河流水动力条件对大型底栖动物分布影响研究进展

大型底栖无脊椎动物(简称"底栖动物")是河流生态系统重要的生物类群,其组成与分布受河流水动力条件影响显著.对世界范围内不同气候带的7条大型河流的研究发现,底栖动物在河流纵向上展现出了明显的分布特征:①山区树线以上,粗颗粒有机物有限,直接收集者占绝对优势,其中流速大的河段以适应流水的摇蚊幼虫为主,流速低的河段以寡毛类为主.②树线以下的上游河段,充足的凋落物进入河流,流速大的河段以抗冲刷能力强的水生昆虫(如蜉蝣目)为主,流速低的河段以寡毛类和摇蚊幼虫为主.③中下游河段以及河口地区,河流比降小、水深大、流速小、底质较细,受一定程度的人类活动影响,寡毛类、摇蚊幼虫和软体动物等较为常见,其中寡毛类和软体动物主要栖息在淤泥底质中,摇蚊幼虫在沙质河中更为常见.底栖动物的物种数量及组成与底质的稳定性、河流含沙量、降水量等因素相关.水动力条件中的底质、含沙量及流速对底栖动物的影响最为显著:①底栖动物物种数随着底质粒径和稳定性的降低而减少,在卵石底质中达到最大值.②含沙量增加导致底栖动物的物种数和密度显著下降.③汛期水动力条件的改变直接导致底栖动物密度和优势种变化,汛期过后则优势种恢复,密度达到年内最大值.研究推测气候通过影响底栖动物食物网来影响其密度,而不是种类.建议今后增强气候变化对底栖动物食物网及密度综合影响的研究.

Research Progress of River Dynamic Influences on the Distribution of Macroinvertebrates

Macroinvertebrates are important biological groups of river ecosystems, and their composition and distribution are significantly affected by river hydrodynamic conditions. Studies on seven large rivers in different climatic zones have found that macroinvertebrates exhibit distinct distribution characteristics in the longitudinal direction of rivers:(1) Above the tree line, the coarse-grained organic matter is limited, and the collectors are dominant. Chironomidae is mainly adapted to live in the river section with fast flow rate, and the slow flow rate section is dominated by Oligochaetes. (2) In the upper reaches that below tree line, a lot of litter falls into river, aquatic insects that possess strong erosion resistibility, such as Ephemerida, dominate in fast flow rate section and Oligochaetes and Chironomidae dominate in slow flow rate section. (3) In the middle and lower reaches of the river and the estuary area where the river gradient is smaller, the water depth is deeper, the flow velocity is slow, the substrate is fine, and it is also affected by human activity are dominated by Oligochaetes, Chironomidae and mollusks. In the middle and lower reaches, Oligochaetes and mollusks mainly inhabit in the silt substrate, and Chironomidae are more common in sandy substrate rivers. The effects of sediment, sediment concentration and flow rate on hydrodynamic conditions are most significant for macroinvertebrates:(1) Species number decreases with substrate particle size and stability decrease, and gets to the maximum in cobble. (2) With the increase in sediment concentration, species number and density decrease significantly. (3) Dominant taxa and species number change with dynamic condition changes in the flood season and after flood season, the dominant species recovers and the density of macroinvertebrates reaches the maximum in a year. This study reckons that the climate influences the density of macroinvertebrate through impacting the food web instead of species. It is suggested that more research on the impact of climate on the density and food web should be conducted.