Potential impact of small hydroelectric power plants on river biota: a case study on macroinvertebrates associated to basaltic knickzones

Abstract Small hydroelectric power plants (SHP) have been considered as an alternative for the generation of electricity with reduced environmental impacts. Nevertheless, no studies have addressed changes in a particular kind of river macrohabitat commonly affected by SHPs, the knickzones. This study aimed to assess the impact of a SHP construction on the aquatic macroinvertebrate fauna associated with two basaltic knickzones located in Sapucaí-Mirim River, Southeast Brazil. The first, considered as a functional knickzone, follows the natural dynamics of the river flow and preserves the original rock substrate. The second, considered as non-functional knickzone, was permanently flooded after the SHP construction and the consolidated rock substrate was changed by fine sediment. Sampling was carried out in two seasonal periods and the data were analysed through multivariate analysis. It was observed differences in composition and structure of the macroinvertebrates community between the knickzones and periods. The functional knickzone exhibited a much higher richness, 72 taxa compared to 44 in the non-functional, as well as a large number of exclusive taxa (38, being only nine exclusive to the non-functional). Diversity, equitability and density mean values were also higher in the functional knickzone. The limnological parameters varied significantly between dry and rainy seasons but not between the distinct knickzones. This kind of macrohabitats and its potential role for the rivers biodiversity is practically unknown. In the scenery of fast SHP expansion, further studies and protection measures are necessary.

摘要：小型水力发电厂（Small hydroelectric power plants, SHP）被视为环境影响更低的电力替代发电方案。然而，目前尚无研究关注小型水力发电厂常影响的一类特殊河流大型生境——裂点带（knickzones）的变化情况。
本研究旨在评估小型水力发电厂建设对巴西东南部萨普卡伊-米林河两处玄武岩裂点带相关水生大型无脊椎动物区系的影响。其中第一处为功能性裂点带，遵循河流水流的自然动态，保留了原始岩石基质；第二处为非功能性裂点带，在小型水力发电厂建成后被永久淹没，其固结岩石基质被细沉积物所替代。
研究于两个季节性采样时段开展调查，并通过多变量分析对数据进行处理。结果显示，不同裂点带及采样时段间的大型无脊椎动物群落组成与结构均存在显著差异。功能性裂点带的类群丰富度显著更高，共计72个分类单元，而非功能性裂点带仅为44个；同时功能性裂点带拥有更多特有类群（38个，而非功能性裂点带仅含9个特有类群）。此外，功能性裂点带的多样性、均匀度及密度平均值也均高于非功能性裂点带。
湖沼学参数在旱季与雨季间存在显著差异，但在不同裂点带之间并无显著区别。这类大型生境及其对河流生物多样性的潜在作用目前几乎未被探明。在小型水力发电厂快速扩张的背景下，亟需开展更多相关研究并制定针对性保护措施。