ARTICLE Diversity of bacterial community during spring phytoplankton blooms in the central Yellow Sea Min Liu, Yi Dong, Wuchang Zhang, Jun Sun, Feng Zhou, Jingling Ren, Shixiang Bao, and Tian Xiao Abstract: Bacterial community diversity and the effects of environmental factors on bacterial community composition during 2 spring phytoplankton blooms in the central Yellow Sea were investigated by using denaturing gradient gel electrophoresis (DGGE) and multivariate statistical analysis. The Shannon–Weaver indices (H=) of bacterial diversity from samples at station B23 were higher than those at station B20. Cluster analysis based on DGGE band patterns indicated temporal variations of bacterial community at the 2 bloom stations but a vertical distribution pattern only at station B20. The predominant bacterial groups were affiliated with Alphaproteobacteria, Gammaproteobacteria, Cytophaga–Flavobacterium–Bacteroides, Deltaproteobacteria, and Actinobacte- ria. The effects of environmental factors on bacterial community were analyzed by canonical correspondence analysis. Bacterial community structures were significantly affected by silicate at station B20 and by Paralia sulcata and Heterocapsa spp. at station B23. From the results, phytoplankton species composition had a significant effect on bacterial community structure during phytoplankton blooms in the central Yellow Sea. Key words: bacterial community, phytoplankton bloom, denaturing gradient gel electrophoresis, canonical correspondence analysis, Yellow Sea. Résumé : Des observations par électrophorèse en gel de gradient dénaturant (DGGE) et des analyses statistiques multivariables ont permis d’examiner la diversité des communautés bactériennes et l’incidence des facteurs environnementaux sur la compo- sition des communautés bactériennes lors de deux efflorescences d’algues au milieu de la mer Jaune. L’indice Shannon–Weaver (H=) exprimant la diversité bactérienne d’échantillons issus de la station B23 était supérieur a ` celui de la station B20. Une analyse de groupement fondée sur les profils de DGGE a révélé des variations temporelles de communautés bactériennes aux deux stations d’efflorescence mais un mode de distribution vertical n’a été observé qu’a ` la station B20. Les principaux groupes de bactéries étaient associés aux Alphaproteobacteria, Gammaproteobacteria, Cytophaga–Flavobacterium–Bacteroides, Deltaproteobacteria et Actinobacteria. L’incidence des facteurs environnementaux sur les communautés bactériennes fut déterminée par une analyse de correspondance canonique. Les structures des communautés bactériennes ont été significativement affectées par le silicate a ` la station B20 et par Paralia sulcata et Heterocapsa spp. a ` la station B23. Ces résultats permettent d’affirmer que la composition des espèces de phytoplanctons a eu une incidence significative sur la structure des communautés bactériennes lors d’efflorescences phytoplanctoniques au milieu de la mer Jaune. [Traduit par la Rédaction] Mots-clés : communautés bactériennes, efflorescences phytoplanctoniques, électrophorèse en gel de gradient dénaturant, analyse de correspondance canonique, mer Jaune. Introduction Bacteria as the member of the microbial food loop are funda- mental engineers and regulators of biogeochemical cycles (Azam et al. 1983; DeLong and Karl 2005). About 50% of organic matter produced by phytoplankton is utilized and remineralized by bac- teria (Cole et al. 1988; Ducklow et al. 1993). During phytoplankton bloom, massive amounts of dissolved, particulate, and colloidal organic matter are generated by primary production and are pro- cessed by the food web (Azam 1998). The concentration and com- position of organic matter are expected to change at different periods during the bloom; this typically affects bacteria (Smith et al. 1995; Fandino et al. 2001). Bacteria, especially heterotrophic bacterioplankton, actively respond to algal bloom by enlarging cell size, increasing cell abundance and the proportion of active cells, shifting substrate-uptake capabilities (Yager et al. 2001), in- creasing bacterial productivity and growth rates (Bird and Karl 1999; Cochlan 2001; Wetz and Wheeler 2004), and adjusting bacterial sur- face (hydrophilic and hydrophobic) properties (Stoderegger and Herndl 2005). Changes of bacterial community structure also were observed during phytoplankton bloom (Riemann et al. 2000; Fandino et al. 2005). Many studies have revealed the close links between phyto- plankton and bacteria, such as the correlation between the con- centration of chlorophyll a (Chl a) and the abundance and production of bacteria (Cole et al. 1988; Suzuki et al. 2001). Bacte- rial community structure is affected not only by the concentra- Received 13 December 2012. Revision received 1 March 2013. Accepted 4 March 2013. M. Liu. Tropical Marine Biological Resources Research Center, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences (CATAS), Haikou 571101, People’s Republic of China; Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences (CAS), Qingdao 266071, People’s Republic of China. Y. Dong, W. Zhang, and T. Xiao. Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences (CAS), Qingdao 266071, People’s Republic of China. J. Sun. College of Marine Science and Engineering, Tianjin University of Science & Technology, Tianjin 300457, People’s Republic of China. F. Zhou. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, People’s Republic of China. J. Ren. Key Laboratory of Marine Chemistry Theory and Technology, Ocean University of China, Qingdao 266100, People’s Republic of China. S. Bao. Tropical Marine Biological Resources Research Center, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences (CATAS), Haikou 571101, People’s Republic of China. Corresponding author: Tian Xiao (e-mail: txiao@ qdio.ac.cn). 324 Can. J. Microbiol. 59: 324–332 (2013) dx.doi.org/10.1139/cjm-2012-0735 Published at www.nrcresearchpress.com/cjm on 12 March 2013. Can. J. Microbiol. Downloaded from www.nrcresearchpress.com by "Institute of Oceanology, CAS" on 05/08/13 For personal use only.