Ecological Research

, Volume 26, Issue 3, pp 615–626

Cascading effects of larval Crucian carp introduction on phytoplankton and microbial communities in a paddy field: top-down and bottom-up controls


    • Port and Airport Research Institute
  • Taisuke Ohtsuka
    • Lake Biwa Museum
  • Kohei Yoshiyama
    • Atmosphere and Ocean Research InstituteThe University of Tokyo
  • Daisuke Nakai
    • Lake Biwa Museum
  • Fujiyoshi Shibahara
    • Agricultural Technology Promotion Center of Shiga Prefecture
  • Masayoshi Maehata
    • Lake Biwa Museum
Original Article

DOI: 10.1007/s11284-011-0820-9

Cite this article as:
Nishimura, Y., Ohtsuka, T., Yoshiyama, K. et al. Ecol Res (2011) 26: 615. doi:10.1007/s11284-011-0820-9


Effects of fish predation propagate through aquatic food webs, where the classical grazing food chain and microbial loop are interwoven by trophic interactions. The overall impact on aquatic food webs is further complicated because fish may also exert bottom-up controls through nutrient regeneration. Yet, we still have limited information about cascading effects among fish, zooplankton, phytoplankton, and microbes. In this study, we performed a mesocosm experiment to evaluate effects of fish introduction on plankton communities. Six plots were set in factorial combination with fish introduction and rice straw plowing in a paddy field, and the experiment was continued for 4 weeks. Introduction of fish significantly increased chlorophyll a concentrations in smaller size fractions (<15 μm) and abundances of filamentous bacteria (>5 μm in length) and heterotrophic nanoflagellates in 3–15 μm fraction. Microbes in 0.8–3 μm fraction showed increasing but not significant trends in response to fish introduction. These results indicate cascading effects of fish predation operating via two pathways, one through grazing food chain and the other through microbial food web. Phytoplankton community compositions shifted in similar fashion in all plots until 1 week after fish introduction, and then diverged between plots with and without fish thereafter. Bottom-up effects of fish introduction were suggested by increases of total chlorophyll a and inedible phytoplankton species in response to fish introduction. This study provides an example of how fish predation regulates biomass and structure of phytoplankton and microbial communities.


Trophic cascades Food chain Microbial loop HNF Filamentous bacteria

Copyright information

© The Ecological Society of Japan 2011