Abstract  1. We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution [total-P, total-N, NH(4)-N, biological oxygen demand (BOD(5))] from 594 Danish stream sites. Samples were taken over an 11-year time span as part of the Danish monitoring programme on the aquatic environment. Macroinvertebrate communities were sampled in spring using a standardised kick-sampling procedure whereas chemical variables were sampled six to 24 times per year per site. Habitat variables were assessed once when macroinvertebrates were sampled. The plecopteran Leuctra showed a significant negative exponential relationship (r2 = 0.90) with BOD(5) and occurred at only 16% of the sites with BOD(5) above 1.6 mg L-1. Sharp declines with increasing BOD(5) levels were found for the trichopteran families Sericostomatidae and Glossosomatidae although they appeared to be slightly less sensitive than Leuctra. Other plecopterans such as Isoperla showed a similar type of response curve to Leuctra (negative exponential) but occurred at sites with relatively high concentrations of BOD(5) up to 3-4 mg L-1. In contrast, the response curve of the isopod Asellus aquaticus followed a saturation function reaching a plateau above 3-4 mg L-1 BOD(5) and the dipteran Chironomus showed an exponential increase in occurrence with increasing BOD(5) concentration. Macroinvertebrate occurrence appeared to be related primarily to concentrations of BOD(5), NH(4)-N and total-P whereas there were almost no relationships to total-N. Occurrence of a number of taxa showed a stronger relationship to habitat conditions (width and substrate) than chemical variables. Important macroinvertebrate taxa are reduced at concentrations of BOD(5) that are normally perceived as indicating unimpacted stream site conditions. Our results confirmed sensitivity/tolerance patterns used by existing bioassessment systems only to some degree.

Abstract  Phytoplankton biomass is an important indicator for water quality, and predicting its dynamics is thus regarded as one of the important issues in the domain of river ecology and management. However, the vast majority of models in river systems have focused mostly on flow prediction and water quality with very few applications to biotic parameters such as chlorophyll a (Chl a). Based on a 1.5-year measured dataset of Chl a and environmental variables, we developed two modeling approaches [artificial neural networks (ANN) and multiple linear regression (MLR)] to simulate the daily Chl a dynamics in a German lowland river. In general, the developed ANN and MLR models achieved satisfactory accuracy in predicting daily dynamics of Chl a concentrations. Although some peaks and lows were not predicted, the predicted and the observed data matched closely by the MLR model with the coefficient of determination (R (2)), Nash-Sutcliffe efficiency (NS), and the root mean square error (RMSE) of 0.53, 0.53, and 2.75 for the calibration period and 0.63, 0.62, and 1.94 for the validation period, respectively. Likewise, the results of the ANN model also illustrated a good agreement between observed and predicted data during calibration and validation periods, which was demonstrated by R (2), NS, and RMSE values (0.68, 0.68, and 2.27 for the calibration period, 0.55, 0.66 and 2.12 for the validation period, respectively). According to the sensitivity analysis, Chl a concentration was highly sensitive to dissolved inorganic nitrogen, nitrate-nitrogen, autoregressive Chl a, chloride, sulfate, and total phosphorus. We concluded that it was possible to predict the daily Chl a dynamics in the German lowland river based on relevant environmental factors using either ANN or MLR models. The ANN model is well suited for solving non-linear and complex problems, while the MLR model can explicitly explore the coefficients between independent and dependent variables. Further studies are still needed to improve the accuracy of the developed models.

Abstract  In this study, the seasonal variations in distribution and abundance of epipelic and epilithic diatoms were investigated at 4 stations selected on Batman Stream between April and September 2009. Sampling was performed monthly, and water temperature, electrical conductivity, pH and concentrations of total dissolved solid matter, dissolved oxygen, total hardness, organic matter, nitrite, nitrate, total nitrogen, phosphate, total phosphorus, sulphate, silica and chlorophyll-a were measured and analysed. Diatoms (Bacillariophyta) were the most important algal group in Batman Stream, in terms of number of species and abundance. A total of 49 diatom taxa were identified. Navicula, Cymbella, Nitzschia and Gomphonema were richest in species numbers. The taxon numbers in epipelon were higher than those recorded in epilithon. Cymbella affinis, Cyclotella ocellata and Diatoma vulgare occurred with higher individual numbers in epilithon whilst C. affinis, Tabularia fasciculata and Ctenophora pulchella were more conspicuous in epipelon. Batman River has got Class I in water quality according to the Water Quality Criteria.

