Light, temperature, and discharge control stream metabolism, but the response of gross primary production (GPP) and ecosystem respiration (ER) to seasonal variation in these physical drivers may differ in accordance with the types of human activities present in the catchment. Our study examined three mid-order streams in southern Ontario, Canada that differed in anthropogenic nutrient sources (i.e., sewage treatment plant effluent, sewage lagoon effluent, and agriculture), but had comparable light, temperature, and discharge regimes. For each stream, GPP and ER were estimated daily from June through November. Comparisons of paired daily metabolic rates revealed pairwise differences among all streams, with streams receiving sewage effluent having greater rates and variability of GPP and ER than the stream draining agricultural land. The two sewage influenced streams differed only in ER. Temporal patterns of GPP and ER were correlated for all streams throughout the study period and were most affected by seasonal variation in temperature, whereby effluent receiving streams responded more rapidly to increases in temperature. Our findings suggest that managers may need to balance effects of human activities with regional environmental constraints on stream metabolism to maintain and enhance the ecological condition and services of stream ecosystems.

中文翻译：

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加拿大安大略省南部三个中级河流暴露于不同营养来源的代谢机制

光、温度和排放控制河流新陈代谢，但总初级生产 (GPP) 和生态系统呼吸 (ER) 对这些物理驱动因素的季节性变化的响应可能因流域中存在的人类活动类型而异。我们的研究检查了加拿大安大略省南部的三个中级河流，它们在人为营养源（即污水处理厂污水、污水泻湖污水和农业）方面不同，但具有可比的光照、温度和排放制度。对于每个流，从 6 月到 11 月每天估计 GPP 和 ER。成对的每日代谢率的比较揭示了所有河流之间的成对差异，接收污水的河流比排放农业用地的河流具有更大的 GPP 和 ER 速率和可变性。两种受污水影响的流仅在 ER 中不同。GPP 和 ER 的时间模式在整个研究期间与所有河流相关，并且受温度季节性变化的影响最大，因此污水接收流对温度升高的反应更快。我们的研究结果表明，管理者可能需要平衡人类活动的影响与区域环境对河流代谢的限制，以维持和增强河流生态系统的生态条件和服务。