Influence of temperature on respiratory ETS-activity of micro-organisms from Admiralty Bay, King George Island, Antarctica

Abstract

This study describes the respiratory ETS-activity of surface water in an Antarctic coastal area and analyses the effect of temperature on the ETS-activity of organisms living in a consistently low-temperature regime. Secchi disk visibility, temperature, particulate ATP, respiratory electron-transport-system (ETS) activity and bacterial numbers were estimated at ten stations, nine in Admiralty Bay and one off the coast of King George Island in Bransfield Strait in December 1990 and in January 1991. Admiralty Bay was not ice-free in December. Here lower bacterial numbers, ATP and ETS-activities and higher visibilities were found than at the Bransfield Strait station. The lower visibility and higher biomass values and respiration activities in Bransfield Strait can be explained by an earlier start of the primary production in the Strait than in the Bay. In the Bay, at some stations low visibility was not correlated with high values of biomass or activity; the turbidity was caused by material imported from the land to the Bay by meltwater from the ice and snow. In the Bay, the respiratory ETS activity at substrate saturation of the surface layers varied between 6 and 13 μg C·dm −3·d −1 in December and between 5 and 14 μg C·dm −3·d −1 in January, while in Bransfield Strait the values for December and January were 54 and 17 μg C·dm −3·d −1, respectively. The effect of temperature on the respiration activity of the microbial ecosystem of Admiralty Bay (King George Island, Antarctica) was investigated. The temperature optimum of the respiration activity was between 20 and 25°C, and the activation energy calculated from the Arrhenius curve was 75 KJ·mol −1 (=18 Kcal·mol −1), i.e. a strong response to small temperature changes.