Effects of climate change and feeding on the energy budget of three life stages of the cold-water coral Caryophyllia huinayensis

• Main Author: Nierste, Jan Christoph
• Other Authors: Wall, Marlene
• Format: Thesis
• Language: unknown
• Published: 2021
• Subjects: Ocean acidification
• Online Access: https://epic.awi.de/id/eprint/57923/; https://epic.awi.de/id/eprint/57923/1/MSc_Jan_Nierste.pdf; https://hdl.handle.net/10013/epic.14176c89-1612-41cf-8115-1a3b552d1038

Cold-water corals (CWCs) lack the endosymbiotic algae found in tropical corals and are therefore dependent on heterotrophic feeding to meet their metabolic demands. They are important bioengineers providing a habitat for many species from the shallows down to the deep-sea. While it is widely understood that ocean acidification (OA) and rising water temperatures due to the anthropogenic climate change will severely impact CWCs in the near future not much is known about the actual effects on their physiology. Most studies conducted so far only implemented either ocean acidification or elevated temperature as stressors without considering the possible interactions between these two. The results of these studies showed that the response of CWCs to these stressors varies between species, populations and life stages.The aim of this thesis was to investigate how a 6-month exposure to OA (pH 7.5 & Ωarg ~ 0.8) and elevated temperature (+ 4 °C) as single stressor as well as in combination influenced the metabolism of the solitary CWC species Caryophyllia huinayensis over three different life stages of the polyp. Two feeding regiments were implemented to test for potentially mitigating effects of a 12-fold increase in food availability. The results indicate that Caryophyllia huinayensis are able to calcify under ocean acidification with sufficient amounts of food as it predominately increases the energy demand for calcification, while elevated temperature alone increased metabolic rates beyond a point where enhanced food availability could compensate for the detrimental effects and induced mortality. In combination the interaction of OA and elevated temperature act antagonistic leading to metabolic rates similar to those measured at ambient conditions. However, the corals health still deteriorated with mortality rates only slightly lower than under elevated temperature and no mitigating effects of increased food availability. A trend for higher resilience in the intermediate life stage was detected but the response was ...