团头鲂对沉水植物苦草和轮叶黑藻种间关系的影响

There are different morphological submerged macrophytes, the benthic rooted species like Vallisneria natans has less specific leaf area but more roots, and it captures nutrition mainly from the sediment; while the floating species like Hydrilla verticillata has more specific leaf area but no roots, and it captures nutrition fully from water column. We advanced the hypothesis that V. natans and H. verticillata compete on the water nutrition and sunlight, so V. natans would dominant the community in low water nutrition level, while H. verticillata would dominant in high water nutrition level; and the herbivorous fish Megalobrama amblycephala would change the competition between two submerged species. We set up situ and laboratory experiments to prove the hypothesis. We will set up different water nutrition level and test the dynamic of the competition between two submerged macrophytes at the first; and secondary, we will set up different biomass ration of V. natans and H. verticillata with the press of herbivory from M. amblycephala , in order to test the influence of herbivorous fish on the competition between two submerged species; lastly, we will put different density M. amblycephala to the situ enclosures with V. natans and H. verticillata, in order to test influence of different densities of herbivorous fish on the competition between two submerged species. We believe that the results would contribute to use the herbivorous fish as a means to control floating submerged macrophytes.

比叶面积小的多根底栖沉水植物苦草主要从沉积物中获取营养，比叶面积大的无根漂浮沉水植物轮叶黑藻则主要从上覆水中获取营养，因此，水体营养盐含量低时，苦草占优势，水体营养盐含量高时，则轮叶黑藻占优势。底栖草食性鱼类团头鲂的加入可能会改变苦草与轮叶黑藻的竞争格局。为了验证这一假说，本项目拟设置原位围隔和室内可控实验，通过改变水体营养盐条件、两种植物生物量配置比例、团头鲂投放密度等影响因素，根据上覆水营养盐含量、沉积物再悬浮速率、浮游生物生物量、沉水植物生物量、植物生长速率、植物形态变化、植物有性和无性繁殖等指标，研究分析团头鲂对不同类型沉水植物种间关系和水环境的影响，探讨底栖草食性鱼类在调控沉水植物群落中的作用，为湖泊生态系统修复和管理提供理论支撑。

本项目通过四年的工作，设置了一系列控制实验，研究了苦草与轮叶黑藻的竞争及其对水环境的影响，团头鲂对苦草和轮叶黑藻竞争格局调控作用及其对水环境的影响，以及团头鲂对沉水植物苦草种群的调控作用。结果表明，苦草和轮叶黑藻的组合配置对维持水体清水态有较好效果，但黑藻容易在竞争中取胜，淘汰苦草，引起水质恶化；加入团头鲂后，能够有效控制黑藻的竞争优势，使二者达到平衡，对清水态水体的维持有利；团头鲂的牧食作用比草鱼的牧食作用的破坏程度低，相对温和，对苦草种群的破坏作用小，使苦草保持合适的高度，而且能促进苦草密度增加，从而降低水体磷含量，抑制浮游植物生长，有利于维持水体的清水状态。以上研究结果，为湖泊生态修复提供了有力的理论支撑，能够指导水体生态修复的水生植物配置和管理。