has provided knowledge about teachers' understanding of sustainable development, different teaching traditions and approaches, but knowledge is still lacking about teachers' views on including different sustainability-promoting actions. The aim of the article is to study Eco-School teachers ' and instructors' views
Effects of ambient and enhanced UV-B radiation (UVBR) on marine microbial plankton communities were assessed in a model ecosystem at Kristineberg Marine Research Station (KMRS) on the Swedish west coast. The system consisted of 16 aquaria (40 l) filled with surface seawater and semicontinuously run by replacing 10 l of their contents with filtered seawater twice a day. The aquaria were placed outdoors and the ambient solar radiation was reduced by 70% using neutral screens. Four different levels of UVBR were applied, each in 4 replicates: nothing, ambient, ambient +10% and ambient + 20%. The enhanced UVBR was supplied by fluorescent tubes whose intensity was modulated by the ambient radiation to give a constant percentage increase. Variables measured were nutrients (N, P, Si), composition of phytoplankton species and pigments, bacterial and primary productivity, and bacterial cell numbers. Statistically significant UVBR effects were found for carbon allocation, size distribution of primary productivity and phytoplankton species composition. It was also found that UVBR exposure during the development of the phytoplankton communities increased their sensitivity to UVBR in short-term carbon dioxide fixation measurements. We propose that this was due to an adaptation of the community to UVBR, including an increased production of components within the photosynthetic apparatus damaged by UVBR. The UVBR had no significant effect on the total biomass of phytoplankton and bacteria. KEY WORDS: UV-B radiation · Primary production · Marine microbial plankton · Plankton · PigmentResale or republication not permitted without written consent of the publisher Aquat Microb Ecol 25: 75-86, 2001 the experiments (Cabrera et al. 1997, Keller et al. 1997, Wulff et al. 2000 when the succession is high. Smaller effects observed later in the experiments can be due to, for example, competition for resources (nutrient or space) or UVBR adaptation of the community (Laurion et al. 1998, Odmark et al. 1998.Not only the consequences on biomass and productivity are important when analysing UVBR effects in microbial communities; other important factors include UVBR-mediated changes in size distribution within the plankton community and carbon allocation to different biomolecules. Both of these factors are indicative of the status of the community and are important for the value of phytoplankton as prey. It has previously been assumed that larger cells are generally less sensitive to UVBR than smaller cells (Karentz et al. 1991, Bothwell et al. 1993. Wängberg et al. (1996b) found that the smaller algae were more sensitive if the analysis was reduced to a single class of diatoms (Centrales), but not when the whole community was analysed. In the study of Laurion et al. (1998) the fraction of total chlorophyll a (chl a) in picoplankton increased significantly when the community was shielded from UVBR. Recently Mostajir et al. (1999) found that UVBR reduced the number of large (5 to 20 µm) but not small (< 5 µm) phytoplankton, which the...
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