Otoliths are frequently used to infer environmental conditions or fish life history events based on trace-element concentrations. However, otoliths can be comprised of any one or combination of the ...three most common polymorphs of calcium carbonate-aragonite, calcite, and vaterite-which can affect the ecological interpretation of otolith trace-element results. Previous studies have reported heterogeneous calcium carbonate compositions between left and right otoliths but did not provide quantitative assessments of polymorph abundances. In this study, neutron diffraction and Raman spectroscopy were used to identify and quantify mineralogical compositions of Chinook salmon Oncorhynchus tshawytscha otolith pairs. We found mineralogical compositions frequently differed between otoliths in a pair and accurate calcium carbonate polymorph identification was rarely possible by visual inspection alone. The prevalence of multiple polymorphs in otoliths is not well-understood, and future research should focus on identifying otolith compositions and investigate how variations in mineralogy affect trace-element incorporation and potentially bias environmental interpretations.
Challenges exist in the wastewater treatment of dyes produced by the world's growing textiles industry. Common problems facing traditional wastewater treatments include low retention values and ...breaking the chemical bonds of some dye molecules, which in some cases can release byproducts that can be more harmful than the original dye. This research illustrates that track-etched polycarbonate filtration membranes with 100-nanometer diameter holes can be functionalized with azo dye direct red 80 at 1000 µM, creating a filter that can then be used to remove the entire negatively charged azo dye molecule for a 50 µM solution of the same dye, with a rejection value of 96.4 ± 1.4%, at a stable flow rate of 114 ± 5 µL/min post-functionalization. Post-functionalization, Na
and NO3
ions had on average 17.9%, 26.0%, and 31.1% rejection for 750, 500, and 250 µM sodium nitrate solutions, respectively, at an average flow rate of 177 ± 5 µL/min. Post-functionalization, similar 50 µM azo dyes had increases in rejection from 26.3% to 53.2%. Rejection measurements were made using ultraviolet visible-light spectroscopy for dyes, and concentration meters using ion selective electrodes for Na
and NO3
ions.
A major pathway of messenger RNA degradation in eukaryotic cells is initiated by shortening of the poly(A) tail, which, at least in yeast, triggers a decapping reaction, thereby exposing the mRNA to ...5' --> 3' degradation. Decapping is the key step in this decay pathway because the transcript body is rapidly degraded following decapping. Accordingly, decapping is the site of numerous controls, including inhibition of decapping by the poly(A) tail and modulation of mRNA decapping rate by specific sequences. Moreover, a specialized decay pathway that degrades aberrant transcripts triggers rapid mRNA decapping independently of poly(A)-tail shortening. We have identified a yeast gene, termed DCP1, that encodes the decapping enzyme, or an essential component of a decapping complex. The protein Dcp1 is required for the normal decay of many unstable and stable yeast mRNAs, as well as mRNAs that are decapped independently of deadenylation. These results indicate that mRNA-specific rates of decapping, and thus decay, will result from differences in the interaction of the DCP1 decapping enzyme with individual transcripts.
Injury and mortality of fish during downstream passage through hydropower turbines is among the leading direct impacts of hydropower. Understanding the relationships among various strike variables ...and injury and mortality rates are necessary for improvements in turbine design. We subjected three species of fish to simulated blade strike in laboratory studies with different blade thicknesses, impact velocities, and body orientations to develop relationships between these variables and probability of injury and mortality. Midbody strikes resulted in higher mortality than head strikes, and tail strikes produced the least mortality. Lateral strikes caused more mortality than dorsal and ventral strikes, and higher strike velocities and thinner blades contributed to increased mortality. Several injury types were significantly associated with increased mortality, including injuries to the operculum, gills, viscera, heart, liver, swim bladder, muscle, and bone fractures. Results from this study will be used to define biologically based design criteria that can be used by turbine designers to improve designs (e.g., increased leading-edge thickness and slower turbine speeds) to minimize the probability and impact of blade strike.
