Abstract  The U.S. Geological Survey determined seasonal variability in nutrients, carbon, and algal biomass in 22 wadeable streams over a 1-year period during 2007 or 2008 within three geographically distinct areas in the United States. The three areas are the Upper Mississippi River Basin (UMIS) in Minnesota, the Ozark Plateaus (ORZK) in southern Missouri and northern Arkansas, and the Upper Snake River Basin (USNK) in southern Idaho. Seasonal patterns in some constituent concentrations and algal responses were distinct. Nitrate concentrations were greatest during the winter in all study areas potentially because of a reduction in denitrification rates and algal uptake during the winter, along with reduced surface runoff. Decreases in nitrate concentrations during the spring and summer at most stream sites coincided with increased streamflow during the snowmelt runoff or spring storms indicating dilution. The continued decrease in nitrate concentrations during summer potentially is because of a reduction in nitrate inputs (from decreased surface runoff) or increases in biological uptake. In contrast to nitrate concentrations, ammonia concentrations varied among study areas. Ammonia concentration trends were similar at UMIS and USNK sampling sites with winter peak concentrations and rapid decreases in ammonia concentrations by spring or early summer. In contrast, ammonia concentrations at OZRK sampling sites were more variable with peak concentrations later in the year. Ammonia may accumulate in stream water in the winter under ice and snow cover at the UMIS and USNK sites because of limited algal metabolism and increased mineralization of decaying organic matter under reducing conditions within stream bottom sediments. Phosphorus concentration patterns and the type of phosphorus present changes with changing hydrologic conditions and seasons and varied among study areas. Orthophosphate concentrations tended to be greater in the summer at UMIS sites, whereas total phosphorus concentrations at most UMIS and USNK sites peaked in the spring during runoff and then decreased through the remainder of the sampling period. Total phosphorus and orthophosphate concentrations in OZRK streams peaked during summer indicating a runoff-based source of both nutrients. Orthophosphate concentrations may increase in streams in the late summer when surface runoff composes less of total streamflow, and when groundwater containing orthophosphate becomes a more dominant source in streams during lower flows. Seston chlorophyll a concentrations were greatest early in the growing season (spring), whereas the spring runoff events coincided with reductions in benthic algal chlorophyll a biomass likely because of scour of benthic algae from the channel bottom that are entrained in the water column during that period. Nitrate, ammonia, and orthophosphate concentrations also decreased during that same period, indicating dilution in the spring during runoff events. The data from this study indicate that the source of water (surface runoff or groundwater) to a stream and the intensity of major runoff events are important factors controlling instream concentrations. Biological processes appear to affect nutrient concentrations during more stable lower flow periods in later summer, fall, and winter when residence time of water in a channel is longer, which allows more time for biological uptake and transformations. Management of nutrient conditions in streams is challenging and requires an understanding of multiple factors that affect in-stream nutrient concentrations and biological uptake and growth.

Abstract  The Mississippi Department of Environmental Quality is required to develop restoration and remediation plans for water bodies not meeting their designated uses, as stated in the U.S. Environmental Protection Agency's Clean Water Act section 303(d). The majority of streams in northwestern Mississippi are on the 303(d) list of water-quality limited waters. Agricultural effects on streams in northwestern Mississippi have reduced the number of unimpaired streams (reference streams) for water-quality comparisons. As part of an effort to develop an index to assess impairment, the U.S. Geological Survey collected water samples from 52 stream sites on the 303(d) list during May-June 2006, and analyzed the samples for nutrients and chlorophyll. The data were analyzed by trophic group as determined by total nitrogen concentrations. Seven constituents (nitrite plus nitrate, total Kjeldhal nitrogen, total phosphorus, orthophosphorus, total organic carbon, chlorophyll a, and pheophytina) and four physical property measurements (specific conductance, pH, turbidity, and dissolved oxygen) were determined to be significantly different (p 0.05) between trophic groups. Total Kjeldhal nitrogen, turbidity, and dissolved oxygen were used as indicators of stream productivity with which to infer stream health. Streams having high total Kjeldhal nitrogen values and high turbidity values along with low dissolved oxygen concentrations were typically eutrophic abundant in nutrients), whereas streams having low total Kjeldhal nitrogen values and low turbidity values along with high dissolved oxygen concentrations were typically oligotrophic (deficient in nutrients).

Abstract  The influence of environmental factors on biotic responses to nutrients was examined in three diverse agricultural regions of the United States. Seventy wadeable sites were selected along an agricultural land use gradient while minimizing natural variation within each region. Nutrients, habitat, algae, macroinvertebrates, and macrophyte cover were sampled during a single summer low-flow period in 2006 or 2007. Continuous stream stage and water temperature were collected at each site for 30 days prior to sampling. Wide ranges of concentrations were found for total nitrogen (TN) (0.07-9.61 mg/l) and total phosphorus (TP) (< 0.004-0.361 mg/l), but biotic responses including periphytic and sestonic chlorophyll a (RCHL and SCHL, respectively), and percent of stream bed with aquatic macrophyte (AQM) growth were not strongly related to concentrations of TN or TP. Pearson's coefficient of determination (R2) for nutrients and biotic measures across all sites ranged from 0.08 to 0.32 and generally were not higher within each region. The biotic measures (RCHL, SCHL, and AQM) were combined in an index to evaluate eutrophic status across sites that could have different biotic responses to nutrient enrichment. Stepwise multiple regression identified TN, percent canopy, median riffle depth, and daily percent change in stage as significant factors for the eutrophic index (R2 = 0.50, p < 0.001). A TN threshold of 0.48 mg/l was identified where eutrophic index scores became less responsive to increasing TN concentrations, for all sites. Multiple plant growth indicators should be used when evaluating eutrophication, especially when streams contain an abundance of macrophytes.

