Do microplastics, Vibrio bacteria, and warming water temperatures impact the health and physiology of the Northern Star Coral, Astrangia poculata?

As oceanic plastic pollution increases, scientific studies of their effects on marine organisms have grown in number. In particular, there has been a research emphasis on the physiological and negative health effects of microplastics. There are fewer investigations, however, that consider synergistic effects of microplastics on marine organisms in combination with other stressors. This study quantified changes in respiration rates and visual health of Astrangia poculata, a temperate, scleractinian coral, when exposed to microplastics, microplastics filmed with disease causing bacteria, and warming temperatures. A. poculata fragments were exposed to 4 different temperatures: 22 °C, 25 °C, 28 °C, and 32 °C. Experiment 1 at 22 °C compared effects of exposure to microplastics filmed with either Vibrio alginolyticus or Vibrio coralliilyticus; no difference was found between the responses of A. poculata to the two different bacteria. At the higher temperatures, coral fragments were exposed to "clean" microplastics or V. coralliilyticus-filmed microplastics for 2 weeks. Although respiration rates and visual health responded significantly to warmer temperatures, significant changes were not observed in response to bacteria or microplastics. This result is in contrast to multiple studies of microplastic exposure in tropical coral species. Therefore, A. poculata may be less susceptible to multiple stressors, such as microplastics, compared to tropical coral species. This study adds to a growing body of literature surrounding stress responses of temperate corals and highlights important response differences in non-tropical taxa.