The Littoral Zone

Various annual algae species have colonized the littoral cliffs on the eastern, southern and western shores of Surtsey. In the beginning, there were only a few species with a small cover, but in recent years several species can be found in the sublittoral zone with a total cover over 60%. The most common species are diatoms and the green filamentous seaweed Ulothrix flacca, which together make up over 80% of the vegetative cover in the sublittoral zone.

In the beginning, definite algal communities could not be found. Now, however, there are two distinct communities. In the upper part of the littoral zone there is a green belt consisting mainly of the green algae Ulothrix flacca, the link frond (Ulva intestinalis) and Urospora penicilliformis. Below this belt is a brown zone with symbiotic diatoms and brown algae, including Petalonia fascia, the knotted wrack (Ascophyllum nodosum) and the red alga purple laver (Porphyra umbilicalis). Shore animals were rare. The one most often found was the acorn barnacle (Semibalanus balanoides), which colonizes the lower part of the littoral zone each spring but disappears in the winter.