Nitrous oxide fluxes in a coastal Mediterranean area: the Balearic Sea case study

Abstract

Nitrous oxide gas is the third most important GHG after carbon dioxide, with a global warming potential 300 times larger compared to carbon dioxide on a century timescale. Nitrous oxide production shows large spatial and temporal variability and emission estimates for aquatic systems are uncertain. Specifically, coastal areas are poorly represented in global estimates of marine nitrous oxide emissions. Here, we report nitrous oxide concentrations and air-sea fluxes from the coastal area of the Balearic Islands (Western Mediterranean Basin). Nitrous oxide levels and related biogeochemical variables were measured in three coastal sampling sites between 2018 and 2022, with two located close to the densely populated island of Mallorca and one in a pristine area in the Cabrera Archipelago National Park. Nitrous oxide concentrations in seawater during the study period ranged from 6.5 to 9.5 nM, without significant differences between the sampling sites. Averaged estimated nitrous oxide fluxes oscillated between -1.6 and 1.7 µmol m-2 d-1. All sites generally behaved as weak nitrous oxide sources following a strong seasonal pattern throughout the sampling period.