Cyanobacterial Richness Research Articles

Cultivating Resilience in Dryland Soils: An Assisted Migration Approach to Biological Soil Crust Restoration.

Land use practices and climate change have driven substantial soil degradation across global drylands, impacting ecosystem functions and human livelihoods. Biological soil crusts, a common feature of dryland ecosystems, are under extensive exploration for their potential to restore the stability and fertility of degraded soils through the development of inoculants. However, stressful abiotic conditions often result in the failure of inoculation-based restoration in the field and may hinder the long-term success of biocrust restoration efforts. Taking an assisted migration approach, we cultivated biocrust inocula sourced from multiple hot-adapted sites (Mojave and Sonoran Deserts) in an outdoor facility at a cool desert site (Colorado Plateau). In addition to cultivating inoculum from each site, we created an inoculum mixture of biocrust from the Mojave Desert, Sonoran Desert, and Colorado Plateau. We then applied two habitat amelioration treatments to the cultivation site (growth substrate and shading) to enhance soil stability and water availability and reduce UV stress. Using marker gene sequencing, we found that the cultivated mixed inoculum comprised both local- and hot-adapted cyanobacteria at the end of cultivation but had similar cyanobacterial richness as each unmixed inoculum. All cultivated inocula had more cyanobacterial 16S rRNA gene copies and higher cyanobacterial richness when cultivated with a growth substrate and shade. Our work shows that it is possible to field cultivate biocrust inocula sourced from different deserts, but that community composition shifts toward that of the cultivation site unless habitat amelioration is employed. Future assessments of the function of a mixed inoculum in restoration and its resilience in the face of abiotic stressors are needed to determine the relative benefit of assisted migration compared to the challenges and risks of this approach.

Summer dynamics of cyanobacteria in an oligo-mesotrophic temperate lake in Northwest Ireland

Despite the potential adverse consequences they can impart on biotopes, cyanobacteria are an understudied component of lake plankton communities in Ireland. This study, in summer 2019, examined cyanobacterial diversity and associated environmental variables in a lake previously impacted by algal blooms, in north-west Ireland. Vertical profiling showed that photosynthetic pigment concentrations were spatially heterogenous for the majority of the survey. However, water column homogeneity was observed towards the end of the survey, coinciding with increases in pigment concentrations. Sunshine hours, nutrient concentrations and wind speed were stable throughout the survey. Spatial homogeneity in pigments was attributed to an increase in minimal temperatures observed in the water column. PCR-DGGE analysis identified patterns in community composition, indicating a rise in cyanobacterial richness concomitant to increase in temperature and photosynthetic pigments. Band sequencing analysis identified phylotypes similar to the toxigenic species Microcystis sp. These were prominent at the end of the survey and coincided with the presence of the mcyE gene and low levels of microcystins, as indicated by real time PCR and ELISA analyses. The summer background presence of toxigenic cyanobacteria with potential bloom-forming capacity highlights the importance of annual lake cyanotoxin monitoring to inform resource management to protect human and animal health.

Sedimentary DNA records long‐term changes in a lake bacterial community in response to varying nutrient availability

AbstractMicrobial communities play important roles in lake ecosystems and are sensitive to environmental change. However, our understanding of their responses to long‐term change such as eutrophication is limited, as long‐term lake monitoring is rare, and traditional paleolimnological techniques (pigments and microfossils) are restricted to a low taxonomic resolution, or organisms with well‐preserved structures. Sedimentary DNA (sedDNA) is a promising technique to reconstruct past microbial communities in sediments, but taphonomic processes and the ability of sedDNA to record bacterial pelagic history accurately are largely unknown. Here, we sequenced the 16S rRNA gene in triplicate sediment cores from Esthwaite Water (English Lake District) which has concurrent long‐term monitoring and observational data. The sediment record spanned 113 years and included an episode of increased nutrient availability from the 1970s, followed by a more recent decline. Trends in bacterial community composition were broadly similar among the three sediment cores. Cyanobacterial richness in the sediment cores correlated significantly with that of cyanobacteria in a 65‐year microscopy‐based monitoring record, and some known pelagic bacterial taxa were detected in the sediment. sedDNA revealed distinct shifts in community composition in response to changing lake physicochemical conditions. The relative abundance of cyanobacteria closely reflected nutrient enrichment, and Proteobacteria, Bacteroidetes, and Verrucomicrobia were relatively more abundant in recent sediments, while Chloroflexi, Firmicutes, Acidobacteria, Nitrospirae, Spirochaetes, and Planctomycetes declined in more recent sediments. Following lake restoration efforts to reduce nutrient enrichment, the relative abundance of cyanobacteria returned to pre‐1970 levels, but the bacterial community did not fully recover from the period of intense eutrophication within the time scale of our study. These results suggest that sedDNA is a valuable approach to reconstruct lake microbial community composition over the 100‐year time scale studied, but an improved understanding of DNA deposition and degradation is required to further the application of sedDNA in paleolimnology.

