OOS 45-2 - Colonization and ecosystem development on Surtsey volcanic island, Iceland

Thursday, August 10, 2017: 1:50 PM
D135, Oregon Convention Center
Borgthor Magnusson1, Sigurdur H. Magnusson1, Erling Olafsson1 and Bjarni D. Sigurdsson2, (1)Icelandic Institute of Natural History, Gardabaer, Iceland, (2)Agricultural University of Iceland, Hvanneyri, Iceland

Surtsey, the newest of volcanic islands off the south coast of Iceland, was formed in an eruption during 1963–1967 and reached an area of 2.7 km2. Due to constant oceanic erosion the island had reduced to 1.3 km2 by 2016. Surtsey was protected as a Nature Reserve for scientific research in 1965 and access restricted, and in 2008 the island was inscribed on the UNESCO World Heritage List. Biological colonization of the island has been followed annually from 1964. The main emphasis has been on plants, invertebrates, birds, soil formation and ecosystem development and function.


Plant colonization started off slowly in 1965, first to enter were mainly shore plants dispersed by sea currents to the island. By 1974 ten species of vascular plants had become established. In the following decade there were, however, only two successful colonizers. In 1970 the first seabirds were found breeding on the island. Their numbers were low and impact on vegetation limited in the beginning. In 1985 a dense colony of seagulls started to form upon the island, rising to several hundred breeding pairs in a few years. This brought about a great increase in dispersal and establishment of new plant species on the island, development of lush vegetation and invertebrate communities within the colony that enabled land birds to breed on the island a decade later. A new study of soil development indicates that the seagulls transfer 45 - 50 kg N ha-1 annually from sea to land within their colony while the surrounding, barren areas receive only 1 - 2 kg N ha-1 as atmospheric deposition. The wave of new plant colonization and establishment that followed the seagull invasion in 1985 continued for two decades. The number of vascular plants found alive in any year peaked at 65 species in 2007 followed by a declining trend. In 2016 a total of 74 species had been found on the island since 1965, of these 60 were alive and 39 had established viable populations. From 2002 there have been few changes in the bird fauna which consists of seven species of seabirds and four land birds breeding on the island in most years. A study of vegetation in permanent plots on Surtsey and neighboring islands indicates that, with continued erosion, loss of habitats and increasing impact of seabirds a lush, species-poor grassland will develop and persist on Surtsey, as on the older islands.