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Numerical studies on ecological effects of artificial mixing of surface and bottom waters in density stratification in semi-enclosed bay and open sea

2008; Elsevier BV; Volume: 214; Issue: 2-4 Linguagem: Inglês

10.1016/j.ecolmodel.2008.02.023

1872-7026

Kentaro Mizumukai, Toru Sato, Shigeru Tabeta, Daisuke Kitazawa,

Geology and Paleoclimatology Research

An apparatus, which mixes waters in upper and lower layers in density stratification and discharges the mixture at the middle depth, has made a remarkable success in enhancing water quality for ecosystems in a small semi-enclosed bay. In this study, we conducted numerical simulations by using a three-dimensional tidal current model and an ecosystem model to predict the effects of the apparatus in two different seas; a larger semi-enclosed bay and the area around a solitary island in the open sea. Isahaya Bay in Ariake Sea was chosen as the former case to see how effectively the apparatus can reduce oxygen-deficient water, and the sea around Okinotori-shima Island represents the latter, where we are interested in the effect of the apparatus on fertilisation; how much primary production can be increased. As a result, it is suggested that the apparatus reduced up to 70% of oxygen-deficient water in Isahaya Bay during the neap tide in high summer, although it is not very effective in fertilising around the solitary island; only 0.3% of chlorophyll-a was increased in the area affected by the apparatus.