Abstract  The Klamath River in California is listed as impaired for temperature, nutrients, and low DO/organic enrichment. The North Coast Regional Board is developing TMDLs in collaboration with Oregon and USEPA to address these impairments. For TMDL development, Tetra Tech is applying a set of linked simulation models consisting of CE-QUAL-W2 (for reservoirs) and RMA (for free-flowing reaches). The TMDL runs have primarily addressed numeric criteria for DO and temperature. Tetra Tech, under contract to EPA Region IX and the California State Water Resources Control Board also developed an approach for calculating nutrient numeric endpoints (NNE) for use in California Water Quality Programs (Tetra Tech, 2006). The “Technical Approach to Develop Nutrient Numeric Endpoints for California,” referred to as the California NNE approach, is a risk-based approach in which targets are developed for response variables (or secondary indicators) such as algal density. These response targets can then be converted to site-specific nutrient targets through use of modeling tools. The California NNE approach recognizes that there is no clear scientific consensus on precise levels of nutrient concentrations or response variables that result in impairment of a designated use. To address this problem, waterbodies are classified in three categories, termed Beneficial Use Risk Categories (BURCs). BURC I waterbodies are not expected to exhibit impairment due to nutrients, while BURC III waterbodies have a high probability of impairment due to nutrients. BURC II waterbodies are in an intermediate range, where additional information and analysis may be needed to determine if a use is supported, threatened, or impaired. Tetra Tech (2006) lists consensus targets for response indicators defining the boundaries between BURC I/II and BURC II/III. Tetra Tech (2006) also documents a set of relatively simple but effective spreadsheet tools for application in lake/reservoir or riverine systems to assist in evaluating the translation between response indicators and nutrient concentrations or loads. One important use of the NNE is for setting initial nutrient endpoints for waterbodies requiring nutrient TMDLs. Tetra Tech (2007), under contract with USEPA, conducted a case study of potential NNE endpoints on the Klamath River. That study, “Nutrient Numeric Endpoints for TMDL Development: Klamath River Case Study”, addressed only periphyton in the riverine portion of the watershed and used water quality data for 2000-2003, coupled with periphyton observations from 2004. Since that time, significantly more data have become available, and corrections have been made to earlier data. At the request of the North Coast Regional Water Quality Control Board, USEPA has funded this follow-on study. The two major purposes are (1) to extend the NNE analysis to the two reservoirs (Iron Gate and Copco) on the California portion of the Klamath system, and (2) to update the stream periphyton analysis to reflect more recent and corrected data.

Abstract  These studies were conducted to determine the impacts of natural and anthropogenic perturbations on plants and algae in southern California streams. I examined correlations between algae and nitrogen, phosphorus, and land for 24 streams in southern California, and conducted nutrient diffusing substrata experiments to determine the nutrient limiting growth of benthic algae. Algal biomass increased with urbanization, reaching high levels in the most urbanized streams (up to 408 mg chla m-2). Total nitrogen, total phosphorus, and chlorophyll concentrations were tightly positively correlated with the proportion of upstream land covered by impervious surfaces. At lower nutrient concentrations, algal growth appeared to be limited by nitrogen availability, whereas phosphorus appeared to limit growth in streams subject to greater human influence. Biomass of floating mats of macroalgae (Enteromorpha sp.) responded positively to experimentally increased light and nutrient availability, increasing by up to 800% over four weeks. I also measured impacts of plant dominance in southern California streams. Ludwigia hexapetala reached high biomass (0.98±0.03 kg m -2) downstream of a wastewater treatment plant on the Ventura River, California. The abundance of green macroalgae was reduced, and that of diatoms increased, in the presence of Ludwigia. Ludwigia’s rates of growth and nitrogen uptake increased with increasing nutrient availability, accounting for considerable decreases in dissolved nitrate. The dominance of this plant on the river was highly variable over multiple years, with biomass greatly reduced by scouring during winters with high rainfall, then requiring several consecutive years of low flows to re-establish dominance. A conceptual model is presented for predicting primary producer community and biomass changes in streams in southern California in response to land use changes, particularly urbanization. Increases in light availability result in changes in algal community, from benthic diatoms to green macroalgae, and the inclusion of vascular plants. Increases in nutrient concentrations alone typically result in increases in algal biomass without shifts in type of algae present. However, streams draining extremely urbanized catchments may show a decrease in plant and algal biomass as increases in resource availability are offset by increases in temperature or toxins which depress or inhibit algal growth.

