Lake respiration is supported by a mixture of autochthonous and allochthonous resources, but the relative significance and interaction of these sources are uncertain across gradients of primary production and organic matter inputs. We manipulated autochthonous resources by adding inorganic nitrogen and phosphorus to two lakes during three summers and monitored a third reference lake. Allochthonous resources were measured as fluorescent dissolved organic matter (FDOM). In the reference and two experimental lakes, daily estimates of respiration were made from continuously deployed oxygen sensors. Daily mean values of temperature and FDOM were determined from high-frequency measurements along with daily measures of chlorophyll a, an index of phytoplankton biomass. We analyzed time series of respiration and tested models that used combinations of the independent variables chlorophyll, FDOM, and temperature. The best models included all three of the independent variables. Respiration increased twofold over the temperature range of 14.5–28.6°C. Respiration increased in association with phytoplankton blooms caused by the nutrient additions, but did not track blooms closely, because of large day-to-day variability. Respiration varied positively with FDOM that was primarily allochthonous and differed among lakes and years. We did not detect an interaction between chlorophyll and FDOM despite the large number of observations and range of chlorophyll and FDOM. Hydrologic, climatic, and land use changes are altering temperature and inputs of nutrients and organic matter to lakes. Our results indicate that these changes may lead to linear responses in ecosystem processes like respiration for the wide range of inputs represented in this study.

中文翻译：

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浮游植物生物量、溶解有机物和温度在整个湖泊营养添加中驱动呼吸

湖泊呼吸由本土和外来资源的混合支持，但这些来源的相对重要性和相互作用在初级生产和有机物质输入的梯度上是不确定的。我们通过在三个夏季向两个湖泊添加无机氮和磷来操纵本地资源，并监测第三个参考湖泊。外来资源被测量为荧光溶解有机物 (FDOM)。在参考湖和两个实验湖中，每天呼吸的估计是通过连续部署的氧传感器进行的。温度和 FDOM 的日平均值由高频测量值以及叶绿素a 的每日测量值确定，浮游植物生物量指数。我们分析了呼吸的时间序列并测试了使用自变量叶绿素、FDOM 和温度组合的模型。最好的模型包括所有三个自变量。在 14.5-28.6°C 的温度范围内，呼吸增加了两倍。呼吸增加与营养添加引起的浮游植物大量繁殖有关，但由于每天的变化很大，因此没有密切跟踪大量繁殖。呼吸随 FDOM 呈正变化，FDOM 主要是外来的，并且在湖泊和年份之间存在差异。尽管叶绿素和 FDOM 有大量观察和范围，但我们没有检测到叶绿素和 FDOM 之间的相互作用。水文、气候和土地利用的变化正在改变湖泊的温度和营养物质和有机物质的输入。