Individual protein balance strongly influences δ<Superscript>15</Superscript>N and δ<Superscript>13</Superscript>C values in Nile tilapia,<Emphasis Type="Italic"> Oreochromis niloticus</Emphasis>

Although stable isotope ratios in animals have often been used as indicators of the trophic level and for the back-calculation of diets, few experiments have been done under standardized laboratory conditions to investigate factors influencing ¹⁵N and ¹³C values. An experiment using Nile tilapia [Oreochromis niloticus (L.)] was therefore carried out to test the effect of different dietary protein contents (35.4, 42.3, and 50.9%) on ¹⁵N and ¹³C values of the whole tilapia. The fish were fed the isoenergetic and isolipidic semi-synthetic diets at a relatively low level. ¹⁵N and ¹³C values of the lipid-free body did not differ between the fish fed the diets with different protein contents, but the trophic shift for N and C isotopes decreased with increasing protein accretion in the individual fish, for N from 6.5 to 4 and for C in the lipid-free body from 4 to 2.5. This is the first study showing the strong influence of the individual protein balance to the degree to which the isotopic signature of dietary protein was modified in tissue protein of fish. The extrapolation of the trophic level or the reconstruction of the diet of an animal from stable isotope ratios without knowledge of the individual physiological condition and the feeding rate may lead to erroneous results.     

Important elements and characteristics of hearing conservation programs and determination of their effectiveness

Results of on-site interviews with industrial personnel involved in hearing conservation programs (HCPs) show common deficiencies in personnel training and program implementation, reducing HCP effectiveness in protecting employees from occupational hearing loss. Audiometric data base analysis (ADBA) provides procedures which allow HCP ineffectiveness to be detected before many employees develop significant noise-induced hearing loss. If HCP procedures are corrected, based on ADBA results, then audiometry serves to prevent hearing loss rather than simply detecting its occurrence. The paper presents criterion ranges for ADBA procedure results as recommended by the ANSI S12.12 Working Group for Evaluation of HCPs.     

Impacts of Rotational Grazing and Riparian Buffers on Physicochemical and Biological Characteristicsof Southeastern Minnesota, USA, Streams

We assessed the relationship between riparian management and stream quality along five southeastern Minnesota streams in 1995 and 1996. Specifically, we examined the effect of rotationally and continuously grazed pastures and different types of riparian buffer strips on water chemistry, physical habitat, benthic macroinvertebrates, and fish as indicators of stream quality. We collected data at 17 sites under different combinations of grazing and riparian management, using a longitudinal design on three streams and a paired watershed design on two others. Continuous and rotational grazing were compared along one longitudinal study stream and at the paired watershed. Riparian buffer management, fenced trees (wood buffer), fenced grass, and unfenced rotationally grazed areas were the focus along the two remaining longitudinal streams. Principal components analysis (PCA) of water chemistry, physical habitat, and biotic data indicated a local management effect. The ordinations separated continuous grazing from sites with rotational grazing and sites with wood buffers from those with grass buffers or rotationally grazed areas. Fecal coliform and turbidity were consistently higher at continuously grazed than rotationally grazed sites. Percent fines in the streambed were significantly higher at sites with wood buffers than grass and rotationally grazed areas, and canopy cover was similar at sites with wood and grass buffers. Benthic macroinvertebrate metrics were significant but were not consistent across grazing and riparian buffer management types. Fish density and abundance were related to riparian buffer type, rather than grazing practices. Our study has potentially important implications for stream restoration programs in the midwestern United States. Our comparisons suggest further consideration and study of a combination of grass and wood riparian buffer strips as midwestern stream management options, rather than universally installing wood buffers in every instance. RID=" ID=" The Unit is jointly sponsored by the US Geological Survey, Biological Resources Division; the Minnesota Department of Natural Resources; the University of Minnesota; and the Wildlife Management Institute.     

Future bioenergy trade in the EU: modelling trading options from a cost-effectiveness perspective

The purpose of this paper is to analyse under what conditions, with respect to CO₂ emission-reduction and biofuels-for-transport targets, the trading in the EU of CO₂ credits and solid and/or liquid biofuels is cost-effective from the perspective of an optimisation energy systems model. We use the PEEP model covering the EU27 (except Bulgaria, Malta, and Cyprus) to generate insights about the cost-effectiveness of different options under different policy scenarios. Trade in CO₂ credits is a cost-effective option, in all relevant policy scenarios. Trade in some biofuels (mainly from central and eastern European countries to the EU15) is cost-effective in all assessed scenarios. In the case of CO₂ targets (whether national or at the EU level) there is trade in solid biofuels. When biofuels-for-transport targets are also implemented, trading both solid and liquid biofuels is cost-effective.     

Comparison of concentrations of toxic elements in the hair of first-year students of RUDN University from different regions of the world: a cross-sectional study

Environmental Science and Pollution Research - Due to the development of the metallurgical and energy industries and the operation of incinerators, more and more environmental pollution is...