全球变化下台湾海峡小型水母种群数量增加的原因及机制

Small jellyfish play an important role in the material and energy flows in marine ecosystems. Based on our previous studies, its population density has increased greatly during the past 30 years around in Taiwan Strait. However, the causes and mechanism of its population variation was still undiscovered. This study proposed thress hypotheses to explain the increase of small jellyfish population density in Taiwan Strait: the increased reproductivity of local population of polyp stage, the increased reproductivity of local population of medusa stage, and the increased transportation flux from the ocean currents. Aiming at understanding the inner mechanism of the above ecological process, the main scientific aims of this project including: 1) to study the life histories of the small jellyfish species and the mechanisms by which environmental factors regulate the different developmental stages; 2) to measure the feeding effects and estimate the ecological status of small jellyfish in the local planktonic food web; 3) to discover how the ocean currents influence the spatial distribution of small jellyfish through evaluation of genetic diversity. Belonging to a part of global change and population dynamics research, the variation trends of physicochemical environmental factors of sea water, food available and the influence of the ocean current were studied in order to examine the three hypotheses above, and to disclose the response model of marine food plankton ecosystem to global change in Taiwan Strait.

小型水母在我国近海生态系统中具有非常重要的生态学地位。项目组前期研究发现台湾海峡小型水母的种群数量大幅增加，然而原因和机制尚不清楚，是来自本地种群繁殖加快还是海流输送增加呢？本项目拟从小型水母基础生物学、生态学入手：1）通过受控模拟实验及自然海区调查，结合环境长期变化背景，研究台湾海峡主要小型水母生活史，关键发育阶段的生态适应策略以及关键控制因素；2）开展摄食效应研究，评估小型水母的生态地位；3）开展遗传多样性研究，查明海流对小型水母种群变动的影响。该研究属于全球变化和种群动力学的研究范畴，旨在查明海水理化环境、食物可利用性和海流等对台湾海峡小型水母种群数量长期变动的影响机制，揭示全球变化下台湾海峡浮游生态系统的响应模式及机制。

小型水母在台湾海峡生态系统中具有非常重要的生态学地位，本研究从食物可利用性、海水理化环境和海流等对台湾海峡小型水母种群数量变动的影响方面，揭示全球变化下台湾海峡浮游生态系统的响应模式及机制。主要研究结果包括：（1）本研究基于高通量测序技术分析了双生水母、卵形瓜水母和球型侧腕水母现场摄食组成，结果表明：台湾海峡小型水母现场摄食具有较高的多样性；管水母单营养体与多营养体的食物类群具有相似性；栉水母不同发育期的食物组成差异较大。高通量测序技术是深入探究水母现场食物组成新的技术手段，三种水母的现场食物组成结果为台湾海峡水母摄食生态学的研究提供了重要参考；（2）台湾海峡小型水母的优势种为管水母类的拟细浅室水母、大西洋五角水母、双生水母，以及水螅水母类的半口壮丽水母和四叶小舌水母。两个季节的优势种组成及平均丰度有所不同，春季五种水母均为优势种，夏季仅有双生水母成为优势种；（3）综合聚类、MDS标序以及PCA分析，同时结合小型水母生态习性以及DCCA分析，可以将小型水母划分为受台湾海峡南部海域南海次表层水及黑潮支流影响明显、多是适应高温高盐的种类构成的远岸群集，和北部的大陆沿岸海域附近相对低温低盐的种类构成的近岸群集；（4）春季影响台湾海峡小型水母分布的主要环境因子是水温和溶解氧，夏季影响台湾海峡小型水母分布的主要环境因子是水温、盐度和溶解氧；浙闽沿岸流、粤东沿岸流对台湾海峡小型水母优势种的丰度有补充作用，南海暖流、黑潮支流则对台湾海峡小型水母，特别是管水母的多样性起决定作用，这些海流共同控制了台湾海峡小型水母群落结构的时空变化。