Mediterranean seagrasses as carbon sinks: methodological and regional differences

[摘要] The increasing rates of CO 2 due to anthropogenicactivities are causing important potential climate threats for theMediterranean Sea: ocean acidification and warming. In this region, twoseagrass species, Posidonia oceanica and Cymodocea nodosa , can play a crucial role in climate changemitigation. Seagrasses can act as carbon sinks, buffer lowering pH valuesduring the day and storing carbon in the sediment underneath their meadows.However, available data documenting these processes are scattered andcollected using different methodologies, which makes its interpretation andgeneralization very challenging. In this study, we analyzed published andunpublished data (collected for this study) on seagrass community metabolismto compare two methodologies, benthic chambers and multiparametric sensors,and evaluate trends through time for these two species. Furthermore, weanalyzed seasonal trends of both seagrass species' metabolicrates and their variation between the eastern and western Mediterraneanbasins. Most evaluated meadows, 80.9 %, were autotrophic. Calculatedmetabolic rates differ between methodologies, with multiparametric sensorsestimating rates almost an order of magnitude higher, 143.22±28.21  (SE) mmol O 2  m −2  d −1 for net community production (NCP)compared to an average of 18.75±3.80  (SE) mmol O 2  m −2  d −1 for measurements with benthic chambers. However, sensors arenot able to differentiate between habitats and only useful to assessseagrass metabolism at a broader community level, whereas benthic chambersare capable of evaluating rates at the species level and confirm that P. oceanica is moreproductive compared to C. nodosa . We found similar metabolic rates in the eastern andwestern Mediterranean regions for P. oceanica with the benthic-chamber technique andhigher NCP in the west based on sensor measurements.

[学科分类] 大气科学