Surtsey, a young volcanic island under strict protection from human activities, provides a unique natural laboratory to study soil formation on newly formed land. In July 2024, we examined 20 soil profiles across the island under varying influence of seabird activity and vegetation cover. Although all profiles reflected early-stage pedogenesis, seabird activity and vegetation clearly enhanced horizon development and organic matter accumulation, as reflected by frequent O and Bw horizons at vegetated sites within bird colonies. In contrast, sparsely vegetated or barren sites outside seabird colonies showed minimal organic matter accumulation, with no O-horizons and only occasional weakly developed Bw horizons. Our visual descriptions of soil profiles corroborate previous studies showing the strong role of ornithogenic inputs in organic matter and nutrient accumulation on the island. Future research should aim to better understand the influence of ornithogenic inputs and vegetation on weathering processes and the formation of secondary pedogenic minerals in soils of the island.

This paper aims to provide an overview on the status of breeding birds and visitors on Surtsey since 2008 and is a continuation from Petersen’s overview from 2009 of the status after the formation of the island. Specific ornithological expeditions to Surtsey have not taken place since 2003, besides a visit in Surtsey in May 2025. Annual research expeditions have been undertaken in mid-July in 2009–2025. Although the timing is not optimal for bird observations, various information regarding birds has been collected during those visits, including general observations on the presence - absence of known breeding species and regular visitors as well as anecdotes of new species for the island. Gull and fulmar nests have been counted annually on monitoring plots since 2003. Evening counts of gulls present in the colony were performed annually during July visits between 2011 and 2016, in 2023 and in May 2025. One aerial survey was conducted in June 2023 and the gull colony photographed. In May 2025 a breeding bird survey on ground nesting land birds was carried out. By 2025, a total of 95 bird species has been recorded for Surtsey, on the island itself and close by offshore. Out of those, 59 are regular breeders in Iceland, 24 are vagrants and the rest are migrants and winter visitors. Only four species have been recorded for the first time on Surtsey since 2008, of which three are vagrants and one an Icelandic breeder. During the same time, three new breeding species have been recorded, and all of them have been irregular breeders since.

Surtsey island was formed in a volcanic eruption south of Iceland in 1963 – 1967 and has since then been protected and monitored by scientists. It is the youngest island in the Vestmannaeyjar archipelago. The archipelago is of volcanic origin, but the other islands are ca. 5 000 to 40 000 yrs old. The first two moss species were found on Surtsey as early as 1967 and several new bryophyte species were discovered every year until 1973 when regular sampling ended. Systematic bryophyte inventories in a grid of 100 m × 100 m quadrats were made in 1970 – 1972 and 2008. Here we report results from an inventory in 2018, when the same quadrats of the grid system as in 2008 were searched for bryophytes. In addition, we surveyed the bryophyte flora of Elliðaey – a ca. 5 000 yrs old island at the more sheltered north-eastern end of the archipelago. On Surtsey, distributional expansion and contraction of earlier colonists was revealed as well as presence of new colonists. Total number of taxa increased from 43 to 59 between 2008 and 2018. The average species richness increased from 4.5 taxa/quadrat in 2008 to 6.6 taxa/quadrat in 2018 (empty quadrats omitted): 32 quadrats showed an increase in species richness; three quadrats showed no change; ten quadrats showed a slight decrease of 1 – 2 taxa, while one quadrat showed a considerable decrease of 7 taxa – that quadrat was within the lush grassland of the gull colony where bryophytes were outcompeted by the graminoids. Quadrats with the strongest increase in species richness were also within areas affected by seabirds but had not been as overgrown with grassland. On Elliðaey, the predominant habitat was grassland, like the one at the centre of the gull colony on Surtsey. On the island, we registered 22 taxa; 13 were also found on Surtsey in 2018, 4 have been found on Surtsey in earlier surveys and 4 species have never been found on Surtsey. We predict the species richness on Surtsey will continue to grow but level off before starting to decrease as the lava fields disappear and grassland becomes more dominant. Continued monitoring, without long breaks, is essential to evaluate how fast the bryophyte vegetation develops in the years to come.

Seabirds can play a vital role in primary succession by transferring nutrients from sea to land. Here, we examine the effects of sparse seabird colonies on primary succession at the Breiðamerkurjökull glacial fore-field in SE-Iceland. The area is generally characterized by low vegetation cover, where mosses are dominant, with scattered, grassy vegetation “islands” (bird hummocks) formed through point-centered influence of seabirds. The aim of this study was to assess the influence of bird presence on vegetation and soil properties. This was done by examining how vegetation and soil properties changed with the distance from bird hummocks and the influence of time on that relationship. Total vegetation cover and grass and forb cover were found to be significantly affected by the birds’ presence, as well as the concentration of soil organic matter and pHH2O . These results demonstrate the importance of seabirds as natural fertilizers in primary succession and early soil formation processes.

