Aerobic anoxygenic phototrophic bacteria (AAnPB) are bacteriochlorophyll a-containing photoheterotrophic organisms that rely on phototrophy and heterotrophy processes for energy acquisition. Here, we demonstrate the ubiquitous distribution of AAnPB in the Uwa Sea and their relatively larger cell size among members of the bacteria community. The contribution of AAnPB in terms of cell number to the total bacterial abundance ranged from 3.5 % to 7.9 %. The mean cell volume for AAnPB was 2.78 +/- A 0.72 times larger than the mean cell volume of the total bacteria. The ratio of the contribution of their biovolume to the total bacteria was estimated to be 9.7-22 %.