Sensitivity of winter phytoplankton communities from Andean lakes to ultraviolet-B radiation

HELBLING, E.W.; VILLAFAÑE, V.E.; BARBIERI, E.S.

REVISTA CHILENA DE HISTORIA NATURAL

SOC BIOLGIA CHILE

Año: 2001 vol. 74 p. 273 - 282

0716-078X

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; text-align:justify; text-indent:9.05pt; line-height:150%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-family:"Times","serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Calibri; mso-bidi-theme-font:minor-latin; mso-fareast-language:EN-US;} .MsoPapDefault {mso-style-type:export-only; text-align:justify; text-indent:9.05pt; line-height:150%;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> During July of 1999 sampling was carried out in five Andean lakes to determine the sensitivity of winter phytoplankton communities to ultraviolet - B radiation (UV-B, 280-320 nm).  The studied lakes, Moreno, El Trébol, Nahuel Huapi, Gutiérrez and Morenito, located in the Patagonia region (41 °S, 71 °W, 800 m a.s.l), had attenuation coefficients for UV-B that ranged from 0.36 m-1 (Lake Moreno) to 2.8 m-1 (Lake Morenito).  The samples were inoculated with labeled carbon (NaH14CO3) and incubated in an illuminated chamber (UV-B = 0.35 W m-2; UV-A (320-400 nm) = 1.1 W m-2; and PAR (400-700 nm) = 10.8 W m-2) at 10 °C.  The phytoplankton cells were exposed to UVR (280-400 nm) + PAR (quartz tubes) and UV-A + PAR (quartz tubes covered with Mylar-D).  The total duration of the experiments was 4 hs and two samples were taken from each treatment every hour.  In Lakes Moreno, El Trébol, Nahuel Huapi and Gutiérrez, the photosynthetic inhibition increased linearly with UV-B doses, while in Lake Morenito just a slight relationship was observed.  After receiving a dose of 1.25 KJ m-2 (UV-B), phytoplankton from Lake Morenito had the highest cumulative photosynthetic inhibition (44%), whereas in Lakes Moreno, El Trébol, Nahuel Huapi and Gutiérrez the inhibition was of 22%, 11%, 5% and 1%, respectively.  However, at the end of incubation period and after receiving doses of 5 KJ m-2 the most inhibited phytoplankton cells were from Lake Moreno (70%) and the most resistant (27%) was from Lake Gutiérrez.  The kinetics of inhibition was different in each lake, and transparent lakes, with higher proportion of large cells, had higher inhibition rates.  The results suggest that a relative increase in UV-B radiation (e.g., produced by a decrease in stratospheric ozone), would have a greater impact on microplankton from clear lakes, while pico- and nanoplankton from less transparent lakes will be less affected.