Metabolic and phylogenetic profiles of microbial communities from a mariculture base on the Chinese Guangdong coast

This study examined the phylogenetic and metabolic features of microbial communities in Baisha Bay mariculture areas of Nan’ao Island, a mariculture base on the Chinese Guangdong coast. Large seaweed ( Gracilaria lemaneiformis ) cultivation zones (LZ), fish culture zones (FZ), and control zones (CZ) were sampled. According to community-level physiological profiling, d -mannitol, d -mannitol/α- d -lactose, and d -mannitol/α-cyclodextrin were the carbon sources with the highest utilization rates in CZ, LZ, and FZ, respectively ( R s > 1.9). Denaturing gradient gel electrophoresis analysis showed that the dominant bacteria in CZ and LZ were Alphaproteobacteria (39.9 and 34.5%, respectively), whereas in FZ they were Flavobacteria (32.2%). The Shannon diversity in CZ and LZ was significantly higher than in FZ ( P < 0.05). Some opportunistic pathogens, such as Vibrio , Pseudoalteromonas and Loktanella , were abundant in FZ. The microbial communities and most of the dominant bacteria in FZ were more affected by environmental factors including salinity, chemical oxygen demand and total phosphorus. Some bacteria, such as Brevundimonas and Polaribater , have the potential to degrade agar in seaweed, and were isolated from samples rich in algae which are dominant in LZ. The cultivation of G. lemaneiformis created the notable structures and functions of macroalgae-associated bacterial communities that were less affected by the environmental factors examined.