Search for: All records

Abstract. While the importance of carbon cycling in estuaries is increasingly recognized, the role of benthic macrofauna remains poorly quantified due to limited spatial and temporal resolution in biomass measurements. Here, we ask: (1) To what extent do benthic macrofauna contribute to estuarine carbon cycling via respiration and calcification? and (2) How well can routinely collected environmental variables predict their biomass? We analyzed data from 8128 benthic samples collected from the Chesapeake Bay between 1995 and 2022 and estimated associated carbon fluxes using empirical relationships. We then used generalized additive models to relate observed and modeled environmental variables to the biomass. Biomass was highest in the upper mainstem of the Bay (Upper Bay) and upper Potomac River Estuary, the largest tidal tributary of the Bay. In the Upper Bay, benthic macrofauna respired 18 %–45 % of the estimated organic carbon supply. Calcification-driven alkalinity reduction reached 6.31 ± 2.84 mol m−2 yr−1 in the Potomac River Estuary, aligning with prior estimates of alkalinity sinks in the tributary and highlighting the potential importance of calcifying fauna in alkalinity dynamics. Estimated CO2 production in the Upper Bay from benthic respiration and calcification (151 g C m−2 yr−1) also exceeded observed air–sea CO2 fluxes (74.5 g C m−2 yr−1). Generalized additive models revealed that low salinity, moderate dissolved oxygen, and elevated nitrate best predicted high-biomass zones, with the three predictors explaining 52 % of biomass deviance. These predictive relationships offer a pathway to estimate macrofaunal biomass and associated carbon fluxes in systems where direct biomass measurements are sparse. Our findings demonstrate that benthic macrofauna play a substantial and spatially structured role in estuarine carbon cycling. Incorporating their contributions into estuarine biogeochemical models will improve predictions of ecosystem responses to environmental and anthropogenic change. 

Many estuaries experience eutrophication, deoxygenation and warming, with potential impacts on greenhouse gas emissions. However, the response of N₂O production to these changes is poorly constrained. Here we applied nitrogen isotope tracer incubations to measure N₂O production under experimentally manipulated changes in oxygen and temperature in the Chesapeake Bay—the largest estuary in the United States. N₂O production more than doubled from nitrification and increased exponentially from denitrification when O₂was decreased from >20 to <5 micromolar. Raising temperature from 15° to 35°C increased N₂O production 2- to 10-fold. Developing a biogeochemical model by incorporating these responses, N₂O emissions from the Chesapeake Bay were estimated to decrease from 157 to 140 Mg N year⁻¹from 1986 to 2016 and further to 124 Mg N year⁻¹in 2050. Although deoxygenation and warming stimulate N₂O production, the modeled decrease in N₂O emissions, attributed to decreased nutrient inputs, indicates the importance of nutrient management in curbing greenhouse gas emissions, potentially mitigating climate change. 

Estuarine environments are characterized by strong spatial gradients and high temporal variability that are difficult to fully capture with discrete field measurements. This is particularly the case in the Chesapeake Bay, the largest estuary in the continental United States. This archive provides a climatological atlas of physical and biogeochemical conditions for the Chesapeake Bay based on numerical model results of 1985-2023. The atlas includes surface and bottom conditions on a fine longitude/latitude grid with a monthly frequency. The environmental variables are stored in a NetCDF file with abundant metadata that can be used in software such as QGIS, Python, R, Matlab or GNU Octave. A 50+ page documentation in PDF format provides additional information on the environmental variables, the numerical model used to generate the climatology, and an evaluation of the model skill over the period of the atlas. The documentation also includes ready-made visualizations for each environmental variable.