Dissolved Oxygen and Triple Oxygen Isotope Measurements Provide Different Insights into Gross Oxygen Production in a Shallow Salt Marsh Pond

Journal Article Resource
March 2021

Parallel grid ditches were dug in approximately 90% of mid-Atlantic and New England salt marshes in the 1920s through the 1940s. Today, managers must navigate the effects of past actions when making decisions about marsh hydrology and drainage that impact human health, ecosystem services, and marsh sustainability. Managers must also consider how stressors such as sea-level rise impact marshes. A collaborative research project helped to address this challenge by working iteratively with end user groups to develop a decision support tool for marsh hydrology management strategies that promote sustainability and delivery of valuable ecosystem services under future sea-level scenarios.

About this article

This 2020 article which appeared in Estuaries and Coasts describes a study that evaluated rates of gross oxygen production over different time scales in a shallow temperate salt marsh pond as part of a 2017-2020 collaborative research project.

Abstract

The metabolism of estuarine environments is often estimated by measuring changes in dissolved oxygen concentrations. A central assumption of common oxygen-based approaches is that oxygen consumption rates (primarily respiration) are similar under light and dark conditions. Evaluating this assumption is critical, especially in benthic-dominated systems, because differences between daytime and nighttime respiration could result in underestimation or overestimation of ecosystem productivity. We evaluated rates of gross oxygen production over hourly to seasonal time scales in a shallow, temperate salt marsh pond. To assess whether a dissolved oxygen diel mass balance underestimated gross oxygen productivity, we compared rates using this traditional approach and using the triple oxygen isotope tracer of photosynthesis. The methods agreed well over daily to seasonal time scales. However, during midday periods of peak light and productivity, the triple oxygen isotope approach resulted in higher hourly scale gross oxygen production rates. The timing and magnitude of this short-term difference is consistent with light-dependent oxygen uptake fluxes including photoreduction and/or light-stimulated community respiration. Finally, aquatic vegetation was associated with variability in productivity across the pond. Such small-scale environmental heterogeneity is evidence that this shallow pond was not laterally well mixed, and likely contributes to the dynamism of these common estuarine environments.

Citation: 

Howard, E.M., A.C. Spivak, J.S. Karolewski, K.M. Gosselin, Z.O. Sandwith, C.C. Manning, and R.H.R. Stanley. 2020. Dissolved oxygen and triple oxygen isotope measurements provide different insights into gross oxygen production in a shallow salt marsh pond. Estuaries and Coasts. doi.org/10.1007/s12237-020-00757-6.