During August–September 2012, we sampled six hydropower reservoirs in southeastern United States for CO2 and CH4 emissions via three pathways: diffusive emissions from water surface; ebullition in ...the water column; and losses from dam tailwaters during power generation. Estimates of average areal emission rates of CO2 attributable to the six reservoirs (i.e., reservoir plus tailwater emissions) ranged from 994 to 2760 mg·m−2·day−1, which is low to moderate compared to CO2 emissions rates reported for tropical hydropower reservoirs and boreal ponds and lakes, and similar to rates reported for other temperate reservoirs. Similar average rates for CH4 were also relatively low, ranging from 6 to 187 mg·m−2·day−1. On a whole-reservoir basis, estimates of total emissions of CO2 ranged 10-fold, from 42,740 kg per day for Fontana to 501,151 kg per day for Guntersville, and total emissions of CH4 ranged over 30-fold, from 251 kg per day for Fontana to 9153 kg per day for Allatoona. Emissions through the tailwater pathway varied among reservoirs, comprising from 19% to 65% of total CO2 emissions and 0% to 84% of CH4 emissions, depending on the reservoir. Emission rates were significantly correlated with several reservoir morphological and water quality characteristics, including metrics related to vertical stratification (e.g., minimum water column temperature and maximum dissolved oxygen) and reservoir productivity (e.g., water transparency and chlorophyll a concentration).
Emissions of CO2 and CH4 from freshwater reservoirs constitute a globally significant source of atmospheric greenhouse gases (GHGs), but knowledge gaps remain with regard to spatiotemporal drivers of ...emissions. We document the spatial and seasonal variation in surface diffusion of CO2 and CH4 from Douglas Lake, a hydropower reservoir in Tennessee, USA. Monthly estimates across 13 reservoir sites from January to November 2010 indicated that surface diffusions ranged from 236 to 18,806 mg·m−2·day−1 for CO2 and 0 to 0.95 mg·m−2·day−1 for CH4. Next, we developed statistical models using spatial and physicochemical variables to predict surface diffusions of CO2 and CH4. Models explained 22.7% and 20.9% of the variation in CO2 and CH4 diffusions respectively, and identified pH, temperature, dissolved oxygen, and Julian day as the most informative predictors. These findings provide baseline estimates of GHG emissions from a reservoir in eastern temperate North America, a region for which estimates of reservoir GHGs emissions are limited. Our statistical models effectively characterized non-linear and threshold relationships between physicochemical predictors and GHG emissions. Further refinement of such modeling approaches will aid in predicting current GHG emissions from unsampled reservoirs and forecasting future GHG emissions.
The effect of coal ash exposure on fish health in freshwater communities is largely unknown. Given the large number of possible pathways of effects (e.g., toxicological effect of exposure to multiple ...metals, physical effects from ash exposure, and food web effects), measurement of only a few health metrics is not likely to give a complete picture. The authors measured a suite of 20 health metrics from 1100+ fish collected from 5 sites (3 affected and 2 reference) near a coal ash spill in east Tennessee over a 4.5‐yr period. The metrics represented a wide range of physiological and energetic responses and were evaluated simultaneously using 2 multivariate techniques. Results from both hierarchical clustering and canonical discriminant analyses suggested that for most species × season combinations, the suite of fish health indicators varied more among years than between spill and reference sites within a year. In a few cases, spill sites from early years in the investigation stood alone or clustered together separate from reference sites and later year spill sites. Outlier groups of fish with relatively unique health profiles were most often from spill sites, suggesting that some response to the ash exposure may have occurred. Results from the 2 multivariate methods suggest that any change in the health status of fish at the spill sites was small and appears to have diminished since the first 2 to 3 yr after the spill. Environ Toxicol Chem 2014;33:1903–1913. Published 2014 Wiley Periodicals, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.
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