Cyanobacteria species dominance and diversity in three Australian drinking water reservoirs

The objective of this study was to identify correlations between environmental variables and cyanobacterial diversity, succession and dominance in three Australian water supply reservoirs. We assessed up to 15 years of in-lake water quality monitoring data from Lake Wivenhoe and Lake Tingalpa (Queensland), and Lake Myponga (South Australia). Lakes Wivenhoe and Tingalpa, subject to a subtropical climate, had higher cyanobacterial richness than Lake Myponga in temperate South Australia. Richness in the subtropical lakes was positively correlated (P < 0.05) with total cyanobacteria biomass, and cyanobacteria biovolume > 0.03 mm3/l (Alert level 1; World Health Organization) was often composed of multiple cyanobacteria species. Peaks in total cyanobacteria biomass and diversity occurred in all three lakes from late spring to early autumn. Unicellular picocyanobacterial dominance was negatively correlated (P < 0.05) with total nitrogen while dominance of colonial and filamentous species with larger cells (e.g. Microcystis spp., Raphidiopsis spp., Dolichospermum circinale) was positively correlated (P < 0.05) with total phosphorus. Among the species with larger cells, diazotrophic D. circinale often dominated when total nitrogen was at low concentrations. Our results support decision making for selecting cyanoHAB control strategies based on single- or multi-species dominance and reinforce that new monitoring technologies could support species-level assessments.

Land degradation effects on composition of pioneering soil communities: An alternative successional sequence for dryland cyanobacterial biocrusts

Abstract In drylands, soil surfaces in interplant spaces are usually covered by biocrusts, which consist of communities of heterotrophic and chemoautotrophic bacteria, cyanobacteria, mosses, lichens, microalgae, fungi and other organisms. Cyanobacteria are of special interest because of their capacity to promote biocrust succession or increase soil fertility and stability. Therefore, some studies have analyzed their communities in different ecosystems, focusing on how different factors, such as temperature or altitude, influence their composition. Nevertheless, to our knowledge, the relationship between ecosystem degradation and cyanobacterial community composition has not yet been studied in depth. This could be determinant for the successful development of tools for restoring degraded biocrusts by cyanobacterial inoculation. Thus, the objective of this study was to analyze the effect of the ecosystem degradation level on cyanobacteria composition from topsoil communities, where they are keystone pioneering organisms. To do this, we analyzed the cyanobacterial diversity by molecular sequencing (16S rRNA gene) of the DNA extracted from biocrusts at different developmental stages, which were collected from three ecosystems in southeastern Spain. The selected ecosystems represent different “land-condition” states as a result of degradation processes. In one of them soil was removed by mining (the Gádor quarry), the second is a natural badland area (El Cautivo) where water erosion is intense, and the third ecosystem is a well-preserved area (Balsa Blanca). Our findings show that cyanobacterial richness decreases (up to 28 OTUs) as degradation increases and biocrust developmental stage decreases. Also, the relative abundances of most of the species were significantly correlated with the degradation state of the sampling site, either showing a positive or negative trend. Two of the species which increased in abundance with site degradation, and were especially abundant in incipient biocrusts, were Leptolyngbya frigida and Trichocoleus desertorum, while other species, also showing an increase in abundance with degradation, but having a higher relative abundance in most developed biocrusts, were Nostoc commune, Tolypothrix distorta and Scytonema sp. The significant correlation of these species with degradation at different biocrusts developmental stages, suggests an alternative developmental sequence for drylands, at least in more degraded ecosystems. In less degraded ones, the composition of the major cyanobacterial groups followed the common pattern of bundle-forming cyanobacteria (54.7%) pertaining to the Microcoleus genus followed by other non-heterocystous filamentous (17.4%), unicellular/colonial (7.5%) and heterocystous cyanobacteria (1.1%). In comparison, the cyanobacterial groups dominating the most incipient biocrusts, colonizing the most degraded soil, were the filamentous non-heterocystous (50.7%) and the bundle-forming cyanobacteria (48.9%). Therefore, our results show that some cyanobacterial species, which do not belong to traditional pioneer genera, are frequent colonizers of degraded soils, and then, they could be potentially used for producing a more efficient inoculum for inducing biocrust formation and restoring degraded soils. Finally, it is also remarkable that L. frigida appears as dominant in some biocrusts from drylands (up to 74.9% of abundance) being therefore demonstrated its wide distribution in nonpolar biomes and its capacity to also inhabit degraded arid soils.

