Studies of Decomposition rate and release of nutrients Ammonium, Nitrates, Nitrites, and Phosphatesions during the decomposition of Oryza coarctata in the laboratory experiment.

Abstract

he vegetation, other than the mangroves in Indus delta, for example Oryza coarctata is also the
source of nutrients for the adjacent coastal environment. The O. coarctata is the major vegetation on
the tidal mudflatds of Keti- Bunder (Hajambro creek), Indus delta, other than the Avicennia marina
and Rhizophora mucronataplanted mangrove forest. This is the first report of decomposition rates of O.
coarctata in the laboratory. The decomposition of O. coarctata. was conducted to evaluate the nutrients
(ammonium, nitrate, nitrites, phosphates) during the decomposition. The decomposition rate was more
rapid during this early phase and O. coarctata. decomposed up to 40 % during the first 7 days.
Afterwards, the Oryzasp. decomposed slowly and gradually and remained up to 40% of the dry mass.
Therefor e, about 60% of the organic matter present in the O. coarctatacan decompose completely in the
aerobic conditions of the aquatic environment. The ammonium ions concentration was found 2.75
μM/L at 7th day and highest value was 6.38 μM/L at 124th day of exp eriment. So the amount of
ammonium ions increased during the phase of decomposition. The nitrate ions concentration was 1.95
μM/L at 7th day and increased to 2.71 μM/L at 15th day of decomposition, and afterwards the
concentration of nitrate decreased gradually and lowest value 0.129 μM/L was recorded in the last day
of the experiment. The nitrite ions concentration was found 1.80 μM/L and gradually increased to
3.33 μM/L at 60th day and the lowest value was 3.05 μM/L. The initial concentration of the phosphate
ions was 0.84 and decresed gradually during the phase of decomposition to its lowest value at 0.7
μM/L. The concentration of the nitrogen in the O. coarctata was initially between 1- 1.5 mg DW, which
increased to about 2 mg DW at the 7th day of the decomposition. The % DW nitrogen contents than
decreased suddenly at 15th day reaching up to about 1 mg DW of the decomposed material. This
decrease of the t otal DW Nitrogen is very important, as it is the source of the nutrients to the adjacent
ecosystem. The results are also strongly correlated with the nutrients values.