Association of Chemical Aggregates and Fungal Moieties Affecting Native Environmental Films

Abstract

Fungi are prevalent microorganisms in environmental films. Their impacts on the film chemical environment and morphology remains poorly defined. Here we present microscopic and chemical analyses fungi impacts to environmental films over long- and short-time scales. We report bulk properties of films accumulated for 2 months (February and March 2019) and 12 months to contrast short and longer-term effects. Bright field microscopy results show that fungi and fungal-associated aggregates cover close to 14% of the surface after 12 months and include significant numbers of large (tens to hundreds of μm in diameter) particles aggregated with fungal colonies. Data acquired for films accumulated over shorter times (2 months) suggest mechanisms that contribute to these longer-term effects. This is important because the film's exposed surface will determine what additional material will accumulate over the ensuing weeks or months. A combination of scanning electron microscopy and energy dispersive X-ray spectroscopy provides spatially resolved maps of fugal hypha and nearby elements of interest. We also identify a "nutrient pool" associated with the fungal hypha which extend orthogonally to the growth direction to ca. 50 μm distances. We conclude that fungi have both short-term and long-term effects on the chemistry and morphology of environmental film surfaces. In short, the presence (or absence) of fungi will significantly alter the films' evolution and should be considered when analyzing environmental film impacts on local processes.

Figure 1

Optical microscopy of a 12 month environmental film. Red circles highlight selected centers of fungi growth with aggregation and large reach across the surface (top). Bottom images show the large-particle aggregating capacity of the fungi (bottom four images).

Figure 2

SEM image (top) of fungi in an environmental film. Red arrow shows the direction of the fungi growth, and purple arrows show the extent of the nutrient pool. EDS elemental intensities along the horizontal white line are shown below with most intensity localized near the hyphae.