Abstract  To define water quality, the European Water Framework Directive (WFD) demands complex assessments through physicochemical, biological, and hydromorphological controls of water bodies. Since the biological assessment became the central focus with hydrochemistry playing a supporting role, an evaluation of the interrelationships within this approach deems necessary. This work identified and tested these relationships to help improve the quality and efficiency of related efforts. Data from the 384 km(2) Weisseritz catchment (eastern Erzgebirge, Saxony, Germany and northern Bohemia, Czech Republic) were used as a representative example for central European streams in mountainous areas. The data cover the time frame 1992 to 2003. To implement WFD demands, the analysis was based on accepted German methods and classifications, WFD quality standards, and novel German methods for the biological status assessment. Selected chemical parameters were compared with different versions of the German Saprobic Index, based on macroinvertebrate indicator taxa. Relevant dependencies applicable for integrated stream assessment were statistically tested. Correlation analysis showed significant relationships. The highest scores were found for nutrients (NO(2)(-), N(inorg), and total N), salinity (Cl(-), SO(4)(2-), conductivity), and microelements (K(+), Na(+), Ca(2+), Mg(2+)). The Saprobic Index used in the Integrated Assessment System for the Ecological Quality of Streams and Rivers throughout Europe using Benthic Macro-invertebrates program seems to be the most sensitive indicator to correlate with chemical parameters.

Abstract  This study aimed to characterize the abundance and community structure of epilithic algae and to examine the effects of intensive agriculture in mountain streams of the Wuling area. There were significant seasonal variations in epilithic algal biomass, with higher values in spring and winter and lower values in summer and fall. Effects of agriculture on the subtropical streams of the Wuling area were significant and varied with the extent of agriculture in the catchment. The biomass was significantly higher in Yousheng Stream with a larger area of agriculture than in other streams. Diatoms were the most abundant species, contributing over 85% to the total cell number. Most of these were pennatae diatoms, of which the genus Achnanthidium was the most abundant in the area. However, the communities showed clear seasonal and spatial changes. BIOENV analysis suggested that the combination of water temperature, conductivity, NO(2)+NO(3) and SiO(2) concentrations and current velocity comprised the major factors explaining seasonal changes in the community, while the combination of NO(2)+NO(3) and SiO(2) concentration and grazer density comprised the major factors affecting spatial changes. Changes in abundance and community structure of epilithic algae can be used to monitor the effects of agriculture in tropical/subtropical mountain streams.

Abstract  1. There is compelling evidence that anthropogenic disturbance can decrease biodiversity and impair ecological functioning. A major challenge to biodiversity-ecosystem function research is to disentangle the effects of biodiversity loss on ecosystem functions from the direct effects of human disturbance.

2. We studied the influence of human disturbance (acidification and eutrophication) and a natural stressor (low pH due to bedrock geology) on leaf-shredding macroinvertebrates, fungal decomposers and leaf decomposition rates in boreal streams. We used pyrosequencing techniques to determine fungal richness and assemblage structure.

3. Decomposition rates were higher in anthropogenically disturbed than in circumneutral reference or naturally acidic sites, but did not differ between the latter two groups. Macroinvertebrate richness was higher in circumneutral than in human-impacted or naturally acidic sites, and shredder evenness was highest in circumneutral sites. Fungal evenness was also lower in human-disturbed than in reference sites, whereas fungal richness did not vary among site groups.

4. Decomposition rate in fine-mesh bags was related positively to current velocity and fungal dominance, while in coarse-mesh bags, it was related positively to total phosphorus. In anthropogenically disturbed streams, the effects of low pH were overridden by eutrophication, and increased decomposition rates resulted from disturbance-induced increase in species dominance rather than richness. Furthermore, decomposition rates were positively correlated with abundances of dominant taxa, suggesting that ecosystem processes may be driven by a few key species.

5. Synthesis and applications. Our results suggest that leaf decomposition rates are insensitive to natural background variation, supporting the use of decomposition assays, preferably accompanied by molecular analysis of fungal assemblages, to assess stream ecosystem health. Instead of focusing solely on diversity, however, more emphasis should be placed at changes in dominance patterns, particularly if management aims are to improve stream ecosystem functioning.

