Carbon dioxide flux from intensive aquaculture shrimp farming applying biofloc system of Setiu Terengganu, Malaysia

Abstract

Study on the Carbon dioxide, CO2 flux was conducted from the intensive shrimp farming Setiu Terengganu which applying Biofloc Technology system (BFT) started from March until the end of July subjected to different Day of Culture (DOC) of shrimp ponds. The study was done to identify either the shrimp culture pond applying BFT contribute as the carbon sources or help in sequestrated CO2 in the farm and local area. C: N ratio of 10: 1 was applied to remove the nitrogenous waste in the ponds. Water parameters were analyzed using YSI multiprobe 556 and the Total Inorganic Carbon was analyzed using TOC-L SHIMADZU 5000A machine. The carbon flux (CO2 from water to atmosphere) and the partial pressure of CO2, pCO2 were calculated and analyzed using CO2SYS software. About 52 different DOC of shrimps cultured ponds were analyzed for it carbon emission. The results showed a mean CO2 flux about 20.78 ± 21.28 mmol m−2 d−1 and mean partial pressure, pCO2 about 785.8 ± 804.71 μatm respectively. The pCO2 were in ranges between 18.7μatm to 3049.7μatm and were identified that 13 out of 52 ponds have the pCO2 > 1000μatm, 12 ponds have pCO2 > 500μatm to 900μatm and 27 ponds have pCO2 < 400μatm which still present the atmospheric equilibrium (360μatm) suggested that the most of the shrimp pond still available as carbon sinker even though some of the pond act as sources of atmospheric CO2. Larger size of shrimp cultured mostly around DOC 80 and above recognized tend to produce higher pCO2 up to>1000μatm- 3000μatm (DOC102 produced pCO2 of 1639.03μatm; DOC 86 produced pCO2 of 2324.9μatm; DOC94 produced pCO2 of 3049.μatm; DOC95 produced pCO2 of 2940.6μatm and DOC97 produced pCO2 of 1108.6μatm). This might be due to more production of CO2 from respiration of large shrimp and the heterotrophic activity came from the more excessive of shrimp excretion produced by larger size shrimp as compared to smaller size of shrimp cultured respectively. Increase of pCO2 will lead to the increases of CO2 in the atmosphere as can be proved by the relationship of pCO2 and CO2 in dry air, which well correlated (r2 = 1 of the linear regression) and for CO2 flux with pCO2 relationship also were well correlated (r2 = 0.999 of the linear regression) with slope of respectively 1.040 and 0.026. The escape of CO2 to the atmosphere was identified come from the heterotrophic activities in the shrimp pond that applying BFT. This BFT is known as bioremediation agent and dominated by heterotrophic bacterial to synthesize the organic carbon loaded and the excessive protein loaded from uneaten feed in the shrimp pond. The heterotrophic activity from the biofloc organisms plus the respiration from the large size of shrimp and microbial in the ponds was recognized as the contributor of CO2 flux in the farming area.