Growth rates of the cold-water coral Desmophyllum dianthus during an ex-situ experiment in the Azores

We conducted a medium-term (4 months) multiple stressor experiment with the cold-water coral Desmophyllum dianthus under future environmental conditions (IPCC RCP 8.5 scenarios for 2100), and sediment plumes generated during the potential extraction of seafloor massive sulphides. The experiment followed a two-step approach, where during the first 3 months, corals were exposed to four different treatments combining predicted scenarios of ocean acidification (pCO2/pH) and food availability. Two levels of pCO2 conditions were considered: natural habitat present day conditions (~500 µatm, 720 m depth) and IPCC RCP8.5 scenario (1000 µatm; IPCC, 2019), corresponding to pHT values of 7.93 and 7.66, respectively. In addition, two food availability regimes were recreated: high frequency of feeding (food delivered twice a day / 7 days a week) and low frequency of feeding (food delivered every other day). There were six replicate 13 L aquaria per treatment (4 D. dianthus per aquaria) at a temperature of 10.5 ± 0.1 ºC. During the fourth month of the experiment, suspended polymetallic sulphide particles generated during potential mining activities were added to half of the aquaria under the climate change scenarios at a concentration of 10 mg/l, making 8 treatments in a fully crossed experimental design for the 3 factors tested (OA, food, mining particles). Growth rates were measured using the buoyant weighing technique (Jokiel et al. 1978), using a balance (Mettler-Toledo ME204T) with a precision of 0.1 mg. Corals were weighed twice during the experiment: 1-2 weeks after the start of the experiment and just before the second phase of the experiment with PMS addition, which corresponded to a time interval of 63-71 days.我们针对冷水珊瑚柱形杯珊瑚（Desmophyllum dianthus）开展了为期4个月的多胁迫因子中期实验，实验设置了2100年政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, IPCC）第八代典型浓度路径8.5（Representative Concentration Pathway 8.5, RCP 8.5）情景下的未来海洋环境，以及潜在海底块状硫化物开采过程中产生的沉积物羽流条件。实验采用两步法开展：前3个月内，珊瑚被置于4种不同的处理组中，各组结合了预测的海洋酸化（Ocean Acidification, OA）情景与食物供给水平。实验设置了两种二氧化碳分压（pCO₂）条件：其一为当前自然栖息地的环境条件（约500微大气压，水深720米），其二为IPCC RCP8.5情景（1000微大气压；IPCC，2019），二者对应的pHT值分别为7.93与7.66。此外，实验还设置了两种食物供给模式：高频投喂（每日投喂2次，每周7天）与低频投喂（隔日投喂1次）。每个处理组设置6个13升的重复水族箱，每个水族箱内饲养4株柱形杯珊瑚，实验水温控制为10.5±0.1℃。实验的第4个月，我们向气候变化情景组中半数的水族箱内加入了潜在采矿活动产生的悬浮多金属硫化物颗粒，投放浓度为10毫克/升。至此，本实验针对3个测试因子（海洋酸化、食物供给、采矿颗粒）采用完全交叉实验设计，共得到8种处理组。珊瑚生长速率采用浮力称重法（Jokiel等，1978）进行测定，使用精度为0.1毫克的梅特勒托利多（Mettler-Toledo）ME204T电子分析天平。实验期间共对珊瑚进行2次称重：分别为实验开始后的1~2周，以及加入多金属硫化物颗粒实验阶段前，两次称重的时间间隔为63~71天。