Abstract  We investigated relationships between sestonic chlorophyll (Chl), total phosphorus (TP), and total nitrogen (TN) at 23 sites an 13 streams in the Missouri Ozarks. There was a strong curvilinear relationship between mean sestonic Chi and both mean TP (R-2 = 0.78) and mean TN (R-2 = 0.70). Both models were improved when catchment area was included with either TP (R-2 = 0.90) or TN (R-2 = 0.84). Limited to 17 sites without point source nutrient additions, the relationship between sestonic Chi and both TP and TN was linear Including catchment area strengthened linear models with either TP (R-2 = 0.94) or TN (R-2 = 0.84). Land use (percent row crop or percent forest), together with catchment size, was also a good predictor of sestonic Chl in Ozark streams without point sources. When catchment area and TP or TN were used to predict sestonic Chi on specific dates following catastrophic flooding, models were less accurate than those based on long-term averages, but still explained 55-74% of the variance in sestonic Chi. Our results demonstrate that sestonic Chi is closely associated with nutrients and catchment area in Ozark streams and that nutrient - sestonic Chl models may have broad application in running waters.

Abstract  A better understanding of the controls on algae and dissolved O2 in agricultural streams of Illinois is needed to aid in development of nutrient standards. We investigated the relationships between dissolved nutrients, algal abundance, and dissolved O2 in five streams in east-central Illinois from March through November 2004. The streams drained watersheds from 25 to 777 km2 that were dominated by row crop agriculture. Three sites had open canopies and two were bordered by a narrow forest of deciduous trees. Algal abundance was measured as chlorophyll-a (chl-a) concentration in the water column (sestonic) and on the streambed (periphytic). Mean NO3-N concentrations ranged from 5.5 to 8.8 mg N L(-1) and did not relate to algal abundance. Sestonic chl-a values ranged from nearly zero to >15 mg m(-3) with no differences between open and shaded streams and only a weak correlation with dissolved reactive P (mean concentrations were 44-479 microg L(-1)). The results suggest that sestonic chl-a is a poor criterion for assessing nutrient-related problems in these streams. Greatest periphytic chl-a occurred during low flow from August through October, but periphyton occurred consistently in only two of the five streams. The abundance of filamentous algae explained 64% of the variation in diel O2 saturation, but was not correlated with nutrients. Currently it appears that hydrology and light, rather than nutrients, control algal abundance in these streams, and in the agricultural landscape of east-central Illinois, it may not be possible to reduce nutrient concentrations sufficiently to limit filamentous algal blooms.

Abstract  The Clean Water Action Plan of 1998 provides a blueprint for federal agencies to work with states, tribes, and other stakeholders to protect and restore the Nation's water resources. The plan includes an initiative that addresses the nutrient-enrichment problem of lakes and streams across the United States. The U.S. Environmental Protection Agency (USEPA) is working to set nutrient criteria by nationwide nutrient ecoregions that are an aggregation of the Omernik level III ecoregions. Because low levels of nutrients are necessary for healthy streams and elevated concentrations can cause algal blooms that deplete available oxygen and kill off aquatic organisms, criteria levels are to be set, in part, using the relation between chlorophyll a and concentrations of total nitrogen and total phosphorus. Data from Pennsylvania and West Virginia, collected between 1990 and 1998, were analyzed for relations between chlorophyll a, nutrients, and other explanatory variables. Both phytoplankton and periphyton chlorophyll a concentrations from lakes and streams were analyzed separately within each of the USEPA nutrient ecoregions located within the boundaries of the two states. These four nutrient ecoregions are VII (Mostly Glaciated Dairy), VIII (Nutrient Poor, Largely Glaciated Upper Midwest and Northeast), IX (Southeastern Temperate Forested Plains and Hills), and XI (Central and Eastern Forested Uplands). Phytoplankton chlorophyll a concentrations in lakes were related to total nitrogen, total phosphorus, Secchi depth, concentration of dissolved oxygen, pH, water temperature, and specific conductivity. In nutrient ecoregion VII, nutrients were not significant predictors of chlorophyll a concentrations. Total nitrogen, Secchi depth, and pH were significantly related to phytoplankton chlorophyll a concentrations in nutrient ecoregion IX. Lake periphyton chlorophyll a concentrations from nutrient ecoregion XI were related to total phosphorus rather than total nitrogen, Secchi depth, and pH. In all cases, Secchi depth was inversely related to the chlorophyll a concentrations in a lake. Nutrient ecoregion VIII had too few samples for any type of analysis. Streams within the different nutrient ecoregions had many variables that were significantly related to periphyton chlorophyll a concentrations. These variables consisted of total nitrogen, total phosphorus, drainage area, percent forest cover, several macroinvertebrate indices, pH, basin slope, total residue, total suspended solids, and water temperature. Nutrients were not significantly related to periphyton chlorophyll a in streams within nutrient ecoregions VII or IX but were in nutrient ecoregion XI. Drainage area, percent forest cover, and several invertebrate indices were significant variables in nutrient ecoregion VII. Percent forest cover and several invertebrate indices had a negative relation with chlorophyll a concentrations in these streams. Percent forest cover and basin slope had a negative effect on periphyton in nutrient ecoregion IX streams. Light availability was more critical to periphyton growth in streams than nutrients. Ecoregion XI had enough samples to do seasonal analyses. Summer-season periphyton chlorophyll a concentrations in nutrient ecoregion XI streams were positively related to total phosphorus and drainage area but negatively related to percent forest cover. Summer-season phytoplankton in streams was related to different variables within the same nutrient ecoregion. Both total nitrogen and total phosphorus were positively related with chlorophyll a concentrations as well as basin slope, total residue, and total suspended solids but negatively related to pH. The winter stream phytoplankton chlorophyll a concentrations were related to water temperature only.