Abstract  Many streams within the United States are impaired due to nutrient enrichment, particularly in agricultural settings. The present study examines the response of benthic algal communities in agricultural and minimally disturbed sites from across the western United States to a suite of environmental factors, including nutrients, collected at multiple scales. The first objective was to identify the relative importance of nutrients, habitat and watershed features, and macroinvertebrate trophic structure to explain algal metrics derived from deposition and erosion habitats. The second objective was to determine if thresholds in total nitrogen (TN) and total phosphorus (TP) related to algal metrics could be identified and how these thresholds varied across metrics and habitats. Nutrient concentrations within the agricultural areas were elevated and greater than published threshold values. All algal metrics examined responded to nutrients as hypothesized. Although nutrients typically were the most important variables in explaining the variation in each of the algal metrics, environmental factors operating at multiple scales also were important. Calculated thresholds for TN or TP based on the algal metrics generated from samples collected from erosion and deposition habitats were not significantly different. Little variability in threshold values for each metric for TN and TP was observed. The consistency of the threshold values measured across multiple metrics and habitats suggest that the thresholds identified in this study are ecologically relevant. Additional work to characterize the relationship between algal metrics, physical and chemical features, and nuisance algal growth would be of benefit to the development of nutrient thresholds and criteria.

Abstract  Rapid human population growth engenders landuse changes and alters nutrients, algal biomass (as chlorophyll a [chl a]), and dissolved O2 concentrations (DO) in streams, but quantitative information on these relationships is limited in regions with a Mediterranean climate. We surveyed macroalgal % cover and chl a and physicochemical factors in spring and summer at 15 stream and estuarine sites in a catchment in southern California with a mosaic of undeveloped, agricultural, and urban areas to examine relationships among land use, nutrients, algae, and DO. We used nutrient diffusing substrata (NDS) at 12 sites to assess the nutrient(s) limiting algal growth. Algal chl a and pH often exceeded suggested or mandated water-quality impairment thresholds at sites affected by human activity, particularly those downstream from a wastewater treatment plant. Total N (TN) affected total and benthic algal chl a in spring and summer, total P (TP) affected benthic algal chl a in summer, and light influenced algae in summer. N was the sole or primary limiting nutrient at ½ of the sites and was colimiting with P at another ? of the sites. Nutrient ratios (molar TN?TP) were poor predictors of algal responses to nutrient enrichment. Diel changes in dissolved O2 were related positively to discharge and negatively to algal chl a, particularly when floating macroalgae were present. In June, N, chl a, and macroalgal % cover were positively related to human landuse patterns at the subcatchment scale, whereas in September, P and chl a were related to landuse patterns at more local scales (500 m, 1000 m). Mediterranean streams present a variety of challenges for water-quality managers because of high seasonal and interannual variation in discharge and nutrient flux, high accumulations of algae during the dry season, low nutrient thresholds that generate nuisance algal blooms, and human population growth and associated changes in landuse patterns.

Abstract  The species composition of benthic diatoms was related to environmental conditions in streams throughout the western US to develop diatom traits, indicators for assessment of biological condition and indicators for diagnosing stressors. We hypothesized that indicators based on species traits determined for subsets of streams with similar natural landscape features would be more precisely related to environmental conditions than would be indicators calculated based on species traits for all Streams in the data set. The ranges of many environmental conditions were wide among western streams, and these conditions covaried greatly along a major environmental gradient characterized by positive correlations among % watershed disturbed by agricultural and urban land uses (% WD), conductivity, total N, total P, and % fine sediments. Species traits were calculated for 242 diatom taxa. Weighted average (WA) methods were used to define species environmental optima, and regression approaches were used to determine whether species were sensitive or tolerant to environmental conditions indicated by % WD, total P, total N, a nutrient multivariate index, pH, conductivity, % fine sediments, % embeddedness, and a watershed disturbance multivariate index. Indicators based on WA optima and sensitive/tolerant traits were highly correlated with these environmental conditions. Natural and anthropogenic conditions varied greatly among classes of streams grouped by climate regions, but indicators developed for the entire western US were consistently more accurate than were regional indicators. Indicators for individual stressors, such as total P, conductivity, and % embeddedness, were highly correlated with values of respective stressors, but covariation among all indicators and stressors indicated that only 1 environmental gradient was reliably reflected by the indicators. Thus, robust indicators of the biological condition of diatom assemblages were developed for streams of the western US, but development of stressor-specific indicators will require application of additional analytical approaches.

