CONICET | Buscador de Institutos y Recursos Humanos

Phytoplankton cells are important primary producers that contribute with a substantial share to CO2 fixation in marine ecosystems, since marine diatoms represent 40% of the total primary production in the ocean. Recently, in situ Fe supplementation to the Southern Atlantic Ocean was performed, as an attempt to control the atmospheric production of CO2, and to increase the primary productivity. The main goal of this study was to assess the effect of Fe supplementation on the growth of the Antarctic diatoms under culture conditions. Antarctic diatoms were collected at Caleta Potter, 25 de Mayo Island (62° 14´S, 58° 38´W), isolated and grown with f-2 medium in presence of the addition of Fe from 2.5 to 900 μM. Chlorophyll-a content was measured spectrophotometrically, was 2150  58 and 2766 95 mg/ml in log phase from control (11 μM) and cells exposed to 100 μM Fe, respectively. The exposure to higher Fe concentrations (200 to 900 μM) lead to a decrease in chlorophyll-a content, understood as a decrease in the growth of diatoms cells. The maximum rate of growth (μmax) was reached at day 9 under control conditions, however under lower Fe concentrations, it was observed a delay in reaching μmax of 1 to 3 days. Intracellular Fe content, evaluated spectrophotometrically, increased from 0.08  0.01 to 15.5  0.9 nmol/mg prot for extra-cellular Fe concentrations from 100 to 500 μM. However, at an Fe content of 900 μM in the extra-cellular medium, a significant decrease in the intra-cellular Fe (2.2  0.3 nmol/mg prot) was seen. These results suggested a strong dependence of diatom growth on Fe supplementation, however, an excess of Fe could affect cellular growth having a negative impact on phytoplankton that could be due to catalytically generation of active oxygen radicals. Supported by University of Buenos Aires and CONICET.