Some lichenized ascomycetes synthesize melanic pigments in their upper cortices when exposed to ultraviolet light and high solar radiation. Our previous work showed that melanized chloro- and cyanolichens from both high light and more shaded habitats were less photoinhibited than pale ones during controlled exposure to high light. However, protection from high light might not necessarily be the consequence of just sun-screening by melanins in upper cortices. An inherent problem with earlier experiments was that the photobionts of melanized thalli might have received more light than those beneath pale cortices. The photobionts may therefore have possessed other light-induced tolerance mechanisms that gave protection from photoinhibition. Here, we aimed to test directly the inherent tolerance of lichen photobionts to photoinhibition. The method involved removing the lower cortices and medullas of three lichen species, Cetraria islandica, Crocodia aurata and Lobaria pulmonaria, and exposing the photobionts to light from below. Results confirmed that most of the improvement in tolerance to photoinhibition in melanized lichens derives from fungal melanization in the upper cortex. However, in C. islandica, the most heavily melanized species, algae from melanized thalli possessed a significantly higher tolerance to photoinhibition than those from pale thalli, suggesting that photobionts can also adapt themselves to high light.

This is the first study to examine the tolerance of Antarctic springtails (Collembola) to ultraviolet radiation (UV). Survival of extended attenuated exposure to sunlight was examined for both individuals and aggregations of the species Gomphiocephalus hodgsoni Carpenter over a 10 day period. Both individuals and aggregations demonstrated significantly higher survival and moult rates from control treatments kept in the dark to those exposed to UV. A photo-inhibitive element to moulting is indicated that may function to protect post-ecdysial springtails when their emergent cuticles are more sensitive to the external environment. DNA damage was measured in springtails directly exposed to sunlight for 5 h on a clear sunny day. Significant differences were found between treated animals and controls kept in the dark. There was some reduction of damage 12 and 24 h after exposure, when springtails had been placed in the dark to recover. This indicates the up-regulation of DNA repair mechanisms, with the 12 h treatment in particular showing no significant difference with controls. In addition to providing a first look at UV tolerance in these soil arthropods, these findings recommend employing strict protocols for collections of sample material for subsequent biological analysis in order to minimize the interactive effects of photo-damage.

This investigation was motivated by the lack of ultraviolet radiation (UVR, 280–400 nm) studies on Antarctic benthic marine microalgae. The objective was to estimate the impact of UV-B (280–315 nm) and UV-A (315–400 nm), on photosynthetic efficiency, species composition, cell density and specific growth rate in a semi-natural soft-bottom diatom community. In both experiments, cell density increased over time. The most frequently observed species were Navicula cancellata, Cylindrotheca closterium, Nitzschia spp., and Petroneis plagiostoma. For both experiments, a shift in species composition and a decreased photosystem II (PSII) maximum efficiency (Fv/Fm) over time was observed, irrespective of treatment. UVR significantly reduced Fv/Fm on days 3 and 10 (Expt 1), disappearing on the last sampling date. A similar trend was found in Expt 2. A significant UV effect on cell density was observed in Expt 1 (day 10) but not in Expt 2. No treatment effects on species composition or specific growth rate were found. Thus, the UV effects were transient (photosynthetic efficiency and cell density) and the growth of the benthic diatoms was generally unaffected. Overall, according to our results, UVR does not seem to be a threat to benthic marine Antarctic diatoms.

We have determined the base composition (percentage of guanine-cytosine base pairs, GC%) of total DNA from Euphausia superba to be 32% ± 0.5%. This is the lowest GC% recorded for a metazoan. Low GC% DNA has high concentrations of thymine (T) residues and consequently a greater abundance of adjacent T residues [T(n) arrays]. Ultraviolet B (280–320 nm, UV-B) radiation damages DNA primarily at (T)n arrays, so we suggest that krill DNA may be more susceptible to damage from increased levels of UV-B radiation over the Southern Ocean than the DNA of other Antarctic organisms.

The effects of UV-A and UV-B (Cracow District, Poland, 50°04′N, 19°57′E; 220 m a.s.l.) on oxygen consumption were studied in common toad Bufo bufo (L.) tadpoles (Gosner stage 27). Ecologically relevant chronic doses of UV were simulated in the laboratory. Larvae separated for experiment were derived from UV-exposed or not exposed embryos. After hatching, tadpoles in stages 24–27 were treated with UV-A or UV-B. UV-A caused significant increases in oxygen consumption in larvae grown from untreated embryos, whereas no changes occurred in tadpoles irradiated with UV-A during embryonic and larval development. UV-B caused significant decreases in oxygen consumption in all exposed tadpoles. The changes were larger in larvae derived from eggs not exposed to UV-B than in tadpoles grown from UV-B-treated embryos. Our results suggest that ambient levels of UV-A and especially UV-B may affect the metabolic rate of common toad larvae living in shallow habitats. Affected respiration may retard development as well as increase the susceptibility of tadpoles to ecologically relevant pathogens. On the other hand, it seems that UV-irradiation induces some adaptive processes during embryonic development, which increase the resistance of the larval respiratory system to solar UV radiation.