AbstractWe used liquid chromatography high-resolution tandem mass spectrometry to analyze the lipidome of turtlegrass (Thalassia testudinum) leaves with extremely high phosphorus content and extremely low phosphorus content. Most species of phospholipids were significantly down-regulated in phosphorus-deplete leaves, whereas diacylglyceryltrimethylhomoserine (DGTS), triglycerides (TG), galactolipid digalactosyldiacylglycerol (DGDG), certain species of glucuronosyldiacylglycerols (GlcADG), and certain species of sulfoquinovosyl diacylglycerol (SQDG) were significantly upregulated, explaining the change in phosphorus content as well as structural differences in leaves of plants growing under diverse phosphate concentrations. These data suggest that seagrasses are able to modify the phosphorus content in leaf membranes dependent upon environmental phosphorus availability.