For these reasons, there has long been an interest in understanding what bryophyte-associated microbes do, and what is their contribution to ecosystem processes. īryophyte-associated microbiomes are involved in multiple ecosystem-level processes such as N 2 fixation and methane oxidation. The individual phenotype of bryophytes is indeed the result of complex interactions between the combined expression of the host and associated microbiomes, which together form the so-called bryosphere. These microbial communities are involved in the development, growth, and health-in other words, all functions-of bryophytes. Like all plants, bryophytes associate with microbes. Bryophytes are thus a conspicuous component of the understory vegetation of many forest ecosystems, and even the dominant vegetation of wetlands such as peatlands. Widespread and abundant in many terrestrial ecosystems, the morphological and ecophysiological attributes of bryophytes allow them to grow in habitats that most vascular plants cannot colonize such as water, exposed rocks and soil, tree trunks, and leaves. More particularly, high abundances of photosynthetic microbes have been found in peatlands and tropical rainforests, where they regularly colonize bryophytes.īryophytes play a central role in many mesic ecosystems, as they form a zone of nutrient accumulation and transformation. More mesic ecosystems have been less studied than arid systems despite regular microscopic observations and DNA hits showing that photosynthetic microbes occur in other terrestrial biomes. Generally, these crusts are dominated by one large group of photosynthetic organisms, such as Cyanobacteria in high pH environments and Chlorophyta in more neutral to acidic environments, although other taxonomic groups such as Bacillariophyta, Eustigmatophyceae, and Xanthophyceae can also be commonly found but in lower proportions. Most of our knowledge about terrestrial photosynthetic microbes comes from drylands, such as hot and cold deserts, where they build biological crusts on soil surface. They encompass myriads of life forms and styles, with Cyanobacteria and Chlorophyta being the most commonly reported phyla in DNA-based global diversity surveys. ).Įmerging evidence has shown that photosynthetic microbes occur in a variety of terrestrial habitats, including sub-surface soils, exposed rocks, and bryophytes. While these photosynthetic microbes have key ecological and biogeochemical roles, they are thought to make a minor contribution to terrestrial primary productivity, compared to plants (but see refs. However, many photosynthetic terrestrial bacteria and protists use inorganic CO 2 in addition to light as an energy source. These organotrophs are highly involved in terrestrial C releases such as CO 2 and CH 4 respiration fluxes at the global scale. Most microorganisms use organic carbon (C) derived from vegetation or predation as energy and carbon sources. Over the last decade, environmental DNA studies revealed that terrestrial systems harbour diverse microbial communities, with significant implications in biogeochemical cycles. Terrestrial photosynthetic microbes clearly have the capacity to take up atmospheric C in bryophytes living under various environmental conditions, and therefore potentially support rates of ecosystem-level net C exchanges with the atmosphere. Our investigations clearly show that photosynthetic microbes associated with bryophyte effectively contribute to moss C uptake despite species turnover. Low moss water content and light conditions were not favourable to the development of photosynthetic protists in the tropical rainforest, which indirectly reduced the overall photosynthetic microbial C uptake. Our findings revealed that such patterns were driven by the proportion of photosynthetic protists in the moss microbiomes. We found that photosynthetic microbes take up twice more C in the boreal peatland (~4.4 mg CO 2.h −1.m −2) than in the tropical rainforest (~2.4 mg CO 2.h −1.m −2), which corresponded to an average contribution of 4% and 2% of the bryophyte C uptake, respectively. #Nebela tincta protists drivers#We interrogate their contribution to bryophyte C uptake and identify the main drivers of that contribution. Here, we study photosynthetic microbial communities associated with bryophytes from a boreal peatland and a tropical rainforest. In terrestrial systems, photoautotrophs occur in a variety of habitats, such as sub-surface soils, exposed rocks, and bryophytes. While they critically influence primary productivity in aquatic systems, their importance in terrestrial ecosystems remains largely overlooked. Photosynthetic microbes are omnipresent in land and water.
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