Abstract  We surveyed algal cover, algal biomass, and physical and chemical factors at 14 sites representing a range of land use types in the Malibu Creek watershed in southern California, USA. We also conducted nutrient diffuser Substrate experiments to identify the nutrient limiting algal growth. Algal biomass increased with urbanization, reaching very high levels in the most urbanized streams (up to 322.4 mg chlorophyll a center dot m(-2)). Total nitrogen, total phosphorus, and benthic and total chlorophyll concentrations were positively correlated with the proportion of upstream land covered by impervious surfaces. Relationships between land use and algal biomass or nutrient concentrations were evaluated at 100 m, 500 m, and whole subwatershed scales. The closest relationships were found at the 500 m scale, where 56% of the variation in total chlorophyll could be explained by the proportion of land within a 500 m radius upstream covered by impervious surfaces. Floating macroalgae were observed in the summer in pools with high nutrient and light levels, whereas benthic algal biomass was positively related to total phosphorus concentrations and current speed. Other methods of determining nutrient limitation (nutrient diffuser substrate experiment, molar N/P ratios in stream water) produced conflicting results, possibly because algal growth was saturated by high nutrient levels at some of the study sites.

Abstract  1. Algal-community metrics were calculated for periphyton samples collected from 976 streams and rivers by the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Programme during 1993-2001 to evaluate national and regional relations with water chemistry and to compare whether algal-metric values differ significantly among undeveloped and developed land-use classifications.

2. Algal metrics with significant positive correlations with nutrient concentrations included indicators of trophic condition, organic enrichment, salinity, motility and taxa richness. The relative abundance of nitrogen-fixing algae was negatively correlated with nitrogen concentrations, and the abundance of diatom species associated with high dissolved oxygen concentrations was negatively correlated with both nitrogen and phosphorus concentrations. Median algal-metric values and nutrient concentrations were significantly lower at undeveloped sites than those draining agricultural or urban catchments.

3. Total algal biovolume did not differ significantly among major river catchments or land-use classifications, and was only weakly correlated with nitrate (positive) and suspended-sediment (negative) concentrations. Estimates of periphyton chlorophyll a indicated an oligotrophic-mesotrophic boundary of about 21 mg m(-2) and a mesotrophic-eutrophic boundary of about 55 mg m(-2) based on upper and lower quartiles of the biovolume data distribution.

4. Although algal species tolerance to nutrient and organic enrichment is well documented, additional taxonomic and autecological research on sensitive, endemic algal species would further enhance water-quality assessments.

Abstract  Increased nutrient concentrations in streams and rivers have altered biological Structure and function. Manipulative studies have provided insights into different mechanisms by which changes in nutrient concentrations influence aquatic biota. but these studies are limited in spatial scope and in their quantification of nutrient effects oil aggregate measures of the invertebrate assemblage. Observational data provide it complementary Source of information to manipulative studies, but these data must be analyzed Such that the potential effects Of Spurious correlations are minimized. Propensity scores, a technique developed to analyze human health observational data, are applied here to estimate the effects of increased nutrients oil the total taxon richness of stream invertebrates in a large observational data set collected from the western United States. The analysis indicates that increases in nutrient concentration are strongly associated with and Cause decreases in invertebrate richness ill large, but wadeable, open-canopied streams. These decreases in invertebrate richness were not mediated by periphyton biomass, a commonly proposed mechanism by which nutrients influence invertebrates. fit smaller, closed-canopied streams, increases in nutrients Were associated with small increases in total richness that were not statistically significant. Using propensity scores can greatly improve the accuracy of insights drawn from observational data by minimizing the potential that factors other than the factor of interest may Confound the results.

