Rapid Geomorphic and Habitat Stream Assessment Techniques Inform Restoration Differently Based on Levels of Stream Disturbance

Visual‐based rapid assessment techniques provide an efficient method for characterizing the restoration potential of streams, with many focusing on channel stability and instream habitat features. Few studies, however, have compared these techniques to see if they result in differing restoration priorities. Three rapid assessment techniques were contrasted at three wild trout streams in western New York with different amounts of channel disturbance. Two methods focused only on geomorphic stability, whereas the third addressed physical habitat condition. Habitat assessment scores were not correlated with scores for either geomorphic assessment method and they varied more between channels with different degrees of disturbance. A model based on dynamic equilibrium concepts best explains the variation among the streams and techniques because it accounts for a stream's capacity to maintain ecological integrity despite some inherent instability. Geomorphic indices can serve as effective proxies for biological indices in highly disturbed systems. Yet, this may not be the case in less disturbed systems, where geomorphic indices cannot differentiate channel adjustments that impact biota from those that do not. Dynamically stable streams can include both stable and unstable reaches locally as characterized by geomorphic methods and translating these results into restoration priorities may not be appropriate if interpretations are limited to the reach scale.     

Effects of Land Use and Climate Change on Stream Temperature II: Threshold Exceedance Duration Projections for Freshwater Mussels

We developed a stochastic hourly stream temperature model (SHSTM) to estimate probability of exceeding given threshold temperature (T) for specified durations (24 and 96 h) to assess potential impacts on freshwater mussels in the upper Tar River, North Carolina. Simulated daily mean stream T from climate change (CC) and land‐use (LU) change simulations for 2021‐2030 and 2051‐2060 were used as input to the SHSTM. Stream T observations in 2010 revealed only two sites with T above 30°C for >24 h and Ts were never >31°C for more than 24 h at any site. The SHSTM suggests that the probability, P, that T will exceed 32°C for at least 96 h in a given year increased from P = 0, in the 20th Century, to P = 0.05 in 2021‐2030 and to P = 0.14 in 2051‐2060. The SHSTM indicated that CC had greater effects on P for 24 and 96 h durations than LU change. Increased P occurred primarily in higher order stream segments in the downstream reaches of the basin. The SHSTM indicated that hourly stream T responded to LU change on the daily scale and did not affect stream T for durations >24 h. The SHSTM indicated that known thermal thresholds for freshwater mussels could be exceeded within the next 50 years in many parts of the upper Tar River basin in North Carolina, which could have negative consequences on the recruitment of freshwater mussels.     

Bedded Sediment Conditions and Macroinvertebrate Responses in New Mexico Streams: A First Step in Establishing Sediment Criteria

Excess fine sediments in streambeds are among the most pervasive causes of degradation in streams of the United States. Simple criteria for acceptable streambed fines are elusive because streambed fines and biotic tolerances vary widely in the absence of human disturbances. In response to the need for sediment benchmarks that are protective of minimum aquatic life uses under the Clean Water Act, we undertook a case study using surveys of sediment, physical habitat, and macroinvertebrates from New Mexico streams. Our approach uses weight of evidence to develop suggested benchmarks for protective levels of surficial bedded sediments <0.06 mm (silt and finer) and <2.0 mm (sand and finer). We grouped streams into three ecoregions that were expected to produce similar naturally occurring streambed textures and patterns of response to human disturbances. Within ecoregions, we employed stressor response models to estimate fine sediment percentages and bed stability that are tolerated by resident macroinvertebrates. We then compared individual stream sediment data with distributions among least‐disturbed reference sites to determine deviation from natural conditions, accounting for natural variability across ecoregion, gradient, and drainage area. This approach for developing benchmark values could be applied more widely to provide a solid basis for developing bedded sediment criteria and other protective management strategies in other regions.     

