Influence of benthic regeneration on the biogeochemical cycle of CO2 in littoral ecosystems

Abstract

The benthic fluxes of inorganic carbon were measured in the Bay of Cádiz, located in the SW of the Iberian Peninsula (Southern Europe). The values measured ranged between 74 and 224 mmol m^–2 d^–1, which are higher than most reported fluxes. They were linearly correlated with the organic carbon content in surface sediments. For the Bay of Cádiz, a carbon budget is proposed. It was determined that 53% of the benthic inorganic carbon production is used by the phytoplankton of the area, and 43% is exported by tides to other littoral areas. The rest of the benthic production, together with direct emission of CO₂ from intertidal sediments to the atmosphere, yielded a maximum net flux of 5.6 · 10⁸ mol C y^–1. If extrapolated to coastal areas globally, these values are particularly significant. Taking 44 mmol m^–2 d^–1 as an average value for benthic fluxes of dissolved inorganic carbon, it is estimated that the benthic CO₂ production by coastal ecosystems is about 4.2 · 10¹⁴ mol y^–1, similar to the estimated annual CO₂ emissions to the atmosphere from the burning of fossil fuels.