Context
The DYNOX project aimed to elucidate the role of seasonal hypoxia as a driving mechanism for the exchange of the potent greenhouse gas (GHG) nitrous oxide (N2O) across the sediment-water-air interfaces in anthropogenically impacted coastal regions. To this end, we employed a comprehensive and innovative observational approach in Lake Grevelingen (Netherlands), which is a saline coastal reservoir that experiences seasonal hypoxia as a result of limited water exchange after two dams were built in the 60s-70s. The measurement strategy consisted of novel shipboard measurements, laboratory-based incubation experiments and analysis of archived samples. This comprehensive approach allowed an unprecedented analysis of the fluxes of N2O from a shallow eutrophic coastal ecosystem and its natural variability in response to the onset of seasonal hypoxia. The results of DYNOX aimed not only close gaps in data and fundamental understanding in the field of Earth and Environmental Sciences, but also provided valuable data to the Essential Ocean Variables Framework of the Global Ocean Observing System, and will serve as a scientific basis for issuing recommendations to local authorities on priority locations for cost-effective environmental monitoring. Hence, the project results are a direct contribution to the research and innovation framework programme “Horizon Europe”, within the mission area “Healthy oceans, seas, coastal and inland waters”, as well as to the UN Sustainable Development Goals (SDG) by addressing SDG 13 “Climate Action” and SDG 14 “Life Below Water”.
Main goals
Considering the substantial lack of understanding of the biogeochemical cycling of N2O within marine sediments and the influence of seasonal hypoxia on the emissions of this gas towards the atmosphere, DYNOX employed a multidisciplinary approach to elucidate the role of seasonal hypoxia as a driving mechanism for the exchange fluxes of N2O across the sediment-water-air interfaces in an anthropogenically impacted coastal system, thereby addressing a central task in the improvement of predictions of the ocean’s role under future climate scenarios. To this end, DYNOX addressed the following specific objectives:
Objective 1: Ascertain the spatial and temporal variability of sources and sinks of N2O within coastal sediments in response to the seasonal onset of hypoxia.
Objective 2: Constrain the water column budget of N2O and its variability under seasonally changing environmental settings, as well as the vertical distribution in association with different production pathways.
Objective 3: Quantify the transfer of N2O across the sea-air interface and its temporal and spatial variability.
