Effects of UV radiation in arctic and alpine freshwater ecosystems

13.5 Conclusions

We have seen that there are some aspects of alpine and arctic freshwater localities, in spite of low intensities of UVR, that could make organisms in these ecosystems particularly vulnerable to UVR;

• Their frequent shallowness, offering no depth refugium for the biota

• Their low levels of DOC and other UV-absorbing compounds.

• The low levels of nutrients of thus low primary production

• The frequent low temperatures that could slow down the anti-oxidant expression and cellular repair mechanisms that are coping with UV-induced damage.

There are nevertheless rather scattered and somewhat contrasting information on effects of UVR in Arctic and alpine habitats. Part of this can be accredited experimental condition and stage or condition of the tested organisms, but it does probably also reflect a real difference in UVR susceptibility among taxa and species. Adaptations such as vertical migration or the presence of UVR protective pigments suggest a major need for UV-protection in arctic and alpine localities. Thus alpine and arctic freshwaters communities are evolutionary shaped towards tolerance to a variety of challenges including high exposure to UVR. These evolutionary adaptations of behaviour, pigmentation and enzymes reflects the organisms’ past experience with UV. Such adaptations clearly have their costs, yet such costs may be quite subtle and hard to detect.