Acclimatization and health change of Acropora palmata after depth induced stress response in Cozumel, Mexico

Sammanfattning

Coral reefs are an important ecosystem for maintaining healthy oceans, but they now face serious threats. In response to these threats, fragmentation and coral gardening are becoming increasingly important. However, researchers have conducted little research on how coral health develops during depth-induced environmental stress, which is common in restoration work. The purpose of this study is to evaluate how Acropora palmata responds and to provide insight into how resistant the colonies in the area are to depth induced stress. In this experiment, I moved A. palmata fragments from three different colonies from two meters depth to eight meters depth and then back to two meters depth in the local area, where health parameters were measured approximately every week for 50 days. The health parameters evaluated were fragment growth, polyp growth, polyp extension, bleaching index, average health change per day, and algae growth. I found that overall health improved, and the surviving fragments showed less bleaching, more polyp extension, and some growth of individual polyps after being moved, indicating that they prefer the shallower depth. However, increased algal growth and unexpectedly low fragment growth were also observed, creating uncertainty regarding the true health status of the fragments. I also found significant differences between colonies in bleaching index, daily health change index, and polyp extension, driven by the 35% fragment mortality observed in colony 3. This indicates that the colonies may have different genetic backgrounds, leading to differences in adaptation and survivability. These findings highlight the need for individualized knowledge and management of each colony, regardless of their spatial proximity. Keywords: Coral growth, stress response, acclimatization, restoration, coral bleaching