Chatila K, Demers S, Mostajir B, Gosselin M, Chanut JP, Monfort P, Bird D
Ultraviolet radiation, UVB, Bacteria, mesocosm, light manipulation, 1.5 m3, St. Lawrence estuary, Quebec, Canada
With the continuing increase of ultraviolet-B radiation (UVBR: 280–320 nm) fluxes toward the Earth’s surface, there is concern regarding a possible negative impact on heterotrophic bacterioplankton. The effects of enhanced UVBR on a natural bacterioplankton community were studied during a 7-day experiment conducted in mesocosms (1500 L). Four light regimes were tested:natural light, 280 to 313 nm excluded UVBR, and two levels of UVBR enhancement. During the first 3 days of the experiment characterized by high inorganic nutrient concentrations (nitrates > 1 ?molL?1 and ammonium > 0.1 ?mol L?l), UVBR had no effect on both bacterial abundances and activities. From day 4 to the end of the experiment, nitrate concentrations remained low (