The functional ecology of Najas flexilis
In this study, all Scottish post 1980 Najas flexilis sites were surveyed for the presence or absence of Najas flexilis. In addition, all pre 1980 mainland sites were visited and 10 Irish sites across the Irish geographic range and presence or absence of Najas flexilis recorded. The environmental conditions required for Najas flexilis growth, including water and sediment chemistry, light and exposure were evaluated. These environmental conditions are compared between present and extinct sites. Measurement of specific plant traits, leaf area and reproductive number, from a representative sample of the population is used as a method for assessing the condition of the population in response to the environment. Models show that the concentration of phosphate in the sediment and water and magnesium in the water, along with the alkalinity and either light or calcium in the sediment can predict 67 - 88% of the variation in the plant traits of Najas flexilis. The community in which Najas flexilis grows was recorded from all sites visited. Two approaches were used a quantitative micro-habitat approach which is concerned only with the plants growing in the immediate vicinity of Najas flexilis and a qualitative whole lake approach. The suitability of these two approaches as a site condition monitoring tool for Najas flexilis is considered. The applicability of the Standing Water Type (SWT) classification to the community groups attained from whole lake approach and the applicability of National Vegetation Classification (NVC) scheme to the community groups attained from micro-habitat approach is considered. The lake scale qualitative approach elucidated significant differences in lake water pH, alkalinity and the concentration of total oxidised nitrogen and dissolved reactive phosphate in the water as well as differences in phosphate, calcium and iron in the sediment.