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 the Journal of Geophysical Research: Biogeosciences describes a study that examined pond development and properties in salt marshes in order to better characterize them under different management and sea level rise scenarios as part of a 2017-2020 collaborative research project.

Abstract

The spatial extent of shallow ponds is expanding in many salt marshes, due to hydrologic management practices and sea-level rise, among other factors. Accounting for ponds in ecosystem biogeochemical models is important for predicting how marshes may change in the future. It is impractical to characterize every marsh pond because they can account for a large fraction of the landscape. Developing predictive relationships between pond properties and easily measured attributes, such as dimensions or distance from marsh landscape features, could facilitate integration of ponds into ecosystem models. We found that pond biogeochemistry changes dramatically day to night, reflecting a combination of primary production and heterotrophic (i.e., microbial) respiration. However, abundances of primary producers, and their effects on whole-pond oxygen metabolism, did not change predictably with pond surface area or volume. Pond properties also did not vary according to location within the marsh. Instead, each pond was unique. The processes affecting pond development are therefore highly localized and might reflect long periods of tidal isolation in the high marsh.