close-up of dried brown algae strands, phaeophyceae, on sandflat at low tide of wadden sea, lower saxony, germany

algae fronds ribbons strands tendrils black brown dried east frisian island ecosystem europe european flat lay german germany halophyte juist kalfamergat low tide marshes marshland nature overhead view phaeophyceae salt marsh sand sandbank sandflat sandflats seaweed tidal flats topdown unesco world heritage wadden sea waddensea wetland wetlands