Successional shifts of phototrophic community composition in biological soil crusts on coastal and inland dunes

Abstract

Aim Biological soil crusts (biocrusts) are autonomous ecosystems consisting of prokaryotic and eukaryotic microorganisms growing on the topsoil. They colonize global climatic zones, including temperate dunes. This study examines changes in the community structure of biocrust phototrophic organisms along a dune chronosequence at the Baltic Sea compared to an inland dune in Northern Germany. Methods The community composition and their shift between different successional stages of dune development were related to physico-chemical sediment properties. A vegetation survey followed by species determination and sediment analyses were conducted. Results The findings highlighted a varying phototrophic community composition regarding the different dune successional stages. In both study sites, a shift from algae-dominated biocrusts in younger to lichen- and moss-dominated biocrusts in later successional dune types was observed. This underlined a zonation from young to mature biocrusts along a dune chronosequence. The algae community of the two study sites shared 50% of the identified species while the moss and lichen community shared less than 15%. This indicates a more generalized occurrence of the algal species along both dune chronosequences. The mosses and lichens showed a habitat-specific species community. Moreover, an increase in the organic matter and moisture content with advanced biocrust development was detected. The enrichment of phosphorus in the different biocrust types showed a similar relationship. Conclusion This relation is explainable by biomass growth and potential phosphorus mobilization from the underlying sediment by microorganisms. The observed biocrust development supported nutrient enrichment and biomass accumulation and potentially maintained in turn soil formation.