Studies on primary succession and biological surveys in Surtsey have described the presence of different organisms including plants, soil fauna and fungi. However, since the last fungal census of 2008, based on visual observations, no further studies on fungal communities on the island have been published. In the present study, we aimed to expand the knowledge of the fungal communities of Surtsey using Internal Transcribed Spacer (ITS2) metabarcode sequencing to survey soil samples from 23 permanent plots, within and outside a gull colony. Additionally, we related fungal community composition to soil and ecosystem environmental variables that have been analyzed from these plots previously. We report at least 18 new genera and 44 new species for Iceland and 56 new species for Surtsey in this metabarcode survey, likely representing a combination of established organisms as well as those that may be present as dormant propagule bank. Our data indicate that fungal communities differ in areas with and without sea gulls as well as those that differ in soil substrate. Further, the community composition correlates with the number of gull nests, vegetation cover, ecosystem respiration, total N and exchangeable P. This survey provides new insights on the fungal community dynamics in relation to other biotic and abiotic factors. These findings complement what available data on soil biosphere on Surtsey and improve our understanding of primary succession.

Several human boot tracks and trackways are preserved in palagonitized tuff in Surtsey Island, south Iceland. The underlying palagonitized substrate is made of reworked tephra debris talus and slump material that lies partly on top of lava flows erupted in 1964–1965 in Surtungur tuff crater and 1966–1967 in Surtur tuff crater. This stratigraphic information along with other evidence from the nature of the sediments, alteration history of the deposits and the record of human presence on the island indicate the tracks were formed in the years between 1967 and 1970. The exquisite preservation and consolidation of the tracks coincide with a period of rapid geomorphic changes in the early stages of development of the island, when the newly formed tephra was still unconsolidated and easily mobilized by mass movements, wind and runoff. Furthermore, cooling magmatic intrusions generated hydrothermal activity on the island speeding up diagenesis of the tephra and the cementation of the boot tracks in the substrate. Expulsion rims preserved in some of the boot tracks suggests the tracks were formed in moderately cohesive substrate, followed by rapid burial of the prints in heavy wind and/or storm. Three boot sizes were identified suggesting the tracks were made by at least three persons, and documentation of the boot anatomy, measurements on angle of gait, stride and pace reveal the direction of movement for each trackway. Intense erosion of the tuff cones has exhumed the tracks to the surface that stand today as a testimony to impressively rapid geological cycles for preservation and exhumation and the role of unstable and rapidly changing environments, the aftermath of high-energy events, in capturing and preserving ichnites. These boot tracks are the first fossil tracks described for Iceland and the first record in the world of boot tracks preserved in sedimentary rocks.

Surtsey and the older islands in the Vestmannaeyjar archipelago offer a unique possibility to study how sub-Arctic ecosystems develop from unvegetated mineral substrate that lacks soil cover to grasslands with thick Brown Andosol soils. The present study was carried out on Surtsey, Heimaey and Elliðaey in 2013 and involved an incubation of resin membranes in the 0-10 cm topsoil layer in different ecosystems, which were either inside or outside seabird colonies. We compared the effects of seabird presence on soil nutrient availability as well as the importance of time for soil development (at least ca.1600 years vs. 50 years). Further we looked for build-up of Cd and Pb within the seabird colonies. Seabird presence enhanced the availability of most nutrients (N, P, K, Mg, Ca, S, Fe, Mn and Zn) except B and Cu, irrespective of the age of the islands. Soil age was also a significant factor for nutrient availability for all macro- and micronutrients except B. Nutrient ratios indicated that N was the most limiting nutrient in all ecosystems, except in the thicker tephra soils on Surtsey where low P availability may lead to co-limitation. The role of P in ecosystem function on Surtesy warrants a futher study. No accumulation of Cd and Pb was found within the seabird colonies.

Petrographic studies of thin sections from the 1979 and 2017 Surtsey drill cores provide new insights into microstructural features in basaltic lapilli tuff sampled from the principal structural and hydrothermal zones of the volcano. These describe narrow rims of fine ash on altered glass pyroclasts in thin sections of the 2017 cores, characteristics of granular and microtubular structures in the original thin sections of the 1979 core, and glass alteration in diverse environments. The narrow ash rims follow the outlines of glass pyroclasts in the subaerial tuff cone and in submarine and sub-seafloor deposits; they suggest complex eruptive and depositional processes. The tubular microstructures resemble endolithic microborings in older oceanic basalt; they suggest possible microbial activity. Tubule lengths indicate rapid growth rates, up to 30 µm in ~15 years. Comparisons of glass alteration in thin sections prepared immediately after drilling in 1979 and 2017 indicate differential time-lapse alteration processes in the structural and hydrothermal zones of the volcano. In contrast, thin sections of the 1979 core prepared after 38 years in the repository reveal labile glass alteration during archival storage. The oven-dry density of the sub-seafloor lapilli tuff decreases in 2017 samples with high porosity and water absorption and increases in 2017 samples with a compact ash matrix and lower water absorption. The petrographic descriptions and material measurements provide a foundational reference for further investigations of explosive eruption and deposition of basaltic tephra at Surtsey and the subsequent alteration of these deposits in the volcanic environment and, potentially, the curatorial environment.