@misc{oai:repo.qst.go.jp:00067773,
 author = {Takeda, Hiroshi and Sugai, Kazunori and Fuma, Shoichi and Kawabata, Zenichiro and Suzuki, Akira and 武田 洋 and 菅井 一憲 and 府馬 正一},
 month = {Apr},
 note = {Ecological toxicity of urea as nitrogen fertilization was evaluated using an experimental model ecosystem, namely microcosm. The microcosm used in this study was an aquatic microbial ecosystem consisting of flagellate algae Euglena gracilis as a producer, ciliate protozoa Tetrahymena thermophila B as a consumer, and bacterium Escherichia coli DH5 as a decomposer. The microcosm at the developing and mature stages was loaded with urea at final concentrations of 10, 50, 100, 500 mM. The effects observed at the developing stage were different from those at the mature stage. With the addition of urea at 500 mM, all species in the microcosm at the developing stage died out and their coexisting system was disrupted, but the microcosm system at the mature stage was sustainable. Some effects observed in the microcosm were also different from those observed in the pure culture system, in which urea was more significantly hazardous to Tetrahymena and Euglena. Thus, the effects of urea on the three species varied according to the conditions of their cultivation. This result indicates that community-level effects could not be evaluated from the effects investigated in the pure-culture system and should be used model ecosystems such as microcosm., SETAC Europe 14th Annual Meeting},
 title = {Ecotoxicity Evaluation of urea using an experimental model ecosystem},
 year = {2004}
}