广东横石水河流域溪流大型底栖动物漂流的昼夜节律

比较了广东横石水河流域二条相邻的3级溪流大型底栖动物的漂流种类组成及昼夜节律，其中一条溪流受广东大宝山矿外排的酸性矿山废水严重污染，水体pH值仅为3.45且重金属严重超标，而另一条为相邻的清洁溪流.结果表明：清洁溪流中大型底栖动物的数量和种类远比受酸性矿山废水污染的溪流丰富.在清洁溪流中共采获漂流底栖动物6 871头，隶属10目52类群，其中水生昆虫的数量和种类占绝对优势 (99.5%).但总漂流密度占优势的类群（相对多度超过5%）不多，主要集中在以下几种水生昆虫：七鳃假二翅蜉 (28.5%)、宜兴似动蜉 (13.8%)、短脉纹石蛾(13.2%)、白背锯形蜉（7.5%)、摇蚊科(6.5%) 和肖扁泥甲(5.0%).蜉蝣目种类和数量最多，占全部漂流底栖动物总个体数的65%，其中又以四节蜉科居多，占蜉蝣目总个体数的63%.毛翅目昆虫的数量（18%）仅次于蜉蝣目.大型底栖动物的漂流表现出明显的昼夜节律，漂流主要在夜间进行，未发现有日漂者.漂流密度高峰出现在21:00和2:00，漂流密度分别为（70.3±10.8）和（289.0±124.6） 头·100 m^-3.大多数优势种类漂流高峰出现的时段略有不同，但有些优势种类（如摇蚊科和肖扁泥甲）并未表现出明显的漂流昼夜差异.在受酸性矿山废水污染的溪流中，漂流动物只有1种嗜酸性的多足摇蚊，其漂流活动也在夜间进行，并有3个明显的漂流高峰，分别出现在19:00、0:00和4:00，最高漂流密度仅为（6.7±5.2)头·100m^-3.说明酸性矿山废水不仅降低了溪流中漂流底栖动物的物种多样性和数量，也改变了其漂流模式.

Diel rhythm of benthic macroinvertebrate's drift in streams in Hengshishui River watershed of Guangdong, China

An investigation was conducted on the species composition and diel rhythm of benthic macroinvertebrate's drift in two adjacent 3rd order streams in the Hengshishui River watershed of Guangdong, China. One of the streams was seriously polluted by acid mine drainage (AMD) discharged from the Guangdong Dabaoshan Mine, with a very low pH (3.45) and high contents of heavy metals that exceeded the Chinese National Standards for surface water, and the another adjacent was a clean stream. The results showed that the individuals and species of benthic macroinvertebrates were much more in clean stream than in AMD-polluted stream. In the drift samples from clean stream, a total of 6871 macroinvertebrate individuals belonging to 52 taxa of 10 orders were collected, among which, 99.5% were aquatic insects. However, the total drift density was dominated by a few taxa, of which, the dominant drift taxa with relative abundance in excess of 5% included Pseudocloeon morum (28.5%), Cinygmina yixingensis (13.8%), Cheumatopsyche sp. (13.2%), Serratella albostriata (7.5%), Chironomidae (6.5%), and Psephenoides sp. (5.0%). The most abundant drifter both in species and in individuals was Ephemeroptera, constituting 65% of the entire caught (dominated by Baetidiae, which represented 63% of total mayfly individuals), followed by Trichoptera (18%). The macroinvertebrate's drift showed significant diel rhythm, i. e., the drift was strongly nocturnal, with the peaks at 21:00 and 2:00, and the average drift densities being (70.3 +/- 10.8) and (289.0 +/- 124.6) ( ind x 100 m(-3)), respectively. No diurnal drifter was observed. Most dominant drift taxa showed slightly differences in their drift peaks, but some dominant taxa, e. g., chironomids and Psephenoides sp., showed no clear diel rhythm of drift. Polypedilum sp., an acidophilic species of Chironomidae, was the only drift animal found in AMD-polluted stream, which had three distinct drift peaks, i. e., at 19:00, 0:00 and 4:00, with the highest drift density being only (6.7 +/- 5.2) (ind x 100 m(-3)). It was indicated that AMD not only reduced the numbers and species diversity of drift benthic macroinvertebrates, but also altered their drift patterns.