Abstract. Oxygen-depleted regions of the global ocean are rapidly expanding, with
important implications for global biogeochemical cycles. However, our
ability to make projections about the future of oxygen in the ocean is
limited by a lack of empirical data with which to test and constrain the
behavior of global climatic and oceanographic models. We use
depth-stratified plankton tows to demonstrate that some species of planktic
foraminifera are adapted to life in the heart of the pelagic oxygen minimum
zone (OMZ). In particular, we identify two species, Globorotaloides hexagonus and Hastigerina parapelagica, living within the
eastern tropical North Pacific OMZ. The tests of the former are preserved in
marine sediments and could be used to trace the extent and intensity of
low-oxygen pelagic habitats in the fossil record. Additional morphometric
analyses of G. hexagonus show that tests found in the lowest oxygen environments are
larger, more porous, less dense, and have more chambers in the final whorl.
The association of this species with the OMZ and the apparent plasticity of
its test in response to ambient oxygenation invites the use of G. hexagonus tests in
sediment cores as potential proxies for both the presence and intensity of
overlying OMZs.
Hypoxia Tolerance and Metabolic Suppression in Oxygen Minimum Zone Euphausiids: Implications for Ocean Deoxygenation and Biogeochemical Cycles