Northeastward reverse migration of birds over Nova Scotia,Canada, in autumn

Summary During 4 seasons of study, small numbers of birds flew overland to the NNE-E, counter to the main SW migration, intermittently throughout the autumn (31 July – 16 November). Radars also detected overwater reverse migration (RM) from New England to Nova Scotia and from Nova Scotia toward Newfoundland. RM occurred at all hours of the day and night, especially when few birds were migrating SW. Most but not all cases of RM occurred with following SW winds. RM was more common with cloud and/or poor visibility than in fair weather, but was not restricted to cloudy occasions. Mean tracks were correlated with wind direction, but were not consistently downwind. Tracks tended to be closer to downwind in early than in late autumn, and on clear than on overcast nights. Dispersion in tracks was not discernibly related to weather variables, time of day or night, or magnetic disturbance. Eleven hypotheses concerning the reasons for reverse migration in autumn are evaluated; cases of RM recorded in this study are attributable to at least three of these hypotheses (late summer dispersal, hurricanes, dawn reorientation toward coast) and possibly to several others.     

Sorption of the natural endocrine disruptors,oestrone and 17 beta-oestradiol in the aquatic environment

Adsorption of hydrophobic contaminants at the particle/water interface is one of the key processes controlling their fate in the aquatic environment. The sorption of the natural female hormones oestrone and 17-oestradiol has been studied under simulated riverine conditions. Both the kinetics and the effects of varying fundamental environmental parameters (e.g. sediment properties) on the thermodynamic equilibrium partition coefficient (K _p) have been studied in continuous and batch sorption experiments, respectively. Results showed that the sorption of oestrone and 17-oestradiol by sediment was relatively slow, reaching equilibrium in 50 days. In addition, relatively small adsorption of both oestrone and 17-oestradiol onto the sediment was observed, with K _p values between 200 and 250 mL g^–1. The comparable K _p values of the two compounds reflect their structural similarity. It can be concluded that the two endocrine disruptors, oestrone and 17-oestradiol remain primarily in association with the aqueous phase.     

Insect cell-based impedance biosensors: a novel technique to monitor the toxicity of environmental pollutants

Cell biosensors are currently emerging as novel, sensitive techniques to monitor the toxicity of environmental pollutants. Here, we have developed electric cell-substrate impedance sensing (ECIS) for on-line monitoring of the behavior of insect cells. Cells were cultured on a microarray of eight small gold electrodes, deposited on the bottom of tissue culture wells. Upon inoculation, cells showed a tendency to drift downward and attached to the gold surface precoated with the protein Concanavalin A to accelerate the cell attachment. The impedance increased because the cells acted as insulating particles to restrict the current flow. The resulting impedance, a coordination of many biological reactions within the cell, was continuously monitored in real-time to reveal information about cell spreading and micromotion. As the cell behavior was sensitive to external chemicals, the applicability of ECIS for inhibition assays was demonstrated with HgCl₂, 2,4,6-trinitrotoluene (TNT), 2-amino 4,6-dinitrotoluene (2-ADNT) and 1,3,5-trinitrobenzene (TNB). Electronic Publication     

A preliminary study of the phycological degradation of natural stone masonry

For many years it has been realised that the weathering of stone is not merely determined by physical and chemical factors but also by biological agents. When the stone in question is a historic building or monument, the damage done constitutes an irretrievable loss of our heritage and history. Laboratory studies have commenced in Paisley to study the effect of photoautotrophs on the major sedimentary rock forming minerals, with a view to expanding this work to study the overall effect of these micro-organisms on heritage masonry. Tests were carried out on Albite, Calcite, Dolomite, Orthoclase, Siderite and Quartz, using axenic cultures of the following: Chlorella vulgaris, Chlorococcum tetrasporum, Scenedesmus obliquus, Oocystis marsonii, Stichococcus bacillaris. The rock chips were immersed in either water or bolds basal media and exposed to a mix of the micro-organisms listed above and then tested weekly for their pH, fortnightly for the waters chemical composition using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and visually utilising the universitys SEM facilities. Work so far has revealed biologically mediated etching of minerals, a well-defined pH profile over a period of 90 days, as well as a variety of elemental release patterns for the different minerals.     

Bayesian analysis under ordered functions of parameters

Ordered parameter problems arise in a wide variety of real world situations and are dealt with extensively in the literature. Traditional frequentist methods for dealing with these problems are rather complicated theoretically, especially when sample sizes are small. Bayesian methods are not widely used because high dimensional numerical integration is often required. However, Markov chain Monte Carlo methods provide alternatives to such numerical integration and also deal with ordered parameter problems in a straightforward manner. Little is known about the situation where functions of parameters are ordered. Such problems may seem to be of little practical concern initially, but one can readily see their importance in situations where ordering is placed on the means and variances of several normal or Gamma populations. For the Gamma distribution we will present real examples where we will analyze monthly precipitation data from San Francisco, California and Oakland Mills, Iowa. For the San Francisco data we will simultaneously order both monthly precipitation means and variances. For the Iowa data we will place ordering on seasonal average while still estimating monthly means. Our results show that we would obtain sharper, more accurate inference when order restrictions are employed.     