Abstract  Variation in watershed land use is known to influence the physical and chemical conditions in resident streams; however, few studies have evaluated variation in ecosystem structure and function, in a quantitative sense, whereby specific environmental break-points in land use could be defined. We conducted seasonal sampling (spring, summer, and fall of 2005-2006) in 43 third order streams that were representative of conditions throughout the mid-Atlantic region. Stream physical, biological, and chemical conditions were measured as represented by 19 environmental variables (physical-chemical), in addition to benthic chlorophyll concentrations and the relative abundance of diatom species collected from each stream. Watershed forest cover explained significant variation in stream benthic chlorophyll (stepwise linear regression, r(2) = 39.2 %) as selected from a set of relevant variables (total nitrogen, total phosphorus, % Forest cover, and stream temperature). Benthic chlorophyll (range 0.1 to 917 mg m(-2)) and nutrient tolerant diatom guilds were inversely correlated with forest cover, while nutrient sensitive diatom species had a positive correlation. Loess trend analysis coupled with regression tree analysis (RPART) identified abrupt changes in benthic chlorophyll and the relative abundance of diatom nutrient guilds at breakpoints of 60 % and 80 % forest cover. Despite the correlative nature of this study, the findings here suggest individual ecosystems may exhibit abrupt changes in ecosystem function following declines in forest cover, particularly at the breakpoints identified here.

Abstract  The taxonomic composition and size structure of benthic macroinvertebrate assemblages from twelve streams were studied in relation to differences in trophic conditions. Orthocladiinae (Diptera: Chironomidae) were numerically dominant at 11 of the 12 sites, however the Hydropsychidae (Trichoptera) attained the highest biomass. Principal component analysis revealed differences in the composition of assemblages among rural and urban sites. Rural sites had higher densities of sensitive taxa such as Ephemeroptera, Chironominae and Simuliidae, while urban sites had higher densities of tolerant taxa such as Oligochaeta. Site scores on the first principal component, explaining the most taxonomic variability between regions, were significantly related to the nutrient differences between the rural and urban streams. The mean annual spectrum for the entire assemblage followed a unimodal distribution peaking at the 8 $\mu$g (dry mass) size class. Polynomial regression models fitted to the abundance per size class for the entire assemblage revealed a weak positive relationship with total phosphorus (TP). Subsequent analyses on the mean size spectra of seven dominant taxa revealed that the Oligochaeta and Hydroptilidae have significantly higher densities in the urban sites, which contain high TP, while the Ephemeroptera and Chironominae have significantly lower densities in these sites. The three other dominant taxa, including the Hydropsychidae, Tanypodinae and Orthocladiinae showed less obvious differences in densities per size class between regions. These results demonstrate that although the size spectra of the entire community may not be greatly influenced by differences in stream eutrophication, the spectra of certain key taxa do show responses of a higher magnitude. This discrepancy in detecting responses suggests that the size distribution of entire benthic assemblages is resilient to differences in stream productivity, despite significant changes in the taxonomic composition.

