附着生物—铜锈环棱螺生态化学计量关系对水体氮磷浓度变化的响应机制

Trophic link between periphyton and snails plays an important role in energy transfer in freshwater foodweb. Eutrophication process commonly accompanied by increasing concentrations of nitrogen and phosphorus in water column, which changed the ecological stoichiometric relationship between periphyton and snails associated with the declined C:N/C:P ratio of periphyton. Do growth and reproduction of snails affected by declined food C:N/C:P ratio? What strategies will be adapted to maintain stoichiometric homeostasis？To answer these questions, we try to examine the periphyton-Bellamya aeruginosa relationship in reponse to nitrogen and phosphorus concentration based on field investigation and controlled experiment by using ecological stoichiometry methods. The aims of this study are to characterize the C/N/P stoichiometry of periphyton and B. aeruginosa in shallow lakes differing in trophic status, to explore the effects of food C:N:P ratio on growth and reproduction of B. aeruginosa, and to elucidate the adaptive strategies of B. aeruginosa in response to imbalanced element ratio. The results of this study are helpful to understanding the population dynamics of gastropods and community succession of macrozoobenthos in freshwater ecosystem under eutrophication, and to the conservation of gastropods.

附着生物-螺类之间的营养关系是淡水生态系统食物网中能量向高营养级传递的重要环节。富营养化一般伴随着水体氮磷浓度升高，使得附着生物C:N和C:P比降低，进而导致附着生物-螺类之间的化学计量关系发生变化。水体氮磷浓度升高导致的附着生物C:N和C:P比降低会影响螺类的生长与繁殖吗？螺类对食物元素比变化的主要适应对策又如何？为回答上述问题，本项目拟以长江中下游螺类优势种-铜锈环棱螺为研究对象，通过野外调查，阐明不同营养水平湖泊附着生物和铜锈环棱螺的碳氮磷化学计量特征及其影响因素；通过控制实验，培养具有不同碳氮磷比的附着生物喂食螺，分析附着生物C:N和C:P比变化对铜锈环棱螺生长和繁殖的影响，揭示铜锈环棱螺应对元素比不平衡采取的主要适应对策。本研究结果可加深对水体富营养化进程中螺类种群动态和底栖动物群落演替规律的认识，并为螺类资源的保护提供基础数据支撑。

附着生物—螺类之间的营养关系是淡水生态系统食物网中能量向高营养级传递的重要环节。长江中下游地区是我国淡水湖泊分布最为密集的区域，不断加剧的富营养化是目前该地区湖泊面临的主要问题之一，而关于富营养化对淡水螺类影响的研究较少。富营养化一般伴随着水体氮磷浓度升高，使得附着生物C:N和C:P比降低，进而导致附着生物—螺类之间的化学计量关系发生变化。水体氮磷浓度升高导致的附着生物C:N和C:P比降低会影响螺类的生长与繁殖吗？环棱螺种群如何响应？为回答上述问题，本项目以长江中下游螺类优势种—铜锈环棱螺为研究对象，通过野外调查，研究了不同营养水平湖泊附着生物和铜锈环棱螺的碳氮磷化学计量特征及其影响因素；通过控制模拟实验，研究水体氮磷浓度变化对附着藻生长率和碳氮磷化学计量特征的影响，并培养具有不同碳氮磷比的附着生物喂食螺，分析附着生物C:N和C:P比变化对铜锈环棱螺生长和繁殖的影响，基于周年控制实验分析了富营养化对环棱螺种群数量和动态的影响。研究发现，本地区湖泊中铜锈环棱螺体内N、P含量与营养状态指数显著正相关，环棱螺生长速率与营养盐浓度呈单峰关系，适宜环棱螺生长的溶解性无机氮浓度为1.5~2.0 mg/L、溶解性无机磷浓度为0.25~0.5 mg/L，表明其对营养盐耐受能力较强，现阶段长江中下游地区湖泊营养盐浓度一般不会抑制其生长。过高营养负荷抑制螺类生长，进而降低螺类对附着藻类的牧食能力，会削弱其对水生植物生长的促进作用。本研究结果丰富了淡水生态系统生态化学计量学研究，加深了对于富营养化进程中螺类群落演替规律的认识，研究结果可为螺类多样性保护和水生植物恢复提供基础数据支撑。