Response of Sphagnum Peatland Testate Amoebae to a 1-Year Transplantation Experiment Along an Artificial Hydrological Gradient

Peatland testate amoebae (TA) are well-established
bioindicators for depth to water table (DWT), but effects of
hydrological changes on TA communities have never been
tested experimentally. We tested this in a field experiment by
placing Sphagnum carpets (15 cm diameter) collected in hummock,
lawn and pool microsites (origin) at three local
conditions (dry, moist and wet) using trenches dug in a
peatland. One series of samples was seeded with microorganism
extract from all microsites. TA community were analysed
at T0: 8–2008, T1: 5–2009 and T2: 8–2009. We analysed the
data using conditional inference trees, principal response
curves (PRC) and DWT inferred from TA communities using
a transfer function used for paleoecological reconstruction.
Density declined from T0 to T1 and then increased sharply
by T2. Species richness, Simpson diversity and Simpson
evenness were lower at T2 than at T0 and T1. Seeded communities
had higher species richness in pool samples at T0.
Pool samples tended to have higher density, lower species
richness, Simpson diversity and Simpson Evenness than hummock
and/or lawn samples until T1. In the PRC, the effect of
origin was significant at T0 and T1, but the effect faded away
by T2. Seeding effect was strongest at T1 and lowest vanished
by T2. Local condition effect was strong but not in line with
the wetness gradient at T1 but started to reflect it by T2.
Likewise, TA-inferredDWTstarted to match the experimental
conditions by T2, but more so in hummock and lawn samples
than in pool samples. This study confirmed that TA responds
to hydrological changes over a 1-year period. However, sensitivity
of TA to hydrological fluctuations, and thus the accuracy
of inferred DWT changes, was habitat specific, pool TA
communities being least responsive to environmental changes.
Lawns and hummocks may be thus better suited than pools for
paleoecological reconstructions. This, however, contrasts with
the higher prediction error and species’ tolerance for DWT
with increasing dryness observed in transfer function models.