Abstract  This report reviews activities conducted by the Academic Advisory Committee to the Virginia Department of Environmental Quality (DEQ) between July and December 2006. Activities were conducted for the purpose of developing recommendations for DEQ regarding nutrient criteria for freshwater rivers and streams. In its June 2006 report to DEQ, the AAC recommended that DEQ establish nutrient criteria for rivers and streams by addressing independently the two effects described by the Environmental Protection Agency (EPA): localized and downstream-loading effects. The current report and activities address nutrient criteria development within that framework. Section I of this report addresses the development of screening values for wadeable streams. Reference (i.e., characteristics of relatively undisturbed or least disturbed streams) and effect-threshold concentrations for in-stream nutrients that have been suggested by other studies are reviewed. Reference values for total nitrogen (TN) and total phosphorus (TP) tend to vary by U.S. EPA's Nutrient Ecoregions and are generally higher in the eastern portions of the state than in the west. Effect-threshold values derived from other studies tend to vary more widely in part due to the variety of effect endpoints that have been employed in developing these threshold-concentration estimates. A review of TMDL studies that have been completed for nutrient-impaired streams revealed few usable reference concentrations because they are generally load-based studies (and do not report the streamflow information that could be used to calculate nutrient concentrations). An analysis of DEQ monitoring data found that Stream Condition Index (SCI, an indicator of benthic macroinvertebrate community status) values tend to vary negatively with nutrient concentrations. When using a statewide data set, these data allow the development of statistically significant regression models of the in-stream nutrient-SCI relationships. Application of these models yields "critical values" (i.e., nutrient values corresponding with the SCI = 60 impairment threshold) for TN (0.8 mg/L), total Kjeldahl nitrogen (TKN) (0.3 mg/L), and TP (0.05 mg/L). However, even after a data-selection process intended to focus analysis on sites where no influence by non-nutrient stressors is evident, the variability of SCI response to nutrients is large; thus, the analysis did not allow direct derivation of appropriate screening values.

Abstract  Using a spatially extensive urban database constructed from the Maryland Biological Stream Survey (MBSS), we describe the relationships of nutrients in small-order streams to eight defined categories of percent catchment urbanization, correlations between chloride and conductivity in urban streams, and relationships between nutrients and chloride with two Maryland-specific indices of biotic integrity for benthic macroinvertebrates and fish assemblages. Stream nutrients become elevated with increasing percent catchment urbanization, followed by increases in all four measured nitrogen species and total phosphorus at catchment urbanization levels greater than 10%. There was a strong collinear relationship (r ² = 0.90) between chloride and conductivity (trimeans) across all eight urbanization classes, where Cl (mg/L) = −0.397 + 0.188*conductivity (μS/cm). Critical values for all water quality parameters with the two Maryland biological indices were derived using quantile regression, with significant regressions developed for 11 of 16 water quality parameters and the two biotic indices. For nitrate (NO₃-N), the critical thresholds between fair and poor stream quality for the two Maryland biological indices were 0.83 mg/L (benthic macroinvertebrate assemblages) and 0.86 mg/L (fish assemblages). Increasing stream nutrient and chloride levels, associated with widespread catchment urbanization intensity, now affect many small streams in Maryland, with implications for decreasing water quality in major tributaries and the Chesapeake Bay.

Abstract  Water eutrophication is a global problem, and one of the major environmental problems in China. At present, its studies in China are mainly focused on lakes and reservoirs, whereas a few on rivers. Based on the stress-response of benthic macroinvertebrate assemblages to water nutrients, we used the nonparametric deviance reduction (change point analysis) to compute the breakpoints of nutrients concentrations, in the upper reaches of Xitiao Stream in Zhejiang. The results indicated that the breakpoints of total nitrogen (TN) and total phosphors (TP) were 1.409 mg x L(-1) and 0.033-0.035 mg x L(-1), respectively. The TN and TP concentrations at reference sites were lower, while those at urban sewage- polluted sites were higher than the thresholds. In latter case, a serious degradation of benthic macroinvertebrates assemblages could be induced. To establish water nutrients criteria with relation to aquatic organisms would make the biological monitoring play a full role in water management, and provide scientific data to estimate the total maximum daily load (TMDL) of TN and TP in water body.

