CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus Gualtar, 4710-057 Braga, Portugal.
CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus Gualtar, 4710-057 Braga, Portugal.
Sci Total Environ. 2020 Jun 1;719:137361. doi: 10.1016/j.scitotenv.2020.137361. Epub 2020 Feb 19.
Freshwater mussels are undergoing rapid global declines due to habitat loss and fragmentation, among other factors, but little is known about the effects of small hydropower plants. Here we assessed the impact of small hydropower plants on the abundance and size structure of the imperilled pearl mussel Margaritifera margaritifera. For this, we sampled 66 sites in three Portuguese rivers (Mente, Rabaçal and Tuela) located upstream and downstream of dams and within the reservoirs. Pearl mussels were significantly more abundant upstream than downstream of dams (97.4% more) or within reservoirs (98.5% more). In addition, juveniles were mostly found upstream of dams. The most significant environmental alterations that explained the observed patterns were related to changes in sediment characteristics (accumulation of fine sediments and organic matter in reservoirs) and water chemistry, most notably suspended solids (highest values in reservoirs) and dissolved oxygen (lowest values in reservoirs). Overall, results show that small hydropower plants can deeply affect pearl mussel populations: specimens almost disappeared from the areas within the reservoirs and sites located downstream only retained adults without signs of recent recruitment. Future management measures devoted to the conservation of pearl mussels should take into account the results reported here to avoid the construction of new dams in pearl mussel rivers; improve management of the river flow in downstream areas; and consider the decommissioning of dams in pearl mussel rivers with a particular attention devoted to the re-naturalization of river sections under the influence of the reservoir and downstream areas.
淡水贻贝由于栖息地丧失和破碎化等因素，正在全球范围内迅速减少，但对于小水电站对其的影响知之甚少。在这里，我们评估了小水电站对濒危珍珠贻贝（Margaritifera margaritifera）丰度和大小结构的影响。为此，我们在葡萄牙的三条河流（门特河、拉巴萨尔河和图埃拉河）中，在大坝上下游和水库内共采样了 66 个地点。珍珠贻贝在大坝上游的数量明显多于下游（多 97.4%）或在水库内（多 98.5%）。此外，幼体主要出现在大坝上游。解释所观察到模式的最显著的环境变化与沉积物特征的变化（水库中细沉积物和有机物的积累）和水化学有关，尤其是悬浮物（水库中含量最高）和溶解氧（水库中含量最低）。总的来说，结果表明小水电站会对珍珠贻贝种群产生深远的影响：标本几乎从水库内的区域消失，下游的地点只保留了没有近期繁殖迹象的成年贻贝。未来致力于保护珍珠贻贝的管理措施应该考虑到这里报告的结果，以避免在珍珠贻贝河流上建造新的大坝；改善下游地区的河流流量管理；并考虑在有水库和下游地区影响的河流段进行自然恢复，拆除珍珠贻贝河流中的大坝。
