碩士 / 國立臺灣海洋大學 / 海洋生物研究所 / 92 / Due to the fact that microphytoplankton is more vulnerable to phosphate limitation then nano- and picophytoplankton are in the ocean, alkaline phosphatase activities were used to evaluate the level of phosphate limitation in microphytoplankton in the East China Sea. First, a diatom (Skeletonema costatum strain Kao) isolated from Kaohsiung harbor was used in a series of tests including substrate reaction curves, phosphate-limited cultivations, abrupt changes in ambient phosphate concentrations, and alkaline phosphatase activity changes with the addition of excessive phosphate. In these experiments, the physiological reactions of phytoplankton at high and low phosphate concentrations were monitored. When S. costatum was cultivated at low phosphate concentrations, both rate of cell division and final cell concentration reduced significantly. At the same time, alkaline phosphatase activities became higher, ranged from 1.0 × 10-2 to 5.0 × 10-2 fmol PO43- cell-1 min-1. By contrast, when cultivated at high phosphate concentrations, the alkaline phoshpatase activities were low, ranged from 2.0 × 10-3 to 5.0 × 10-3 fmol PO43- cell-1 min-1. If excessive phosphate was added at a time of several days after inoculation, the alkaline phosphatase activities in low-phosphate cultures decreased, but those in high-phosphate cultures remained at the same level. This property was use to compute an alkaline phosphatase activivty ratio (APA ratio), and experimental results indicated that phytoplankton was not limited by phosphate when APA ratio was lower than 2. This concept was subsequently applied in the field during several oceanographic crusies in 2003 including OR1_691、OR2_1114、OR2_1135 and OR2_1157 to examine spacial and seasonal variations of phosphate limitation in the East China Sea. In August 2003, alkaline phosphatase activities in the East China Sea ranged from between 1.0 × 10-2 to 5.9 × 10-1 fmol PO43- cell-1 min-1. According to values of absolute activities, the region from mid-self to the edge of Kuroshio revealed signs of phosphate shortage, with station 16 as the most serious location. However, APA ratios indicated that phosphate limitation in the East China Sea was centered in the Changjiang River plume. Away from the river plum, the degree of phosphate limitation decreased, and no phosphate limitation was found in the southern part of the East China Sea. As for seasonal variations in the Southern East China Sea, higher alkaline phosphatase activities were found on the edge of Kuroshio in August and September, at about 2.0 × 10-1 fmol PO43- cell-1 min-1 . The highest value was observed during the November cruise, reaching 5.5 × 10-1 fmol PO43- cell-1 min-1 near Mazu island, and 9.3 × 10-1 fmol PO43- cell-1 min-1 on the edge of Kuroshio. However, all APA ratios observed in the Southern East China Sea was lower than 2.6 regardless of seasons. The highest value of APA ratio was found in September, which may indicate weak phosphate limitation in that month. In comparison, the highest APA ratio in Changjiang plume was 5.03, much higher than values observed in the Southern East China Sea. This supports the conclusion that phytoplankton in the Southern East China Sea was not phosphate-limitated.
| Identifer | oai:union.ndltd.org:TW/092NTOU5270003 |
| Date | January 2004 |
| Creators | Chi-Yu Shih, 時繼宇 |
| Contributors | Jeng Chang, 張正 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 77 |
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