Dissolved oxygen (DO) was slightly lower than the standard values (6.1 - 6.6 ppm at 20 - 30 oC, 1 atm, [12]) except at Si Racha pier (site 6), Si Racha Shipping area (site 7) and Leam Chabang pier (site 8), where the deep sea piers were located causing high water turbulence and a lower organic content (data not shown)