Biological Soil Crusts from Coastal Dunes at the Baltic Sea: Cyanobacterial and Algal Biodiversity and Related Soil Properties

Abstract

Biological soil crusts (BSCs) are known as "ecosystem-engineers" that have important, multifunctional ecological roles in primary production, in nutrient and hydrological cycles, and in stabilization of soils. These communities, however, are almost unstudied in coastal dunes of the temperate zone. Hence, for the first time, the biodiversity of cyanobacterial and algal dominated BSCs collected in five dunes from the southern Baltic Sea coast on the islands Rügen and Usedom (Germany) was investigated in connection with physicochemical soil parameters. The species composition of cyanobacteria and algae was identified with direct determination of crust subsamples, cultural methods, and diatom slides. To investigate the influence of soil properties on species composition, the texture, pH, electrical conductivity, carbonate content, total contents of carbon, nitrogen, phosphorus, and the bioavailable phosphorus-fraction (PO4 (3-)) were analyzed in adjacent BSC-free surface soils at each study site. The data indicate that BSCs in coastal dunes of the southern Baltic Sea represent an ecologically important vegetation form with a surprisingly high site-specific diversity of 19 cyanobacteria, 51 non-diatom algae, and 55 diatoms. All dominant species of the genera Coleofasciculus, Lyngbya, Microcoleus, Nostoc, Hydrocoryne, Leptolyngbya, Klebsormidium, and Lobochlamys are typical aero-terrestrial cyanobacteria and algae, respectively. This first study of coastal sand dunes in the Baltic region provides compelling evidence that here the BSCs were dominated by cyanobacteria, algae, or a mixture of both. Among the physicochemical soil properties, the total phosphorus content of the BSC-free sand was the only factor that significantly influenced the cyanobacterial and algal community structure of BSCs in coastal dunes.

Algal richness in BSCs in forests under different management intensity with some implications for P cycling

“…2), which is a similar or slightly lower species richness compared to the other reports on BSCs from temperate regions at open sites (Langhans et al, 2009;Schulz et al, 2016), but similar or higher compared to the previous reports on algae from forest bulk soil (Khaybullina et al, 2010;Novakovskaya and Patova, 2008;Starks et al, 1981). Nevertheless, the given number most probably underestimates the real algal richness, since our results are based on the enrichment cultivation followed by morphological identification.…”

“…Phototrophic microorganisms were identified as Cyanobacteria, Chlorophyta, Streptophyta, and some Stramenopiles (Eustigmatophyceae). Diatoms were regularly found in direct observations but were excluded from the analyses as the mentioned enrichment cultivation was not suitable for this group of microalgae (e.g., Schulz et al, 2016).…”

“…In semiarid and arid environments, BSCs were studied, for example, in deserts of Israel and the USA but also in polar regions (Borchhardt et al, 2017;Flechtner et al, 1998;Kidron et al, 2010). In temperate regions, dunes with sparse vascular plant vegetation or disturbed areas in open sites (e.g., former mining sites) typically promote the development of BSCs (T. Langhans et al, 2009;Lukešová, 2001;Schulz et al, 2016;Szyja et al, 2018).…”

“…While the role of BSC in the C-and N-cycle is well documented, little is known about their role in P cycling. Recent studies indicated that the number of microalgal species in BSCs can be related to the soil P content (Baumann et al, 2017;Schulz et al, 2016). Nevertheless, the effect of environmental factors that shape BSC communities and in turn affect soil characteristics is still unstudied.…”

“…Filamentous cyanobacteria, especially representatives from the genus Microcoleus, are often dominant phototrophic organisms in BSCs from drylands and dunes of temperate regions (Garcia-Pichel et al, 2001;Schulz et al, 2016). They are described as important members of BSC communities due to their ability to produce sticky mucilage sheaths and extracellular polymeric substances, thus forming a network between soil particles (Gundlapally and GarciaPichel, 2006).…”