Environmental controls on the spatial and temporal distribution of testate amoebae in two British minerotrophic mires

Geary, Andrew. P

Abstract

This is the first study in the British Isles detailing the spatial and temporal distribution and controls on testate amoebae within minerotrophic brown-moss dominated mires. The study covers a full annual cycle at two mires, Max Bog in North Somerset and Shapwick Heath on the Somerset Peat Moors, between 1st June 2009 and 31st May 2010. Groundwater and host substrate samples were collected fortnightly and quarterly. Precipitation inputs compared well with 30-year averages, which revealed that total rainfall was typical, despite there being an unusually wet summer and dry spring recorded at each site. Water table depth responded differentially to precipitation at both sites, with Shapwick Heath far more responsive. This is likely to be a result of a combination of site topography and the nature of the underlying substrate.
Spatially, each site had specific testate amoebae communities which were strongly linked to substrate. This was particularly evident at Max Bog. Spatial variability across both mires was driven by the relative abundance of a few key species. A larger number of more variable species then contributed at the individual biotope level. No vertical micro-distribution in the bryophytes was observed which was probably owing to the lack of both mixotrophic species and the moisture gradient.
Temporal analysis showed that testate amoebae exhibited seasonal responses which were variable between the two sites and were represented by compositional change in the warmer periods of spring and summer. The strength and pattern of seasonality varied between communities inhabiting different biotopes. Seasonal shifts in bryophyte communities were generally represented by shifts in species dominance, while in other biotopes, seasonal variability was driven by species presence and absence. No vertical difference in seasonality was recorded in the bryophytes.
Substrate variables were the principal controls on the broader species spatio-temporal distribution, particularly pH and Ca2+. There was very limited influence of both the water table and groundwater variables at Max Bog. Groundwater was far more influential at Shapwick Heath, although secondary to substrate variables. There was no consistent pattern of control between communities.
Four test types were recorded overall. The numerically dominant test type at both sites was idiosomic. Although they exhibited some spatial variability, temporally they were stable. Major differences were due to relative fluctuations of xenosomes and protein-calcium tests. Vertically, there was no difference in test type composition. The dominance of the idiosome tests can have a significant impact on the quality of palaeo-environmental reconstruction in minerotrophic mires through the loss of ecological information and the potential underestimation of depth to water table (DWT). Furthermore, the use of testate amoebae in hydrological reconstructions in these systems may be severely limited, owing to the strong link with host substrate. The data suggest, however, that fen-dwelling testate amoebae may be useful in bio-monitoring, mire restoration and conservation research.

Citation

Geary, A. P. Environmental controls on the spatial and temporal distribution of testate amoebae in two British minerotrophic mires. (Thesis). University of the West of England. Retrieved from https://uwe-repository.worktribe.com/output/816060

• Thesis Type: Thesis
• Publicly Available Date: Dec 12, 2023
• Keywords: testate amoebae, minerotrophic mires, fens, peatlands, brown moss, peatland ecology, peatland testate amoebae, test dissolution, fen bog transition, brypohytes, test preservation, mire ecology, mire palaeoecology, mire hydrochemistry, testate amoebae cont
• Public URL: https://uwe-repository.worktribe.com/output/816060
• Award Date: Jun 9, 2014