An investigation into the influences of catchment nutrient export and climatic effects on the trophic status of a small inter-drumlin lake, Milltown Lake, Co. Monaghan.

Veerkamp, Vicky (2020) An investigation into the influences of catchment nutrient export and climatic effects on the trophic status of a small inter-drumlin lake, Milltown Lake, Co. Monaghan. Doctoral thesis, Dundalk Institute of Technology.

PDF (PhD thesis) - Published Version Download (8MB)

Abstract

Eutrophication is an on-going problem in lakes that are nutrient enriched. In addition, lakes are now subject to changes in the local weather, which is linked to climate change. Understanding the way that climate affects nutrient export and changes within lakes is critical if lakes are to be improved and protected in the future. This thesis has examined this by looking at number of different factors, which include: (1) the role of nutrients exported from the surrounding landscape and how agricultural mitigation measures (e.g. comparing a fenced stream with a vegetative buffer strips to an unfenced stream which had no fencing installed), can be used to decrease nutrient loss from the land to water, (2) examining local climatic factors and their role, either directly or indirectly, in influencing lake biota, particularly in lakes where nutrient supplies are not limiting, and finally (3) determining how phytoplankton richness is influenced by changes in water column stability during the onset of spring stratification. The study within the catchment found net retention of nutrients (TP and TN) occurred during the Grazing season (cattle grazing in the field) in the fenced stream reach, while during the Open season (slurry spreading permitted, but cattle still indoors) the reverse was seen for TP only, suggesting that different processes were controlling export of nutrients in both the fenced and unfenced reach. Despite the net TP release in the Open season, the estimated TP and TN loads on an annual basis were lower for the fenced stream, compared to that of the unfenced stream. Regarding local climatic factors, results showed that in the epilimnion of Milltown Lake, surface nutrient loading (mainly P) and light were more significant than internal lake nutrient resuspension, while N availability was more influential in controlling the standing crop of phytoplankton at the lower lake depths. In general, catchment management strategies are devised to reduce nutrient loads from the surrounding catchment in order to protect and improve catchment waterbodies, which this study has shown to be achieved through the implementation of streamside fencing with a vegetative buffer strip. However, this study has also shown that more attention is needed in understanding the internal lake sediment nutrient release, should catchment load be reduced, it is this legacy source of nutrients that is likely to play a significant role in determining a lake’s trophic status.

Item Type:	Thesis (Doctoral)
Subjects:	Science > Biology Science > Chemistry Science > Physics
Research Centres:	UNSPECIFIED
Depositing User:	Eleanor Jennings
Date Deposited:	18 Nov 2020 18:22
Last Modified:	18 Nov 2020 18:22
URI:	https://eprints.dkit.ie/id/eprint/730

Actions (login required)

View Item

Downloads