Meeting Abstract
Large regions of the pelagic ocean are hypoxic between depths of 150 m and 1000 m. Recent observations indicate that deoxygenated waters are shoaling and compressing the thickness of the vertical habitat of overlying marine ecosystems. Marine organisms ranging in size from tiny zooplankton to large predatory fish utilize the vertical habitat to forage for food and avoid predators. One adaptation that determines the tolerance of organisms to hypoxic conditions is the oxygen affinity of oxygen-transport proteins, hemoglobin and hemocyanin. Oxygen affinity is quantified relative to the oxygen tension at which hemoglobin/hemocyanin is 50% oxygenated, which is referred to as P50. Temperature is an additional environmental factor that needs to be considered because oxygen affinity is sensitive to temperature for many species and there are thermoclines in the ocean water column. P50 is adjusted for the effect of temperature by using the heat of oxygenation in the van’t Hoff equation. P50 depth is the depth in the ocean water column at which the oxygen tension equals P50. We use temperature data and bias-corrected oxygen data from the World Ocean Atlas 2009 to determine the global distribution of P50 depths for a range of oxygen affinities and heat of oxygenation values. The areas of ocean where there are P50 depths are the Pacific Ocean, Arabian Sea, and Bay of Bengal. Heat of oxygenation had an effect on the vertical position and areal extent of P50 depths. The vertical distance between P50 depths was regionally variable – in some areas P50 depths were similar while in other areas P50 depths were separated by >100 m. Based on these results, we predict that habitat compression will alter species interactions in regions where vertical distances between P50 depths are increasing or decreasing.
