Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands

Abstract

Soil microbial communities significantly contribute to global fluxes of nutrients and carbon. Their response to climate change, including winter warming, is expected to modify these processes through direct effects on microbial functions due to osmotic stress, and changing temperature regimes. Using four European peatlands reflecting different frequencies of frost events, we show that peatland testate amoeba communities diverge among sites with different winter climates, and that this is reflected through contrasting functions. We found that exposure to harder soil frost promoted species β-diversity (species turnover) thus shifting the community composition of testate amoebae. In particular, we found that harder soil frost, and lower water-soluble phenolic compounds, induced functional turnover through the decrease of large species (-68%, >80μm) and the increase of small-bodied mixotrophic species (i.e. Archerella flavum; +79%). These results suggest that increased exposure to soil frost could be highly limiting for large species while smaller species are more resistant. Furthermore, we found that β-glucosidase enzymatic activity, in addition to soil temperature, strongly depended of the functional diversity of testate amoebae (R=0.95, ANOVA). Changing winter conditions can therefore strongly impact peatland decomposition process, though it remains unclear if these changes are carried-over to the growing season.

Tipping point in plant–fungal interactions under severe drought causes abrupt rise in peatland ecosystem respiration

“…Enzymes were quantified in microplates following Jassey, Chiapusio, Gilbert, Toussaint, & Binet () and Jassey et al. (). Fluorescence of hydrolases was monitored spectrophotometrically with an excitation wavelength of 365 nm and emission detection at 450 nm (BioTek, SynergyMX) while oxidation rates of oxidases were monitored spectrophometrically at 600 nm (Table S3).…”

Making sense of environmental sequencing data: Ecologically important functional traits of the protistan groups Cercozoa and Endomyxa (Rhizaria)

“…In soils, testate amoebae have been useful as indicators of ecological conditions. For example, the functional traits of testate amoebae allowed researchers to: (a) successfully reconstruct past environmental changes in bogs and peatlands (Fournier, Lara, Jassey, & Mitchell, ; Marcisz et al, ); (b) reflect several abrupt ecological changes in the last 800 years in a mountain wetland ecosystem, with increased anthropogenic modifications leading to a shift towards myxotrophic taxa (Kajukało, Fiałkiewicz‐Kozieł, Gałka, Kołaczek, & Lamentowicz, ); (c) reveal that harder soil frost shifted the community composition of testate amoebae towards smaller, myxotrophic species (Jassey et al, ); and (d) study their dependence on plant functional types (Jassey et al, ). Using the functional traits of ciliates, complex predator–prey interactions models could be assessed (Tirok & Gaedke, ).…”

Taxonomic and functional traits responses of Sphagnum peatland testate amoebae to experimentally manipulated water table

“…Traits used for FD analysis should ideally relate to niche characteristics and/ or directly or indirectly to ecosystem processes (Mlambo, 2014;Violle et al, 2007). The FD approach was initially developed for macroscopic organisms such as plants, fishes and soil invertebrates, for which different sets of traits have been validated and more recently for microorganisms (Arrieira et al, 2015;Barnett et al, 2007;Fournier et al, 2016Fournier et al, , 2015Fournier et al, , 2012Jassey et al, 2016;Lamentowicz et al, 2015;Marcisz et al, 2016;van Bellen et al, 2017;Violle et al, 2011). Our focus here is on the impact of climate change on testate amoebae living in Sphagnum peatlands.…”

“…Their decay-resistant shell, well preserved in peat and sediments after the organisms' death, allows past climates to be reconstructed by inferring ancient local conditions through testate amoeba community structures (Chambers et al, 2012;Talbot et al, 2010). In addition, testate amoebae functional traits can also be defined in accordance with functional diversity assumptions and be used for biomonitoring or paleoreconstruction (Fournier et al, 2015;Jassey et al, 2016;Kajukało et al, 2016;van Bellen et al, 2017).…”