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  Nutrient enrichment, in particular by nitrogen and phosphorus, can result in the proliferation of algal biomass and may have implications for ecosystem health. The United States Environmental Protection Agency (EPA) has required the states to develop nutrient criteria for waterbodies within their jurisdictions. In response to the development of nutrient criteria guidance documents by EPA, based in part at least upon the assumptions of periphyton and water column chlorophyll a (chl a) relationships with total nitrogen (TN) and total phosphorus (TP), nutrient and chl a data collected as part of NCASI’s Long-Term Receiving Water Study (LTRWS) were examined to determine spatial and temporal variation in nutrient concentrations, periphyton chlorophyll a (chl a), and water column chl a, and nutrient-chl a relationships. Nutrient and chl a patterns were examined in the four LTRWS rivers (Codorus Creek, and the Leaf, McKenzie, and Willamette Rivers) with respect to spatial (site relative to mill location) and temporal (year and season) variation to determine the applicability and relevance of EPA’s guidelines to these systems. Measured TN and TP concentrations were not influenced by the mill discharges at any of the four study locations. Seasonal nutrient concentrations were generally greatest in Codorus Creek (TN=2.4 to 5.3 mg/L, TP=0.08 to 0.18 mg/L) with mean seasonal TN and TP concentrations in the other rivers ranging from 0.07 to 1.1 mg/L and 0.05 to 0.22 mg/L, respectively. Mean seasonal TN concentration in the LTRWS river tributary streams was greater than concentrations in the main channels of Codorus Creek and the Willamette River, but similar or lower to that seen in the Leaf and McKenzie Rivers.

Abstract  Biocriteria are becoming increasingly adopted into monitoring programs and formally adopted into water quality standards intended to protect waters from deterioration. Biological monitoring programs have typically focused on fish and macroinvertebrate communities, largely excluding benthic algae communities. However, many states are examining the use of algal communities, especially diatoms, as ecological indicators because of their clear response to physical and chemical environmental changes, brief life cycles and rapid rates of reproduction, and specific ecological requirements that correlate strongly with environmental conditions. Spatial and temporal patterns of diatom diversity (Diatom Species Richness, Shannon-Wiener Diversity Index, % Dominant Taxa) and ecological descriptive (%Achnanthes minutissima, Pollution Tolerance Index, % Sensitive Diatoms, % Motile Diatoms) measures were examined in the Long-Term Receiving Waters Study (LTRWS) rivers (Codorus Creek, Leaf River, McKenzie River, Willamette River) to determine the usefulness of this group in determining site differences. Additionally, the relationship between these metrics and the concentration of total nitrogen (TN) and total phosphorus (TP) was studied. The only clear spatial pattern in metric response occurred in diversity measures in Codorus Creek. However, this pattern was unrelated to the mill location with sites in the upper reach (both upstream and downstream of mill effluent) having greater species richness and diversity than sites in the lower reach of the study area. Metric patterns were more variable across sites and sampling periods in the other LTRWS rivers, but unrelated to mill location. The relationship between metric score and TN and TP concentrations was river-dependent. In Codorus Creek and the McKenzie and Willamette Rivers, metric-nutrient patterns collected from rock substrates were generally weak. Formost metric-nutrient relationships, nutrient concentration accounted for less than 5% of the variation in metric response, with ecological descriptive measures showing stronger nutrient relationships than diversity metrics. There was a relatively strong relationship between algal metrics and nutrient concentrations in the Leaf River, but relationships differed with natural (sand) or artificial (Hester-Dendy Plate (HD) Samplers) substrate. For both substrate types, there was a relationship between TN and TP and motile diatoms (negative) and sensitive diatoms (positive). Significant relationships between TN and TP and Shannon-Wiener Diversity Index (negative) and % Dominant Taxa (positive) were seen only with algal communities on HD samplers. For most Leaf River metrics, the amount of variation in measures explained by nutrient concentration was greater for TP (21 to 66%) than for TN (29 to 33%). The ratio of TN:TP accounted for a significant amount of variation in all HD sampler algal metrics except % Achnanthes minutissima. In contrast, only the percent abundance of sensitive diatoms was significantly related to TN:TP in sand communities. The ratio of TN to TP accounted for 26 to 61% of the variation in metric response for all metrics showing significant TN:TP relationships. Variation in metric response across sites was not related to a measured Stressor and Biocriteria are becoming increasingly adopted into monitoring programs and formally adopted into water quality standards intended to protect waters from deterioration. Biological monitoring programs have typically focused on fish and macroinvertebrate communities, largely excluding benthic algae communities. However, many states are examining the use of algal communities, especially diatoms, as ecological indicators because of their clear response to physical and chemical environmental changes, brief life cycles and rapid rates of reproduction, and specific ecological requirements that correlate strongly with environmental conditions. Spatial and temporal patterns of diatom diversity (Diatom Species Richness, Shannon-Wiener Diversity Index, % Dominant Taxa) and ecological descriptive (% Achnanthes minutissima, Pollution Tolerance Index, % Sensitive Diatoms, % Motile Diatoms) measures were examined in the Long-Term Receiving Waters Study (LTRWS) rivers (Codorus Creek, Leaf River, McKenzie River, Willamette River) to determine the usefulness of this group in determining site differences. Additionally, the relationship between these metrics and the concentration of total nitrogen (TN) and total phosphorus (TP) was studied. The only clear spatial pattern in metric response occurred in diversity measures in Codorus Creek. However, this pattern was unrelated to the mill location with sites in the upper reach (both upstream and downstream of mill effluent) having greater species richness and diversity than sites in the lower reach of the study area. Metric patterns were more variable across sites and sampling periods in the other LTRWS rivers, but unrelated to mill location. The relationship between metric score and TN and TP concentrations was river-dependent.