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

Abstract

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

Combining limnological and palaeolimnological data to disentangle the effects of nutrient pollution and climate change on lake ecosystems: problems and potential

“…Note that data for Loch Leven in Fig. 2 are taken from core LEVE11 as well as LEVE12 and the ‘point of change’ for White Lough is derived from diatom analysis of WHI‐12 (Anderson et al. , 2012).…”

“…, 2012) show a full history of eutrophication beginning in the first part of the nineteenth century when Aulacoseira ambigua (Grunow) Simonsen, Stephanodiscus parvus/ minutulus, Stephanodiscus hantzschii Grunow and C. pseudostelligera began to replace A. subarctica, Tabellaria flocculosa (Roth) Kützing and oligotrophic Cyclotella taxa that characterised the pre‐eutrophication flora. At White Lough, the pre‐eutrophication plankton flora was characterised by Cyclotella ocellata Pantocsek, a diatom typical of nutrient‐poor water (Anderson et al. , 2012).…”

Using palaeolimnological and limnological data to reconstruct the recent history of European lake ecosystems: introduction

“…Anderson et al. (2012) use palaeolimnological methods to reconstruct the ecological response of the lake to changes in nutrient P‐loading (derived from documentary evidence, geochemical analyses and hydrological modelling) and climate (precipitation variability) over approximately the last 100 years.…”

Long-Term Trends and Temporal Synchrony in Plankton Richness, Diversity and Biomass Driven by Re-Oligotrophication and Climate across 17 Danish Lakes

“…For example, in the last decades, trends towards warmer lake water [17][18][19][20], changes in thermocline depth and delay in turnover [21] as well as alterations in lake-catchment interactions [22] have been documented. Furthermore, changes in plankton richness [23], phenology [24][25][26], community composition [27,28] and trophic interactions [29,30] have been recorded as a reaction to long-term warming.…”