Response of testate amoebae to peatland drain blocking

: implications for biomonitoring of peatland restoration efforts

Abstract

Peatlands are a globally significant habitat, known for their increasingly vital role as carbon stores. However, growing anthropogenic exploitation of peatlands, coupled with significant disruption of the nitrogen cycle, presents a major management challenge. Peatlands are threatened by drainage for agriculture, forestry, and peat harvesting in the UK and Ireland, which can significantly affect their ability to sequester and store atmospheric carbon. Furthermore, ammonia (NH₃) emissions, which are mostly sourced from agricultural activity, are frequently deposited at critically high rates in the UK and Ireland. The degradation of peatland habitats is increasingly being counteracted through rewetting and drain blocking restoration, which is essential to maintain their effectiveness as carbon sinks and stores. However, due to often being situated near significant agricultural activity in the UK and Ireland, essential peatland restoration risks being diminished by excessive NH₃ deposition.

Microbial assemblages are a known to be a useful tool for monitoring environmental change and tracking restoration success, although research into how peatland management interventions affect microbial assemblages is limited. Testate amoebae (a group of unicellular shelled protists that are commonly used for palaeohydrological reconstruction in peatlands ), are increasingly utilised in contemporary biomonitoring of peatlands. Presented as three interlinked studies, this thesis aims to assess the efficacy of testate amoebae as a microbial peatland biomonitoring tool, by sampling contemporary testate amoebae assemblages at seven peatlands across Northern Ireland, UK.

The first study focusses on the response of testate amoebae to drain blocking restoration on three small highly connected lowland raised bogs. Sphagnum moss was sampled adjacent to sites of damming and control sites, in a before-after control-impact (BACI) experimental design. The second study expands the methods of the first study across three larger lowland raised bogs to investigate if the results of the first study are replicable on larger, more complex peatlands. Additionally, in this second study sampling occurred for a longer period after restoration measures were complete, and a greater range of testate amoebae analysis methods were employed. In the final study the application of testate amoebae as seasonal NH₃ deposition biomonitoring tool is investigated on six large peatlands. NH₃ deposition-sensitive Sphagnum moss was sampled adjacent to NH₃ monitoring sites once per season for a year in order to characterise the response of testate amoebae to agricultural activity-linked NH₃ deposition. In combination these three studies are compared to gain a greater understanding of the response of testate amoebae to NH₃ deposition and peatland restoration efforts.

Across the three studies testate amoebae demonstrated strong potential as a peatland restoration and NH₃ deposition biomonitoring tool. Following rewetting restoration, overall taxa diversity increased, and wet-indicator taxa became more abundant. Functional trait analysis further supported the value of testate amoebae as a biomonitoring tool, with the proliferation of taxa with non-compressed tests indicating potentially effective rewetting. In contrast, at sites with critically high NH₃ deposition, multivariate analysis revealed significant shifts in testate amoebae assemblages, with a notable decline in taxa diversity occurring in spring, countering the findings of previous research.

These findings provide the first empirical evidence linking a testate amoebae response to agricultural activity-linked seasonal NH₃ deposition, while expanding on limited previous testate amoeba-based peatland restoration biomonitoring research. Additionally, these studies reinforce the broader applicability of testate amoebae as a peatland restoration and NH₃ deposition biomonitoring tool. Although there remain key areas where further research is needed, testate amoebae are a valuable peatland biomonitoring tool that can be used to support restoration monitoring campaigns and are a cost-effective and approachable alternative when long-term monitoring is not possible.

Thesis is embargoed until 31 July 2028.

Date of Award	Jul 2025
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Graeme Swindles (Supervisor) & Helen Roe (Supervisor)