Changes in Sediment and Diatom Deposition in Lower Lough Erne <i>c.</i> 1920–90
2003
Gibson, C. E. | Anderson, N. J. | Zhou, Q. | Allen, M. | Appleby, P. G.
An 800mm sediment core taken from Lower Lough Erne covered the period <i>c</i>. 1920‐ 94. The core was dated with <sup>210</sup>Pb. A marked increase in overall dry matter deposition rate over the period was punctuated by periods of much more rapid deposition. These were tentatively ascribed to periods of drainage or channel disturbance upstream of the core site. Elemental analyses of the sediment material showed marked temporal trends in percentage composition. Iron and manganese showed a downward step at about 1960, and horizons more recent than this were poorer in both elements. Total nitrogen and total carbon content increased up the core throughout the period. Percentage sulphur decreased up the core in the period before 1960, whereas calcium and phosphorus increased up the core in the period after 1960. Diatom analysis indicates a long-term eutrophication trend with the shift from <i>Aulacoseira</i> spp. to small <i>Stephanodiscus</i> and related species after approximately 1960. The arrival of <i>Skeletonema subsalsum</i>recorded in the core <i>c</i>. 1980 coincides with its documented arrival in the lake. The cause of this invasion is unknown. The changes in geochemistry and diatom assemblages are probably linked to increases in nutrient supply (from sewage and diffuse agricultural sources) and hence to increases in primary production.
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