Ecosystem metabolism and nutrient uptake in an urban, piped headwater stream
Ecosystem metabolism and nutrient uptake in an urban, piped headwater stream
复制标题
城市管道源头河流中的生态系统代谢和养分吸收
作者：
A. Hope;W. McDowell;W. Wollheim
管道溪流或地下溪流通常与城市化有关。尽管它们在许多城市流域中普遍存在，但关于管道流河段的生态结构和功能的经验证据很少。本研究测量了美国新罕布什尔州达勒姆的一条城市河流Pettee Brooks的生态系统代谢、养分吸收和相关特征。佩蒂溪有高氯化物和营养盐浓度，底栖生物量低，总初级生产力（GPP），生态系统呼吸（ER）和营养吸收率低，沿着其整个长度在夏季。春季是一个时期的生物活性升高，增加光的可用性在流的非管道部分导致显着更高的GPP，ER，NH4的吸收，和PO4的吸收，在这些开放的河段。管道到达佩蒂溪的水质，溶解O2浓度，温度和排放方面的开放达到相似。管道河段，但是，有显着减少轻，浅沉积物，没有碎片坝。光的情况下抑制自养活动的管道达到，导致GPP的完全丧失，以及底栖AFDM和叶绿素a生物量显着减少。在管道到达异养活性受损程度不相同的自养活动。减少ER在管道河段在夏季，但我们没有发现显着降低DOC或营养吸收率管道河段比开放河段。管道河段的碳消耗，没有显着的本地或异地碳补充，必须主要依靠上游输入的有机质。这些结果表明，虽然管道流的生态条件可能会退化超出其他城市河流河段的程度，管道河段可能仍然维持一些可衡量的生态系统功能。
Piped streams, or streams that run underground, are often associated with urbanization. Despite the fact that they are ubiquitous in many urban watersheds, there is little empirical evidence regarding the ecological structure and function of piped stream reaches. This study measured ecosystem metabolism, nutrient uptake, and related characteristics of Pettee Brook—an urban stream that flows through several piped sections in Durham, New Hampshire, USA. Pettee Brook had high chloride and nutrient concentrations, low benthic biomass, and low rates of gross primary productivity (GPP), ecosystem respiration (ER), and nutrient uptake along its entire length during summer. Spring was a period of elevated biological activity, as increased light availability in the un-piped sections of the stream led to substantially higher GPP, ER, NH4 uptake, and PO4 uptake in these open reaches. Piped reaches of Pettee Brook were similar to open reaches in terms of water quality, dissolved O2 concentration, temperature, and discharge. Piped reaches did, however, have significantly less light, shallower sediments, and no debris dams. The absence of light inhibited autotrophic activity in piped reaches, resulting in the complete loss of GPP as well as a significant reduction in benthic AFDM and chlorophyll a biomass. Heterotrophic activity in piped reaches was not impaired to the same extent as autotrophic activity. Reduced ER was observed in piped reaches during the summer, but we failed to find significantly lower DOC or nutrient uptake rates in piped reaches than in open reaches. Carbon consumption in piped reaches, which do not have significant autochthonous or allochthonous carbon replenishment, must rely primarily on upstream inputs of organic matter. These results suggest that although ecological conditions in piped streams may be degraded beyond the extent of other urban stream reaches, piped reaches may still sustain some measurable ecosystem function.