawl averaged 33.7 fish per trawl, with a low of 13.9 in Oregon and a high of 68.0 in California. Species richness averaged 3.53 fish species per trawl, with a low of 2.63 in Oregon and a high of 5.46 in California. A report on the frequency of fish pathologies will be produced separately by NOAA. Obtaining the target organisms (flatfish) for tissue analysis of contaminants proved difficult, and tissue analyses were conducted on only 53% of the total stations occupied. Thus cumulative distribution functions were not computed. There was no consistent spatial pattern in location of maximum fish tissue metal concentrations, with highest values of mercury being recorded in several California estuaries, highest arsenic and lead values being recorded in several Washington estuaries, and highest copper values being recorded in an Oregon estuary. Maximum fish tissue residues for total PCBs were associated with urbanized estuaries in California, which were also associated with highest sediment concentrations of these contaminants. Tissue residues of DDT and its metabolites were considerably higher than other pesticides measured. A total of 187 samples of benthic infauna (>1 mm) were obtained using either grabs or a combination of smaller corers to obtain equivalent surface area (0.1 m2). Reflecting the wide geographic distribution of sampling, a total of 841 non-colonial benthic taxa were recorded. Species richness ranged from 1 to 157 taxa per sample. Lowest species richness tended to be associated with low salinity sites, and highest species richness was associated with salinities > 30 psu. About 50% of the area of small West Coast estuaries had species richness ≤ 17 species per sample. The northern California intensive study sites tended to have lower species richness and Hʹ diversity values than other stations. Benthic infaunal abundance averaged 1378.9 individuals per sample, with lowest mean abundance per sample in Washington estuaries and highest mean abundance values in California estuaries, particularly the northern California intensive study sites. About 50% of the area of small West Coast estuaries had mean infaunal abundance ≤ 151 individuals per sample. Two amphipod species (Americorophium spinicorne, Americorophium salmonis), which had extremely high abundances in several northern California locations, made up 54 % of total infaunal abundance in the study. Among the 10 most abundant taxa at all study sites, nonindigenous and cryptogenic (species of uncertain geographic origin) species made up 6 % of total infaunal abundance. The 1999 Western Coastal EMAP study provides the first quantitative assessment of the condition of the small estuaries of Washington, Oregon and California. When these data are combined with the data collected in 2000 from the three largest estuarine systems on the West Coast (Puget Sound, Columbia River, San Francisco Bay), there will exist the first comprehensive data set for evaluating the overall condition of all estuarine systems of the West Coast.