Climate forcing of diatom productivity in a lowland, eutrophic lake: White Lough revisited

摘要: Summary 1. In cultural landscapes, lake response to climate can be masked by land-use change and nutrient loss from their catchments. Palaeolimnological methods were used reconstruct the ecological of diatoms in a eutrophic lowland (White Lough, Co. Tyrone, Northern Ireland) altered P loading precipitation variability over c. 100 years. 2. 210Pb-dated sediment cores analysed determine diatom assemblage variability, biogenic silica concentration, geochemical phosphorus concentration accumulation rate. Manure agricultural N surplus data collated documentary sources. Long-term trends annual temperature derived Armagh Observatory. 3. Diatom community turnover 1890 until c. 1960 was limited, assemblages dominated Aulacoseira subarctica; after this date, changes primarily reflected eutrophication sequence owing increased diffuse inputs associated with intensification land use (external factor three). 4. Diatom Si profiles compared North Atlantic Oscillation (NAO) records, an index regional weather patterns. Biogenic exhibited c. 7-year cycle, which tracked cycle similar timescale record for dry summers. In turn, related variation NAO. 5. Monitoring 1971 2007 nitrate exports Blackwater River showed that these too followed roughly 7-year at least up 2000, summers sharp increases export. It is argued production White Lough reflects cyclic behaviour constraints nitrogen availability places on spring bloom cyanobacteria.