CHARACTERIZATION OF HYDROLOGIC CONDITIONS TO SUPPORT PLATTE RIVER SPECIES RECOVERY EFFORTS1

ABSTRACT: Efforts are under way to recover habitat for several threatened and endangered species in and along the Platte River in central Nebraska. A proposed recovery program for these species requires a means of characterizing “wet” versus “normal” versus “dry” hydrologic conditions in order to set corresponding Platte River instream flow targets. Methods of characterizing hydrologic conditions in real time were investigated for this purpose. Initially, 10 watershed variables were identified as potentially valuable indicators of hydrologic conditions. Ultimately, six multiple linear regression equations were developed for six periods of the year using a subset of these variables expressed as frequencies of nonexceedence. The adequacy of these equations for characterizing conditions was assessed by evaluating their historic correlation to subsequent flow in the central Platte River (1947–1994). These equations explained 54 to 82 percent of variability in the observed flow exceedences in the validation datasets, depending upon the period of year evaluated. These equations will provide initial criteria for setting applicable flow targets to determine, in real time, whether water regulation projects associated with the species recovery effort can divert or store flows without conflicting with recovery objectives.     

What's wrong with virtual trees? Restoring from stress in a mediated environment

Restorative environments are environments that can help restore depleted attention resources or reduce emotional and psychophysiological stress. These effects have been demonstrated not only in real environments, but also in mediated (projected, broadcasted, etc.) environments. However, the importance of simulation qualities to restoration outcomes has not been systematically studied. The present experiment investigates the importance of immersion in a mediated environment in relation to restoration. Is a projected natural environment more restorative when one is more immersed in it, and hence feels more present in it? The hypothesis was that a more immersive projection would show stronger stress-reducing effects of a mediated restorative environment. After performing a stress-inducing task, participants watched a nature film on either a high or low immersive screen. Physiological measurements (heart period and skin conductance level) were taken throughout the experiment. In addition, we measured self-reported affect and presence using the ITC-Sense of Presence Questionnaire. Significant effects of the screen size manipulation appeared on physiological measures, but not on self-reported affect. The data showed an interaction between screen size and restorative phase on heart period and skin conductance level, indicating stronger restoration for the immersive screen condition over time. We therefore conclude that immersion enhances restorative potential of a mediated natural environment. Self-reported affect did correlate significantly with experienced presence, illustrating the relevance of this experiential counterpart of immersion, although a mediating effect of presence has not yet been established.     

The use of Littorina littorea for tributyltin (TBT) effect monitoring - Results from the German TBT survey 1994/1995 and laboratory experiments

Field investigations and laboratory experiments were performed to test the applicability of the intersex phenomenon in Littorina littorea for biological TBT-effect monitoring and to give further insights into toxicological aspects of intersex development. The intensity of the phenomenon is correlated with the degree of TBT contamination in the environment. Statistically highly significant correlations of biological indices and TBT concentrations in tissue and sediment exist. Intersex can be induced only in juvenile and sexually immature females and its intensity depends on the ontogenetic stage of development during TBT exposure. For the first time, malformations in male periwinkles closely related to the TBT contamination can be described; the reduction of male mamilliform penial glands shows highly significant correlations to TBT concentrations in tissues. The intersex phenomenon in Littorina littorea is proposed for a biological TBT-effect monitoring in those areas where the dogwhelk Nucella lapillus, as the more sensitive species in European surveys, is absent. The intersex index (ISI) as the mean value of the intersex stages in a sample should be used as the most sensitive biological parameter for the assessment of the TBT contamination in Littorina littorea.     

