Abstract
Zooplankton from clear alpine lakes thrive under high levels of solar UV radiation (UVR), but in glacially turbid ones they are more protected from this damaging radiation. Here, we present results from experiments done with Cyclops abyssorum tatricus to assess UV-induced DNA damage and repair processes using the comet assay. Copepods were collected from three alpine lakes of differing UV transparency ranging from clear to glacially turbid, and exposed to artificial UVR. In addition, photoprotection levels [mycosporine-like amino acids (MAAs) and lipophilic antioxidant capacity] were estimated in the test populations. Similar UV-induced DNA damage levels were observed among the copepods from all lakes, but background DNA damage (time zero and dark controls) was lowest in the copepods from the glacially turbid lake, resulting in a higher relative DNA damage accumulation. Most DNA strand breaks were repaired after recovery in the dark. Low MAA concentrations were found in the copepods from the glacially turbid lake, while the highest levels were observed in the population from the most UV transparent lake. However, the highest lipophilic antioxidant capacities were measured in the copepods from the lake with intermediate UV transparency. Photoprotection and the ability to repair DNA damage, and consequently reducing UV-induced damage, are part of the response mechanisms in zooplankton to changes in water transparency caused by glacier retreat.
Highlights
Organisms from clear alpine lakes have to cope with different stresses including periods of high UV radiation (UVR, 280 – 400 nm) intensities (Sommaruga, 2001)
Levels of carotenoids, which act against photo-oxidative stress, are comparable in C. abyssorum tatricus (Tartarotti et al, 1999) to those found in other copepod species from diverse alpine aquatic systems (Hessen and Sørensen, 1990; Persaud et al, 2007), and the content of UV-absorbing mycosporinelike amino acids (MAAs) in these populations is among the highest reported for freshwater organisms (Tartarotti et al, 2004; Tartarotti and Sommaruga, 2006; Persaud et al, 2007)
The copepod C. abyssorum tatricus commonly occurs in alpine lakes ranging from highly UV transparent to glacially turbid
Summary
Organisms from clear alpine lakes have to cope with different stresses including periods of high UV radiation (UVR, 280 – 400 nm) intensities (Sommaruga, 2001). In clear alpine lakes in this region, planktonic organisms are exposed to UVR throughout the entire water column, even to the shortest wavelengths in the UVB range (280– 315 nm). Copepod populations living in turbid alpine lakes resulting from direct glacier discharge, are protected from high levels of UVR. This difference in UV transparency is reflected at the level of photoprotective responses such as copepod MAA contents Our observations suggest that C. abyssorum tatricus populations from alpine lakes of different UV transparency will respond differently to UV stress at the molecular level
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