Ultraviolet damage and counteracting mechanisms in the copepod Boeckella poppei from Antarctic freshwater lakes

VANINA ROCCO,; OSCAR OPPEZZO,; RAMÓN PIZARRO,; RUBEN SOMMARUGA,; MARCELA FERRARO,; HORACIO ZAGARESE

LIMNOLOGY AND OCEANOGRAPHY

Año: 2002 vol. 47 p. 829 - 836

0024-3590

The process of ozone depletion over the Antarctic continent has resulted in the increase of incident ultraviolet-B (UVB) radiation, whose effects may be damaging to living organisms. To counteract the negative effects ofultraviolet radiation (UVR), aquatic organisms may display one or more strategies: (1) avoidance (i.e. deep distribution);(2) photoprotection through the use of ‘‘sunscreen’’ compounds, such as mycosporine-like amino acids(MAAs); and (3) enzymatic repair of the damage. The effects of UVR were assessed on four populations of thecopepod Boeckella poppei from Antarctic lakes using laboratory and field experiments. The results were related tomeasurements of DNA enzymatic repair activity and MAA concentration. This is the first study that combines thesemeasurements in zooplankton. Boeckella poppei was highly tolerant to UVR (LD50 5 2.2–2.78 J cm22). However,measurements of photorecovery (comparison of UVB mortality in the presence and absence of photoreactivatinglight) and dosage of photolyase activity indicated low rates of enzymatic repair, which may be the result of lowtemperatures typical of Antarctic lakes. Three different MAAs were identified, both in phytoplankton and copepods:porphyra-334, mycosporine-glycine, and shinorine. The population of B. poppei from Lake Boeckella had the lowestMAA concentration, as well as the lowest tolerance to artificial and natural UVR. These findings support the ideathat UV tolerance in this species is related to the accumulation of MAAs. A comparison of the strategies used tocope with potentially damaging levels of UVR by different species of Boeckella indicates a high degree of plasticityin this genus, which has probably been key for its success to colonize a wide range of UV environments.