Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Dry mass of the coral nubbins (3 per experimental aquarium) was assessed by means of the buoyant weight technique (Jokiel et al. 1978, Davies, 1989), using an analytical balance (OHAUS AX124, precision 0.1 mg). The dry mass was calculated considering the nubbin net weight in water, the water density and the skeletal density of D. cornigera (2.63 g/cm3; Movilla et al. 2014). Measurements were performed just once the acclimation time finished and after 2 , 4, 6 and 9 months under the experimental conditions. Skeletal growth rates were calculated as the slope of the linear regression between the logarithmically transformed dry mass and the experimental time (%/day) (Orejas et al. 2011).

Description: Deep-water ecosystems are characterized by relatively low carbonate concentration values and, due to ocean acidification (OA), these habitats might be among the first to be exposed to undersaturated conditions in the forthcoming years. However, until now, very few studies have been conducted to test how cold-water coral (CWC) species react to such changes in the seawater chemistry. The present work aims to investigate the mid-term effect of decreased pH on calcification of the two branching CWC species most widely distributed in the Mediterranean, Lophelia pertusa and Madrepora oculata. No significant effects were observed in the skeletal growth rate, microdensity and porosity of both species after 6 months of exposure. However, while the calcification rate of M. oculata was similar for all colony fragments, a heterogeneous skeletal growth pattern was observed in L. pertusa, the younger nubbins showing higher growth rates than the older ones. A higher energy demand is expected in these young, fast-growing fragments and, therefore, a reduction in calcification might be noticed earlier during long-term exposure to acidified conditions.

Description: A 9-month aquarium experiment with the cold-water Dendrophyllia cornigera was conducted to investigate the single and combined effects of warming, acidification and deoxygenation on its ecophysiological response. The experiment took place at the Aquarium finisterrae (A Coruña, Spain) between 2022-05-06 and 2023-02-24. Treatment values for each parameter (current in situ vs. climate change) were: 12 °C and 15 °C (temperature); ~7.99 and 7.69 (pH); ~8.63 mg/L and 6.45 mg/L (dissolved oxygen concentration). A total of eight treatments (with 3 replicates each, 5 L aquaria) were set up. Raspberry-based controllers were set to modify and monitor the water temperature, pH and dissolved oxygen in every treatment. Values for temperature (ºC), pH (NBS scale) and oxygen (% air saturation) were registered every 15 minutes in a database. The parameters were measured using PT100 temperature sensors, and Atlas Scientific Lab Grade pH and Dissolved Oxygen sensors. Every set of sensors was placed on each header tank, corresponding to each treatment (8 in total). Parameter setpoint values for each header tank were finely adjusted on the controller to ensure the treatment target values on each experimental aquaria. Oxygen sensors from treatments with ambient oxygen (~8.63 mg/L) were removed from the system due to calibration issues. Here, an example of the results for temperature, pH and oxygen for every header tank over 24 hours on 31st of December 2022 is presented. Values for pH (total scale) and dissolved oxygen (mg/L) were calculated using AquaEnv (Hofmann et al. 2010) and respR (Harianto et al. 2019) R packages, respectively, using the in situ temperature and salinity (35.1).