Testate Amoeba Species- and Trait-Based Transfer Functions for Reconstruction of Hydrological Regime in Tropical Peatland of Central Sumatra, Indonesia

Abstract

Tropical peatlands play an important role in carbon storage and in water regulation on a landscape level. However, our understanding of their ecology and long-term hydrological dynamics remains limited. Transfer functions, constructed on the basis of biological indicators (proxies) with known ecological preferences, allow us to infer past environmental conditions and serve as a basis for prediction of future changes in peatlands. Here, we use testate amoebae to develop the first species-and functional trait-based transfer functions for the Southeast Asia. This provides a valuable tool for future reconstructions of past hydrological changes in tropical peatlands, their development, and climatic changes. Surface samples for testate amoeba analysis were taken in various biotopes along two transects across the Sungai Buluh peatland in Central Sumatra. The following environmental characteristics were measured: water table depth (WTD), light intensity, pH, total C and N concentrations. The analysis of the surface samples revealed 145 morphotypes of testate amoebae belonging to 25 genera. A significant fraction of the variance in testate amoeba morphotypes and functional trait composition was explained by WTD and pH. The wide WTD range (0-120 cm) seems more valuable for reconstruction than the extremely short pH gradient (2.5-3.8). Thus, transfer functions were developed only for WTD, based on weighted averaging model for morphotypes and multiple linear regression for functional traits. Both speciesand trait-based model have a predictive ability for WTD reconstruction. For traits, the best performance of the model was reached by including five morphological traits: shell width, aperture shape, aperture invagination, shell shape and shell compression.

Testate Amoeba Functional Traits and Their Use in Paleoecology

“…It was shown for Trigonopyxis that test size, increased on average by 20 µm, with decreasing temperature (from 19 to 9 • C mean annual temperature) and increasing precipitation (from 2200 to 4500 mm year −1 ; Schulz et al, 2018). Similarly, the test size of H. subflava in peatlands of Indonesia, Peru and Panama ranged from 35 to 140 µm, and different test sizes correlated differently with water table depth in both modern and paleo samples of peatlands (Swindles et al, 2014(Swindles et al, , 2016(Swindles et al, , 2018Biagioni et al, 2015;Krashevska et al, 2020). Therefore, H. subflava test size changes from small to large can be considered as an indicator trait of frequent hydrological changes from drier to wetter conditions in tropical peatlands, whereas in highand mid-latitude peatlands this species is considered as an unambiguous indicator of dry conditions (Charman et al, 2000).…”

“…However, the application of this classification in subsequent functional ecology studies was limited. Lousier, 1974;Wanner and Xylander, 2005;Laggoun-Défarge et al, 2008;Fournier et al, 2012Fournier et al, , 2015Jassey et al, 2013aJassey et al, ,b, 2016Fiałkiewicz-Kozieł et al, 2015;Lamentowicz et al, 2015;Arrieira et al, 2016;Krashevska et al, 2016Krashevska et al, , 2020Marcisz et al, 2016, Marcisz et al, 2020Gałka et al, 2017;Koenig et al, 2017Koenig et al, , 2018aMcKeown et al, 2019;Macumber et al, 2020 Length/size/shell size (µm) Lamentowicz et al, 2009a;Fournier et al, 2012;Gomaa et al, 2012;Fiałkiewicz-Kozieł et al, 2015;Krashevska et al, 2016Krashevska et al, , 2020Schwind et al, 2016a,b;Koenig et al, 2017Koenig et al, , 2018avan Bellen et al, 2018;Marcisz et al, 2019 Frontiers in Ecology and Evolution | www.frontiersin.org No Gomaa et al, 2012;Lansac-Tôha et al, 2014;Lahr et al, 2019;Krashevska et al, 2020;Macumber et al, 2020 Lousier, 1974;Fournier et al, 2012Fournier et al, , 2015Fournier et al, , 2016…”

“…Position of the aperture within the test: acrostomic, plagiostomic, axial Protected/hidden apertures are interpreted as adapted to decreasing soil moisture content; Aperture position represents the ability to survive in thin water film and thus the ability to remain active and contribute to the food web in dry conditions Yes Bonnet, 1964;Lousier, 1974;Chardez and Lambert, 1981;Laggoun-Défarge et al, 2008;Fournier et al, 2012;Krashevska et al, 2012Krashevska et al, , 2020Jassey et al, 2013a,b;Fiałkiewicz-Kozieł et al, 2015;Fournier et al, 2015;Lamentowicz et al, 2015;Marcisz et al, 2016;Koenig et al, 2017Koenig et al, , 2018aMarcisz et al, 2020 Aperture shape Shape of the aperture can be circular, oval, slit-like, irregular…”

“…Yes Han et al, 2011;Gomaa et al, 2012;Macumber et al, this issue;Lahr et al, 2019;Krashevska et al, 2020 Aperture size (µm) Width of the shell aperture Related to prey size and food web functioning Yes Jassey et al, 2013aJassey et al, ,b, 2016Meyer et al, 2013;Gomaa et al, 2014;Fournier et al, 2015;Marcisz et al, 2016;Koenig et al, 2017Koenig et al, , 2018aKrashevska et al, 2020;Marcisz et al, 2020 (Continued) Frontiers in Ecology and Evolution | www.frontiersin.org Heal, 1964;Schönborn, 1965;Yeates and Foissner, 1995;Gilbert et al, 2000Gilbert et al, , 2003Jassey et al, 2012Jassey et al, , 2015Krashevska et al, 2012Krashevska et al, , 2020Marcisz et al, 2014bMarcisz et al, , 2015Marcisz et al, , 2016Marcisz et al, , 2019Marcisz et al, , 2020Fournier et al, 2015;Payne et al, 2016;Gałka et al, 2017;Koenig et al, 2017Koenig et al, , 2018aRatcliffe et al, 2017;Creevy et al, 2018;van Bellen et al, 2018;Herbert et al, 2019;Basińska et al, 2020;Lamentowicz et a...…”

Testate amoebae (Amorphea, Amoebozoa, Cercozoa) as bioindicators: a scientometric review

“…The properties of testaceans that deem them suitable for biological indicators are many and diverse in number. The test formation (endogenous or exogenous origin) and composition (proteinaceous, agglutinate-mineral, siliceous, calcareous, agglutinate-mineral-siliceous, and agglutinate-siliceous), test size and morphology, pseudostome shape and position can reveal effects of the environment on species' and or the organism's impact on ecosystem processes (Schwind et al, 2016;Violle et al, 2007;Krashevska et al, 2020). When in contact with environmental fluctuation, testaceans can adapt and recast their richness, diversity, abundance, biomass and species size (Laggoun-Défarge et al, 2008).…”