Benzoyl Chloride Derivatization Advances the Quantification of Dissolved Polar Metabolites on Coral Reefs

Extracellular chemical cues constitute much of the language
of
life among marine organisms, from microbes to mammals. Changes in
this chemical pool serve as invisible signals of overall ecosystem
health and disruption to this finely tuned equilibrium. In coral reefs,
the scope and magnitude of the chemicals involved in maintaining reef
equilibria are largely unknown. Processes involving small, polar molecules,
which form the majority components of labile dissolved organic carbon,
are often poorly captured using traditional techniques. We employed
chemical derivatization with mass spectrometry-based targeted exometabolomics
to quantify polar dissolved phase metabolites on five coral reefs
in the U.S. Virgin Islands. We quantified 45 polar exometabolites,
demonstrated their spatial variability, and contextualized these findings
in terms of geographic and benthic cover differences. By comparing
our results to previously published coral reef exometabolomes, we
show the novel quantification of 23 metabolites, including central
carbon metabolism compounds (e.g., glutamate) and novel metabolites
such as homoserine betaine. We highlight the immense potential of
chemical derivatization-based exometabolomics for quantifying labile
chemical cues on coral reefs and measuring molecular level responses
to environmental stressors. Overall, improving our understanding of
the composition and dynamics of reef exometabolites is vital for effective
ecosystem monitoring and management strategies.