Solar ultraviolet-B radiation influence on Sphagnum bog and Carex fen ecosystems: first field season findings in Tierra del Fuego, Argentina

Stratospheric ozone depletion occurs over Tierra del Fuego, southern Argentina and Chile, in the austral spring and summer due to the precession of the Antarctic ‘ozone hole’ and the general erosion of the ozone layer. Plots receiving either near-ambient or reduced UV-B radiation were established using different louvered plastic film filters over Sphagnum bog and Carex fen ecosystems in October 1996. In the Sphagnum bog system, growth measurements during the late spring and summer showed no significant differences in the moss Sphagnum magellanicum, or the vascular plants (Empetrum rubrum, Nothofagus antarctica, and Tetroncium magellanicum) between near-ambient and attenuated UV-B radiation treatments. In the Carex fen system, leaf length and spike height did not differ in the two dominant species, Carex decidua and C. curta, between UV-B radiation treatments. The length of individual spikelets of C. curta under near-ambient UV-B radiation was less than under the reduced UV-B radiation treatment, but this was not evident in C. decidua. No differences in seed number, seed mass, or viability were seen in either Carex species between the UV-B treatments. Two important constituents of the microfauna that inhabit the Sphagnum bog are testate amoebae and rotifers. These both appeared to be more numerous under near-ambient UV-B radiation than under reduced UV-B radiation. The subtle responses of the Sphagnum and Carex ecosystems may become more apparent in subsequent years as the treatments are continued. Trophic-level changes, such as the differences in number of amoebae and rotifers, may be more sensitive to solar UV-B radiation than growth and productivity of the vegetation.     

The reduction of aboveground Calamagrostis epigeios mass and tiller number by enhanced UV-B in a dune-grassland ecosystem

Since early May 1997 dune-grassland vegetation in the Netherlands has been exposed to enhanced levels of ultraviolet-B (UV-B) radiation. Expected increases in the amount of biologically effective UV-B (UV-B_BE) upon a reduction of the stratospheric ozone layer with 15% were calculated and artificially supplemented.In June and September 1998, above- and belowground vegetation samples were taken. Of the dominant species Calamagrostis epigeios and Carex arenaria aboveground mass accumulation, leaf weight (LW), leaf area (LA), specific leaf area (SLA) and tiller number were assessed separate from the remaining vegetation.The results of our study indicate alterations in the vegetation structure due to UV-B supplementation. In June, a significant reduction due to UV-B supplementation in number of tillers and aboveground dry weight per soil area unit was found for C. epigeios. As C. epigeios is the most dominant species of the dune-grassland, these effects indicate a change in vegetation structure due to UV-B enhancement. Indications of UV-B effects on other parameters, such as the number of tillers of C. arenaria and aboveground plant dry weight of the group of species other than C. epigeios and C. arenaria, may also represent changes in vegetation structure. The LA and LW data show the same patterns as the mass accumulation trends. No significant UV-B effects on the SLA of the species or of the total vegetation could be found.Trends in patterns of species dry weight accumulation and partitioning of dry weight between species groups are different in June and September. This may indicate seasonal dependence of UV-B responses. Also, the consistently reducing trend in total and aboveground plant dry weight may indicate deleterious effects of UV-B on total plant matter accumulation. Possible causes of observed trends and effects are discussed.     

Divergent pheromone-mediated insect behaviour under global atmospheric change

While the effects of global atmospheric changes on vegetation and resulting insect populations(‘bottom‐up interactions’) are being increasingly studied, how these gases modify interactions among insects and their natural enemies (‘top‐down interactions’) is less clear. As natural enemy efficacy is governed largely by behavioural mechanisms, altered prey finding and prey defence may change insect population dynamics. Here we show that pheromone‐mediated escape behaviours, and hence the vulnerability of insects to natural enemies, are divergent under atmospheric conditions associated with global climate change. Chaitophorus stevensis, a common aphid on trembling aspen trees, Populus tremuloides, have diminished escape responses in enriched carbon dioxide (CO₂) environments, while those in enriched ozone (O₃) have augmented escape responses, to alarm pheromone. These results suggest that divergent pheromone‐mediated behaviours could alter predator–prey interactions in future environments.     

Understanding and Managing the Risks to Health and Environment from Global Atmospheric Change: A Synthesis

The global atmosphere is changing. Anthropogenic activities are increasing the concentrations of greenhouse gases and releasing synthetic compounds that deplete stratospheric ozone and increase UV-B radiation. Changes of temperature in the Northern Hemisphere during the past century strongly suggest that we are now in a period of rapid global warming relative to the past millennium. Increased concentrations of greenhouse gases are absorbing outgoing infrared radiation in the lower atmosphere, warming the troposphere and cooling the lower stratosphere. Research is beginning to indicate that losses of stratospheric ozone and increases of greenhouse gases are interdependent. Increased greenhouse gases have been implicated in the observed strengthening of stratospheric wind vortices around both poles, in turn setting the stage for further depletion of ozone and increases in UV-B radiation. Although the uncertainties are still large enough to make it difficult to assess health and ecological risks, decisions must be made. Research on indicators of risks to human health and the environment can help reduce the uncertainties in these risks and shorten the time between recognizing the risks of atmospheric change and taking concrete mitigative and adaptive actions.     

Removal of MS-2 and PRD-1 bacteriophages from an ultrapure water system

Viruses must be removed from the ultrapure water environment, as they have the potential to deposit on microelectronic devices and generate killer defects. Controlled and well-defined challenges by MS-2 and PRD-1 bacteriophages were treated in a pilot-scale ultrapure water system using ultraviolet radiation (UV), ozone, mixed bed ion exchange adsorption, and reverse osmosis filtration technologies typical of those used in industrial systems. Applying a first order kinetic model to the data generated rate constants for MS-2 removal by UV-185, 50 mg L⁻¹ ozone, mixed bed ion exchange or reverse osmosis filtration of 15.5, 12.9, 3.9, and 10.4 min⁻¹, respectively, and PRD-1 removal of 13.8, 15.5, 8.2, and 11.9 min⁻¹, respectively. In all cases, removal of viruses by oxidative mechanisms such as ozone and UV were far superior to adsorption and filtration mechanisms. A theoretical viral population balance was generated to model the removal of the bacteriophages by these unit operations. This model relates the inlet time-dependent profile of viruses to the output, destruction, and accumulation profiles; it also relates these profiles to the unit operation’s treatment mechanisms including oxidation, adsorption, and filtration. This model is the first step in generating a site-independent theoretical model to project the persistence of viruses in ultrapure water systems. Received 19 October 1998/ Accepted in revised form 29 May 1999