Beyond 2020 >> The Burrishoole catchment >> BURRISHOOLE BLOG >> Lake Sediments Provide a Window to the Past in Lough Feeagh

Lake Sediments Provide a Window to the Past in Lough Feeagh

Project blog by Ryan Smazal (PhD student on SEQUESTER)

SEQUESTER is funded under the Landscape funding programme of the HEA through the DkIT Research Office.  The project is supervised by Prof. Eleanor Jennings (DkIT) and Dr Catherine Dalton (Mary Immaculate College, University of Limerick)

Just as historical documents and archaeological evidence have recorded the history of humans, lake sediments serve as important caretakers of the history of lakes. Lakes are frequently chosen as sites for palaeoenvironmental investigations, studies that use sediment core records to explore past environments, because they are sensitive to landscape and climate change. Lough Feeagh (Figure 1a) is just one example of a lake with a story to tell. Located in the Burrishoole catchment in Co. Mayo, Ireland, Lough Feeagh is a glacial freshwater lake that has an area of 410 ha and  a maximum depth of 46 m (de Eyto et al., 2016). In 2017, an 8 m sediment core was extracted from Lough Feeagh by the BEYOND 2020 team and colleagues in NUIG (Figure 1b, Figure 3) as part of the Marine Institute funded BEYOND 2020 project (Figure 2). Using this core, the SEQUESTER (SEdiment Quantities – UndErstanding Sediment Temporal Environment Records) Project seeks to provide palaeoenvironmental context for environmental changes and tipping points in the Burrishoole catchment.

Figure 1. a. the mountains overlooking Lough Feeagh, Mayo (photo credit: Mary Dillane). b. the coring operation at Lough Feeagh (photo credit: Elvira de Eyto). 

Figure 2.  map of the Burrishoole Catchment, with inset of Ireland. The red star is the location of Lough Feeagh, and the orange star is the location of Lough Furnace.

Changes in the environment and the climate have happened for millennia, bringing forth Ice Ages and Warming Periods alike. Because global temperatures have consistently been on the rise over the past 200 years due to greenhouse gas emissions, there have been a variety of more recent but significant environmental impacts. In order to understand what responses in the water body may be like, looking to the past can provide a vast array of information about the impact of climate change on the surrounding environment. Lake sediment is accumulated from catchment in-wash and within-lake sources, at rates that vary over space and time, and this sediment preserves physical, chemical and biological indicators (Burge et al., 2017). Generally, aquatic sediments are undisturbed and accumulate less than terrestrial sediments, and according to the Law of Superposition, maintain the order in which they were laid down allowing for more precise and accurate analysis, including determining chronology (Burge et al., 2017).

 Figure 3. the sediment core from Lough Feeagh laid out with the uppermost part of the core at the top left and the bottom of the core at the bottom right. The deepest and therefore the oldest sediment core is on the right, with each core one metre in length. 

The main palaeoenvironmental proxies include identification of biological remains, as well as geochemical and stratigraphical analysis. Biological fossils of plants and animals are frequently found in sediment cores, and by identifying and analysing them, inferences on both the landscape and in-lake processes can be made. Pollen, spores, and other non-pollen palynomorphs, which are washed into the lake or from aquatic species, have been used to interpret what past landscapes have looked like and how land use has impacted the surrounding environment, such as at the nearby Céide Fields (O’Connell et al., 2020). Other fossilized organisms, such as diatoms, are used to understand in-lake processes including salinity and conductivity and have been used at Lough Furnace in a previous palaeoenvironmental investigation (Cassina et al., 2013), and also in Lough Feeagh to reconstruct its recent history (Dalton et al., 2014). Combining these different types of proxies together in a multi-proxy study not only strengthens the investigation, but also shows how the surrounding landscape and lake react to change simultaneously or independently. Data from these proxies then can provide ecosystem management planners with valuable information as to possible scenarios and assist with understanding modern day lake conditions. Additionally, this understanding will allow for the integration of the large cluster of high frequency monitoring projects that occur at the Burrishoole Catchment with key palaeoenvironmental data.

As Lough Feeagh drains into Lough Furnace (Figure 2), a brackish, 141 ha coastal lagoon, it is an important site for monitoring and understanding Atlantic salmon (Salmo salar L.), sea trout (Salmo trutta L.), and European eel (Anguilla Anguilla) in different stages of life. The BEYOND 2020 project, which is supported by the Marine Institute, is also exploring the use of historical eDNA (environmental DNA) in the same core that is being being analysed for the SEQUESTER project.  This work is being undertkaen by BEYOND 2020 project partners UCD and will contribute to understanding some of the past pressures and responses of these species. 

 Figure 4. the sediment core from 6-7m. This part of the core shows the transition from clay to organic sediments; the circular holes are the sample sites for eDNA.  

The collaboration between these two projects presents an opportunity to understand the past environments that these key modern-day species have lived in, how that environment has varied over time, and potential indicators of how these species may have reacted to changes in the future. While the extent of environmental variation is yet to be revealed, these palaeoenvironmental investigations will add critical, long-term context to the environmental history of Lough Feeagh and the Burrishoole catchment. 

Cited literature:

  • Burge, David & Edlund, Mark & Frisch, Dagmar. (2018). Paleolimnology and resurrection ecology: The future of reconstructing the past. Evolutionary Applications 11, 42-59. https://doi.org/10.1111/eva.12556.
  • Cassina, F., Dalton, D., Dillane, M., de Eyto, E., Poole, R., Sparber, K. (2013). A multi-proxy palaeolimnological study to reconstruct the evolution of a coastal brackish lake (Lough Furnace, Ireland, during the late Holocene. Palaeogeography, Palaeclimatology, Palaeoecology, 383-384, 1-15. https://doi.org/10.1016/j.palaeo.2013.04.016
  • O’ Connell, M., Molloy, K.,  Jennings, E. (2020). Long-term human impact and environmental change in mid-western Ireland, with particular reference to Céide Fields – an overview. E&G Quaternary Science Journal, 69, 1-32.  https://doi.org/10.5194/egqsj-69-1-2020
  • de Eyto E., Jennings E., Ryder E., Sparber K., Dillane M., Dalton C., et al. (2016). Response of a humic lake ecosystem to an extreme precipitation event: physical, chemical and biological implications. Inland Waters 6, 483–498. https://doi.org/10.1080/IW-6.4.875
  • Dalton C., O’Dwyer B., Taylor D., de Eyto E., Jennings E., Chen G., et al. (2014). Anthropocene environmental change in an internationally important oligotrophic catchment on the Atlantic seaboard of western Europe. Anthropocene 5, 9–21. https://doi.org/10.1016/j.ancene.2014.06.003

Additional Links:

https://www.dkit.ie/beyond-2020

https://www.marine.ie/Home/home

https://youtu.be/I3BNUWhWrKk  (video of the core extraction)