Role of phytoliths in carbon stabilization of Zostera marina L. plants: One unreported mechanism of carbon sequestration in eelgrass beds.

It is generally considered that the main carbon sequestration capacity of seagrass beds depends on the burial of organic matter in anaerobic sediments, and plants in aerobic conditions contribute little to carbon sequestration due to decomposition. However, the role of phytolith-occluded carbon (PhytOC) in eelgrass to protect against aerobic degradation shows a long term mechanisms of carbon stabilization that is poorly understood. Eelgrass is a silicon-rich plant, and plants with a high silicon content generally contain phytoliths that occlude carbon. Thus, it is speculated that eelgrass contains phytoliths and sequesters carbon through PhytOC. To confirm this inference, eelgrass in Swan Lake, Yangjia Bay and Shuangdao Bay, China, was investigated. The solids extracted from eelgrass did not discolor when they were exposed to iodine, and their morphology was similar to the phytoliths of land plants. Thus, these solids were phytoliths rather than starch grains. The phytolith morphology varied with eelgrass habitat and plant part, but it was mainly irregular. The sequestrated carbon stock of eelgrass plants through PhytOC in Shuangdao Bay in March, June and November were 87.30, 252.70 and 36.09 mg/m2, respectively. Thus, PhytOC is a potentially important and unrealized form of carbon sequestration in eelgrass beds. • Contrary to previous thinking, eelgrass contains phytoliths. • The main type of phytolith in eelgrass is irregular. • Carbon sequestration of eelgrass plants through PhytOC is important. [ABSTRACT FROM AUTHOR]