School of Public and Environmental Affairs, Indiana University, Bloomington, 702N. Walnut Grove Ave, Bloomington, IN, 47405, USA.
Environ Manage. 2019 Sep;64(3):258-271. doi: 10.1007/s00267-019-01187-2. Epub 2019 Jul 29.
The transport and processing of nutrients and organic matter in streams are important functions that influence the condition of watersheds and downstream ecosystems. In this study, we investigated the effects of streambed sediment removal on biogeochemical cycling in Fawn River, a gravel-bottomed river in Indiana, U.S.A. We measured stream metabolism as well as nitrogen (N) and phosphorus (P) retention in both restored and unrestored reaches of Fawn River to examine how sediment removal affected multiple biogeochemical functions at the reach scale. We also assessed the properties of restored and unrestored streambed sediments to elucidate potential mechanisms driving observed reach-scale differences. We found that sediment removal led to lower rates of primary productivity and ecosystem respiration in the restored reach, likely due to macrophyte removal and potentially due to changes to sediment organic matter quality. We found minimal differences in N and P retention, suggesting that these processes are controlled at larger spatial or temporal scales than were examined in this study. Denitrification enzyme activity was lower in sediments from the restored reach compared to the unrestored reach, suggesting that restoration may have decreased N removal. Our results indicate that most near-term changes in biogeochemical function following restoration could be attributed to macrophyte removal, although effects from sediment removal may emerge over longer timescales.
溪流中养分和有机物质的输送和处理是影响流域和下游生态系统状况的重要功能。在这项研究中，我们调查了河床上沉积物清除对美国印第安纳州 Fawn 河生物地球化学循环的影响。我们测量了溪流代谢以及 Fawn 河恢复和未恢复段的氮（N）和磷（P）保留，以检查沉积物清除如何影响流域尺度上的多种生物地球化学功能。我们还评估了恢复和未恢复的河床沉积物的性质，以阐明驱动观察到的流域尺度差异的潜在机制。我们发现，沉积物清除导致恢复段的初级生产力和生态系统呼吸速率降低，这可能是由于大型植物的清除，也可能是由于沉积物有机质质量的变化。我们发现氮和磷保留的差异很小，这表明这些过程受比本研究中所研究的更大的空间或时间尺度控制。与未恢复段相比，恢复段沉积物中的反硝化酶活性较低，这表明恢复可能减少了氮的去除。我们的结果表明，恢复后生物地球化学功能的大多数近期变化可能归因于大型植物的清除，尽管沉积物清除的影响可能会在更长的时间内显现。
