Relationship between dissolved organic carbon and bacterial community in the coastal waters of Incheon, Korea

Bacteria constitute a large domain of prokaryotic microorganisms present in marine ecosystems and play a significant role in energy flow and nutrient cycling. Bacterial community changes may affect organisms of higher trophic levels. We conducted field monitoring to study the relationship between dissolved organic carbon (DOC) and the bacterial community in the coastal waters of Incheon, Korea. Results showed that abiotic factors, such as temperature, salinity, dissolved oxygen ( DO), pH, and dissolved inorganic nutrients, were not significantly different among the sampling sites during the study period. On the other hand, nutrient conditions were significantly different among the sites between 2012-2013 and 2014. Nitrogen was the limiting factor from 2012 to 2013, and phosphate in 2014. Biotic data showed that DOC affected both bacterial abundance and bacterial composition. A similar fluctuation pattern was observed for phytoplankton and Chlorophyll a. However, a close correlation was not observed between phytoplankton and other variables. Redundancy analysis (RDA) and Pearson correlation analysis of abiotic and biotic factors also showed that DOC concentration and bacterial abundance were correlated. Therefore, DOC appears to be an important factor affecting bacterial abundance and composition in the coastal waters of Incheon, Korea.