Organochlorine contamination in shorebirds from Washington state and the significance for their falcon predators

Arctic-breeding shorebirds collected in western Washington state during winter and spring, and a comparative sample collected in coastal California during the winter were analyzed for organochlorine contaminants to determine the potential impact of these residues on populations of peregrine falcons (Falco peregrinus) and merlins (F. columbarius) which prey upon shorebirds in western Washington. Dunlins (Calidris alpina), an important winter prey for falcons in western Washington, were collected between 1975 and 1981. During winter 1980–81, dunlins carried low organochlorine residues; DDE levels ranged from 0.01 to 1.2 ppm, and PCB levels ranged from 0.02 to 0.82 ppm (wet weight). Levels of other organochlorine contaminants (HCB, Chlordane compounds, Dieldrin, and Heptachlor Epoxide), analyzed in a subsample of dunlins, were consistently lower than DDE and PCB levels, and ranged from 0.001 to 0.22 ppm (wet weight). Dunlins in western Washington did not significantly increase their DDE or PCB burdens over the 1980–81 winter. A decline in DDE residues between 1978 and 1981 was noted, and declines in PCB residues from both 1975 and 1978 to 1980–81 were noted. Residues in other wintering shorebirds from western Washington were similar. Wintering sanderlings (Calidris alba) from California, revealed much higher DDE contamination than in Washington (up to 32 ppm, wet weight). Spring migrant shorebirds in western Washington contained both low and very high DDE residues (up to 417 ppm, wet weight). There is evidence suggesting these high DDE concentrations are accumulated along the Pacific coast of North America.     

Mitochondrial energetics of benthic and pelagic Antarctic teleosts

Antarctic fauna are highly adapted to the frigid waters of the Southern Ocean. This study describes the in vitro temperature sensitivity of oxygen consumption rates measured in liver mitochondria from the pelagic notothenioid Pleuragramma antarcticum between 5 and 35 °C. Oxygen fluxes were measured after the addition of millimolar levels of pyruvate, malate, succinate and glutamate (state II, LEAK) and saturating levels of ADP [state III, oxidative phosphorylation (OXPHOS)]. State III respiration significantly decreased above 18.7 °C. A comparison of the oxidative capacities among P. antarcticum and other notothenioids showed significant differences in state III respiration, where benthic species exhibited about 50 % lower rates than P. antarcticum. In addition, state III respiration rates normalized per milligram of mitochondrial protein of P. antarcticum were up to eight times higher than state III rates reported in the literature for other notothenioids. The comparatively high respiration rates measured in this study may be explained by our approach, which engaged both complexes I and II under conditions of oxidative phosphorylation. State III rates of independently activated complexes I and II were found to range from 42 to 100 % of rates obtained when both complexes were activated simultaneously in the same species. The remarkable tolerance of P. antarcticum OXPHOS toward warmer temperatures was unexpected for an Antarctic stenotherm and may indicate that thermal sensitivity of their mitochondria is not the driving force behind their stenothermy.     

Kinetic studies of imazapyr photolysis and characterization of the main photoproducts

The fate of imazapyr (2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid), a broad-spectrum herbicide in the imidazolinone family, has been studied upon UV irradiation. Most of the photoproducts occurring during the photodegradation have been characterized by means of liquid chromatography and mass spectrometry coupled techniques (LC-MS). The use of high resolution mass spectrometry has allowed to maximize the chemical information obtained from a single LC-MS analysis. The degradation of a 10?ppm imazapyr solution leads to pyridine derivatives which remain in solution during 50–100?h while the imazapyr is completely degraded after 6?h.     

