Regulation of CO2 by the sea in areas around Latin America in a context of climate change

Abstract

Anthropogenic activitiesare increasing the atmospheric carbon dioxide (CO2); around a third ofthe CO2 emitted by these activities has been taken up by the ocean.Nevertheless, this marine ecosystem service of regulation remains largelyinvisible to society and not enough is known about regional differences andtrends in sea-air CO2 fluxes (FCO2), especially in the SouthernHemisphere. The objectives of this work were as follows. First to put values ofFCO2 integrated over the exclusive economic zones (EEZ) of five Latin-Americancountries (Argentina, Brazil, Mexico, Peru, and Venezuela) into perspectiveregarding total country-level greenhouse gases (GHG) emissions. Second, toassess the variability of two main biological factors affecting FCO2 at marineecological time series (METS) in these areas. FCO2 over the EEZs were estimatedusing the NEMO model, and GHG emissions were taken from reports to the UNFramework Convention on Climate Change. For each METS the variability inphytoplankton biomass (indexed by chlorophyll-a concentration, Chla)and abundance of different cell-sizes (Phy-Size) were analyzed at two timeperiods (2000-2015 and 2007-2015). Estimates of FCO2 at the analyzed EEZsshowed high variability among each other, and non-negligible values in thecontext of greenhouse gas emissions. The trends observed at the METS indicated,in some cases, an increase in Chla(e.g., EPEA-Argentina) and a decrease in others (e.g., IMARPE-Peru). Evidenceof increasing populations of small size-phytoplankton was observed (e.g., EPEA-Argentina,Ensenada-Mexico), which would affect the carbon export to the deep ocean. Theseresults highlight the relevance of ocean health and its ecosystem service ofregulation when discussing carbon net emissions and budgets.