Table_1_Tracking Jellyfish Swarm Origins Using a Combined Oceanographic-Genetic-Citizen Science Approach.xlsx

Biological invasions of jellyfish may critically affect ecosystems and ecosystem services, yet their complex life cycle makes tracking their origins and dispersal vectors a challenging task. Here we combine citizen science observations, oceanographic modeling, and population genetics to track swarms of the invasive nomad jellyfish, Rhopilema nomadica, across the Eastern Mediterranean Sea. Jellyfish observations were recorded by citizens from two Israeli beaches in two consecutive years. A Lagrangian model coupled with a high-resolution 3D hydrodynamic model (SINMOD) was then used to simulate drift of ephyrae from probable polyp bed locations. Finally, mitochondrial DNA (mtDNA) sequence was constructed to examine swarm connectivity. Temporal (both seasonal and interannual) variation in observed swarms generally exceeded spatial differences between the two surveyed beaches. Early detection of swarms by citizens in offshore waters and the higher offshore particle distribution shown by the drift model, point to considerable offshore transport of the swarms. However, a higher probability was found for a nearshore location of the polyp beds, as nearshore origins were more closely correlated to hits on target beaches. R. nomadica released as ephyrae in early spring were likely to reach target beaches 200-300 km down current within two to three months as swarms of young adults in the early summer bathing season. R. nomadica populations exhibited little temporal or spatial genetic differentiation, a typical feature of a species that has recently undergone rapid population expansion. The offshore transport, the lack of genetic structure, and the interannual differences in both hydrodynamics and citizen scientist observations, all indicate decentralized swarm origins. This type of interdisciplinary approach can thus provide viable tools to track bloom formations. Understanding the complexity of jellyfish swarm dynamics supports future management strategies such as forecasting, preparedness and public education.

水母生物入侵可能对生态系统及生态系统服务造成严重冲击，但其复杂的生命周期使得追踪其起源与扩散媒介成为一项极具挑战性的任务。本研究结合公民科学观测、海洋学建模与种群遗传学方法，对东地中海海域入侵性游移水母（Rhopilema nomadica）的群聚种群进行追踪。研究团队连续两年在以色列两处海滩收集了民众上报的水母观测记录。随后，将拉格朗日模型（Lagrangian model）与高分辨率三维水动力模型SINMOD耦合，对潜在螅状体栖息地释放的碟状幼体（ephyrae）的漂移过程进行数值模拟。最后，通过构建线粒体DNA（mtDNA）序列以分析种群连通性。观测到的水母群的时间（含季节与年际）变化整体大于两处调查海滩间的空间差异。民众在外海水域早期发现的水母群，以及漂移模型显示的外海扩散颗粒物占比更高的特征，均表明水母群存在显著的外海输送过程。不过，螅状体栖息地更可能位于近岸区域，因为近岸起源与目标海滩的观测匹配度更高。早春以碟状幼体形式释放的该物种个体，可在2至3个月内顺流输送200至300公里，并于初夏游泳季以年轻成体群的形式抵达目标海滩。该种群几乎未表现出显著的时间或空间遗传分化，这是近期经历快速种群扩张物种的典型特征。外海输送现象、缺乏遗传结构，以及水动力条件与公民科学观测中的年际差异，均表明水母群的来源具有分散性。此类跨学科研究方法可为追踪水母水华形成提供可行工具。深入理解水母群动态的复杂性，可为预警预报、应急准备与公众教育等后续管理策略提供科学支撑。