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Sediment condition of the shoreward area in Tokyo Bay was mapped using sediment condition classification system based on echo features. This system enabled us to classify large areas of sediment in high resolution, with the echo trace output grouped by geometric pattern. The sediment condition was categorized by moisture content, which was correlated to the echo trace output. The high resolution sediment condition map showed that good condition sediments were intermittently spaced in the shoreward area that was previously presumed to be totally covered by sludge. This result provides important information about more efficient restoration of the shoreward area in Tokyo Bay because we can now zone the restoration area and carry out sand capping on localized areas.

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Fine root decomposition, mortality, and production are fundamental components of belowground carbon dynamics in mangrove ecosystems. Mangroves are highly productive ecosystems with huge carbon stocks; however, information on the dynamics of submerged fine roots in mangrove soils is limited. To estimate fine root production in several sites of mangrove communities on Pohnpei Island, Micronesia, we estimated continuous inflows using a simple mass balance model to combine ingrowth core and litterbag experimental results. According to our findings, previously reported mangrove fine root production values were severely underestimated because the fine root decomposition process was disregarded during the experimental period. We estimated that annual fine root production up to 0.3 m in depth ranged from 13.8 (Bruguiera gymnorrhiza in a landward plot) to 56.3 Mg ha À1 year À1 (B. gymnorrhiza in a seaward plot). However, comparing the fine root production with respect to the unit of stem cross-section area increase in the sample tree, the fine root production of Rhizophora spp. was greater than that of other species. The annual fine root mortality and decomposition to annual fine root production was 70%-105% and 11%-52% of annual production, respectively.The annual fine root production estimated here was much higher than that previously reported. These findings begin to quantify the contribution and importance of highly productive mangrove fine roots for carbon sequestration in blue carbon ecosystems. Moreover, this study provides new insights into the organic carbon dynamics in mangrove soils with mangrove vegetation succession.