Abstract  The principal environmental factors influencing the seasonal dynamics of phytoplankton were examined from September 1997 to July 1998 in three stations along a 26-km stretch of the lowland course of River Adige (northeast Italy). Nutrient concentrations did not appear to be limiting for the phytoplankton growth. Annual minimum concentrations of reactive and total phosphorus, and dissolved inorganic nitrogen were 22 mu g P l-1, 63 mu g P l-1 and 0.9 mg N l-1, respectively. The most critical forcing factors were physical variables, mainly water discharge and other variables related to hydrology, i.e. suspended solids and turbidity, which acted negatively and synchronously by diluting phytoplankton cells and decreasing light availability. Higher algal biomass was recorded in early spring, in conditions of lower flow velocity and increasing water temperature. In late spring and summer, higher water discharge caused a decrease in phytoplankton biomass. Conversely, low algal biomass in late autumn and winter, during low discharge, was mainly related to low water temperatures and shorter photoperiod. Physical constraints had a significant and measurable effect not only on the development of total biomass, but also on the temporal dynamics of the phytoplankton community. Abiotic and biotic variables showed a comparable temporal development in the three sampling stations. The small number of instances of spatial differences in phytoplankton abundance during the period of lower flow velocity were related to the increasing importance of biological processes and accumulation of phytoplankton biomass.

Abstract  

 

This work presents research into the taxonomic composition of macroinvertebrate communities in streams that are under the influence of agricultural pollution A total of 67 macroinvertebrate taxa (including 61 identified species) belonging to 40 families have been identified in the explored streams. The greatest species richness is recorded for the Trichoptera (18 species/1 taxa) and Mollusca (12 species). The molluscs Gyraulus albus, amphipods Gammarus pulex, caddisflies Hydropsyche pellucidula and oligochaetes are detected in all examined streams. There, the number of total benthic macroinvertebrate taxa is highly variable, ranging from 16 to 40. Results show that the examined streams depending on the benthic macroinvertebrate taxonomic composition and predominance of seperate macroinvertebrate groups undergo different pollution. Intolerant to pollution taxa such as Plecoptera, which are the most sensitive to pollution insects, have been found only in 5 of 12 examined streams and in low abundances. The richness and diversity of macrozoobenthos in some streams appear to respond to the water quality deterioration. The present study has found out that in the stream where the total macroinvertebrate taxa, EPT taxa richness are the lowest and a relative abundance of gatherers is the highest, the values of NH₄-N, NO₃-N, total N, PO₄-P and total P in the stream water are the highest, too.

Abstract  Although picophytoplankton (PP) (0.2-2 μm) are ubiquitous in lakes and oceans, their importance in rivers has rarely been studied. We examined PP assemblages during the ice-free period in five rivers of a temperate region varying in trophic state (9-107 μg/L total phosphorus) and water discharge (1-87 m3/s). In these rivers, PP abundance reached concentrations as high as those observed in lakes and oceans (∼104-105 cells/mL). The highest density of PP (4.9 × 105 cells/mL) was observed in the most eutrophic river when the water temperature (28°C) and total phosphorus (293 μg/L) were highest. For the most part, PP abundance was dominated by non-phycoerythrin-containing cyanobacteria; phycocyanin-rich cells accounted for ∼75% of PP abundance in all the rivers. In multiple regression analyses, water temperature and nitrate concentrations explained about half of the variation in PP abundance across the rivers. Discharge had no effect on PP abundance or biomass, whereas it had a significant negative effect on total algal biomass among the rivers. The PP contribution to total chlorophyll-a averaged 27% (ranging 16-46%) and did not decline with increasing nutrients as found in lakes and oceans. The PP biomass from microscopic enumerations reached a maximum of 9% of total phytoplankton biomass, comparable with that observed in lakes. The results of this study demonstrate the importance of including picophytoplankton when analysing phytoplankton communities in rivers. © 2013 The Author.

