采砂业对洞庭湖底流区大型底栖动物结构和多样性的影响

The expanding sand-mining industry has been causing serious problems linked to environment, society and ecological security, resulting into such direct consequences as physical devastation, water pollution and ecological catastrophes. However, the knowledge about the damages of sand mining toward biological phenomena of inland waters remains yet limited, among others. It is especially true for hyporheic-zone macrozoobenthos although they are directly attacked by these activities. Herein, we address this issue by choosing the Dongting Lake as one-case study, one lake experiening the most heavy sand exploitation in the mid-lower Yangtze River which is the “hardest hit” area nationwide. Our interestings focus mainly on the impacts of sand excavation on key aspects of macrozoobenthos activities involving different levels of its structure and biodiversity in different spatio-temporal scales and scenarios. We first exploit the key life-history traits (e.g., population size, natality and mortality, sex ratio, growth and reproduction ability) and autoecology under mining pressure by choosing some representatives of macrozoobenthic species. Then we seek their different strategies to this anthropological disturbance and detect the key ways and forces driving their population decline/maintanance/robustness. Second, we portray the magnitude of key patterns of some important assemblage characteristics (e.g., richness, density and abundance) responses to mining intensity. Then we identify the driving extrinsic (envorenmental variables) and intrinsic factors (representing by spatial distances), integrate them into one proposed framework, and partition their relative contribution to community distribution patterns. Thus, we will determine the key processes and driving forces created by sand operations. Thirdly, through exploring the patterns of three aspects of species diversity (α, β and γ), especially the β diversity which links α to γ diversity, we will estimate the influences of species diversity by major courses and forces along sand dredging gradient, and detect the relative importance of α and β to γ diversity. Finally, we will establish the quantitative relationship between macrozoobenthos resource variables and sand activities based on above studies to predict and assess the impact of this human intervention on macrozoobenthos. These stereoscopic and multidimentional scientific probes should remarkably promote the knowledge about the alterations of biological activites producing by sand-mining industry, escalate more in-depth explorations involving such scientific issues as ecosystem structures and functions caused by this industy.Furthermore, our study will deepen the public’s understanding about the perniciousness of sand activity，and more importantly, provide solid knowledge and technique for national lawmakers to legislate laws to control and regulate the current indiscriminate sand-mining industry.

大规模和无序的采砂业已产生严重的环境、社会和生态安全问题。而我们对采砂业破坏内陆水体生命活动的认识仍十分有限，特别是底流区大型底栖动物。项目拟以掘砂最为严重的洞庭湖为研究案例，开展采砂业对大型底栖动物重要生命活动影响的研究。在种群水平上，研究代表性物种的关键生活史特征和种群生态学，揭示在采砂压力下它们的种群衰退/维持/茁壮机制。在群落水平上，描述组成和结构等群落特征的变动规律，探索挖沙驱动这些格局变化的关键过程和机制。在生物多样性方面，刻画在掘砂强度梯度下物种多样性三个层面(α、β和γ)的格局及驱动这些格局的关键途径和作用力。在系统把握关键驱动要素的基础上，构建底栖动物对挖沙行为响应的数学模型，预测和评估挖沙对底栖动物资源量的影响。为进一步探索采砂业对水生态系统结构的破坏和功能的改变等科学问题打下基础，为提高大众对采砂业危害性的认识提供科学知识，为国家制定管控采砂业的法律提供科技支撑。

本项目在充分调研洞庭湖挖沙业状况的基础上，结合野外原位观测和室内实验，以南洞庭湖为研究地域，系统开展挖沙业对水环境和底栖动物结构、功能和多样性方面的研究，并评估停止挖沙一年后水环境和底栖动物的自然恢复状况。主要成果如下：1) 显著改变水环境和底质。增加水深和浊度，降低营养盐浓度，提升细沙和粉沙含量，降低中沙和粘土含量。采砂停止后，采砂区水环境能快速恢复。2) 破坏群落组成和结构。持续降低采砂区的物种数和丰度。在临近区，挖沙早期提升群落丰度；在挖沙后期，这些指标均显著降低。采砂停止后，挖沙区和临近区的物种数和丰度均明显回升。3) 改变物种和功能多样性格局。挖沙区的物种和功能gamma和alpha多样性持续下降，beta多样性先升高后降低。临近区的alpha、beta和gamma多样性先增加后降低。4) 显著改变群落功能性状和结构。导致多个功能性状的下降和丧失。采砂停止后，多个性状能够快速恢复。5) 生态位过程和中性过程共同驱动群落变异。中性过程对物种群落变异的影响随着采砂的深入而持续增大，生态位过程(水质)的作用变小；生态位过程(水质和底质)在采前期和采砂期调控功能群落，中性过程则控制恢复期的功能群落。本项目的完成，填补了挖沙业影响内陆水体环境和底栖动物多样性的研究空白，扩展了人类对挖沙业影响水体生态系统结构和功能的认知水平，丰富和完善了湖泊底栖动物的共存和聚合理论和集合群落理论，为进一步开展挖沙业影响其它内陆水体的研究奠定坚实的基础，为推动我国制定管控采砂业的法律法规提供科学依据。