Phenolic chemistry of the seagrass Zostera marina Linnaeus: First assessment of geographic variability among populations on a broad spatial scale.

The variability of the phenolic content of thirteen populations of Zostera marina L. (six narrow-leaved and seven wide-leaved ecotypes) from different geographical zones, i.e., Baltic Sea, Mediterranean, East and West Atlantic, and East Pacific coasts was evaluated. Depending on the location, three to five phenolic acids and nine to fourteen flavonoids were identified of which an undescribed flavonoid sulfate. The phenolic concentrations of the thirteen populations differ among countries and among sites within countries. However, the same individuals were found almost everywhere. Substantial phenolic concentrations were found at all study sites with the exception of Puck Bay (Baltic Sea). Some geographical differences in the flavonoid content were observed. The highest phenolic diversity was found with specimens from the French Atlantic coast and the lowest with the Northeastern American sample (Cape Cod, MA). Regardless of their leaf width, the content of phenolic compounds was found to be similar and mainly characterized by rosmarinic acid and luteolin 7,3'-disulfate. The results demonstrate that geographic origin influences the phenolic composition of Z. marina primarily in terms of concentration, but not in terms of individual compound identity, despite the large geographic scale and the contrasting climatic and environmental conditions associated with it. This work is the first study to consider the spatial variability of phenolic compounds for a seagrass species on a spatial scale covering four bioregions. This is also the first to compare the phenolic chemistry of the two ecotypes of Z. marina.