The marine vegetation of the Azores differs significantly from that of Northern Europe and North America, particularly due to the absence of the large brown macroalgae known as kelps. Instead, it shows a closer resemblance to the marine flora of Madeira and the Canary Islands.

A comparison with other North Atlantic marine floras suggests that the Azores function as a natural bridge, linking Northern Europe, the Mediterranean, and the wider region of Macaronesia — which includes the archipelagos of the Azores, Madeira, the Canary Islands, and Cape Verde — to the tropical and subtropical coasts of the Americas.

Some cold-water species, such as the red alga Schizymenia dubyi, reach their southern distribution limit in the Azores. In contrast, other species, like the green alga Anadyomene stellata, find here their northernmost range of occurrence.

There are also endemic or regionally restricted species. For example, the green alga Codium elisabethae and the brown alga Cystoseira abies-marina are, so far, only known within the Macaronesian archipelagos.

Additionally, the Azorean marine ecosystem includes unexpected visitors — non-native species that were likely introduced to the archipelago. Notable examples include the small red alga Symphyocladia marchantioides, now highly abundant along the Azorean coasts and believed to have originated in the Southern Hemisphere, as well as Asparagopsis armata, a species native to the Pacific Ocean.

Together, these elements highlight the Azores not as isolated islands, but as a dynamic ecological crossroads where distinct marine biotas converge, interact, and evolve.