PARENT SESSION
Oral Session # 85: GIS and Remote Sensing II; Ecological Modeling III.
Presiding: Y Lin
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 203.

Evaluation of Carbon and Nutrient Fixation Effect in An Artificial Lagoon.

Nakatani, Naoki^*,1, Okuno, Taki¹, Otsuka, Koji¹, ¹ Osaka Prefecture University, Sakai, Osaka, Japan

ABSTRACT- Quality of seawater significantly depends on quantitative relationship between pollution load and natural purification capacities. Water quality in an enclosed sea, where the big industrial cities are surrounded, is chronically bad since the pollution load is much higher than the natural purification capacities. In order to purify the seawater, several coastal eco-techniques have been proposed already. An artificial lagoon, having calm water area surrounded by rubble-mound breakwater, is one of the solutions. Many researchers have pointed out that the artificial lagoon has several water purification functions, such as wave breaking re-aeration, biological contact oxidation in the rubble-mound breakwater, transparency increase due to sinking of suspended matter, carbon and nutrient fixation of seaweed, oxygen supply of seaweed, creation of sound biological material circulation. However, the water purification mechanisms by seaweed and its biological process have not been clarified yet. This paper deals with the water purification mechanism, and also the prediction method of carbon and nutrient fixation in the artificial lagoon by using the coastal ecosystem model. The numerical simulation model is constructed as material circulation of carbon, nitrogen and phosphorus. The predicted results show that the fixation of carbon and nutrient mainly depend on the seaweed biomass, and that the total fixation decreases year by year, because of the accumulation of the sedimentary organic matter. The rock filter is not so effective for the carbon and nutrient fixation. The fixation efficiency increases as the depth of the inner sea is decreasing. At first, the results of field investigation are summarized, and then the ecosystem model is introduced as the prediction method. In order to evaluate the carbon and nutrient fixation effects in the lagoon, the prediction method, a conservation model of the materials, is proposed for the evaluation. .

Key words: Artificila lagoon, Concervation model, Coastal Sea, Ecosystem