Microbiology of eutrophic (Ornithogenic and Hydrocarbon-Contaminated) soil

Abstract

Antarctic soils are typically low in carbon, nitrogen and phosphorus. Ornithogenic and hydrocarbon-contaminated soils, however, could be considered eutrophic. In this chapter, we review the microbial composition of ornithogenic and hydrocarbon-contaminated soils. Ornithogenic soils form in soils under bird nesting sites. These include those that form under penguin colonies of coastal soils and under bird nests in coastal soils and on nunataks. The soils currently occupied by birds have high levels of C, N and P and a low C:N ratio. The diversity and abundance of microbes in the soils depends on whether they are currently occupied by birds have been abandoned or are adjacent to the colony. Bacteria dominate occupied soils with Firmicutes reported to be prevalent, but in abandoned soils, Proteobacteria are dominant. Among the nematodes Panagrolaimus is most commonly reported from ornithogenic soils. Extensive areas of growth of visible photosynthetic microbes occupy soils adjacent to ornithogenic soils. Prasiola spp and Phormidium spp. are the dominant algae and cyanobacteria, respectively, that are reported. Most investigations of hydrocarbon-contaminated Antarctic soils have focused on heterotrophic bacteria, with a few reports of fungi. Hydrocarbon spills on soils typically occur next to research stations and result in an increase in soil C and a high C:N ratio. The result is a shift in microbial communities towards hydrocarbon-degrading species, predominantly from the Proteobacteria phylum. Among the hydrocarbon-degrading bacteria isolated from Antarctic soils are members of the genera Pseudomonas, Sphingomonas and Rhodococcus. These genera have been observed widely in contaminated temperate soils and have the capability to degrade hydrocarbons. Filamentous fungi from the Ascomycota phylum commonly isolated from contaminated soils include those from the Cadophora, Trichoderma and Mortierella genera, but their ability to degrade hydrocarbons is not always known. There is limited knowledge on the effect of hydrocarbons on Archaea, invertebrates or photosynthetic microbes in hydrocarbon-contaminated Antarctic soil. Our knowledge of eutrophic soils of Antarctica is sparse.