Abstract:
Theporal variation of dissolved silicate and biogenic silicate in sediments from 11 stations along the Bangpakong estuary were studied in April, June, September and December, 2002. Dissolved silicate content in the water column at each station varied temporally. The dissolved silicate concentration in June was significantly higher than that of the other sampling period and the lowest concentration was found in December. The distribution pattern of dissolved silicate along the estuary was rather similar in all sampling periods; low content in upstream of the river, the highest content in the middle part of the river and the content decreased again at the river month as well as in the sea. The amount of rainfall and fresh water discharged tended to be the major factor controlling dissolved silicate content in the Bangpakong estuary. However, dissolved silicate in April may be resulted from regeneration of biogenic silicate in sediment. The biogenic silicate in sediment of the Bangpakong estuary was found to vary temporally. In April the biogenic silicate in the sediment was significantly higher than that in the other sampling period. In June, its content was lower than the detection limit at all stations. In September low content of biogenic silicate in sediment was found in the upstream and middle stations of the river as well as in the sea, whereas low content of biogenic silicate at all stations was found in December. The accumulation of biogenic silicate in sediments in the Bangpakong estuary may be controlled by biological process (growth of diatom), chemical process (dissioved solution of biogenic silicate) and water circulation in the estuary which may cause re-supension of the sediments.