The air-sea CO2 gas transfer velocity is generally expressed as a function only of the wind speed U10. However, there exists considerable disagreement among the observed values. The disagreement is especially large in the context of the different sea surface conditions (wind wave growth and swell etc.). Consequently, many models of the air-sea CO2 gas transfer velocity are proposed by field and laboratory experiments. In this study, we evaluate the estimated global air-sea CO2 gas flux using the different some air-sea CO2 gas transfer velocity models (field experiment model, laboratory experiment model and hybrid model considering wave breaking). The 6-hourly wind speed and mean period of wind and wave data sets by ECMWF were used. The maximum difference of annual global air-sea CO2 gas flux was 0.76 PgC/year. The annual global air-sea CO2 gas flux of each laboratory experiment models were the smallest value, and each hybrid models were near value to each field experiment models. The difference of each model in low latitude is large, same as the difference in middle latitude. This shows that the difference of the result of each model in low latitude is significant for the estimation of air-sea CO2 gas flux.
A simple method based on physico-chemical property of sediment to estimate the similarity of tidal flat as benthic habitat was proposed. In the study, six tidal flats extending on river mouth in the Ariake Bay (Chikugo river mouth, Shiota river mouth, Rokkaku river mouth, Kikuchi river mouth, and Isahaya Bay) could be classified into five groups from results of the cluster analyses of sediment properties (particle-size distribution, water content and sulphide), and multidimensional scaling (MDS). The classified sediment groups showed the characteristic biota on biomass and species composition, indicating that biota in tidal flat will be estimated by sediment property.
