Cold comfort for krill? Respiratory consequences of diel vertical migration by Meganyctiphanes norvegica into deep hypoxic waters

Diurnal vertical migration of krill Meganyctiphanes norvegica into hypoxic waters in the Gullmarsfjord, Sweden would appear to be made possible only b y the fact that the deep hypoxic waters are much colder than the surface wa ters. The ability to regulate O-2 uptake over a wide range of PO(2)s increa sed dramatically at low temperatures (P-c decreased from 8-11 kPa at 15 deg reesC to 4-6 kPa at 7 degreesC) due to a temperature-related decrease in me tabolic rate (Q(10) >2) Our experiments examining respiratory regulation an d L-lactate accumulation at different O-2/temperature combinations suggest that if the deep waters below the pycnocline had been characterised by the same thigh) temperature as found at the surface, then the physiological tol erances or capacities of individuals of this krill population would hare be en insufficient to permit residence in those waters of more than a few hour s.