Comparative Metabolomics Approach Detects Stress-Specific Responses during Coral Bleaching in Soft Corals

Chronic
exposure to ocean acidification and elevated sea-surface
temperatures pose significant stress to marine ecosystems. This in
turn necessitates costly acclimation responses in corals in both the
symbiont and host, with a reorganization of cell metabolism and structure.
A large-scale untargeted metabolomics approach comprising gas chromatography
mass spectrometry (GC–MS) and ultraperformance liquid chromatography
coupled to high resolution mass spectrometry (UPLC–MS) was
applied to profile the metabolite composition of the soft coral Sarcophyton ehrenbergi and its dinoflagellate symbiont.
Metabolite profiling compared ambient conditions with response to
simulated climate change stressors and with the sister species, S. glaucum. Among ∼300 monitored metabolites, 13
metabolites were modulated. Incubation experiments providing four
selected upregulated metabolites (alanine, GABA, nicotinic acid, and
proline) in the culturing water failed to subside the bleaching response
at temperature-induced stress, despite their known ability to mitigate
heat stress in plants or animals. Thus, the results hint to metabolite
accumulation (marker) during heat stress. This study provides the
first detailed map of metabolic pathways transition in corals in response
to different environmental stresses, accounting for the superior thermal
tolerance of S. ehrenbergi versus S. glaucum, which can ultimately help maintain a viable symbiosis and mitigate
against coral bleaching.