ABSTRACT: Heterotrophic bacteria are key biogeochemical regulators in freshwater systems. Through both decomposition and production of organic matter, bacteria link multiple biogeochemical cycles together. While there has been a significant amount of work done on understanding the role of microbes in the aquatic carbon cycle, important linkages with other biogeochemical cycles will require more information about how organic matter transformations impact other nutrients, such as phosphorus. In this study, we conducted a culture-based laboratory experiment to examine the production of dissolved organic matter (DOM) by heterotrophic bacteria under varied nutrient conditions. In addition to quantifying the production of dissolved organic carbon (DOC), we also measured the production of dissolved organic phosphorus (DOP) and characterized the microbially produced organic matter using optical properties. Results demonstrated that measurable amounts of DOC and DOP were produced by heterotrophic bacteria under nutrient regimes ranging from carbon-limitation to strong phosphorus-limitation. Additionally, optical characterization of DOM revealed that the organic matter produced by bacteria grown under high phosphorus conditions was highly aromatic with similar optical properties to terrestrially derived organic matter. Overall, these findings suggest that heterotrophic bacteria can be important producers of organic matter in freshwaters and that continued trends of increased nutrient concentrations (eutrophication) may fundamentally change the composition of microbially produced organic matter in freshwater systems.

中文翻译：

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P限制驱动水生细菌产生DOM的变化

摘要：异养细菌是淡水系统中的关键生物地球化学调节剂。通过分解和产生有机物，细菌将多个生物地球化学循环联系在一起。尽管在了解微生物在水生碳循环中的作用方面已进行了大量工作，但与其他生物地球化学循环的重要联系将需要更多有关有机物转化如何影响其他养分（例如磷）的信息。在这项研究中，我们进行了一项基于文化的实验室实验，以检查在各种营养条件下异养细菌产生的可溶性有机物（DOM）。除了量化溶解有机碳（DOC）的产量，我们还测量了溶解有机磷（DOP）的产生，并利用光学性质对微生物产生的有机物进行了表征。结果表明，异养细菌在从碳限制到强磷限制的营养体系下产生了可测量的DOC和DOP。此外，DOM的光学表征表明，在高磷条件下生长的细菌产生的有机物是高度芳香的，其光学性质与陆生有机物相似。总体，