The effects of temperature and CO2 on growth rate, bleaching and recovery of the finger coral Porites porites

All over the world, coral reefs are under pressure of global change. A possibility exists for stressors to act together and cause more severe effects onto traits. Our thesis project tries to assess the effects of global greenhouse warming and ocean acidification onto the growth rate (calcification) of the Caribbean species Porites porites by using a one-species long-term laboratory case study and evaluating the bleaching and recovery responses. We found a significant CO2 effect (at an intermediate temperature only: growth rate higher at lower CO2 levels) and temperature effect (for all temperatures except between 29°C-30°C at low pCO2 treatments) onto growth rate, but no evidence of an interaction effect between temperature and CO2, meaning these two stressors act independently from each other. We indicate that the optimum temperature for coral growth lies between 29°C and 30°C, but a tendency of an altered curve (size and/or shape) at 900 ppm, compared to the curve at 390 ppm, does exist. A recovery of 0% at a pCO2 treatment of 390 ppm and a recovery of 20% of the growth rate at 900 ppm was observed. In total only 10% of all corals survived and recovered after a period of bleaching. Subsequently, we noted bleaching responses to be more severe (acting faster) at the high pCO2 treatment of 900 ppm. Our results support the hypothesis of some coral species and herein some individuals (genets) being able to survive and adapt, adjust or to be resilient under predicted future conditions.

ISCED Categories

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0511 - Biology", "0521 - Ecology