Measurements of the photosynthetic rate of a tropical estuary using the 14C method

A seasonal variation in net photosynthetic rates and extracellular 14C-D.O.M. (dissolved organic matter) values of subsurface water samples at three predetermined stations of a tropical estuary in Terengganu was observed. The values were high during the dry season and low during the wet season. The net photosynthetic values ranged between 57.4 and 94.2 g C.1-1h-1 whilst the extracellular 14C-D.O.M. values ranged between 30.1 and 18.3% of the total 14C-photosynthetic rate. The inorganic nitrate and reactive phosphorus levels at the four stations were high but the inorganic ammonium nitrogen level was low during the wet season. The occurence of a high level of nitrate nitrogen could be attributed to increased nitrification processes whilst that of ammonium nitrogen could be due to bacteria mineralisation of decomposition. (author)