Response of an Antarctic Lake Heterotrophic Community to High Dissolved Oxygen

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Abstract
The upper waters of Lake Hoare, Antarctica, contain dissolved oxygen at about three times the normal saturation (≥42 mg liter −1 ). The response of the heterotrophic plankton community to this high dissolved oxygen was evaluated by the criteria of CFU and d -[ U - 14 C]glucose assimilated-respired. High dissolved oxygen was not inhibitory to d -[ U - 14 C]glucose assimilation-respiration compared with normal atmospheric dissolved oxygen in Lake Hoare water. The d -[ U - 14 C]glucose was assimilated and respired optimally at 12°C in Lake Hoare. The d -[ U - 14 C]glucose assimilated-respired in the upper saturated atmospheric dissolved oxygen waters of Mountain Lake, Va., was inhibited in contrast to Lake Hoare ( P < 0.05). CFU formation was inhibited in both lakes. CFU represent <1% of the fluorochrome-stained direct counts in Lake Hoare. Lake Hoare planktobacteria are smaller than the planktobacteria in Mountain Lake. ATP size fractionation revealed that 39% of the ATP biomass was <0.5 μm in Lake Hoare.