Mediterranean seagrasses as carbon sinks: regional and methodological differences /

The increasing rates of CO2 due to anthropogenic activities are causing one of the most potential climate threats for the Mediterranean Sea: Ocean Acidification. In this region, two endemic species, Posidonia oceanica and Cymodocea nodosa play a crucial role in climate change attenuation. Through their metabolic activity, they can act as carbon sinks and therefore buffer lowering pH values during the day. In this study we analyse the metabolism of these two endemic species through their Gross Primary Production, Community Respiration and Net Community Production rates. To evaluate these metabolic parameters, two methodologies were used: benthic chambers and multiparametric probes. Furthermore, we analysed trends of both seagrass species metabolic rates and their variation between the Eastern and Western Mediterranean Sea. In addition, metabolic rates of seagrass communities were synthesized from published data on seagrass community metabolism to evaluate trends through time. Our analysis revealed that there are differences between methodologies as multiparametric probes can assess seagrass metabolism at a community level whereas benthic chamber can evaluate this at a species level. We found significant differences between the two Mediterranean regions with both methodologies and almost all the studied communities were net autotrophic acting as carbon sinks. Key words: Seagrass, Metabolism, Climate Change, Blue carbon.Master of Science in Marine Biological Resources (IMBRSea)The increasing rates of CO2 due to anthropogenic activities are causing one of the most potential climate threats for the Mediterranean Sea: Ocean Acidification. In this region, two endemic species, Posidonia oceanica and Cymodocea nodosa play a crucial role in climate change attenuation. Through their metabolic activity, they can act as carbon sinks and therefore buffer lowering pH values during the day. In this study we analyse the metabolism of these two endemic species through their Gross Primary Production, Community Respiration and Net Community Production rates. To evaluate these metabolic parameters, two methodologies were used: benthic chambers and multiparametric probes. Furthermore, we analysed trends of both seagrass species metabolic rates and their variation between the Eastern and Western Mediterranean Sea. In addition, metabolic rates of seagrass communities were synthesized from published data on seagrass community metabolism to evaluate trends through time. Our analysis revealed that there are differences between methodologies as multiparametric probes can assess seagrass metabolism at a community level whereas benthic chamber can evaluate this at a species level. We found significant differences between the two Mediterranean regions with both methodologies and almost all the studied communities were net autotrophic acting as carbon sinks. Key words: Seagrass, Metabolism, Climate Change, Blue carbon