杂食性鱼类对浮游-底栖藻类资源竞争影响及其恶化水质机理

Planktonic algae and benthic algae coexisting but occupying different habitats in shallow aquatic systems compete for resources of light and nutrient asymmetrically. The outcomes of the competition play a key role in influencing the dynamic of primary production, determining the key characteristics of ecosystems. Aiming at the scientific question of how omnivorous fish affect the competition between planktonic and benthic algae for resources to deteriorate the water quality, the hypothesis of the proposed study is that omnivorous fish would promote planktonic algae over benthic algae by limiting the growth of benthic algae; the decline or loss of benthic algae would deteriorate water quality by stimulating the growth of planktonic algae with the phosphorus being released from the sediment. To test the hypothesis, measures of algae and their resources of nutrients and light in mesocosms with and without omnivorous fish would be conducted to evaluate the effects of the fish and to explore the effect of omnivorous fish on the competition for light and nutrients. Then, experiments would be conducted in aquariums on the key ways involved in the competition, including nutrient excretion, bioturbation of sediment (nutrient release and resuspension) and filtering on planktonic algae (biomass, algae size and light intensity) by the fish. These measurements will be used to evaluate the effects of the fish on stimulating the growth of planktonic algae and inhibiting the growth of benthic algae. And then, measures of phosphorus in microcosms with and without benthic algae would be conducted to illustrate the enhanced release of phosphorus from sediment when loss of benthic algae, which could stimulate the growth of pelagic algae, thereby deteriorating the water quality. The results of this study would shed light on the effect of omnivorous fish on eutrophication of shallow aquatic systems. This study also has important implications for conservation of water environment and management of aquatic systems, especially on the regulation of omnivorous fish.

浮游和底栖藻类可共存于浅水系统不对称地竞争光照和营养盐资源，其竞争结果不仅影响初级生产力变化，还决定浅水系统关键特征。针对杂食性鱼类如何影响浮游-底栖藻类资源竞争而恶化水质的科学问题，研究假设：该鱼类利于浮游藻类生长，不利底栖藻类竞争；底栖藻类消失进一步促进浮游藻类生长而恶化水质。构建中型实验系统，设置有和无杂食性鱼类两处理，比较两处理水层营养盐、水底光照、底栖和浮游藻类生长等变化，探索该鱼类对浮游-底栖藻类资源竞争影响；通过开展杂食性鱼类对该资源竞争影响的关键途径研究即营养盐排泄、对底泥扰动及对浮游藻类滤食等实验，分析其促进浮游藻类生长，不利底栖藻类竞争的原因；结合微型系统实验，阐明底栖藻类消失时底泥磷释放加剧，利于促进浮游藻类生长以加重富营养化；揭示杂食性鱼类恶化水质机理。该研究有助于揭示杂食性鱼类对浅水水体富营养化影响，可为水环境保护和水生系统优化管理，特别是杂食性鱼类调控提供依据。

浮游和底栖藻类可共存于浅水系统中不对称地竞争光照和营养盐资源，其竞争结果不仅影响初级生产力变化，还决定浅水系统关键特征。针对杂食性鱼类如何影响浮游-底栖藻类资源竞争而恶化水质的科学问题，本项目通过试验，比较了有无杂食性鱼类的水生态系统中水层营养盐、水底光照、底栖和浮游藻类生长等变化，研究了该鱼类对浮游-底栖藻类资源竞争影响；明确了杂食性鱼类促进浮游藻类生长，不利底栖藻类竞争的原因；阐明了杂食性鱼类利于促进浮游藻类生长的过程，揭示了杂食性鱼类恶化水质的机理。相关研究结果分别发表在Knowledge and Management of Aquatic Ecosystems、Water、湖泊科学等期刊上。该研究从浮游-底栖藻类资源竞争的角度，揭示了杂食性鱼类利于促进浮游藻类生长、加重水体富营养化，恶化水质的机理，可为水环境保护和水生系统优化管理，特别是杂食性鱼类调控提供依据，具有重要科学意义。. 基于该项目完成论文7篇，其中SCI 论文4篇，EI论文1篇，中文核心期刊2篇；邀请国际同行康奈尔大学Lars Rudstam教授来华并作了题为“Ecological change and fisheries in the North American Great Lakes - effects of nutrient reductions and invasive species”的学术报告；参加了第34届和35届国际湖沼学会大会； 培养硕士研究生4名。圆满完成了研究目标，超额完成了预期结果。