UV radiation and primary production in the Antarctic waters

Abstract

A profiling underwater radiometer was used for the first time in the waters around Indian Antarctic Station (70 degrees 46 minutes S and 11 degrees 44 minutes E) in the summer of 1994. The profiles include natural fluorescence (upwelled radiance at 683 nm), scalar irradiance (photosynthetically active radiation (PAR), computed primary production (pp), diffuse attenuation coefficient, and UVB (308 and 320 nm) and UVA (340 and 380 nm) radiation and ocean temperature all measured as a function of depth from 21/1/94 to 6/3/94. Fifteen stations in the Antarctic waters (69 degrees 53 minutes to 70 degrees 02 second S) and 6 en route (64 degrees 53 minutes 30 degrees 01 minutes S) were analysed. The average values for surface chlorophyll a and pp were higher for temperature than for Antarctic waters (1.68 mg/m sup(3) and 216.56 mgC/m sup(3) /d respectively). The values for column chlorophyll (22.48 mg/m sup(2)) and primary productivity (1023.79 mgC/m sup(2)/d) in the Antarctic waters however, were 2.14 and 1.5 times higher than those in temperate waters. Interestingly, significant positive correlations were observed between primary productivity and PAR, UVA, UVB in the Antarctic and Temperate surface waters. Significant r values were obtained between pp and the above parameters in the Antarctic sub-surface waters determined at discrete depths of 10, 20, 30 and 40 m. However, when the primary productivity values were normalised for PAR, a more negative effect was noticed at the Antarctic surface waters. This response in the photosynthetic parameters could be due to the varied effect of UVA and UVB on phytoplankton