title: Seaweed allelopathy against coral: surface distribution of a seaweed secondary metabolite by imaging mass spectrometry.
abstract: Coral reefs are in global decline, with seaweeds increasing as corals decrease. Although seaweeds inhibit coral growth, recruitment, and survivorship, the mechanism of these interactions is poorly understood. Here, we used field experiments to show that contact with four common seaweeds induces bleaching on natural colonies of Porites rus. Controls in contact with inert, plastic mimics of seaweeds did not bleach, suggesting seaweed effects resulted from allelopathy rather than shading, abrasion, or physical contact. Bioassay-guided fractionation of the hydrophobic extract from the red alga Phacelocarpus neurymenioides revealed a previously characterized antibacterial metabolite, neurymenolide A, as the main allelopathic agent. For allelopathy of lipid-soluble metabolites to be effective, the compounds would need to be deployed on algal surfaces where they could transfer to corals on contact. We used desorption electrospray ionization mass spectrometry (DESI-MS) to visualize and quantify neurymenolide A on the surface of P. neurymenioides, and we found the molecule on all surfaces analyzed, with highest concentrations on basal portions of blades.
authors.affiliation: School of Biology and Aquatic Chemical Ecology Center, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Tiffany D
authors.initials: TD
authors.lastname: Andras
authors.forename: Troy S
authors.initials: TS
authors.lastname: Alexander
authors.forename: Asiri
authors.initials: A
authors.lastname: Gahlena
authors.forename: R Mitchell
authors.initials: RM
authors.lastname: Parry
authors.forename: Facundo M
authors.initials: FM
authors.lastname: Fernandez
authors.forename: Julia
authors.initials: J
authors.lastname: Kubanek
authors.forename: May D
authors.initials: MD
authors.lastname: Wang
authors.forename: Mark E
authors.initials: ME
authors.lastname: Hay
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D037421:Anthozoa / Q000187:drug effects* / Q000502:physiology; D000460:Chlorophyta / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005367:Fiji; D057927:Hydrophobic and Hydrophilic Interactions; D018942:Macrolides / Q000737:chemistry / Q000633:toxicity*; D013058:Mass Spectrometry; D010675:Pheromones / Q000737:chemistry / Q000633:toxicity*; D011157:Population Dynamics; D011753:Pyrones / Q000737:chemistry / Q000633:toxicity*; D000461:Rhodophyta / Q000737:chemistry; D012624:Seaweed / Q000737:chemistry*; D013045:Species Specificity; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D018942:Macrolides; D010675:Pheromones; D011753:Pyrones; C534975:neurymenolide A