Mycosporine-like amino acids in planktonic organisms living under different UV exposure conditions in Patagonian lakes.

BARBARA TARTAROTTI,; GUSTAVO BAFFICO,; PEDRO TEMPORETTI,; HORACIO ZAGARESE

JOURNAL OF PLANKTON RESEARCH

Año: 2004 vol. 26 p. 753 - 762

0142-7873

Mycosporine-like amino acids (MAAs) were studied in zooplankton from 13 Argentinean lakes covering a broad range in altitude, maximum depth, and physico-chemical properties of the water. Four to nine different MAAs (predominant: porphyra-334 and shinorine) were found in the copepods Boeckella gibbosa, B. gracilipes, B. meteoris, and Parabroteas sarsi, and in the ciliate Stentor amethystinus, while MAAs were undetectable in the cladoceran Daphnia middendorffiana. Among the different copepods, maximum MAA concentrations ranged from 0.25 to 1.31% of the dry weight, and contents were generally ~3-7 times (up to 43 times) higher in the animals living in the clearest lakes compared to those occurring in low-UV systems. This variability in the content of MAAs was related with the lake altitude (r2 = 0.71), and the fraction of the water column to which 1% of the surface UVR at 320 nm penetrated (r2 = 0.57). Our data therefore underscore the role of MAAs as sunscreens to decrease potential negative effects of solar radiation, but they also indicate that other environmental factors besides UV transparency play a role in determining MAA concentrations. One lake was selected to obtain additional information on the qualitative composition of MAAs in < 100 μm seston between two sampling sites and over a two months study period (austral summer). Six different MAAs were detected in the samples, with porphyra-334 and palythine being predominant. In the copepods collected simultaneously, low variation in MAA concentrations was found among the two sites and over time. Thus, our results suggest that under similar UV exposure conditions MAA contents of planktonic organisms show low temporal variation.