Different levels of energetic coupling between photosynthesis and respiration do not determine the occurrence of adaptive responses of Symbiodiniaceae to global warming.

ABSTRACT: Disentangling the metabolic functioning of corals' endosymbionts (Symbiodiniaceae) is relevant to understand the response of coral reefs to warming oceans. In this work, we first questioned if there is an energetic coupling between photosynthesis and respiration in Symbiodiniaceae (Symbiodinium, Durusdinium and Effrenium), and second, how different levels of energetic coupling will affect their adaptive responses to global warming. Coupling between photosynthesis and respiration was established by determining the variation of metabolic rates during thermal response curves, and how inhibition of respiration affects photosynthesis. Adaptive responses (not reversible) were studied exposing two Symbiodinium species, with different levels of photosynthesis-respiration interaction, to high temperature (32°C) for one year. We found that some Symbiodiniaceae have a high level of energetic coupling, i.e. photosynthesis and respiration have the same temperature dependency, and photosynthesis is negatively affected when respiration is inhibited. Conversely, photosynthesis and respiration are not coupled in other species. In any case, prolonged exposure to high temperature caused adjustments of both photosynthesis and respiration but these changes were fully reversible. We conclude that energetic coupling between photosynthesis and respiration has wide variation amongst Symbiodiniaceae and does not determine the occurrence of adaptive responses in Symbiodiniaceae to temperature increase.

SUBMITTER: Pierangelini M 

PROVIDER: S-EPMC7590187 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature