Meeting Abstract

79.2  Monday, Jan. 6 10:15  Metabolic depression as a common strategy for diel migrating zooplankton survival in oxygen minimum zones ELDER, L.E.*; SCHNEIDER, J. L.; HANCOCK, L.P.; SEIBEL, B.A.; University of Rhode Island; Univeristy of Rhode Island; Brown University; University of Rhode Island leab83@my.uri.edu

Oxygen minimum zones (OMZs) are predicted to expand as global temperatures and CO₂ levels increase, and oceanic oxygen levels decrease. OMZs occur at intermediate depths in productive regions of the world’s oceans where oxygen consumption is greater than oxygen supply. In such regions, the biomass of permanent deepwater species is limited. However, diel vertical migration is still prevalent, with many species that spend daytime at oxygen levels less than 10µM (1% oxygen). Here we assess the respiratory physiology of some abundant zooplankton that perform diel vertical migrations into OMZs. Oxygen consumption, and lactate production were measured to estimate the aerobic and anaerobic contributions, respectively, to total metabolism under conditions that mimic its day- (1% oxygen, 10^°C) and night-time (21% oxygen, 20^°C) conditions. In all species tested, oxygen consumption was lower in the hypoxic treatment. Anaerobic metabolism was elevated but did not compensate entirely for the reduced rate of aerobic metabolism. This work demonstrates that the vertically migrating zooplankton are employing metabolic depression to survive day time forays into OMZs. Retreat to shallow waters at night is required for foraging and to burn off the accumulated oxygen debt. As global warming continues, OMZs are expected to expand vertically, compressing the nighttime habitat of diel migrating zooplankton, which has implications for the ecology and biogeochemical cycling in the region.