Cu accumulation in the earthworm Dendrobaena veneta in a heavy metal (Cu, Pb, Zn) contaminated site compared to Cu accumulation in laboratory experiments

Earthworms (Dendrobaena veneta) were exposed to heavy metal contaminated soil from a field site under both laboratory and field conditions. In the laboratory study, D. veneta were analysed for Cu after 2 weeks' exposure. The tissue Cu concentration (Cu(W)) increased proportionally with the total extractable soil Cu content (Cu(T)) in soils that contained less than 150 mg Cu kg(-1). In D. veneta exposed to soils containing more than Cu(T) = 150 mg kg(-1), however, we observed no further increase in Cu(W). In a 64-m(2) field plot at a contaminated site, 81 soil samples were taken and analysed for Cu, Pb, Zn and pH. In June 1994, 1000 D. veneta were homogeneously distributed in the plot and sampled after 1, 2 and 5 weeks to analyse for Cu. Additionally, 2000 D. veneta were introduced in September 1994 and sampled after 1, 2 and 4 weeks. At locations where earthworms were removed, the soil Cu content was estimated by disjunctive kriging. Cu concentration factors (ratio of Cu(W) to Cu(T)) in the field experiment were in excellent agreement with those of the laboratory experiment. This indicates that, with a sufficiently high sampling density, it may be feasible to predict earthworm Cu accumulation in the field using a concentration factor determined in the laboratory.     

Effects of composting on phytotoxicity of spent pig-manure sawdust litter

The phytotoxicity of spent pig-manure sawdust litter (spent litter) was evaluated during further composting. Aqueous extracts of the spent litter were prepared by shaking the sample with water (1:10 w/v), and the toxicity of these extracts was determined on relative seed germination, relative root elongation and germination index (GI, a factor of relative seed germination and relative root elongation). The sensitivity of six plant species, namely Brassica parachinensis (Chinese cabbage), Brassica albogalera (Chinese kale), Allium sativum (onion), Cucumis sativus (cucumber), Amaranthus espinosus (Chinese spinach), and Lycopersicon esculentum (tomato) were compared. The effect of different moisture levels during composting on the phytotoxicity of the spent litter was also examined. Phytotoxicity of the spent litter was only evident during the earlier stage of composting (first 14 days) and, that seed germination and root elongation reached 100% (same as the control) towards the end of the composting. The concentrations of the major inhibitors, water-extractable Cu and Zn, and NH4(+)-N of the spent litter, declined during composting, indicating that these inhibitors were gradually eliminated as composting proceeded. Multiple regression analysis showed that the NH4(+)-N content of the spent litter was the most important chemical factor affecting phytotoxicity of the plant species selected for this study. Relative root elongation and GI were more sensitive indicators of phytotoxicity than seed germination. In the present study, the GI's of all plant species were >80% at day 60, indicating that the spent litter had reached its maturation by day 60. The responses of different plant species to the water-extracts of the spent litter were different. Among the six species, Chinese cabbage and Chinese spinach were the most sensitive species, and tomato and cucumber were the least sensitive species to indicate phytotoxicity of the spent litter. Moisture adjustment during the composting process did not affect the results of the phytotoxicity test.     

Evaluation of the biodegradability of copolyesters containing aromatic compounds by investigations of model oligomers

Model oligo esters of terephthalic acid with 1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol have been investigated with regard to their biodegradability in different biological environments. Well-characterized oligomers with weight-average molar masses of from 600 to 2600 g/mol exhibit biodegradation in aqueous systems, soil, and compost at 60°C. SEC investigations showed a fast biological degradation of the oligomer fraction consisting of 1 or 2 repeating units, independent of the diol component used for polycondensation, while polyester oligomers with degrees of polymerization higher than 2 were stable against microbial attack at room temperature in a time frame of 2 months. At 60°C in a compost environment chemical hydrolysis also degrades chains longer than two repeating units, resulting in enhanced degradability of the oligomers. Metabolization of the monomers and the dimers as well by the microorganisms could be confirmed by comparing SEC measurements and carbon balances in a Sturm test experiment. Based on these results degradation characteristics of potential oligomer intermediates resulting from a primary chain scission from copolyesters consisting of aromatic and aliphatic dicarbonic acids can be predicted depending on their composition. These results will have an evident influence on the evaluation of the biodegradability of commercially interesting copolyesters and lead to new ways of tailor-made designing of new biodegradable materials as well.