PREVALENCE AND DRIVERS OF OXYGEN SUPERSATURATION IN DEEP WATERS OF GLOBAL LAKES

Warming of surface waters is associated with declining oxygen concentrations in lake bottom waters, reducing habitat availability for oxygen sensitive cold-water species and altering biogeochemistry. Amidst this backdrop, identifying lake features that may confer some resistance to oxygen loss is imperative. Oxygen supersaturation represents oxygen concentrations exceeding those expected for a given water temperature and atmospheric pressure. Supersaturation is often associated with gross primary production exceeding oxygen consumption by respiration and therefore may indicate resistance to oxygen loss. We used a database of 2,822 lakes across mostly North America and Europe to examine the prevalence and drivers of oxygen supersaturation below the surface mixed layer. We find deep-water supersaturation is most common at the top of the metalimnion, present in > 40% of profiles across lakes having a metalimnion. In the hypolimnion, supersaturation is uncommon, occurring in < 5% of profiles across a representative sample of US lakes. Because the top of the metalimnion can often be relatively warm, hypolimnetic supersaturation may hold more potential for preserving oxythermal habitat for cold-water species. Deep-water supersaturation was most likely in lakes having both low nutrient and dissolved organic matter concentrations. In dystrophic lakes approaching 25 mg/L dissolved organic carbon, the probability of deep-water supersaturation approached 0. Our findings provide a framework for pinpointing lakes likely to better maintain deep-water oxygen as deoxygenation progresses.

Presentation Preference: Oral

Primary Presenter: Stephen Jane, University of Notre Dame (coachman7777@yahoo.com)

Authors:

Stephen Jane, University of Notre Dame  (sjane@nd.edu)

Stuart Jane, University of Notre Dame  (sjones20@nd.edu)