Contribution of aerobic anoxygenic phototrophic bacteria to total organic carbon pool in aquatic system of subtropical karst catchments, Southwest China: Evidence from hydrochemical and microbiological study

<span class="paragraphSection"><div class="boxTitle">Abstract</div>Aerobic anoxygenic phototrophic bacteria may play a particular role in carbon cycling of aquatic systems. However, little is known about the interaction between aerobic anoxygenic phototrophic bacteria and hydrochemistry in groundwater-surface water exchange systems of subtropical karst catchments. We carried out a detailed study on the abundance of aerobic anoxygenic phototrophic bacteria and bacterioplankton, hydrochemistry and taxonomy of bacterioplankton in the Maocun watershed, Southwest China, an area with karst geological background. Our results revealed that bacteria are the important contributors to total organic carbon source/sequestration in the groundwater-surface water of this area. The aerobic anoxygenic phototrophic bacteria, including β–Proteobacteria<span style="font-style:italic;">,</span> also appear in the studied water system. In addition to that, the genus <span style="font-style:italic;">Polynucleobacter</span> of the phototropic β-Proteobacteria shows a close link with those sampling sites by presenting bacterial origin organic carbon on CCA biplot and is found to be positively correlated with total nitrogen, dissolved oxygen and pH (<span style="font-style:italic;">r </span>= 0.860, 0.747 and 0.813, respectively) in the Maocun watershed. The results suggest that <span style="font-style:italic;">Polynucleobacter</span> might be involved in the production of organic carbon and might act as the negative feedback on global warming.</span>

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