Relative importance of biotic and abiotic factors affecting bacterial abundance in Lake Biwa: An empirical analysis

Tek Bahadur Gurung, Maiko Kagami, Takehito Yoshida, Jotaro Urabe

研究成果: Article査読

25 被引用数 (Scopus)


To determine the relative importance of factors affecting bacterial abundance in Lake Biwa, correlation and multiple regression analyses were performed with relevant biotic and abiotic variables. Data used in the analyses were collected weekly from April 1997 to June 1998 at a pelagic site in the north basin. The bacterial abundance ranged from 1 to 7 × 106 cells ml-1, and its spatio-temporal pattern was virtually identical to that in previous studies conducted 12-15 years ago. In the surface layer (0-12.5 m), bacterial abundance was significantly correlated with water temperature and with protozoan and metazoan grazers, but not with chlorophyll a and nutrient concentrations. The results suggest that loss factors rather than growth factors are more important in determining bacterial abundance in this lake. However, grazing effects on bacterial abundance differed among zooplankton. Bacterial abundance correlated negatively with phagotrophic nanoflagellates (PNF) and Daphnia, but positively with Eodiaptomus. Thus, PNF and Daphnia act to reduce the bacterial abundance, while Eodiaptomus acts to stimulate. In contrast, these biotic factors did not explain changes in bacterial abundance in the middle (12.5-25 m) and deep (〉25 m) layers. Instead, the bacterial abundance in the deep layer was highly correlated with vertical mixing regimes, suggesting that bacterial abundance was directly or indirectly affected by abiotic factors. These results indicate that bacterial abundance in Lake Biwa was regulated by different factors at different depths.

出版ステータスPublished - 2001 6月 27

ASJC Scopus subject areas

  • 生態学
  • 水圏科学
  • 水の科学と技術


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