Abstract  Relationships between distribution of periphytic diatoms and environmental variables in 19 rivers of the Lake Ladoga basin (Northwestern Russia) were examined using gradient analysis. On the basis of geology and river water chemistry, the Lake Ladoga basin could be separated into twomain parts, the northern and the southern sub-basin. The rivers in the northern sub-basin are slightly acidic and low in conductivity (mean value 53 mS cm–1); the rivers in the southern sub-basin have neutral to slightly alkaline waters with higher conductivities (mean value 168 mS cm–1). A detrended correspondence analysis (DCA) defined two groups of rivers generally corresponding to the two main parts of the Lake Ladoga basin. Fragilaria capucina var. rumpens, Frustulia saxonica and Tabellaria flocculosa were the typical species for the northern sub-basin, whereas Cocconeis placentula var. euglypta, Ulnaria ulna and Gomphonema parvulum were characteristic species for the southern sub-basin. A canonical correspondence analysis (CCA) identified conductivity, pH, bicarbonate, total phosphorus and water colour as the most important environmental variables related to changes in assemblage structure. Both DCA and CCA ordination showed that conductivity related to geology was the most important variable, while concentration of total phosphorus was the second most important variable. Weighted averaging was used to infer total phosphorus from relative biomass of diatoms. The predictiveability of the inference model was sufficiently strong with r2 = 0.71 and RMSEP = 1.9 mg L–1. These results strongly support the use of a diatom-based inference phosphorus model for indicating eutrophication in the rivers of the Lake Ladoga basin.

Abstract  Water chemistry, periphyton and seston chlorophyll a (CHLa), and biological community data were collected from 321 sites from 2001 through 2005 to (1) determine statistically and ecologically significant relations among the stressor (total nitrogen, total phosphorus, periphyton and seston CHLa, and turbidity) variables and response (biological community) variables; and, (2) determine the breakpoint of biological community attributes and metrics in response to changes in stressor variables. Because of the typically weak relations among the stressor and response variables, methods were developed to reduce the effects of non-nutrient biological stressors that could mask the effect of nutrients. Stressor variable concentrations ranged from 0.30 to 11.0 milligrams per liter (mg/L) for total nitrogen, 0.025 to 1.33 mg/L for total phosphorus, 2.9 to 768 milligrams per square meter (mg/m2) for periphyton CHLa, and 0.37 to 42 micrograms per liter (ug/L) for seston CHLa. Turbidity, another stressor variable, ranged from 0.8 to 65.4 Nephelometric turbidity units (NTUs). When the nutrient and CHLa data were compared to Dodds' trophic classifications, 75.0 percent of the values for total nitrogen, 46.6 percent of the values for total phosphorus, 35.8 percent of the values for periphyton CHLa, and 3.5 percent of the values for seston CHLa, were eutrophic. The invertebrate communities were dominated by families considered highly nutrient tolerant, Chironimidae, (41.7 percent relative abundance), Hydropsychidae, (17.3 percent relative abundance), and Baetidae, (10.2 percent relative abundance). Fish communities were dominated by algivores and nutrient-tolerant species, specifically central stonerollers (13.3 percent relative abundance), creek chubs (9.9 percent relative abundance), and bluntnose minnows (9.3 percent relative abundance). Although not the dominant taxa, white sucker, spotted sucker, green sunfish, and bluegill species were correlated (p ?0.05) with the stressor variables. The median breakpoints ranged from 2.4 to 3.3 mg/L for total nitrogen, from 0.042 to 0.129 mg/L for total phosphorus, from 54 to 68 mg/m2 for periphyton CHLa, from 4.5 to 7.5 ug/L for seston CHLa, and from 14.1 to 16.1 NTU for turbidity. The breakpoints determined in this study, in addition to Dodds' trophic classifications, were used as multiple lines of evidence to show changes in fish and invertebrate community and attributes based on annual exposure to nutrients.

