Articles | Volume 15, issue 17
Research article
04 Sep 2018
Research article |  | 04 Sep 2018

Carbon dioxide and methane fluxes at the air–sea interface of Red Sea mangroves

Mallory A. Sea, Neus Garcias-Bonet, Vincent Saderne, and Carlos M. Duarte

Abstract. Mangrove forests are highly productive tropical and subtropical coastal systems that provide a variety of ecosystem services, including the sequestration of carbon. While mangroves are reported to be the most intense carbon sinks among all forests, they can also support large emissions of greenhouse gases (GHGs), such as carbon dioxide (CO2) and methane (CH4), to the atmosphere. However, data derived from arid mangrove systems like the Red Sea are lacking. Here, we report net emission rates of CO2 and CH4 from mangroves along the eastern coast of the Red Sea and assess the relative role of these two gases in supporting total GHG emissions to the atmosphere. Diel CO2 and CH4 emission rates ranged from −3452 to 7500 µmol CO2 m−2 d−1 and from 0.9 to 13.3 µmol CH4 m−2 d−1 respectively. The rates reported here fall within previously reported ranges for both CO2 and CH4, but maximum CO2 and CH4 flux rates in the Red Sea are 10- to 100-fold below those previously reported for mangroves elsewhere. Based on the isotopic composition of the CO2 and CH4 produced, we identified potential origins of the organic matter that support GHG emissions. In all but one mangrove stand, GHG emissions appear to be supported by organic matter from mixed sources, potentially reducing CO2 fluxes and instead enhancing CH4 production, a finding that highlights the importance of determining the origin of organic matter in GHG emissions. Methane was the main source of CO2 equivalents despite the comparatively low emission rates in most of the sampled mangroves and therefore deserves careful monitoring in this region. By further resolving GHG fluxes in arid mangroves, we will better ascertain the role of these forests in global carbon budgets.

Short summary
Mangroves are capable of storing carbon in their roots, leaves, and in the sediment; however they can also emit carbon as greenhouse gases (GHG) to the atmosphere. In this study, we collected sediment cores and calculated GHG flux rates from mangrove forests along the Red Sea coastline. Using flux rates reported in this study, we determined that Red Sea mangroves are net carbon sinks, storing more carbon than they emit. This study provides rationale to conserve and expand Red Sea mangroves.
Final-revised paper