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The size and dynamics of biogenic silicon (BSi) pools influence silicon (Si) fluxes from terrestrial to aquatic
ecosystems. The research focus up to now was on the role of plants in Si cycling. In recent studies on old forests annual biosilicification rates of idiosomic testate amoebae (i.e. TA producing self-secreted silica shells) were shown to be of the order of Si uptake by trees. However, no comparable data exist for initial ecosystems. We analyzed the protozoic BSi pool (idiosomic TA), corresponding annual biosilicification rates and readily available and amorphous Si fractions along a 10-year chronosequence in a post-mining landscape in Brandenburg, Germany. Idiosomic Si pools ranged from 3 to 680 g Si ha−1 and were about 3–4 times higher at vegetated compared to uncovered spots. They increased significantly with age and were related to temporal development of soil chemical properties. The calculation of annual biosilicification resulted in maxima between 2 and 16 kg Si ha−1 with rates always higher at vegetated spots. Our results showed that the BSi pool of idiosomic TA is built up rapidly during the initial phases of ecosystem development and is strongly linked to plant growth. Furthermore, our findings highlight the importance of TA for Si cycling in young artificial ecosystems.
Accumulation and recycling of biogenic silicon (BSi) in terrestrial ecosystems influence fluxes of dissolved Si from the continents to the oceans, thus act as a filter in the global Si cycle. Although the biogenic control mechanism especially of phytogenic Si pools (phytoliths) has been generally recognized since decades quantitative information on other terrestrial BSi pools is surprisingly rare. For the first time terrestrial protophytic (diatom frustules), protozoic (testate amoeba shells) and zoogenic (sponge spicules) Si pools were quantified in soils of initial ecosystem states. We analyzed spatiotemporal changes of these Si pools in differently aged soils of the artificial catchment ‘Chicken Creek’ in NE Germany. Within a relatively short time span (<10 years) of ecosystem development protophytic, protozoic and zoogenic Si pool sizes increased markedly, whereat protozoic Si pools were the smallest ones with a maximum of 6.2 mg m−2. Zoogenic Si pool size (max. 22.6 mg m−2) is comparable to the one of protophytic Si pools (max. 30.5 mg m−2) although only few sponge spicules (n = 10) and spicule fragments (n = 2) were found. Differences in quantities, dynamics and resistibility against dissolution of various BSi pools indicate their possibility to influence biogeochemical Si cycling relatively rapid (protophytic and protozoic Si pools) or slow (zoogenic Si pool). Spatiotemporal changes of protophytic and protozoic Si pools within the first decade of ecosystem development seem to be mainly controlled by (biotic) small-scale environmental conditions (e.g., vegetation, food sources).
Testate amoeba diversity of a poor fen on mineral soil in the hilly area of Central Honshu, Japan
(2017)
Testate amoebae are a polyphyletic group of ubiquitous unicellular eukaryotic micro-organisms. They occur in high abundances in freshwater and terrestrial habitats, where they play an important role in biogeochemical and ecological processes. Terrestrial amoeba data from small tropical islands are rarely available despite the fact that they are interesting for investigations on global change induced sea level rise, biodiversity and biogeography. Based on a previously published paper on the impact of increased salinity to testate amoebae, the aim of this study is to present data on amoebal biodiversity from two remote, low-lying tropical islets of Tuvalu (South Pacific). In total 47 species and subspecific taxa of testate amoebae were recorded. These findings are based on 21 soil samples from 7 terrestrial habitats examined microscopically. Most species found were relatively small (< 100 μm) and considered as cosmopolitan. Non-metric multidimensional scaling ordination (NMDS) separated the samples by habitat structure and flooding regime rather than islet origin. Despite the apparently remote character of the study sites, human influence on distribution and biogeography of testate amoebae cannot be excluded.
Testate amoebae are a polyphyletic assemblage of unicellular eukaryotes with a specific shell. They occur frequently in soil and freshwater habitats all over the world, important for ecosystem functioning and useful for bio-indication. Terrestrial amoeba data from Borneo or Malaysia are rarely available. In this study, data on species composition and relative abundance were presented along a transect from 1730 m up to 4000 m above sea level from 10 elevational levels on Mt. Kinabalu, Malaysian Borneo. In total 78 morphotypes of testate amoebae were recorded. Most were small (under 100 µm) and supposedly cosmopolitan. However, Certesella certesi with limited geographical distribution and some rare taxa (e.g., Padaungiella lageniformis cordiformis, Placocista jurassica, Trinema chardezi) and two undescribed morphospecies were also observed. Presence/absence and relative abundance data of testate amoebae were associated to elevation with a pronounced change at the tree line, as revealed by non-metric multidimensional scaling ordination analysis. Our data from Southeast Asia contribute to the actual discussion on distributional patterns considering elevation gradients and biogeography of eukaryotic microbes.
