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DNA damage and photosynthetic inhibition induced by solar ultraviolet radiation in tropical phytoplankton (Lake Titicaca, Bolivia)

Published online by Cambridge University Press:  23 July 2001

E. WALTER HELBLING ,
VIRGINIA E. VILLAFAÑE ,
ANITA G. J. BUMA ,
MARCOS ANDRADE  and
FRANCESCO ZARATTI
E. WALTER HELBLING
Affiliation:
Estación de Fotobiología Playa Unión & Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Casilla de Correos N°153, (9100), Trelew, Chubut, Argentina
VIRGINIA E. VILLAFAÑE
Affiliation:
Estación de Fotobiología Playa Unión & Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Casilla de Correos N°153, (9100), Trelew, Chubut, Argentina
ANITA G. J. BUMA
Affiliation:
Department of Marine Biology, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
MARCOS ANDRADE
Affiliation:
Laboratorio de Física de la Atmósfera, Instituto de Investigaciones Físicas, Universidad Mayor de San Andrés, Casilla 3164, La Paz, Bolivia
FRANCESCO ZARATTI
Affiliation:
Laboratorio de Física de la Atmósfera, Instituto de Investigaciones Físicas, Universidad Mayor de San Andrés, Casilla 3164, La Paz, Bolivia
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Abstract

Experiments were conducted during October 1998 in Lake Titicaca, Bolivia (16° S, 68° W, 3810 m a.s.l), to determine the effects of solar ultraviolet radiation (UVR) on phytoplankton photosynthetic rates and DNA damage. Water samples were taken daily and incubated in situ or in simulated in situ conditions using sharp cut-off filters to eliminate various portions of the UVR spectrum. The total inhibition of photosynthesis due to UVR in surface waters was 85%; the greatest part of this inhibition (65%) was due to UVAR (315–400 nm), the rest (20%) being due to UVBR (280–315 nm). The inhibition of photosynthesis decreased with depth so that there were no significant differences among treatments at 1·3 optical depths (KPAR). The loss of carbon assimilation in the integrated production over the euphotic zone (4·6 optical depths) was 17·4%, with 14% due to UVAR and an additional 3·4% due to UVBR. Lake Titicaca phytoplankton had a threshold for inhibition of photosynthesis at about 0·3 W m−2 for UVBR and 5 W m−2 for UVAR, below which no inhibition was detected. Above this threshold, photosynthetic inhibition increased steadily, with UVAR having the greatest effect. Analysis of biological weighting functions (BWFs) indicated that phytoplankton from Lake Titicaca was less sensitive to UVR than phytoplankton from other regions. DNA damage (evaluated through the formation of cyclobutane pyrimidine dimers, CPDs) was observed for a simulated worst-case situation (i.e. samples incubated in full sunlight) and significant CPD accumulation was found as a result of UVBR exposure, but not with UVAR. However, absolute levels of damage were relatively low when compared with results obtained at other locations, also suggesting the low sensitivity of Lake Titicaca phytoplankton to UVR. It seems that UVBR stress in these organisms acts via at least two cellular targets: the photosynthetic apparatus and nuclear DNA. Our results suggest that an eventual enhancement of UVBR, due to ozone depletion, would have little impact on the phytoplankton of Lake Titicaca.

Keywords

cyclobutane pyrimidine dimersDNA damageLake Titicacaphotosynthesisphytoplanktonultraviolet radiation
Type
Research Article
Information
European Journal of Phycology , Volume 36 , Issue 2 , May 2001 , pp. 157 - 166
Copyright
© 2001 British Phycological Society

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