The production-to-respiration ratio and its implication in Lake Biwa, Japan

Jotaro Urabe, Takehito Yoshida, Tek Bahadur Gurung, Tatsuki Sekino, Narumi Tsugeki, Kentaro Nozaki, Masahiro Maruo, Eiichioro Nakayama, Masami Nakanishi

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review


Production-to-respiration (P:R) ratio was estimated at an offshore site of Lake Biwa in order to examine whether the plankton and benthic community is subsidized with allochthonous organic carbon, and to clarify the role of this lake as potential source or sink of carbon dioxide. The respiration rate of protozoan and metazoan plankton was calculated from their biomass and empirical equations of oxygen consumption rates, and that of bacterioplankton was derived from their production rate and growth efficiency. In addition, the carbon mineralization rate in the lake sediments was estimated from the accumulation rate of organic carbon, which was determined using a 210Pb dating technique. On an annual basis, the sum of respiration rates of heterotrophic plankton was comparable to net primary production rate measured by the 13C method. However, when the mineralization rate in the lake sediments was included, the areal P:R ratio was 0.89, suggesting that Lake Biwa is net heterotrophic at the offshore site with the community being subsidized with allochthonous organic carbon. Such a view was supported by the surface water pCO2 that was on average higher than that of the atmosphere. However, the estimate of net CO2 release rate was close to that of carbon burial rate in the sediments. The result suggests that the role of Lake Biwa in relation to atmospheric carbon is almost null at the off-shore site, although the community is supported partially by organic carbon released from the surrounding areas.

Original languageEnglish
Title of host publicationForest Ecosystems and Environments
Subtitle of host publicationScaling Up from Shoot Module to Watershed
PublisherSpringer Tokyo
Number of pages9
ISBN (Print)4431260749, 9784431260745
Publication statusPublished - 2005


  • Carbon budget
  • Heterotrophs
  • Lake metabolism
  • P:R ratio
  • pCO


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