三峡库区不同水文类型支流大型底栖动物对蓄水的响应

为探究三峡水库修建对库区不同水文类型支流大型底栖动物的影响,于2015年7月和2016年1月对三峡水库四条支流的大型底栖动物进行调研,分别对周期性受蓄水影响支流的非回水区与回水区和长期受蓄水影响支流的非回水区与回水区大型底栖动物群落结构进行比较研究,结果表明:⑴7月份三峡水库145米低水位时期共采集到底栖动物655头计59种(属),在受蓄水影响河段采集到底栖动物4种共40头,优势种为日本沼虾(占受蓄水影响区域的57.5%); 1月份三峡水库175米蓄水时期共采集到底栖动物1123头计69种(属),在受蓄水影响河段采集到16种238头,优势种为锯齿新米虾(占受蓄水影响区域的14.2%)。⑵周期性受蓄水影响支流的非回水区与回水区底栖动物密度、生物量和多样性指数无显著差异(P0.05);长期受蓄水影响支流的非回水区与回水区之间底栖动物密度和Pielou均匀度指数无显著差异(P0.05),但非回水区底栖动物生物量显著高于回水区(P0.05),底栖动物多样性和丰富度极显著高于回水区(P0.01)。⑶7月份影响底栖动物分布的主要环境因子共6个,分别是水深、流速、硝态氮、溶解氧、水温和电导率; 1月份影响底栖动物分布的主要环境因子共7个,分别是水温、溶解氧、总磷、流速、深度、电导率和透明度。

Responses of benthic macroinvertebrates in tributaries of different hydrological regimes in the Three Gorges Reservoir region to reservoir impoundment

The construction of the Three Gorges Dam has caused significant changes in aquatic ecosystems. Benthic macroinvertebrates, an important component of aquatic ecosystems, have also been greatly affected by reservoir impoundment. In order to explore the impact of impoundment on their community in tributaries of different hydrological regimes and the role of tributaries in their resource production, benthic macroinvertebrates were investigated in four tributaries (Lixiang River, Yulin River, Quxi River and Longhe River) of the Three Gorges Reservoir in July 2015 and January 2016. In particular, their community, species diversity, and relationship with environmental factors were studied. It was found that (1) In July, a total of 655 benthic macroinvertebrate individuals belonging to 59 species were collected. Among these, 40 individuals (4 species) were collected in the river reaches affected by reservoir impoundment, with Macrobrachium nipponensis being the dominant species comprising 57.5% of these 40 individuals. However, in January, a total of 1123 benthic macroinvertebrates belonging to 69 species were collected. Among these, 238 individuals (16 species) were collected in the river reaches affected by the reservoir impoundment, with Neocaridina denticulata being the dominant species comprising 14.2% of these 238 individuals. (2) No significant differences in the density, biomass, and species diversity of benthic macroinvertebrates were found between the river reaches unaffected and affected by reservoir impoundment in the tributaries periodically affected by reservoir impoundment. However, in the tributaries continuously affected by reservoir impoundment, the biomass of benthic macroinvertebrates in the river reaches affected by reservoir impoundment was significantly lower than that of the benthic macroinvertebrates in the river reaches unaffected by reservoir impoundment (P < 0.05). Furthermore, the Shannon-Wiener diversity index and Margalef species richness index in the river reaches unaffected by reservoir impoundment were significantly higher (P < 0.01) than those indices in the river reaches affected by reservoir impoundment. (3) The canonical correspondence analysis (CCA) showed that, in July, the main environmental factors affecting the benthic macroinvertebrate distribution were water depth, current velocity, water temperature, dissolved oxygen content, specific conductance, and nitrate concentration (NO₃^-). In January, the main environmental factors were water temperature, dissolved oxygen content, total phosphorus (TP), current velocity, water depth, specific conductance, and transparency. These results indicated that the community and species diversity of benthic macroinvertebrates could be affected by reservoir impoundment, and the tributaries play an important role in their conservation. In the tributaries continuously affected by reservoir impoundment, significant differences in the richness and abundance of benthic macroinvertebrates exist between the river reaches unaffected and affected by reservoir impoundment; however, in the tributaries periodically affected by the reservoir impoundment, no significant differences were found.