KOSMOS 2014 mesocosm study: mesozooplankton abundances

Using a mesocosm approach, we investigated ocean acidification effects on a subtropical zooplankton community during oligotrophic, bloom, and post-bloom phases under a range of different pCO2 levels (from ~400 to ~1480 µatm). To do that, we simulated an upwelling event by adding 650 m-depth nutrient-rich water to the mesocosms, which initiated a phytoplankton bloom. The most abundant mesozooplankters were calanoid copepods, which did not respond to CO2 treatments during the oligotrophic phase of the experiment but were found in higher abundance under medium- and high-pCO2 conditions towards the end of the experiment, most likely as a response to increased phyto- and microzooplankton standing stocks. The second most abundant mesozooplankton taxon were appendicularians, which did not show a response to the different pCO2 treatments. Overall, CO2 effects on zooplankton seem to be primarily transmitted through significant CO2 effects on phytoplankton and therefore indirect pathways.

本研究采用中宇宙实验（mesocosm）方法，在寡营养期、浮游植物水华期及水华后期三个阶段，于约400~1480 µatm的梯度二氧化碳分压（pCO₂）条件下，探究了海洋酸化对亚热带浮游动物群落的影响。为开展该实验，我们通过向中宇宙系统中添加650米深度的富营养海水模拟上升流事件，以此启动浮游植物水华过程。实验中丰度最高的中型浮游动物（mesozooplankters）类群为哲水蚤目桡足类（calanoid copepods）：在实验的寡营养阶段，该类群未对二氧化碳分压处理产生响应；但在实验末期，中等及高二氧化碳分压条件下的哲水蚤丰度显著更高，这一现象极有可能源于浮游植物与微型浮游动物现存量提升所带来的间接效应。丰度位列第二的中型浮游动物类群为尾海鞘类（appendicularians），其未对不同二氧化碳分压处理表现出显著响应。整体而言，二氧化碳分压对浮游动物的影响似乎主要通过其对浮游植物的显著调控作用实现，即依托间接传递路径。