Abstract
Abstract. Colonization of life on Surtsey has been observed systematically since the formation of the island 50 years ago. Although the first colonisers were prokaryotes, such as bacteria and blue–green algae, most studies have been focused on the settlement of plants and animals but less on microbial succession. To explore microbial colonization in diverse soils and the influence of associated vegetation and birds on numbers of environmental bacteria, we collected 45 samples from different soil types on the surface of the island. Total viable bacterial counts were performed with the plate count method at 22, 30 and 37 °C for all soil samples, and the amount of organic matter and nitrogen (N) was measured. Selected samples were also tested for coliforms, faecal coliforms and aerobic and anaerobic bacteria. The subsurface biosphere was investigated by collecting liquid subsurface samples from a 181 m borehole with a special sampler. Diversity analysis of uncultivated biota in samples was performed by 16S rRNA gene sequences analysis and cultivation. Correlation was observed between nutrient deficits and the number of microorganisms in surface soil samples. The lowest number of bacteria (1 × 104–1 × 105 cells g−1) was detected in almost pure pumice but the count was significantly higher (1 × 106–1 × 109 cells g−1) in vegetated soil or pumice with bird droppings. The number of faecal bacteria correlated also to the total number of bacteria and type of soil. Bacteria belonging to Enterobacteriaceae were only detected in vegetated samples and samples containing bird droppings. The human pathogens Salmonella, Campylobacter and Listeria were not in any sample. Both thermophilic bacteria and archaea 16S rDNA sequences were found in the subsurface samples collected at 145 and 172 m depth at 80 and 54 °C, respectively, but no growth was observed in enrichments. The microbiota sequences generally showed low affiliation to any known 16S rRNA gene sequences.
Highlights
Microorganisms are typically in great abundance and high diversity in common soil and their integrated activity drives nutrient cycling on the ecosystem scale
A good visual correlation was found between total bacterial counts with the plate count agar method and growth on Reasoner’s 2A (R2A) media from all samples incubated at 22 ◦C (Fig. 3)
We observed a significant correlation between the amount of organic matter in soils and the number of heterotrophic environmental microorganisms grown on two different media at 22 ◦C, and the lowest number of bacteria (1×104–1×105 cells g−1) was measured in pure pumice; the count was significant higher (1×106–1×109 cells g−1) in vegetated soil or pumice with bird droppings (Fig. 3)
Summary
Microorganisms are typically in great abundance and high diversity in common soil and their integrated activity drives nutrient cycling on the ecosystem scale. Organic matter (OM) inputs from plant production support microbial heterotrophic soil communities that drive processes that make nutrients available in the system. This, in turn, supports plant primary productivity and basic food webs on the ground and in the subsurface (Fenchel et al, 2012; Roesch et al, 2007; Schlesinger, 1997; Whitman et al, 1998). Nutrient limitations can constrain plant and food web development, shaping the rate of succession of plant and animal life within the ecosystem (Odum, 1969; Walker and del Moral, 2003). Microbial cells colonizing new volcanic deposits must be successful in either growing autotrophically, by fixing carbon (C) and N using light or inorganic energy sources for growth, e.g. Cyanobacteria and sulfate-reducing bacteria (Edwards et al, 2003; Ernst, 1908; Konhauser et al, 2002), using carbon
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
