Hypoxia sensitivity and respiration of the euphausiid crustacean Meganyctiphanes norvegica from Gullmarn Fjord, Sweden

The oxygen level of the water in the Gullmam Fjord, particularly at the bot tom, becomes hypoxic each year primarily in the winter because of delay in water renewal through currents. Since Meganyctiphanes norvegica is abundant in the bottom waters of the fjord, it was supposed that this species or th is particular fjord population might be hypoxia tolerant. However, oxygen c onsumption measurements showed that M. norvegica regulates its O-2, uptake rate down to 30 % saturation but below that level the oxygen consumption ra te drops and high mortality occurs, indicating hypoxia intolerance.