Gardner, EA; (2016) The ecohydrology and conservation of a coastal sedimentary lake and wetland system: Sheskinmore Lough, Donegal, Ireland. Doctoral thesis , UCL (University College London).

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Abstract

Lowland, shallow, coastal lake systems often comprise a complex array of habitats and species as a consequence of their geomorphic evolution, in combination with marine and terrestrial forcing. But they are also vulnerable to changes in climate and human activities that both influence species assemblages, sediment dynamics, water quality and hydrology. Sheskinmore Lough, located on the west coast of Donegal, northwest Ireland comprises a shallow (<1.5m) freshwater sedimentary lake surrounded by a diverse array of coastal and freshwater wetland and dune habitats supporting a plethora of rare and endangered species. The lake-wetland-dune complex, designated under the EU Habitats and Birds Directives, is managed by the National Parks and Wildlife Service (NPWS) who are concerned that declining water levels are driving negative impacts on protected flora and fauna; however their water management approach is reactionary, lacks an ecohydrological basis and is inherently unsustainable. The aim of this PhD is to inform conservation management strategies via multidisciplinary analysis of the ecohydrology of Sheskinmore Lough and its adjacent wetlands. The thesis examines the contemporary ecohydrology of the system, and reconstructs past environmental change using multiproxy paleolimnological techniques to ascertain the envelope of ecohydrological variability over different timescales. In addition, the research uses a distributed hydrological model to explore the impacts associated with climate change and hydrological management. The results reveal a lake and wetland system that has a complex contemporary ecohydrology set in a complicated coastal environment. Ecological analysis indicates an oligotrophic, circumneutral, shallow lake system, overlying a sedimentary complex dominated by peat and calcareous sandy substrates, fringed by a wetland system comprising fen and mire communities that also favour similar conditions. Hydrology was identified as a key factor influencing the distribution and composition of communities across the site. Operation of the sluice had the greatest impact, causing water levels to fluctuate rapidly (up to 1m in under 7 days) within the lake, with knock-on effects observed across a large part of the wetland system. Paleolimnological analyses revealed two important climatic and geomorphological shifts defining three key phases in the recent environmental and ecohydrological history of the site. First, a change occurred in the mid to late 1500s AD from a drier, sandy environment when the lake was primarily a riverine system, to one that was wetter and dominated by peat and ree dbe ds. The second transition occurred c.1800 AD when the climate became more turbulent, prompting the development of a lake-wetland system. Finally, modelling projections indicate the lake and wetland system are likely to experience increasing impacts in the future due to a more variable climate and lake water levels fluctuating more as a result. Ultimately, hydrological management coupled with climate change presents the greatest potential ecological threat to Sheskinmore Lough. This thesis therefore provides a series of conservation recommendations to enhance the preservation of similar freshwater systems, while the knowledge gained contributes significantly to the understanding of shallow aquatic ecohydrology.

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