Chironomid populations of Lough Neagh with reference to the internal loadings of phosphorus

Abstract

The chironomid population of Lough Neagh was studied from 1994 to 1995. Regular samples were taken along a transect from Traad Point to the deepest part of the Lough from 5 to 25 metres of overlying water depth. Identification was carried out as far as possible by the use of keys and rearing to the adult stage. Little change was noted in the community composition since 1978, although some differences in abundance and distribution were noted. One species new to Ireland was identified.

Attempts to improve the water quality of Lough Neagh by removal of phosphorus at point sources appear to have had no effect on the chironomid community. The effects of short term changes such as a period of drought and calm weather in 1995 m the chironomid community suggest that care needs to be taken when applying water quality indices. The need to survey a range of habitats and consider chemical data is emphasised, as well as the importance of long term study of the chironomid population in order to assess changes in the lough.

A laboratory investigation was carried out to assess the role of chironomid larvae in phosphate cycling in Lough Neagh. The density of Chironomus anthracinus larvae was found to be positively correlated with the release of phosphate from resettled sediment cores. Phosphate release due to both the density of C. anthracinus larvae and the process of diffusion was increased in low oxygen conditions. Increased densities of C. anthracinus larvae in conditions of reduced oxygen saturation of the water column accelerated the onset of anoxia.

Uthe input of phosphate to the lough could be reduced below the level of output, the process of removal of phosphate from the sediment would be hastened by the actions of C.anthracinus larvae, thereby speeding he recovery of the lough.

Date of Award	Aug 1997
Original language	English