| Summary: | 碩士 === 國立中興大學 === 生命科學系 === 91 === Pelagic and benthic community metabolism were measured in situ in the estuary of Tanshui River. The samples were collected from 4 sites every 3 months on 13 January, 14 April and 12 August at spring tides. The changes in dissolved oxygen concentration were measured in cores with water or with undisturbed sediment to determinate the rates of pelagic and benthic community metabolism. Secondly, this study was conducted to determine whether microalgal biomass, invertebrate abundance, and environmental variables in the water column and sediments affect these metabolic rates.
The results showed that variations in oxygen concentration in Tanshui River were affected by the tides. At spring tides, the pelagic community metabolism at 4 sites showed no significant difference. Stepwise multiple regression analyses indicated that 34% of pelagic PB correlated negatively with the NH4+ from the urban sewage. Of 89% of benthic PB was influenced by the DSi and the molar N:Si ratio <1 indicated the Si-limitation. The benthic PB at Waziwei and Guandu was hardly detected. Benthic respiration was influenced by the median size of sediment at 3 sites in Tanshui River. However, that at Chenmei Bridge was influenced by the concnetration of NH4+.
Daily primary production were 93~306 mmol O2 m-3 d-1 for phytoplankton, and 0~72 mmol O2 m-2 d-1 for microalgal. Daily respiration were 35~130 mmol O2 m—3 d—1 for pelagic community, and 6~78 mmol O2 m-2 d-1 for benthic community. The 64~100% of daily primary production was produced by phytoplankton. The 54~98% of daily respiration was consumed by pelagic community. Total community metabolism in the estuary was thus dominated by the pelagic system. The P/R ratio showed that in the estuary of Tanshui River , autotrophy dominated in the pelagic system and heterotrophy in the benthic system.
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