Department of Freshwater Conservation, Brandenburg University of Technology Cottbus Senftenberg, Bad Saarow, Germany; Koblenz-Landau University, Institute of Environmental Sciences, Landau, Germany.
Department of Freshwater Conservation, Brandenburg University of Technology Cottbus Senftenberg, Bad Saarow, Germany.
Sci Total Environ. 2022 Sep 10;838(Pt 1):155950. doi: 10.1016/j.scitotenv.2022.155950. Epub 2022 May 16.
Climate change and anthropogenic water demand have increased the frequency and duration of drying periods across rivers and streams worldwide. However, the biogeochemical processes during the water return in desiccated riverbeds are still unclear. Drying is a complex and diverse process and biogeochemical implications upon flow resumption may depend on attributes of the drying and river sediment characteristics (i.e., organic matter content [OM]). In order to understand the effect of drying duration and intensity on the biogeochemical dynamics following flow resumption, we exposed OM- and non-enriched river sediment from an intermittent river section to three different drying intensities (low: shade and rain; moderate: no shade and rain; high: no shade and no rain), each for three drying durations (10, 30 and 90 days). We determined the sediment-associated microbial respiration and dissolved organic carbon (DOC), ammonium‑nitrogen (NH-N), nitrate‑nitrogen (NO-N) and soluble reactive phosphorus (SRP) net release/retention rates of the nine drying treatments in flow-through microcosms over four days past flow resumption. Under the most intense and prolonged drying, non-enriched sediments showed a lag response in respiration on the first day after flow resumption, while all other treatments had either a linear increase or an early pulse in respiration. After 48 h, respiration remained constant, with minor changes in respiration dynamics regardless of the OM content of the sediment and drying attributes. The drying duration and intensity had greater effects on SRP release/retention soon after the flow resumption, while NH-N and NO-N release/retention rates were more strongly affected four days later. Our results suggest that drying attributes influence the biogeochemical dynamics more strongly during the first 24 h upon flow resumption. However, neither respiration nor nutrient dynamics recovered within four days to levels of the sediments before drying for any drying treatments. Hence, the atrributes of the drying have considerable implications in rivers biogeochemistry upon flow resumption.
气候变化和人为需水增加了世界各地河流和溪流干涸期的频率和持续时间。然而，干涸河床水流恢复期间的生物地球化学过程仍不清楚。干涸是一个复杂而多样化的过程，水流恢复后生物地球化学的影响可能取决于干涸的特征和河流沉积物的特征（即有机质含量[OM]）。为了了解干燥持续时间和强度对水流恢复后生物地球化学动态的影响，我们将间歇性河流段的 OM 富集和非富集河流沉积物暴露于三种不同的干燥强度（低：阴凉和降雨；中：无阴凉和降雨；高：无阴凉和无降雨），每种干燥强度持续 3 种干燥时间（10、30 和 90 天）。我们在水流恢复后四天的流动微生境中，测定了 9 种干燥处理中与沉积物相关的微生物呼吸和溶解有机碳（DOC）、铵态氮（NH-N）、硝酸盐氮（NO-N）和可溶性反应磷（SRP）的净释放/保留率。在最强烈和最长时间的干燥下，非富集沉积物在水流恢复后的第一天出现呼吸滞后反应，而其他所有处理要么呼吸线性增加，要么早期出现脉冲。48 小时后，呼吸保持不变，无论沉积物的 OM 含量和干燥特性如何，呼吸动态变化都很小。干燥持续时间和强度对水流恢复后不久的 SRP 释放/保留有更大的影响，而 NH-N 和 NO-N 释放/保留率在四天后受到更强的影响。我们的结果表明，干燥特性在水流恢复后的头 24 小时内对生物地球化学动态的影响更大。然而，对于任何干燥处理，在四天内，呼吸和养分动态都没有恢复到干燥前沉积物的水平。因此，干燥特性对河流生物地球化学在水流恢复后具有重要意义。
