Spatial and temporal variation of methane emissions in the coastal Balearic Sea, Western Mediterranean

Methane (CH₄) gas is the most important GHG after carbon dioxide, with open ocean areas acting as discreet CH₄ sources and coastal regions as intense but variable CH₄ sources to the atmosphere. Here, we report CH₄ concentrations and air-sea fluxes in the coastal area of the Balearic Islands Archipelago (Western Mediterranean Basin). CH₄ levels and related biogeochemical variables were measured in three coastal sampling sites between 2018 and 2021, with two located close to the densely populated island of Mallorca and one in a pristine area in the Cabrera Archipelago National Park. CH₄ concentrations in seawater during the study period ranged from 2.7 to 10.9 nM, without significant differences between the sampling sites. Averaged estimated CH₄ fluxes during the sampling period for the three stations oscillated between 0.2 and 9.7 μmol m^-2 d^-1 according to a seasonal pattern and in general all sites behaved as weak CH₄ sources throughout the sampling period.