城镇化背景下深圳典型流域鱼类群落特征及驱动因子

理解城镇的快速发展对河流鱼类群落结构的影响，是城镇河流科学管理和生物多样性保护的关键基础。本研究于2019年丰水期（8月）和枯水期（11月），选取我国城镇化典型城市-深圳域内两个处于不同城镇化程度的代表性流域，应用多重统计方法比较分析了流域间鱼类群落结构的差异，并探讨了驱动鱼类群落变异的关键环境要素。结果发现，城镇化程度高的观澜河流域其鱼类种类组成、优势类群、生物多样性指数与城镇化程度低的坪山河流域有明显差别。 具体表现为：城镇化程度高的流域土著敏感种类如异鱲、吸鳅等几近消失，优势类群为外来入侵耐受种类，其物种多样性显著低于城镇化程度低的流域（P<0.05）。同时，外来鱼类在城镇河段其数量占比平均达92.5%，广泛分布于深圳城镇河流中。在环境因素方面，城镇化程度高的观澜河流域水体理化指标总氮、总磷、氨氮、化学需氧量、生化需氧量、高锰酸盐指数均显著性高于城镇化程度低的坪山河流域（P<0.05）。基于Bray-Curtis距离的冗余分析显示：城镇用地占比和总氮是影响观澜河和坪山河流域鱼类群落差异的主要因素。城镇化进程中河流生境的改变已影响到土著鱼类的生物多样性。因此，推动以恢复土著鱼类生物多样性的河流生态治理与保护是今后水生态目标管理的重要方向。

Characteristics of fish communities and driving factors under urbanization in typical river basins in Shenzhen City, China

Understanding impacts of rapid urbanization on structure of river fish communities is the key basis for scientific management and biodiversity conservation for urban rivers. We selected two representative basins with different degrees of urbanization in the typical urbanized city, Shenzhen City, China. Field sampling was conducted in both wet (August) and dry (November) seasons in 2019. We compared and analyzed the differences of fish communities between the two basins using the multiple statistical methods, and explored the key environmental factors driving the variations of fish communities. Results showed that species composition, dominant species, and biodiversity of fish in the highly urbanized Guanlan River Basin were significantly different from those in the less urbanized Pingshan River Basin. In particular, the sensitively indigenous fish species such as Schistura fasciolatus and Parazacco spilurus disappeared while the invasive tolerant species were the dominant species in the highly urbanized basin. Fish biodiversity was significantly lower in the highly urbanized basin than the less urbanized basin (P<0.05). Meanwhile, non-native fish species had spread rapidly in urbanized rivers of Shenzhen City, which accounted for more than an average of 92.5% in the urbanized river sites. For environmental factors, total nitrogen, total phosphorus, ammonia, chemical oxygen demand, biochemical oxygen demand, and permanganate index in the highly urbanized Guanlan River Basin were significantly higher than those of the less urbanized Pingshan River Basin (P<0.05). Redundancy analysis based on the Bray-Curtis distance showed that the proportion of urban land and total nitrogen were the main factors affected the difference of fish communities in the Guanlan and Pingshan River Basins. Changes of river habitat from urbanization reduced biodiversity of the native fishes. Thus, restoring native fish biodiversity in river ecological management and protection is the important direction of aquatic objective-based management.