A 3D numerical model ¡V COHERENS has been applied to construct a coupled hydrodynamic and ecological model for studying Tapeng Bay, which is a coastal lagoon situated in southwest of Taiwan. The simulations have been carried out to study the influences and their interacting mechanisms among the tidal currents, nutrients and micro planktons in the Lagoon. Model results have been compiled for calculating the nutrient fluxes and the primary productions in the Tapeng Bay.
Tapeng Bay is a semi-enclosed coastal lagoon, which has only one tidal inlet for exchanging lagoon water with the coastal currents along the Kaoping coast on the narrow shelf in southwest of Taiwan. The study area is situated in the tropical climate zone where has sunshine through out the year except the rainy days concentrated in the summer season, which is influenced by the southwest monsoon. There are several drainage channels that collect the untreated domestic sewerage and wastewater discharged from the fish farms surround the lagoon. The discharges in these channels are usually low during the dry season. The solid contained in the water are mostly settled on the channel beds. During the raining season, high discharges due to the storm rainfalls re-suspend the sediments and carry into the lagoon. These sediments, which contain high concentrations of suspended solids and nutrients, cause the Bay water highly eutrophied. Therefore, the Bay is fully influenced by the seasonal variations. There are a lot of aquaculture, i.e. oyster farming and fish cage, in the Bay area since the water is calm and rich. But the balance between the nature and the anthropogenic disturbance is breaking.
Besides the water level variation generated from the tidal inlet, the fresh water inflow from 3 major channels are included in the model to simulate their influences to the hydrodynamics and the density driven circulation due to changing salinities and temperatures from these inlets. Plankton, detritus, dissolved nutrients and dissolved oxygen is taking into account as the model variables for this marine eco-system. The plankton growth is mainly generated due to temperature, light intensity and nutrient level. Only the nitrogen cycle has been considered in the model by assuming there are enough supply of phosphate and silicate. Model runs have been carried out according to different seasonal situations of the boundary conditions. Furthermore, climates (heats, lights, winds, etc) are also included in the model to distinct seasonal characteristics.
It is shown, from the model results, that the currents mainly dominate the distribution of nutrients in the Tapeng Bay. The nutrient level controls plankton growth. The nutrient sources are mainly coming from the coastal currents (through tidal inlet) in the wintertime, whereas the summer source was from the drainage channels due to the wash out by the high discharge rates. Beside these, dissolved oxygen concentrations in the Bay water are strongly influenced by the plankton growth rate, faster the photosynthesis higher the DO concentrations.
The eutrophication levels of the Tapeng Bay water have been compiled using the plankton carbon level modeled at various situations. According to the Nixon standard (1995), Tapeng Bay has eutrophication through out the year. Mesotrophic condition can be observed during the wintertime, whereas the hypereutrophic level can be concluded during the raining season.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0822102-092447 |
| Date | 22 August 2002 |
| Creators | Chen, Chun-Nan |
| Contributors | none, none, Jia-Jang Hung, none |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0822102-092447 |
| Rights | unrestricted, Copyright information available at source archive |
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