China S et al. (2018), Fungal spores as a source of sodium salt partic...

ECB-ART-46760

Nat Commun 2018 Nov 19;91:4793. doi: 10.1038/s41467-018-07066-4.

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Fungal spores as a source of sodium salt particles in the Amazon basin.

China S , Burrows SM , Wang B , Harder TH , Weis J , Tanarhte M , Rizzo LV , Brito J , Cirino GG , Ma PL , Cliff J , Artaxo P , Gilles MK , Laskin A .

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In the Amazon basin, particles containing mixed sodium salts are routinely observed and are attributed to marine aerosols transported from the Atlantic Ocean. Using chemical imaging analysis, we show that, during the wet season, fungal spores emitted by the forest biosphere contribute at least 30% (by number) to sodium salt particles in the central Amazon basin. Hydration experiments indicate that sodium content in fungal spores governs their growth factors. Modeling results suggest that fungal spores account for ~69% (31-95%) of the total sodium mass during the wet season and that their fractional contribution increases during nighttime. Contrary to common assumptions that sodium-containing aerosols originate primarily from marine sources, our results suggest that locally-emitted fungal spores contribute substantially to the number and mass of coarse particles containing sodium. Hence, their role in cloud formation and contribution to salt cycles and the terrestrial ecosystem in the Amazon basin warrant further consideration.

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Genes referenced: LOC100887844 LOC100893907

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	Fig. 1. Size distribution and particle-type classes. a Representative SEM image (forward scattered transmitted electron imaging mode) of particles collected at the ZF2 site in Amazonia. Dark green arrows indicate Na-rich particles, blue arrows indicate mixed sulfate and Na-containing particles with minor contributions of Na, and light green color arrows indicate other types of particles, mostly internally mixed dust and biological particles. Scale bar is 5 µm. b Nightime and daytime number fraction of different particle classes for particles collected above canopy (A-canopy) and below canopy (B-canopy). c Size distribution of different particle classes during the nighttime above the canopy. d Size distribution of different particle classes during the nighttime below the canopy. e Size distribution of different particle classes during the daytime above the canopy. f Size distribution of different particle classes during the daytime below the canopy
	Fig. 2. Chemical imaging of Na-containing biological particles. a SEM image b elemental Na map and c EDX spectra of the biological particle. The Cu and Si in the EDX spectra are background peaks originating from the substrate and various instrument parts inside the SEM chamber. STXM images of the same biological particle: d pre edge (1070 eV), e Na peak (1079 eV) and f Na optical density map. Color bars indicate optical density. g–i Representative NanoSIMS images of 23Na+ of selected biological particles showing various distributions of sodium within particles contours. Scale bars are 2 µm
	Fig. 3. Simulation of sodium contribution from biological particles to total sodium budget in the Amazon area. a Comparison of annual-mean model-simulated fungal spore concentrations with previously published observed concentrations at various locations. All model-simulated values are annual means of fungal concentrations simulated using nudged meteorology. Observations are averages over the measurement period for each campaign (mostly between 2 months and 3 years), as previously reported in the literature (a full reference list for the observed spore counts is provided in Supplementary Table 2, together with a map of their geographic locations Supplementary Fig. 8). Dotted lines represent an over- or underestimate of a factor of 10 (10:1 and 1:10, respectively). The pink hexagonal point represents the measured fungal spore concentration in this study, compared with the mean simulated spore concentration from the same time period (26 Jan to 8 Feb 2015). The stars indicate points from literature measurements from tropical rainforests. b Distribution of the simulated daily mean sodium fraction contributed by fungal spores during the wet season (Jan–Jun, 2015). Simulated values are obtained from the model grid point nearest to the ZF2 tower (2.84° S 60.0° W), in the model’s lowest (near-surface) layer. The violin plot displays the kernel density estimation of the underlying distribution, along with the median (white dots), 25th–75th percentile (thick vertical bar), and range (thin vertical line). The shaded regions of the plot represent nighttime (blue shading; 1800–0600) and daytime (yellow shading, 0600–1800). c Percentage of days when fungal spores contributed at least 50% of estimated total sodium during the wet season, assuming that 70% of fungal spores are sodium rich, containing 13% sodium by mass, and sea salt aerosol is composed of 30% Na by mass. Results for the dry season are shown in Supplementary Fig. 12
	Fig. 4. Sources and atmospheric processing of fungal spore particles in the Amazon rainforest. Sodium-containing and sodium-free fungal spore particles are emitted from the Amazon rainforest. Sodium-containing fungal spores exhibit higher hygroscopic growth compared to sodium-free fungal spores. When they are exposed to high humidity conditions, or through cloud processing, fungal spore particles rupture and release submicrometer-to-micrometer size fragments. A substantial fraction of the fragments contain Na, Cl, and K, and appear morphologically similar to dry sea salt particles. These hygroscopic salt fragments can participate in cloud formation

References [+] :

Artaxo, Atmospheric aerosols in Amazonia and land use change: from natural biogenic to biomass burning conditions. 2013, Pubmed, Echinobase