We hypothesized that at the very beginning of terrestrial ecosystem development, airborne testate amoebae play a pivotal role in facilitating organismic colonization and related soil processes. We, therefore, analyzed size and quantity of airborne testate amoebae and immigration and colonization success of airborne testate amoebae on a new land surface (experimental site “Chicken Creek”, artificial post-mining water catchment). Within an altogether 91-day exposure of 70 adhesive traps, 12 species of testate amoebae were identified to be of airborne origin. Phryganella acropodia (51% of all individuals found, diameter about 35–45 μm) and Centropyxis sphagnicola (23% of all individuals found, longest axis about 55–68 μm), occurred most frequently in the adhesive traps. We extrapolated an aerial amoeba deposition of 61 individuals d−1 m−2 (living and dead individuals combined). Although it would be necessary to have a longer sequence (some additional years), our analysis of the “target substrate” of aerial immigration (catchment site) may point to a shift from a stochastic (variable) beginning of community assembly to a more deterministic (stable) course. This shift was assigned to an age of seven years of initial soil development. Although experienced specialists are necessary to conduct these time-consuming studies, the presented data suggest that terrestrial amoebae are suitable indicators for initial ecosystem development and utilization.
Elevation gradients have been useful to study distributional patterns of soil organisms since the time of Humboldt but only recently these patterns have been studied for soil microorganisms. Here we report the results on species diversity and composition of soil- and moss-dwelling testate amoeba assemblages along a 1400 m elevation gradient (904–2377 m a.s.l.) on Mount Fuji (Japan) from temperate forest to alpine vegetation. In total, 95 testate amoeba taxa belonging to 29 genera were identified. The core of testate amoeba assemblages was formed by ubiquitous species such as Trinema lineare, Euglypha laevis, Cryptodifflugia oviformis, and Trinema complanatum. However, several taxa with limited geographic distribution were also observed (e.g., Centropyxis latideflandriana, C. stenodeflandriana, Plagiopyxis cf. barrosi, Heleopera rectangularis, and Distomatopyxis couillardi). Species diversity indices (species richness and Shannon’s index) were characterised by bell-shaped patterns peaking at ∼ 1700 m in the subalpine mixed conifer-deciduous forest. The species composition of testate amoeba assemblages was best explained by the vegetation types which accounted for 12.3% of the total variation. Overall, these findings indicate that elevation effects on species composition of testate amoeba assemblages are strongly mediated by vegetation.
The resting cyst is one of the quietest life stages (i.e. cryptobiosis) with hardly measurable or even ceased metabolic activity. However, are the resting cysts just resting? Here, to our knowledge, we report for the first time radiation hormesis in resting cysts. In the present study, we focused on the proliferative capability of excysted cells from 500–4000 Gy-gamma-irradiated Colpoda cucullus resting cysts by a bioassay method. Generally, excysted cells from irradiated cysts lose their proliferative capability. However, we observed an increased proliferative capability promoted by low doses of irradiation. Cells, which had excysted from 500-Gy-irradiated cysts, restored their proliferation capability with a recovery period of 12 h and 24 h before excysting. Additionally, cells, which had excysted from 500-4000-Gy irradiated cysts, recovered proliferative capability by re-forming resting cysts. Here, the proliferative capability of excysted cells from 500-Gy-irradiated cysts was even higher than that of non-irradiated.
A new species of a testate amoeba, Matsakision ogawaraensis sp. nov., is described from Ogawara pond, Aomori Prefecture, Japan. This is the third species in the genus Matsakision. Matsakision ogawaraensis sp. nov. is distinguished from two other species by the specific form of the shell in apertural view, which is triangular (the shells of other species are circular or elliptic). In addition, it has a chitinous lip around the aperture. For the first time, long needle-like pseudopodia have been observed.
Bodenfauna: Entwicklung der Biodiversität in jungen Böden der Niederlausitzer Bergbaufolgelandschaft
(2007)
Beschalte Amöben - Charakterisierung der frühesten Phase des "Community Assembly" in jungen Böden
(2007)