双齿围沙蚕对洞穴微环境改造与适应的生态行为学研究

During evolution, infauna have developed the physiological and behavioral strategies to cope with the stresses from sedimentary environment. The previous studies showed that the physiological strategy itself could not solve the contradiction of infauna survival and the stresses from sedimentary environment. While the behavioral strategy is much more important because it builds up a burrow microenvironment that essential for the survival of borrowing benthic animals. However, limited published research hasn’t clarified the relationship between behavioral strategy and the burrow microenvironment of benthic animals. The present project will focus on Perinereis aibuhitensis Grube, an important polychaete species in marine benthic ecosystem, in several aspects. First of all, the spatiotemporal variations of burrow structure and microenvironment will be studied to investigate the limiting factors which would provide baseline conditions for further research. Secondly, the relationships between the biological behaviors of polychaete and the microenvironment parameters will be explained by studying their interactions such as burrowing, defecation and biological irrigation. Thirdly, the diffusion regularity of water in the burrow and surrounding microenvironment will be clarified, which will help us to find the interaction mechanism among burrow microenvironment, sediments and overlying water. Finally, a model of P. aibuhitensis bioturbation accelerating the bioelements proliferation at the sediment-water interface will be constructed. The project would be helpful to analyze the important influences of marine infauna bioturbation on the process of accelerating the biogeochemical processes from the perspective of behavior and microenvironment. The results would provide a theoretical basis for clarifying the impacts of benthos eco-physiological activities on benthic ecosystem dynamics.

底栖动物中的底内动物在长期进化过程中形成了独特的生理和行为策略应对沉积环境压力。研究表明，其生理策略往往不足以解决生存与沉积环境压力间的矛盾，而行为策略由于为底内动物特别是穴居型底栖动物建立了赖以生存的微环境而显得尤为重要，但其行为策略与洞穴微环境的关系尚不清楚。本研究拟以底栖多毛类的典型代表—双齿围沙蚕为研究对象，对其典型生境中洞穴结构及其微环境的时空变化特征进行研究，查明洞穴结构及其微环境特点与限制因子；研究其生物灌溉行为与洞穴微环境的相互影响，阐明不同行为过程与洞穴微环境参数间的定量关系；研究其生物扰动作用对洞穴及周围微环境中水输运规律的影响，阐释洞穴微环境与沉积物、上覆水间的物质输运机理；构建双齿围沙蚕驱动的生源要素迁移模型，从行为学和微环境视角深入解析底栖动物的生物扰动对加速沉积物生地化过程的作用过程与机理，为明晰底栖动物的生理生态活动对底栖生态系统动力学过程的影响提供理论依据。

底内动物的耐受能力与沉积环境压力间存在显而易见的矛盾，其通过系列行为过程建立了赖以生存的洞穴微环境，该微环境与其行为过程的关系极其密切，查明两者的关系可以阐释底栖动物环境修复潜力与内在机理。本项目发明了底内动物行为学研究系列装置和方法，突破了底内动物行为学研究装备和方法技术瓶颈，创建了以双齿围沙蚕为代表的底内动物行为学指标体系，为推动水生生物行为学研究做出了原创性贡献。1）查明了双齿围沙蚕洞穴形态结构与沙蚕规格、洞穴微环境时空变化间的定量关系，创建并运用“HEindex”作为底内动物洞穴结构复杂度指数来表征洞穴结构的复杂程度。2）明确溶解氧是洞穴微环境的限制性因子，发现了启动沙蚕生物灌溉行为的溶解氧阈值为0.46-2.98mg/L，该阈值主要由温度和沙蚕规格等因素所决定，首次提出了双齿围沙蚕“最佳溶氧收益策略”概念，其通过最佳溶氧收益策略可以消耗最少的能量而获得最高的溶氧收益。3）潮汐、上覆水环境和沉积物类型均对双齿围沙蚕的行为和洞穴微环境有显著影响，退潮时沙蚕运动减弱，涨潮潮水浸没洞穴后30min内，轴向爬行和径向起伏运动加强，促进洞穴微环境水体交换，之后恢复至退潮前水平；查明双齿围沙蚕幼虫对不同沉积物的被动选择机制，确定后天环境选择是造成其分布不均的主要原因，对于成体，沉积物有机质和硫化氢含量对其行为影响因规格而异；上覆水溶解氧和温度协同影响沙蚕行为，随上覆水溶氧降低和温度升高径向起伏时间增加。4）双齿围沙蚕泵水对沉积物间隙水输运影响较小，24小时内仅能影响洞穴周围5mm以内的间隙水缓慢向洞穴方向扩散，明确洞穴周围沉积物生源要素迁移的主要范围，确定双齿围沙蚕泵水量最大可超过10L/d；建立了以沙蚕泵水为驱动条件的生源要素迁移模型，明确硫、氮、磷等生源要素的溶出效率，创新性地从行为生态学角度解析了双齿围沙蚕加速沉积物矿化和生源要素迁移的生地化过程。