Abstract  Because the Truckee River connects two lakes along the Eastern Sierra Nevada Mountains with different limiting nutrients, this research addresses whether the nitrogen: phosphorus (N:P) balance of the river ecosystem changes longitudinally. Historical (1990 to 2000) total nitrogen:total phosphorus (TN:TP) ratios in river water exhibited the expected gradient from high N:P ratios upstream to low N:P ratios downstream, with the major gradient of the NT balance occurring within the transition between montane and high desert terrain. During 2001, the river contained anomalously low total nitrogen concentrations in the far upper reaches and dissolved inorganic nitrogen concentrations in the lower reaches, resulting in a less apparent longitudinal gradient of NT ratios. Measurements of periphyton growth and physiology (nutrient bioassays and ectoenzyme activities) and stoichiometry during the summer of 2001 also exhibited a complex picture of the spatial variation of N:P balance that was not entirely consistent with a strong N:P gradient. However, the compendium of the indicators did support the overall picture of an overarching longitudinal gradient from high to low N:P ratios. The results suggest that periphyton management efforts in the Truckee River should consider the overall spatial gradient as well as the small-scale dynamics of the stream ecosystem structure.

Abstract  Recent comparisons of benthic macroinvertebrate (BMI) sampling protocols have shown that samples collected from different habitat types generally produce consistent stream classifications and assessments. However, these comparisons usually have not included biological endpoints used by monitoring agencies, such as multimetric indices (e.g., benthic index of biotic integrity [B-IBI]) or observed-to-expected (O/E) indices of taxonomic completeness, as target variables, and estimates of method precision are rarely provided. Targeted-riffle (TR) and reach-wide (RW) benthic samples have been collected at thousands of sites across the western USA, but little guidance is available for understanding: 1) the extent to which raw data sets can be combined in regional or large-scale analyses, 2) the degree of precision afforded by each method, or 3) the efficacy of cross-application of biological indicators derived from one sample type to the other. To address these issues, we used data from 193 sites in California where the Environmental Monitoring and Assessment Program (EMAP) collected the 2 samples side by side. We also conducted a separate study wherein 3 replicates of each sample type were collected from 15 streams to estimate minimum detectable difference (MDD) as a measure of each method's precision. Metrics calculated from TR and RW samples showed similar dose?response relationships to stressor gradients and similar raw scoring ranges. Biological indices (B-IBI, O/E0, and O/E50) derived from RW samples were more precise than those derived from TR samples, but precision differences were not substantial. On average, pairwise differences in any index between TR and RW sample types were much less than the MDD associated with either sampling method. We observed a weak but consistent bias toward higher O/E50 scores from TR samples than from RW samples at the highest elevations and in the largest watersheds. Broad-scale condition assessments were nearly identical when B-IBI and O/E0 were used as endpoints, and assessments based on O/E50 were only slightly less similar. Our analyses indicate that raw data sets and biological indicators derived from TR and RW samples may be generally interchangeable when used in ambient biomonitoring programs. Recent comparisons of benthic macroinvertebrate (BMI) sampling protocols have shown that samples collected from different habitat types generally produce consistent stream classifications and assessments. However, these comparisons usually have not included biological endpoints used by monitoring agencies, such as multimetric indices (e.g., benthic index of biotic integrity [B-IBI]) or observed-to-expected (O/E) indices of taxonomic completeness, as target variables, and estimates of method precision are rarely provided. Targeted-riffle (TR) and reach-wide (RW) benthic samples have been collected at thousands of sites across the western USA, but little guidance is available for understanding: 1) the extent to which raw data sets can be combined in regional or large-scale analyses, 2) the degree of precision afforded by each method, or 3) the efficacy of cross-application of biological indicators derived from one sample type to the other. To address these issues, we used data from 193 sites in California where the Environmental Monitoring and Assessment Program (EMAP) collected the 2 samples side by side. We also conducted a separate study wherein 3 replicates of each sample type were collected from 15 streams to estimate minimum detectable difference (MDD) as a measure of each method's precision. Metrics calculated from TR and RW samples showed similar dose?response relationships to stressor gradients and similar raw scoring ranges. Biological indices (B-IBI, O/E0, and O/E50) derived from RW samples were more precise than those derived from TR samples, but precision differences were not substantial. On average, pairwise differences in any index between TR and RW sample types were much less than the MDD associated with either sampling method. We observed a weak but consistent bi s toward higher O/E50 scores from TR samples than from RW samples at the highest elevations and in the largest watersheds. Broad-scale condition assessments were nearly identical when B-IBI and O/E0 were used as endpoints, and assessments based on O/E50 were only slightly less similar. Our analyses indicate that raw data sets and biological indicators derived from TR and RW samples may be generally interchangeable when used in ambient biomonitoring programs.