Effects of biological elements inflowing from agricultural ecosystems on coastal marine ecosystems

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In a water system, River Bekanbeushi, the Akkeshi-ko estuary, Akkeshi Bay, of the eastern Hokkaido, that inflow of biological elements, nitrogen, from terrestrial area to coastal marine ecosystems, in particular from agricultural area for livestock farming in a whole watershed affects coastal marine production, mainly on dynamics of seagrass beds and mariculture production of the Manila clam and oysters, were studied from following aspects.Typological division and mapping of the watershed by land use type using GIS. Effects of types of land use in the watershed on water quality and their evaluation. Comparative measurements of outflow of water and nutrient concentrations in regular state at the three river-mouths. Comparative measurements of outflow of water and nutrient concentration in sporadic runoff at the three river-mouths. Distribution of water temperature, salinity, nutrient concentrations, and chlorophyll concentration in the Akkeshi-ko estuary by monthly measurements, and est … More imation of nitrogen uptake to Akkeshi-ko ecosystem. Age determination of sediments in the Akkeshi-ko estuary and estimation of sedimentation rate of organic matter. Estimation of nitrogen uptake rate by seagrasses in the Akkeshi-ko estuary. Estimation of nitrogen uptake rate by aquatic macrophytes in a river. Estimation of carbon budget in a clam in experiments. Contribution and its evaluation of benthic and epiphytic diatoms to diets of the clam and oysters. Historical dynamics of seagrass beds in the Akkeshi-ko estuary using aerial photographs. Food web analysis in Akkeshi-ko ecosystem by stable isotope. Construction of an ecosystem model by numerical simulation.In conclusion of their results, high production in the Akkeshi-ko estuary is supported by optimal nutrient inflow from terrestrial ecosystems and by high productiyitiy of seagrass beds in steady state. Although there are plenty of nutrients inflowed at sporadic runoff, it was clarifies that these sufficient nutrients can not contribute to coastal marine mariculture. For controlling on such a dashing runoff by heavy rain and for supply of water in steady state with normal nutrient concentration, it was suggested that the existence of forests and wetlands are very important. Less