Abstract:
Water and sediment qualities in shellfish culture off the coast of Sriracha were investigated in October 2021 (inter-monsoon), January 2022 (northeast monsoon), May 2022 (inter-monsoon), and August 2022 (southwest monsoon). It was found that the general water qualities were within the standard for coastal aquaculture, except dissolved oxygen was below the threshold in October and May. The average values of ammonia, nitrite, nitrate, orthophosphate, and silicate were 39.54±30.71 µg-N/L, 11.54±10.74 µg-N/L, 12.86±11.46 µg-N/L, 21.41±11.78 µg-P/L, and 595.92±307.29 µg-Si/L, respectively. In October, the concentrations of nitrite, orthophosphate, and silicate were highest in all observation periods. In May, the highest levels of ammonia and nitrate were found. Silicate was high in all study periods that may be caused by freshwater runoff and resuspension of the sediment along the coast. Nutrients in seawater were increased from the shellfish culture itself and from external sources, namely Sukreep Canal, south of the aquaculture area and north of Koh Loy whive were transported by the currents into the aquaculture area. Most of the sediment particles in the shellfish culture area were very coarse sand and larger than those without shellfish culture. Water content and total organic matter in the sediment were not different from the surrounding area. This may be due to the rapid rate of decomposition of organic matter and the good water exchange, resulting in less accumulation of organic substances in the sediment.