Effect of irradiance and temperature on photosynthesis and growth of two antarctic benthic diatoms, Gyrosigma subsalinum and Odontella litigiosa

摘要

Light and temperature demands for photosynthesis and growth of two benthic diatoms from Potter Cove, a shallow bay in King George Island, South Shetland Islands (Antarctica), were determined in laboratory cultures. The species investigated were Gyrosigma subsalinum var.antarctica and the Antarctic endemic Odontella litigiosa. The algae exhibited different light requirements for growth and photosynthesis. G. subsalinum was adapted to low light conditions, with a high light utilisation coefficient (a) and low saturating photon irradiances for photosynthesis and growth (similar to25 mumol m(-2) s(-1) and 11 mumol m(-2) s(-1), respectively). Photosynthesis and growth in O. litigiosa were saturated at a photon irradiance of similar to100 mumol m(-2) s(-1). Both benthic diatoms exhibited extremely low upper survival temperature (UST, 5-7degreesC) and growth only occurred over a narrow range from 0 and 7degreesC. Optimal temperature for growth (0degreesC) was slightly lower than optimum temperature for photosynthesis (5 degreesC). The results suggest that G. subsalinum is well-adapted to the low light and constant low temperature conditions present in water depths below 10 m where it occurs. In contrast, O. litigiosa requires more light and is able to tolerate the higher temperatures typical of shallow waters and tide pools. The northern distribution limit of G. subsalinum is the 4 degreesC summer isotherm, i.e. at the northern boundary of the Antarctic region. In contrast, O. litigiosa could potentially also occur in the sub-Antarctic region up to the 7 degreesC summer isotherm.