Biological soil crusts along a climatic gradient in Chile: Richness and imprints of phototrophic microorganisms in phosphorus biogeochemical cycling

Biodiversity of phototrophic microorganisms in South American biological soil crusts (BSCs) and their role in the biogeochemical phosphorus (P)-cycle are unknown. Richness of BSC green algae and cyanobacteria was investigated at four climatically different Chilean sites (arid, semi-arid, Mediterranean, humid). Carbon (C), nitrogen (N), sulfur (S), and P contents, P pools and P speciation as well as spatial P species distribution within the BSCs were investigated. Morphological identification of enrichment cultures revealed 24 green algal and 18 cyanobacterial taxa in total. Irrespective of climatic conditions, each BSC comprised 12 to 15 different phototrophic species. Thereby, green algal richness increased, while cyanobacterial richness decreased with increasing humidity/decreasing mean annual temperature (North to South). Total C, N, and S contents ranged between 6.7 and 41.1 g C kg−1, 0.6–2.8 g N kg−1 and 0.2–0.7 g S kg−1, respectively, and increased in the order crust-free soil < crust-adhering soil < BSC. The total P content in BSCs ranged from 310 to 777 mg kg−1 with lowest concentrations at the arid site and highest concentrations at the semi-arid site. Labile P was highest in BSCs from semi-arid and Mediterranean climate implying no P-shortage for BSC organisms at these sites. In BSCs of all sites, stable and non-extractable P was identified as the major P pool (sequential P fractionation) with Ca-P species dominating at all sites except for the humid site at which Al-P was the main P species as determined by P K-edge X-ray absorption near edge structure, XANES. P K-edge μ-XANES of BSC cross sections revealed apatite hotspots, a potential P source for BSC organisms except for the arid site, where other Ca-P species dominated. Further, elemental mapping of the arid BSC cross section showed distinct accumulation of S and chloride (Cl) containing compounds within green algae and on their outer surface, respectively, raising the question of function/origin of these compounds. In conclusion, this work expands our knowledge on the richness of phototrophic organisms in South American BSCs and characterizes their possible position in the P-cycle along a strong climatic gradient. Our findings suggest that biotic and abiotic factors shape the structure of BSCs phototrophic communities as well as P pools and species at each habitat.

Wet season cyanobacterial N enrichment highly correlated with species richness and &amp;lt;i&amp;gt;Nostoc&amp;lt;/i&amp;gt; in the northern Australian savannah

Abstract. The Boodjamulla National Park research station is situated in the north-western Queensland dry savannah, where the climate is dominated by summer monsoons and virtually dry winters. Under shrub canopies and in between the tussock grasses cyanobacterial crusts almost entirely cover the flood plain soil surfaces. Seasonality drives N fixation, and in the savannah this has a large impact on both plant and soil function. Many cyanobacteria fix dinitrogen that is liberated into the soil in both inorganic and organic N forms. We examined cyanobacterial species richness and bioavailable N spanning 7 months of a typical wet season. Over the wet season cyanobacterial richness ranged from 6 to 19 species. N-fixing Scytonema accounted for seasonal averages between 51 and 93 % of the biocrust. Cyanobacterial richness was highly correlated with N fixation and bioavailable N in 0–1 cm. Key N-fixing species such as Nostoc, Symploca and Gloeocapsa significantly enriched soil N although Nostoc was the most influential. Total seasonal N fixation by cyanobacteria demonstrated the variability in productivity according to the number of wet days as well as the follow-on days where the soil retained adequate moisture. Based on total active days per month we estimated that N soil enrichment via cyanobacteria would be ∼ 5.2 kg ha−1 annually which is comparable to global averages. This is a substantial contribution to the nutrient-deficient savannah soils that are almost entirely reliant on the wet season for microbial turnover of organic matter. Such well-defined seasonal trends and synchronisation in cyanobacterial species richness, N fixation, bioavailable N and C fixation (Büdel et al., 2018) provide important contributions to multifunctional microprocesses and soil fertility.

