rockweed seaweed or bladderwrack, fucus vesiculosus, on rocks at trefor beach on the welsh coast

algae aquatic beach biology bladder bladderwrack botanic brown coast coastal coastline edible environment flora fucus grow iodine landscape leaf leaves marine natural nature plant rock rocks rockweed saltwater sandy sea seashore seaside seaweed shore tide vesiculosus wales water weed welsh wet wrack yellow