Monoterpene chemodiversity of ponderosa pine in relation to herbivory and bark beetle colonization

Summary. Ponderosa pine, Pinus ponderosa Laws. (Pinaceae), forests in Arizona have suffered from a nine-year period of drought and bark beetle, Ips lecontei Swaine (Coleoptera: Scolytidae), outbreaks. Abiotic and biotic stress in ponderosa pine results in the induced synthesis of certain monoterpenes that may in turn affect bark beetle behavior and survival. In this study, we investigate whether induced monoterpene production could result in a different monoterpene composition that remains stored in the needles or the trunk resin of the tree. Needle and resin samples in addition to trunk cores were collected from ponderosa pines at three locations in Arizona. Ungulate browsing induced a significant increase in limonene (P=0.010) and in chemodiversity (P=0.009), a measure of the evenness of distribution among the monoterpenes present in needles. We compared the level of ‘stress’ of the trees by measuring the thickness of annual rings in living trees and those that were killed by bark beetles. Where drought occurred, the spacing of annual rings from the last 10 years of trees killed by bark beetles was significantly smaller (P=0.020) compared to living trees. There was no difference in the monoterpene composition between the core sections of closest spacing of annual rings (stressed years) compared to the sections of widest spacing, which indicates that monoterpenes are distributed evenly throughout the extended resin system. In the area where the degree of drought was less overall, none of the individual monoterpenes present in the resin was related to bark beetle killed trees. However, about half the living pines had resin in which one of the major monoterpenes (α-pinene, Δ³-carene, and limonene) was absent, and these trees had a lower monoterpene chemodiversity compared to trees killed by bark beetles. Trees with these three major monoterpenes, corresponding to the average relative proportion in living pines at that location, may sustain higher selection and colonization by bark beetles.     

Denitrification in nitrate-rich streams: application of N2:Ar and 15N-tracer methods in intact cores.

Rates of benthic denitrification were measured using two techniques, membrane inlet mass spectrometry (MIMS) and isotope ratio mass spectrometry (IRMS), applied to sediment cores from two NO3(-)-rich streams draining agricultural land in the upper Mississippi River Basin. Denitrification was estimated simultaneously from measurements of N2:Ar (MIMS) and 15N[N2] (IRMS) after the addition of low-level 15NO3- tracer (15N:N = 0.03-0.08) in stream water overlying intact sediment cores. Denitrification rates ranged from about 0 to 4400 micromol N x m(-2) x h(-1) in Sugar Creek and from 0 to 1300 micromol N x m(-2) x h(-1) in Iroquois River, the latter of which possesses greater streamflow discharge and a more homogeneous streambed and water column. Within the uncertainties of the two techniques, there is good agreement between the MIMS and IRMS results, which indicates that the production of N2 by the coupled process of nitrification/denitrification was relatively unimportant and surface-water NO3- was the dominant source of NO3- for benthic denitrification in these streams. Variation in stream NO3- concentration (from about 20 micromol/L during low discharge to 1000 micromol/L during high discharge) was a significant control of benthic denitrification rates, judging from the more abundant MIMS data. The interpretation that NO3- concentration directly affects denitrification rate was corroborated by increased rates of denitrification in cores amended with NO3-. Denitrification in Sugar Creek removed < or = 11% per day of the instream NO3- in late spring and removed roughly 15-20% in late summer. The fraction of NO3- removed in Iroquois River was less than that of Sugar Creek. Although benthic denitrification rates were relatively high during periods of high stream flow, when NO3 concentrations were also high, the increase in benthic denitrification could not compensate for the much larger increase in stream NO3- fluxes during high flow. Consequently, fractional NO3- losses were relatively low during high flow.     

Tail beat frequency as a predictor of swimming speed and oxygen consumption of saithe (<Emphasis Type="Italic">Pollachius virens</Emphasis>) and whiting (<Emphasis Type="Italic">Merlangius merlangus</Emphasis>) during forced swimming

Oxygen consumption and tail beat frequency were measured on saithe (Pollachius virens) and whiting (Merlangius merlangus) during steady swimming. Oxygen consumption increased exponentially with swimming speed, and the relationship was described by a power function. The extrapolated standard metabolic rates (SMR) were similar for saithe and whiting, whereas the active metabolic rate (AMR) was twice as high for saithe. The higher AMR resulted in a higher scope for activity in accordance with the higher critical swimming speed (U _crit) achieved by saithe. The optimum swimming speed (U _opt) was 1.4 BL s⁻¹ for saithe and 1.0 BL s⁻¹ for whiting with a corresponding cost of transport (COT) of 0.14 and 0.15 J N⁻¹ m⁻¹. Tail beat frequency correlated strongly with swimming speed as well as with oxygen consumption. In contrast to swimming speed and oxygen consumption, measurement of tail beat frequency on individual free-ranging fish is relatively uncomplicated. Tail beat frequency may therefore serve as a predictor of swimming speed and oxygen consumption of saithe and whiting in the field.     

Oxidation of organic impurities in the recycle and reclaim loops of ultra-pure water plants

 The oxidation of trace organic impurities in ultrapure water by ultraviolet light (UV), ozone, and the combination of UV/ozone is investigated. The emphasis is on the development of a global model to simulate the process that take place in the typical oxidation reactors used in ultrapure water plants. The study also focuses on reaction mechanism for oxidation of multi-component organic impurities. Eighteen organic model compounds are chosen as representative contaminants. The results demonstrate and confirm a significant synergistic effect between UV and ozone oxidation. A mechanism for the synergistic oxidation of organic impurities is proposed and validated with experimental data. The combination of the reaction and the reactor models is used to determine the fundamental kinetic parameters involved in the three oxidation processes. Received: 3 July 1998 / Accepted: 4 September 1998