Abstract  Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams with repeated sampling at each site over a 2-month period. Many measures of algal biomass and nutrient availability were positively correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in either region. Chl a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations. Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic algal biomass occurred in nutrient concentrations between 10 and 30 mu g TP l(-1) and between 400 and 1000 mu g TN l(-1).

Abstract  We assessed land use and landscape characteristics, water chemistry, and diatom species composition in 122 streams of Michigan to evaluate the importance of natural and anthropogenic determinants of diatom species composition. Great variation was observed in land use and landscape characteristics, with only 14 and 4% of that variation among sites explained by the first two principle components axes. Ranges in TP and TN concentrations, as well as high N:P ratios, indicated that most streams were phosphorus limited if nutrients were sufficiently low. Amphora pediculus (Kutzing) Grunow and Cocconeis placentula var. euglypta (Ehrenberg) Grunow were the two most frequently observed of the 425 diatom taxa. Diatom species were characterized according to nutrient requirements based on traits in van Dam et al. (1994). A diatom nutrient index, percent low nutrient diatoms, and percent high nutrient diatoms were three indicators used to characterize species composition and responses to land use and landscape characteristics. The three diatom indicators of species composition were significantly related to both TP and TN. Forward stepwise regression showed that all were related to both natural and anthropogenic landscape-level factors. The proportion of the watershed with high permeability soils (outwash) and the wetland proportion of riparian zones were the two natural factors that were most highly related to diatom species composition; they were negatively related to the diatom nutrient index and percent high nutrient diatoms and positively related to the percent of low nutrient diatoms. Relative effects of natural versus anthropogenic effects on the three indicators of diatom species composition varied, but were relatively similar. Thus natural as well as anthropogenic factors are important determinants of diatom species composition and should be considered with assessing and managing the biodiversity of diatoms in streams.

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  Anthropogenic activities such as agricultural practices can have large effects on the ecological components and overall health of stream ecosystems. Therefore, having a better understanding of those effects and relationships allows for better design of mitigating strategies. The objectives of this study were to identify influential stream variables that correlate with macroinvertebrate indices using biophysical and statistical models. The models developed were later used to evaluate the impact of three agricultural management practices on stream integrity. Our study began with the development of a high-resolution watershed model for the Saginaw River watershed in Michigan for generating in-stream water quality and quantity data at stream reaches with biological sampling data. These in-stream data were then used to explain macroinvertebrate measures of stream health including family index of biological integrity (FamilyIBI), Hilsenhoff biotic index (HBI), and the number of Ephemeroptera, Plecoptera, and Trichoptera taxa (EPTtaxa). Two methods (stepwise linear regression and adaptive neuro-fuzzy inference systems (ANFIS)) were evaluated for developing predictive models for macroinvertebrate measures. The ANFIS method performed the best on average and the final models displayed the highest R-2 and lowest mean squared error (MSE) for FamilyIBI (R-2=0.50, MSE=29.80), HBI (R-2=0.57, MSE=0.20), and EPTtaxa (R-2=0.54, MSE=6.60). Results suggest that nutrient concentrations have the strongest influence on all three macroinvertebrate measures. Consistently, average annual organic nitrogen showed the most significant association with EPTtaxa and HBI. Meanwhile, the best model for FamilyIBI included average annual ammonium and average seasonal organic phosphorus. The ANFIS models were then used in conjunction with the Soil and Water Assessment Tool to forecast and assess the potential effects of different best management practices (no-till, residual management, and native grass) on stream integrity. Based on the model predictions, native grass resulted in the largest improvement for all macroinvertebrate measures. (C) 2012 Elsevier B.V. All rights reserved.