油壺湾の海草藻場における有機炭素・窒素の循環

概要

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Field survey, chamber experiment and decomposition experiment were carried out in the seagrass beds at Aburatsubo Bay, Misaki, Kanagawa Prefecture for understanding cycling of organic carbon and nitrogen. Organic carbon and nitrogen in dissolved and particulate forms were determined in seawater, sediments and seagrass. Concentrations of dissolved organic carbon (DOC) and nitrogen (DON) in October were lower than those in April and July. April and July are productive seasons, while October is a season when consumption of organic matters exceeds production. DOC/DON ratio in seagrass beds in October was higher than those in April and July. The high C/N ratio in October was caused by microbial decomposition, while degradation of seagrass litters and/or suspended organic matter might be done more effectively in April and July. Decomposition process raised up the C/N ratio of seagrass leaves during the degradation process. Moreover, the C/N ratio in sediments is higher in deeper subbottom. Suspended organic matters were decomposed rapidly, whereas seagrass leaves were refractory. The difference of temporal change in C/N ratio between suspended organic matters and seagrass leaves may be due to the different decomposition processes. Contribution of dissolved organic matters (DOM) were greater than that of particulate organic matters (POM) for remineralization.