Effect of Natural Sunlight on Microbial Population in Shrimp Farming Sediment

Abstract

Water quality and disease control is interdependent and linked to the microbial activities in aquaculturesystem. Microbial processes affect water quality factors such as dissolved oxygen, ammonia, nitriteand sulphide. It is known that aquatic bacterioplankton is sensitive to sunlight radiation, which causescellular damage on different cell targets and lead to mutations, cell inactivation, and death. In this study,the effects of natural sunlight on microbial populations in semi-intensive shrimp pond sediment under apond drying period were studied. During pond preparation, water was drained out and the pond sedimentwas left to expose to sunlight for 30 days. Microbial populations prior to exposure were compared to thatafter exposure using traditional methods for cultivating heterotrophic bacteria and denaturing gradient gelelectrophoresis (DGGE) of 16S rRNA. Prior to sunlight exposure, the mean heterotrophic counts were 108cfu/g of wet sediment. After 14 days of sunlight exposure, the mean heterotrophic counts of the sedimentwere declined 10-fold. Using DGGE, the composition of the microbial community in the sediment prior toexposure was compared to that after exposure to sunlight. The data on the effects of pond drying byexposure to sunlight on microbial populations would help improve the shrimp farming practice on the pondpreparation process.

Keywords : Sunlight / Microbial Population / Shrimp Farming Sediment / PCR-DGGE