The Negev Lab

In recent decades, carbon dioxide  levels rapidly increased, causing ocean warming and acidification worldwide. Costal ecosystems are important habitats and play a key role in mitigating climate change by carbon sequestration which is the processes of capturing CO2 and storing it in the sediment by forming organic carbon. Seagrasses are highly efficient in trapping suspended matter and store most of the sequestrated carbon in the sediment. In carbon rich sediments the oxidation of organic matter is the driving force behind most diagenetic reactions which affect the water column as well. The seagrass’s rhizosphere (the zone of influence generated by root growth and activity) creates an oxidizing microenvironment in the sediments, greatly effecting the rates of microbial carbon mineralization, thus creating a complex and strong redox gradient. Since seagrasses profoundly affect the sediments, understating their role in the system and examining the changes they cause, holds an ecological and global importance. The aim of this study is to explore how the subsurface geochemistry is affected by the seagrass (Halophila stipulancea). We compared the porewater geochemistry from vegetated and unvegetated sediments and then incubated the sediment from vegetated and unvegetated area and followed the change in the geochemistry. Our results indicate that while vegetated sediments are more oxidized in the field, after seagrass removal the sediment are more reduced than unvegetated sediments. This implies that although the seagrass enriches the sediment with organic carbon, it keeps the sediment oxidized, while once the seagrass is removed the sediment quickly gets reduced.