The present study tested in the Western Dutch Wadden Sea (WDW) UNESCO World Heritage Site why an on a global scale the aggressive non-indigenous red drift alga Gracilaria vermiculophylla didn’t succeed to overgrow the WDC. In such a multifaceted complex ecosystem like the dynamic WDC it seems like unraveling a Gordian knob in order to describe the inextricable relationship between this seaweed invader suppression and its (a) biotic environment. However, we succeeded at the molecular level to give a convincing reasoning at first grounded in the awareness of a since 1987 river Rhine-North-Sea-WDC severely Phosphorus (P) restricted ecosystem. Our ecological datasets gave via final DCA (Detrended Correspondence Analysis) awareness of the very compelling interaction between Ulva sp. and G.vermiculophylla. Based on LCMS-techniques we discovered that Ulva sp. have the advantage to use the biochemical pathway solely rarely observed in some euckaryotes- to have the potential to produce the betaine lipid diacylglyceryl-O-4’-(N,N,N,-trimethyl)homoserine (DGTS) which replaces the plant/seaweed cell wall structure phosphatidylcholine (PC) “lecithine” under phosphate-limiting growth conditions. Also we hope this lipidomics based compound DGTS can serve as an ecological biomarker in order to protect vulnerable ecosystems like the Wadden Sea (UNESCO World Heritage).