This article describes the integrated dynamics model for suggestion of the regional management toward various social issues such as environmental issue coming up to the surface with the development of the society. The coastal area of Rayong province.
Thailand is primarily based on tourism and fishery and has some problems such as the increment of the beach garbage and the coral reef destruction. For modeling, four scenarios were developed as the regional management policy which was the provision of alternative employment opportunity. Non-scenario simulation showed the fishery was broken down and the increment of the beach garbage and the coral reef destruction lead the tourism decline in this area. On the other hand, the scenario simulations indicated four scenarios had a good impact on all dynamics model factors, especially aquatic resources. Additionally, dynamics simulations implied fishery and the fishing households played the important role in terms of the sustainable development in the coastal area of Rayong province.
In order to evaluate/predict the autonomous ecosystem response in a hypoxic estuary to the environmental measures (tidal flat creation, dredging, sand capping and load reduction etc.) and environmental impact (red tide) while considering the effect of a benthic-pelagic and a tidal flat-hypoxic area coupling, a new multiple coastal ecosystem model, ”ZAPPAI”, was developed.
ZAPPAI can investigate the Oxygen-Carbon-Nitrogen-Phosphorus coupled cycle driven by physical and biochemical processes, and these modeled processes describe the ecosystem network of pelagic-benthic or central bay-tidal flat areas mechanically.
Because of the drastic vertical change of biological metabolism in the benthic system, and of the high effectiveness of benthic biological metabolism for the total oxygen consumption in hypoxic estuaries, ZAPPAI describes the early diagenetic processes accurately by securing the micro scale benthic spatial resolution in the vertical direction. ZAPPAI was applied to Tokyo Bay, one of the most hypoxic and eutrophic estuaries in Japan. Temporal trend and spatial distribution of model variables both in the central bay and tidal flat pelagic/benthic system were in good agreement with the observed data. The calculated oxygen and nutrient fluxes at the water-sediment interface also reproduced the field measurements well. Simulation by using ZAPPAI described (1) both the tidal flat restoration and the load reduction in Tokyo Bay improve hypoxia, although 50% load reduction leads to the decrease of high trophic production, while the tidal flat restoration increases that. (2) former Tokyo Bay with early tidal flats can use more nutrients on higher trophic production and escape from hypoxia compared to present Tokyo Bay without early tidal flats, and (3) former Tokyo Bay with early tidal flats was resistant to red tide impact and could prevent the environmental deterioration spiral compared to present Tokyo Bay without early tidal flats.
Nutrients and Hydrogen sulfide fluxes from a benthic sediment becomes important causes on water pollution in a coastal environment. To understand the mechanism how these benthic fluxes are controlled, we performed a numerical experiment by using the CANDI model that can simulate the diagenetic processes in the sediment. The model results showed that an organic matter provided to a sediment from water column is decomposed by bacteria which uses O2, NO3. MnO2. Fe(OH)3. and SO4 as a substrate. Especially the fraction of decomposition process using SO, as a substrate occupied 70% of all processes, which suggested an anaerobic environment in the sediment. The main factor that determines whether an environment in the sediment is aerobic or anaerobic is a sinking flux of an organic matter from water column. To keep an aerobic environment in the sediment, it is necessary to reduce the sinking flux of organic particulate matter.
Ariake Bay is one of representative semi-enclosed estuary in Japan. Recently, a red tide lias appeared and it has brought serious environment problem and also damage for sea weed aqua-culture. Especially the red tide which appeared in winter 2000-2001, gave serious damage for sea weed aqua-culture. The cause of red tide is mainly attributed to eutrophication in that basin. In the case of Ariake Bay. it is believed that the construction of the wire in Isahaya Bay is another reason of red tide appearance. The dominant species of the red tide appeared in 2000-2001 was Rhizosolenia imbricate which is found mainly in an oligotrophy region. The red tide continued for long term even in a nutrient depleted condition. This situation is different from the cause of red tide generation so far.
In this paper, we examined the cause of the red tide appeared in 2000-2001 by using of numerical model, and found that the maximum cell quota played important role on diatom-blooming and blooming duration.
To observe the bio-sonar behavior of dolphins and porpoises, a miniature stereo acoustic data logger was developed to record the echolocation clicks of small cetaceans. The 'A-tag' device is small enough to be attached to a dolphin or porpoise. A-tag can record the sonar pulse intensity, precise inter-click-intervals, and time difference between sounds arriving at two different hydrophones.
The A-tag works for up to 60 hours continuously and allows observation of the sonar target range of free-ranging odontocetes. The time of arrival at the two hydrophones on the tag allows vocalizations from nearby individuals to be identified. A less invasive tagging technique using a suction cup was also developed. A mean attachment time of 15 hours was obtained on freeranging Unless porpoises in a freshwater system in China. The A-tag proved to be a useful tool for investigating the underwater echolocation behavior of odontocetes.