Thermal and saline tolerance of Antarctic krill Euphausia superba under controlled in-situ aquarium conditions

Abstract

As a key species of the Southern Ocean ecosystem, the thermal and saline tolerances of Antarctic krill (Euphausia superba Dana) are relatively unknown because of the challenging environment and complicated situations needed for observation have inhibited in-situ experiments in the field. Hence, the thermal and saline tolerance of krill were examined under in-situ aquarium conditions with different controlled scenarios. According to the experiments, the critical lethal times of krill were 24 h, 2 h and 0.5 h under 9°C, 12°C, and 15°C, respectively, and the estimated 50% lethal times were about 17.1 h and 1.7 h under 12°C and 15°C, respectively. Additionally, the critical lethal times (the estimated 50% lethal times) of krill were approximately 14 h and 0.5 h (about 22.9 h and 1.7 h) of salinity under 19.7 and 15.9, respectively. The observed critical and 50% lethal times of krill were 0.5 h and approximately 1.4 h, respectively, salinity under 55.2. The critical and 50% lethal temperatures of krill were 13°C and approximately 14.2°C, respectively. Additionally, the critical and 50% lethal salinity was 19.6 and approximately 17.5 for the lower saline (below normal oceanic salinity [34.4]) environment and 50.3 and approximately 53.2 for the higher saline (above 34.4) environment, respectively. The upper thermal and saline preferences of krill can be considered 6°C and 26.8 to 41.2, respectively. These results can provide potential scenarios for predicting the possible fate of this key species in the Southern Ocean.