长期变化背景下球型侧腕水母的幼体繁殖策略、种群动态及生态效应

Within the recent two decades, population of the ctenophore Pleurobrachia globosa showed dramatic increase and gradually dominated the zooplankton community, demonstrating a typical instance of long-term ecosystem changes in the Jiaozhou Bay. Aiming at understanding the inner mechanism of the above ecological process, and based on the unique life history strategy--‘larval reproduction’, the proposed project will firstly focus on the biological processes of larval reproduction, as well as the seasonal, inter-annual variations and regional differences of reproduction and recruitment rates, clarifying the driving effects of larval reproductive strategy to population dynamics and its adaptational significance. Secondly, it will be discussed how the population dynamics responded to the long-term environmental changes in the Jiaozhou Bay. To answer this question, it’s necessary to elucidate the effects of environmental variables to the reproductive strategy and recruitment via controlled experiments, as well as referring to the long-term changing background. Thirdly, we will measure the feeding effects and estimate the ecological status of P. globosa in the local planktonic food web. Larval reproduction has been scarcely studied, especially in P. globosa. From the new perspective of this reproductive strategy and the regulation by environmental variables, our project would be among the research frontiers of long-term change ecology by incorporating mechanistic explanations, and would provide scientific basis for understanding the structure and functioning of the Jiaozhou Bay marine ecosystem after the population arise of P. globosa.

近十余年来，胶州湾球型侧腕水母“从无到有”呈现种群剧增并成为优势种之一。针对此胶州湾海洋生态系统长期变化的典型案例，本项目拟从该物种独特的“幼体繁殖策略”入手，1)系统开展幼体繁殖生物学、现场繁殖、种群补充的季节、年际变动以及海区差异研究，揭示幼体繁殖策略对种群动态的驱动作用及生态适应意义；2)开展受控模拟实验，研究温度、盐度以及食物条件等环境因素对繁殖策略与种群补充的调控，结合环境长期变化背景，阐释球型侧腕水母种群动态对胶州湾长期变化的响应机制；3)开展现场摄食效应研究，评估球型侧腕水母的生态地位。通过以往关注较少的幼体繁殖这一崭新视角，开展繁殖策略及其环境调控研究，将为胶州湾球型侧腕水母种群兴起事件引入机制性解释，符合海洋生态系统长期变化研究的前沿发展方向；鉴于其关键生态地位，开展摄食效应研究，可为理解其种群剧增后的胶州湾海洋生态系统结构与功能提供研究基础。

近十几年来，栉水母球型侧腕水母在胶州湾出现种群剧增乃至暴发现象，成为胶州湾生态系统长期演变的重要特征之一。为理解这一特殊的生态现象，本项目开展了较为系统的探索研究。首先，本项目成功构建了球型侧腕水母种群丰度长期变化时间序列（2000-2014），揭示了胶州湾该种栉水母从无至有的种群发展过程、分布空间变化以及季节与年际变化等；发现该种类于2000年后已经在胶州湾常规出现，并在某些丰度高值时期，成为胶州湾浮游动物的绝对优势种；通过比较我国东海等其主要栖息地海域的丰度，发现其在胶州湾特定季节可形成暴发态势；首次研究并报道了胶州湾球型侧腕水母的幼体繁殖策略，对比研究了该种栉水母在黄海及胶州湾的不同繁殖策略，灵活的繁殖策略对其适应胶州湾海洋环境具有重要生态适应意义；通过多元统计分析并结合现场模拟实验等手段，揭示了球型侧腕水母与胶州湾海洋环境的紧密关联，该种丰度长期变化与胶州湾水温呈现显著正相关关系，与盐度呈现显著的负相关关系，与其浮游动物饵料碳含量浓度无显著相关关系；因此，近几十年来胶州湾及黄海环境水温上升及盐度下降的长期演变规律为球型侧腕水母在胶州湾定居乃至繁盛提供了更为适宜的外部环境；探索了该种栉水母进入胶州湾的可能途径，通过相关分子生物学手段，证实胶州湾种群与黄海、东海种群的流通性；上世纪90年代末期黄海暖流的增强有可能为其入侵胶州湾提供水动力条件；此外，随着同时期港口建设、货运吞吐量的激增，船舶压舱水也可能是其入侵的另一种可能途径。本项目首次针对此威胁胶州湾海洋生态系统典型案例的多个关键过程开展系统研究，所获得的基础研究成果对胶州湾及我国近海类似生态系统可持续发展具有重要意义。