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  Nutrient enrichment is a frequently cited cause for biotic impairment of streams and rivers in the USA. Efforts are underway to develop nutrient standards in many states, but defensible nutrient standards require an empirical relationship between nitrogen (N) or phosphorus (P) concentrations and some criterion that relates nutrient levels to the attainment of designated uses. Algal biomass, measured as chlorophyll-a (chl-a), is a commonly proposed criterion, yet nutrient-chl-a relationships have not been well documented in Illinois at a state-wide scale. We used state-wide surveys of >100 stream and river sites to assess the applicability of chl-a as a criterion for establishing nutrient standards for Illinois. Among all sites, the median total P and total N concentrations were 0.185 and 5.6 mg L(-1), respectively, during high-discharge conditions. During low-discharge conditions, median total P concentration was 0.168 mg L(-1), with 25% of sites having a total P of > or =0.326 mg L(-1). Across the state, 90% of the sites had sestonic chl-a values of < or =35 microg L(-1), and watershed area was the best predictor of sestonic chl-a. During low discharge there was a significant correlation between sestonic chl-a and total P for those sites that had canopy cover < or =25% and total P of < or =0.2 mg L(-1). Results suggest sestonic chl-a may be an appropriate criterion for the larger rivers in Illinois but is inappropriate for small rivers and streams. Coarse substrate to support benthic chl-a occurred in <50% of the sites we examined; a study using artificial substrates did not reveal a relationship between chl-a accrual and N or P concentrations. For many streams and rivers in Illinois, nutrients may not be the limiting factor for algal biomass due to the generally high nutrient concentrations and the effects of other factors, such as substrate conditions and turbidity.

Abstract  Inputs of nutrients (P and N) to freshwaters can cause excessive aquatic plant growth, depletion of oxygen, and deleterious changes in diversity of aquatic fauna. As part of a "National Agri-Environmental Standards Initiative," the Government of Canada committed to developing environmental thresholds for nutrients to protect ecological condition of agricultural streams. Analysis of data from >200 long-term monitoring stations across Canada and detailed ecological study at similar to 70 sites showed that agricultural land cover was associated with increased nutrient concentrations in streams and this, in turn, was associated with increased sestonic and benthic algal abundance, loss of sensitive benthic macroinvertebrate taxa, and an increase in benthic diatom taxa indicative of eutrophication. Chemical thresholds for N and P were defined by applying five approaches, employing either a predetermined percentile to a water chemistry data set or a relationship between water chemistry and land cover, to identify boundaries between minimally disturbed and impaired conditions. Comparison of these chemical thresholds with biological thresholds (derived from stressor-response relationships) produced an approach for rationalizing these two types of thresholds and deriving nutrient criteria. The resulting criteria were 0.01 to 0.03 mg L-1 total P and 0.87-1.2 mg L-1 total N for the Atlantic Maritime, 0.02 mg L-1 total P and 0.21 mg L-1 total N for the Montane Cordillera, -0.03 mg L-1 total P and -1.1 mg L-1 total N for the Mixedwood Plains, and similar to 0.10 mg L-1 total P and 0.39-0.98 mg L-1 total N for the interior prairies of Canada. Adoption of these criteria should result in greater likelihood of good ecological condition with respect to benthic algal abundance, diatom composition, and macroinvertebrate composition.

Abstract  The Cahaba River located in Jefferson County, Birmingham, Alabama has been placed on the 303(d) list by USEPA Region IV and the Alabama Department of Environmental Management as use-impaired from nutrients. In a letter to the County, USEPA stated “The listing of the Cahaba River for nutrients is based on the inability of endangered species to survive or adequately reproduce as a result of alterations of habitat substrate caused by excessive nutrients…”. The premise by USEPA and the US Fish and Wildlife Service is that excessive nutrient levels have caused an algal community shift, from diatoms to filamentous green algae within the river, which has resulted in habitat impairment. Further, the agencies contend that this habitat impairment has led to the extirpation of eight endangered species (2 fishes and 6 molluscs). According to USEPA's TMDL flowchart, if nutrient impairment occurs in rivers dominated by periphytic algae, simple empirical relationships can be used to relate nutrient levels to the cause of impairment, excessive periphytic algae growth. However, in the case of the Cahaba River, a valid empirical relationship between total phosphorus and periphytic chlorophyll a does not exist (r2 = 0.12). We have demonstrated that this is due to various in-stream limiting factors such as light, turbidity, scour, herbivory and possibly herbicide toxicity. In order to model this complex system, we have applied USEPA's AQUATOX model. AQUATOX accounts for additional in-stream processes not available in other water quality models and resulted in a verifiable linkage between total phosphorus and algal biomass. AQUATOX also provided the linkages to ecosystem trophic levels which are important in determining the target level of total phosphorus which is protective of endangered species' habitats. We will describe the data used to define the issues on this TMDL, the process used in the calibration of AQUATOX, and the resulting linkages between total phosphorus and periphytic growth that are key to determining the ultimate target level of total phosphorus used for TMDL development.