KOSMOS Bergen 2015 mesocosm study: C. harengus survival@en

To evaluate the influence of ocean acidification on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities, we deployed eight pelagic mesocosms for 53 days (Mai to July) in Raunefjord, Norway, and enclosed 60 m³ of local seawater containing a natural plankton community under post-bloom conditions. Four mesocosms were manipulated to simulate extreme pCO2 levels of 2069 µatm while the other four served as untreated controls. To investigate the interaction between Hydrozoa and fish larvae influenced by OA ee studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Organisms of both taxa inside and outside the mesocosms were measured over the course of the experiment in regular intervals. The data stems from 55µm and 500µm Apstein net hauls, subsequent microscopic analyses as well as carbon to nitrogen measurements. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study.

为评估海洋酸化（Ocean Acidification, OA）对捕食性浮游生物——如水螅虫纲（Hydrozoa）和鱼类幼体，以及二者在复杂自然群落中的种间相互作用的影响，我们于挪威劳内峡湾（Raunefjord）部署了8个浮游中型实验生态系（pelagic mesocosms），实验周期为53天（5月至7月），围隔了60立方米的本地海水，其内包含藻华后期的自然浮游生物群落。其中4个中型生态系被设置为2069 µatm的极端二氧化碳分压（pCO2）水平组，剩余4个作为未处理对照组。为探究海洋酸化对水螅虫纲与鱼类幼体间相互作用的调控效应，我们通过追踪实验首周内于每个中型生态系中孵化的约2000尾大西洋鲱（Clupea harengus）幼体，以及已在围隔内定殖的水螅虫种群，分析了海洋酸化对食物网顶层类群的诱导变化。实验期间，我们定期对围隔内外的两类群生物进行采样监测。本数据集来源于55μm与500μm孔径的阿普斯坦网（Apstein net）拖网采样、后续的显微形态分析，以及碳氮元素含量测定。在海洋酸化条件下，我们观测到水螅水母类（hydromedusae）的丰度提升20%，但其生物量降低25%；与此同时，实验末期大西洋鲱幼体在高二氧化碳分压组的存活率显著更高（对照组pCO2对应浓度为0.1%，高pCO2组为1.7%）。