Response to temperature and hydrocarbon contamination of protozoa from Antarctic soils.

DOMINGUEZ MS.; VAZQUEZ S.; MAC CORMACK W.

Buenos Aires, Argentina

Congreso; XXXI SCAR and Open Science Conference; 2010

Although protozoa play a key role in the trophic structure of the Antarctic soils, theyhave received little attention. In this work, performed at Jubany Station during February andMarch 2010, the abundance and composition of edaphic protozoa in soils under acute (AC)or chronic (CC) hydrocarbon-contamination was analysed and compared with noncontaminated soil (NC). To evaluate the effect of temperature on protozoan activity,microcosms containing the soils were kept under ambient temperature for 15 days (average:1.5°C). As no trophozoites were observed in this period, microcosms were moved indoor(mean temperature: 10°C). Under this condition, throphozoites were detected after 48 h. InNC soils total protozoa reached 104 individuals per gram (ind/g), ciliates predominating over mastigophores. In contaminated soils an inverse ratio between these groups were observed. No sarcodines were detected in any soil. The acute event of hydrocarbon-contamination severely damaged protozoa population and no trophozoites were detected after one week of incubation at 15°C. After this period, populations tended to recover but exhibited a clear dominance of flagellates over ciliates. AC soil showed counts one order of magnitude lesser than NC soil, while CC reached 105 ind/g. In conclusion, protozoan biology in Jubany Station soils is closely synchronized with temperature, being the disencystment severely affected below 4°C. At least 2 days with temperatures above 4°C is required for protozoa to leave their quiescence state. The higher counts in CC soils could be related with an increase in hydrocarbonoclastic bacteria and thus, with a rise in the bacterivorous populations.