Sedimentary DNA Reveals Cyanobacterial Community Diversity over 200 Years in Two Perialpine Lakes.

Cyanobacterial blooms can produce toxins that affect water quality, especially under eutrophic conditions, which are a consequence of human-induced climate warming and increased nutrient availability. Lakes worldwide have suffered from regular cyanobacterial blooms over the last century. The lack of long-term data limits our understanding of how these blooms form. We successfully reconstructed the past diversity of whole cyanobacterial communities over two hundred years by sequencing genes preserved in the sediments of two perialpine lakes in Switzerland. We identified changes in diversity over time and validated our results using existing data collected in the same two lakes over the past 40 years. This work shows the potential of our approach for addressing important ecological questions about the effects of a changing environment on lake ecology.

Influence of local and global environmental parameters on the composition of cyanobacterial mats in a tropical lagoon.

Cyanobacteria-dominated microbial mat communities thrive widely and year round in coral reefs and tropical lagoons, with periodic massive development of benthic blooms. We studied the diversity and spatiotemporal variation of the cyanobacterial dominance in mats of the shallow lagoon of La Réunion Island in the Indian Ocean by means of denaturing gradient gel electrophoresis and cloning-sequencing approaches targeting the 16S rRNA gene, combined with macromorphological and micromorphological characterization of corresponding phenotypes. The mat-forming cyanobacteria were highly diversified with at least 67 distinct operational taxonomic units identified in the lagoon, encompassing the entire morphological spectrum of the phylum Cyanobacteria, but with striking dominance of Oscillatoriales and Nostocales. It appeared also that selective pressures acting at different geographical scales have an influence on the structure and composition of these mats dominated by cyanobacteria. First, large changes were observed in their diversity and composition in relation to local changes occurring in their environment. Second, from the data obtained on the richness and composition of the mats and from the comparison with similar studies in the world, tropical mats seem to display wider cyanobacterial richness than in temperate and cold areas. Moreover, these tropical mats share more species with mats in other tropical regions than with those in temperate and cold climatic regions, suggesting that marine cyanobacteria in biofilms and mats display a biogeographic structure.

DNA-based molecular fingerprinting of eukaryotic protists and cyanobacteria contributing to sinking particle flux at the Bermuda Atlantic time-series study

We used denaturing gradient gel electrophoresis (DGGE) to examine the protist and cyanobacterial communities in the euphotic zone (0–120m) and in corresponding 150m particle interceptor traps at the Bermuda Atlantic Time-series Study (BATS) in a two-year monthly time-series from May 2008 to April 2010. Dinoflagellates were the most commonly detected taxa in both water column and trap samples throughout the time series. Diatom sequences were found only eight times in the water column, and only four times in trap material. Small-sized eukaryotic taxa, including the prasinophyte genera Ostreococcus, Micromonas, and Bathycoccus, were present in trap samples, as were the cyanobacteria Prochlorococcus and Synechococcus. Synechococcus was usually overrepresented in trap material, whereas Prochlorococcus was underrepresented compared to the water column. Both seasonal and temporal variability affected patterns of ribosomal DNA found in sediment traps. The two years of this study were quite different hydrographically, with higher storm activity and the passing of a cyclonic eddy causing unusually deep mixing in winter 2010. This was reflected in the DGGE fingerprints of the water column, which showed greater phylotype richness of eukaryotes and a lesser richness of cyanobacteria in winter of 2010 compared with the winter of 2009. Increases in eukaryotic richness could be traced to increased diversity of prasinophytes and prymnesiophytes. The decrease in cyanobacterial richness was in turn reflected in the trap composition, but the increase in eukaryotes was not, indicating a disproportionate contribution of certain taxa to sinking particle flux.