Trophic modelling of the Lough Neagh ecosystem, Northern Ireland

Abstract

Lough Neagh is the largest freshwater lake in the British Isles. The lough is animportant multi-purpose resource for the province of Northern Ireland. Previousresearch on the lough was combined with data from this study to analyse trophiccomponents of the Lough Neagh ecosystem. Analysis of the biomass and abundanceof taxonomic groups indicated that size-structuring was important within the system.Macro-invertebrates showed strong evidence of size-structuring over a depth gradientwith biomass, abundance and body-size all increasing with depth. Stable isotopeanalysis showed the lough to be a relatively simple system with strong bases inplanktivory and detritivory. It also highlighted the need for further research into otherpossible base sources within the lake food web. A mass balance trophic model wasconstructed for the system using the user friendly software Ecopath with Ecosim(EwE). Twenty functional groups were used in the analysis and EwE was used toassess the trophic relationship, energy flow and interactions between them. Themodel showed the under-utilisation of phytoplankton and detritus by consumers inthe system and hence the low transfer efficiency of 6.4% for the overall system.Summary statistics sensu Odum showed that the lough is its early stages ofdevelopment and consequently may be prone to perturbations particularlyanthropogenic events. The model allowed for key gaps in the present research onLough Neagh to be pinpointed. It is recommended that any further studies on theLough Neagh ecosystem should include components on the waterfowl populationssurrounding the lough as well as incorporating a bacterial element into any futuremodels. The Ecosim component to EwE was investigated as a management tool forthe lake system. The Ecosim component was capable of predicting general trends butwas not recommended for use as a sole management tool for the ecosystem but ratheras part of an integrated management system.

Date of Award	Sept 2009
Original language	English
Supervisor	DAVID GRIFFITHS (Supervisor) & Brian Rippey (Supervisor)