Polynuclear aromatic compounds in kerosene,diesel and unmodified sunflower oil and in respective engine exhaust particulate emissions

Polynuclear aromatic compounds (PAC) were characterized in diesel fuel, kerosene fuel and unmodified sunflower oil as well as in their respective engine exhaust particulates. Diesel fuel was found to contain high amounts of different PAC, up to a total concentration of 14,740?ppm, including carbazole and dibenzothiophene, which are known carcinogens. Kerosene fuel was also found to contain high amounts of different PAC, up to a total concentration of 10,930?ppm, consisting mainly of lower molecular weight (MW) naphthalene and its alkyl derivatives, but no PAC component peaks were detected in the unmodified sunflower oil. Engine exhaust particulates sampled from a modified one-cylinder diesel engine running on diesel, kerosene and unmodified sunflower oil, respectively, were found to contain significantly high concentrations of different PAC, including many of the carcinogenic ones, in the soluble organic fraction (SOF). PAC concentrations detected at the exhaust outlet indicated that most of the PAC that were present in diesel and kerosene fuels before the test runs got completely burnt out during combustion in the engine whereas some new ones were also formed. The difference between the character and composition of PAC present in the fuels and those emitted in the exhaust particulates indicated that exhaust PAC were predominantly combustion generated. High amounts of PAC, up to totals of 52,900 and 4830?µg?m^?3 of burnt fuel, in diesel and kerosene exhaust particulates, respectively, were detected in the dilution tunnel when the exhaust emissions were mixed with atmospheric air. Significant amounts of PAC were also emitted when the engine was run on unmodified sunflower oil with a total concentration of 17,070?µg?m^?3 of burnt fuel detected in the dilution tunnel. High proportions of the combustion-generated PAC determined when the engine was run on diesel, kerosene and unmodified sunflower, respectively, consisted of nitrogen-containing PAC (PANH) and sulphur-containing PAC (PASH).     

Sorption and leaching behavior of hexaconazole as influenced bysoilproperties

Sorption and leaching behavior of hexaconazole in four different soils (alluvial, red, laterite, and black) was studied using a batch equilibration technique. The values of the Freundlich adsorption constant 1/n_ads ranged from 0.75 to 0.85 for all four soils, showing strong non-linear behavior. Upon stepwise desorption with CaCl₂ solution (10 mmol·L^?1), release of hexaconazole was maximum with the first elution, the amount decreasing with each subsequent one. The leaching behavior under saturated flow conditions was also studied with soil columns packed in polythene tubes. The mobility of hexaconazole was maximum in sandy loam and minimum in black soil.     

Impact of different land uses on polycyclic aromatic hydrocarbon contamination in coastal stream sediments

PAHs are ubiquitous environmental pollutants that can cause adverse health and ecological effects. In the present study, we examined the impact of land use on the concentration and composition of PAHs in 28 coastal stream sediments on the Island of Oahu, Hawaii. In densely populated urban areas, the concentration range of total PAHs in the stream sediments affected by mixed residential and industrial activities (RI) are 0.40-9.05 ppm, which is significantly higher than the 0.36-4.21 ppm detected in the stream sediments affected predominantly by urban residential land uses (UR). The stream sediments affected by agricultural activities (AG) reported a concentration range of 0.09-2.14 ppm, which is lower than those of the RI and UR stream sediments. The molecular weight of PAH is a factor, as only high molecular weight (HMW) PAHs were significantly affected by land uses (ANOVA P = 0.009). Correlation analysis showed that only in the UR stream sediments were significant correlations observed between PAH concentration and two anthropogenic indicators: population density (r = 0.57, P = 0.027) and vehicle density (r = 0.55, P = 0.034). The fractional concentrations of PAHs were analyzed by using PCA analysis, which led to the separate clustering of the RI and AG stream sediments and suggest distinct PAH sources between the two land uses. Two PAH source indicators, including Ant/(Ant + Phe) and Fl/(Fl + Py), indicates that PAHs sources in the RI stream sediments are most likely of petroleum origin, while PAHs in the UR and AG stream sediments most likely came from combustion activities. In addition, the concentration and relative potency of carcinogenic PAHs in the coastal stream sediments exhibited similar patterns as the total PAH concentration with respect to land uses.