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CONDITION OF ESTUARIES OF CALIFORNIA FOR 1999: A STATISTICAL SUMMARY
Citation:
NELSON, W. G., H. LEE, AND J. O. LAMBERSON. CONDITION OF ESTUARIES OF CALIFORNIA FOR 1999: A STATISTICAL SUMMARY. U.S. Environmental Protection Agency, Washington, DC, EPA/620/R-05/004 (NTIS PB2007-107852), 2005.
Impact/Purpose:
To provide a probabilistic assessment of the condition of the small estuaries of California
Description:
As a part of the National Coastal Assessment (NCA), the Western Pilot Study under the Environmental Monitoring and Assessment Program (EMAP) initiated a five year 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.
For California, the focus of the study during 1999 was the small estuaries of the state, excluding San Francisco Bay, which was sampled during the second year of the program in 2000. The study utilized a stratified, random sampling design, with the base study consisting of 50 sites probabilistically assigned within the small estuaries of California. Additionally, an intensification study was conducted that consisted of 30 sites distributed among the mouths of river dominated estuaries in northern California. The two data sets were analyzed separately. 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 both the California small estuaries base study and the Northern California rivers study.
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 species, fish pathological anomalies).
Reflecting the fact that the sampling effort for California small estuaries study 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 10.1 to 32.1 ¿C . The Northern California rivers showed a narrower range of bottom water temperatures from 11.6 ¿C to 21.9 ¿C. About 39% of the area of the California small estuaries had sediments composed of sands, about 46 % was composed of muddy sands, and about 15 % was composed of muds. The Northern California rivers had relatively greater proportions of estuarine area characterized by sands (68%), and less area characterized by muds (4%) or muddy sands (32%). The 90th percentile of area of both the California small estuaries and the Northern California rivers had a sediment TOC level of 1.3 %. The pH of bottom water ranged from 6.6 to 10.2, with values of >9 tending to be associated with low salinity locations.
There was no geographic pattern to high values of chlorophyll a. All water quality indicators generally showed similar patterns in their CDFs, 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 of California small estuaries ranged from 3.4 to 3404 ¿g L-1, but only 2% of estuarine area had nitrate values that exceeded concentrations of 300 ¿g L-1. Approximately 69% of estuarine area of California small estuaries, and 76% of estuarine area in Northern California rivers, had molar ratios of average water column total nitrogen to total phosphorus (N/P) values d 16, suggesting nitrogen limitation.
Approximately 8% of area of California small estuaries and approximately 4% of area of Northern California rivers had a light transmission of d 10% at 1 m. Approximately 63 % of total estuarine area of California small estuaries showed a secchi depth e 3 m. Northern California Rivers were too shallow to measure secchi depth. There was little indication of water column stratification within the California small estuaries or Northern California rivers sampled. The limited stratification is consistent with the large tidal amplitude across much of the region, which should lead to a high degree of water column mixing.
Among pollutant exposure indicators, approximately 7% of estuarine area for the California small estuaries had bottom water dissolved oxygen concentrations d 5 mg/L, and no values were below 3.75 mg/L. There were no observations in the Northern California rivers of bottom dissolved oxygen concentration d 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, mercury, selenium, silver, tin, zinc). With the exception of nickel for which the Effects Range Median concentration (ERM) is unreliable, only chromium exceeded the ERM in e10% of the area of either the California small estuaries or Northern California Rivers. Eighteen percent of area of California small estuaries and 61 % of the area of the Northern California rivers had undetectable concentrations of PAHs. Seventy percent of area of California small estuaries and 84 % of the area of the Northern California rivers had non-detectable levels of total PCBs. Highest levels of organic contaminants generally were associated with urbanized estuaries of southern California. Seventy-four percent of the area of the California small estuaries had undetectable levels of DDT, as did all area of the Northern California rivers.
Sediment toxicity tests with the amphipod Ampelisca abdita found control corrected survivorship d 80 % in only about 1 % of area of California small estuaries. Approximately 39% of the area of the Northern California rivers had control corrected mean survivorship of A. abdita in sediment bioassays < 80%. Approximately 18.8% of the area of the California small estuaries had control corrected mean survivorship of Eohaustorius estuarius in sediment bioassays < 80%. Approximately 24.1% of the area of the Northern California rivers had control corrected mean survivorship of E. estuarius in sediment bioassays < 80%.
Sediment pore water bioassays with three treatment levels of serial dilution were conducted only for the California small estuaries using the sea urchin Arbacia punctulata. Approximately 21.5 % of the area of the California small estuaries had control corrected mean percent fertilization of A. punctulata eggs of < 90 % in the 100% porewater treatment. For the 50 % porewater treatment, 6.7% of estuarine area had values < 93% fertilization. For the 25 % porewater treatment, 5.8 % of estuarine area had values < 95% fertilization.
Approximately 95 % of the area of the California small estuaries had control corrected mean percent embryo development success A. punctulata of d 53 % in the 100% porewater treatment. For the 50 % porewater treatment, 57.4 % of estuarine area had values < 96 % embryo development success. For the 25 % porewater treatment, 2.7 % of estuarine area had values < 93 % embryo development success (Figure 3.2 -41).
Consistently obtaining the target organisms (flatfish) for tissue analysis of contaminants proved difficult, and tissue analyses were conducted for only 33 stations in the California small estuaries and 14 stations in the Northern California rivers. Thus cumulative distribution functions were not computed. There was no consistent spatial pattern in location of maximum fish tissue metal concentrations. The highest concentrations of aluminum, chromium and nickel were in samples from the Big River and the highest concentration of manganese was in the Klamath River, in the Northern California river samples. The highest concentrations of zinc and silver were in Big Lagoon, the highest selenium and lead values were in Long Beach Harbor, and the highest copper value occurred in San Diego Bay. The highest arsenic value was in Humboldt Bay.
Maximum fish tissue residues for total PCBs and pesticides 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.
Benthic infaunal community samples were obtained using either grabs or combining smaller corers to obtain equivalent surface area at 47 sites in the California small estuaries and 25 sites in the Northern California rivers. Reflecting the wide geographic distribution of sampling, a total of 552 non-colonial benthic taxa were recorded. Species richness ranged from 1 to 95 taxa per sample in the California small estuaries, while the maximum species richness in the Northern California rivers was 35 taxa. 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 California small estuaries had species richness d 33.2 species per sample. The northern California rivers tended to have lower species richness and H diversity values, with 50% of the area of these systems having fewer than 6.3 species.
Benthic infaunal abundance averaged 1033 individuals per sample in the California small estuaries, and 5606 individuals per sample in the Northern California rivers. About 50% of the area of California small estuaries had mean infaunal abundance d 368 individuals per sample. In the Northern California estuaries rivers, 50% of the area had benthic densities < 2864 individuals per sample. The California small estuary stations tended to be dominated by annelids while the Northern California rivers were dominated by crustaceans. Two amphipod species (Americorophium spinicorne, A. salmonis) had extremely high abundances in several Northern California rivers. The most abundant species in the California small estuary stations was nonindigenous, and nonindigenous or cryptogenic (suspected nonindigenous) species comprised 6 of the 13 numerically dominant species. In comparison, only one of the 10 numerically dominant species in Northern California rivers was nonindigenous while one other was cryptogenic.
The 1999 Western Coastal EMAP study provides the first probabilistic assessment of the condition of the small estuaries of California. When these data are combined with the data collected in 2000 from the San Francisco Bay estuarine system, there will exist the first comprehensive data set for evaluating the overall condition of all estuarine systems of California.