Comparison of colorimetric pixel intensity versus photosynthetic efficiency metrics to evaluate coral responses to acute heat stress in American Samoa
Abstract/Description/Artist Statement
Coral reef communities are increasingly devastated by prolonged periods of
elevated seawater temperatures that trigger mass coral bleaching events. Coral
species vary in their vulnerability to thermal stress, and while multiple methods
exist to quantify bleaching responses, there remains a need to evaluate their
accuracy and precision. In this study, we compare two coral bleaching assessment
methods, standardized Pixel Intensity photo analysis and dark-adapted
photosynthetic efficiency (Fv/Fm), to determine which more effectively evaluates
the coral heat stress response. Coral fragments from two species, Pocillopora
acuta and Acropora hyacinthus, were collected across four sites in American
Samoa and exposed to thermal stress using the Coral Bleaching Automated Stress
System CBASS, with temperatures ranging from 29 to 38 °C. Dark adapted
photosynthetic efficiency (Fv/Fm) of coral symbionts was measured to calculate
the effective dose 50 (ED50), representing the temperature at which
photosynthetic output declined by 50%. Following exposure, fragments were
photographed with grayscale calibration for Pixel Intensity analysis to quantify
visible bleaching across color channels. We predict PAM ED50 to be the more
reliable metric due to its direct measurement of physiological stress, whereas
Pixel Intensity may be influenced by external factors such as lighting conditions.
Faculty Advisor/Mentor
Daniel Barshis
Faculty Advisor/Mentor Email
dbarshis@odu.edu
Faculty Advisor/Mentor Department
Department of Biological Sciences
College/School Affiliation
College of Sciences
Student Level Group
Undergraduate
Presentation Type
Poster
Comparison of colorimetric pixel intensity versus photosynthetic efficiency metrics to evaluate coral responses to acute heat stress in American Samoa
Coral reef communities are increasingly devastated by prolonged periods of
elevated seawater temperatures that trigger mass coral bleaching events. Coral
species vary in their vulnerability to thermal stress, and while multiple methods
exist to quantify bleaching responses, there remains a need to evaluate their
accuracy and precision. In this study, we compare two coral bleaching assessment
methods, standardized Pixel Intensity photo analysis and dark-adapted
photosynthetic efficiency (Fv/Fm), to determine which more effectively evaluates
the coral heat stress response. Coral fragments from two species, Pocillopora
acuta and Acropora hyacinthus, were collected across four sites in American
Samoa and exposed to thermal stress using the Coral Bleaching Automated Stress
System CBASS, with temperatures ranging from 29 to 38 °C. Dark adapted
photosynthetic efficiency (Fv/Fm) of coral symbionts was measured to calculate
the effective dose 50 (ED50), representing the temperature at which
photosynthetic output declined by 50%. Following exposure, fragments were
photographed with grayscale calibration for Pixel Intensity analysis to quantify
visible bleaching across color channels. We predict PAM ED50 to be the more
reliable metric due to its direct measurement of physiological stress, whereas
Pixel Intensity may be influenced by external factors such as lighting conditions.