Historical changes (1905–2005) in external phosphorus loads to Loch Leven, Scotland, UK

Abstract

This paper reviews historical changes in the total phosphorus (TP) inputs to Loch Leven, Scotland, UK. Data derived from palaeolimnological records suggest that inputs in the early 1900s were about 6 t TP y -1 (0.45 g TP m -2 y -1 ). By 1985, this had risen to about 20 t TP y -1 (1.5 g TP m -2 y -1 ) due to increases in runoff from agricultural land and discharges from point sources. By the late 1970s, increased TP inputs were causing serious degradation of lake water quality. Most noticeably, there had been an increase in cyanobacterial blooms. A catchment management plan was implemented in the early 1990s. This resulted in a 60% reduction in the annual TP input between 1985 (20 t TP y -1 /1.5 g TP m -2 y -1 ) and 1995 (8 t TP y -1 /0.6 g TP m -2 y -1 ). The main reduction was associated with better control of point source discharges, but attempts were also made to reduce inputs from diffuse sources. The reduction in external TP loading to the lake led to a marked decline in TP retention by the lake each year.3

Changing climate and nutrient transfers: Evidence from high temporal resolution concentration-flow dynamics in headwater catchments

“…In summer, or in periods of lower flow than during present day conditions, nutrients will become more concentrated; this will be particularly noticeable in catchments such as Pow Beck, which has a high background concentration of TRP, probably due to numerous small point sources, such as septic tanks. The presence of small point sources such as (possibly unregistered) septic tanks in rural catchments, which contribute to P pollution, is well recognised Jordan et al, 2005b;May et al, 2012;Withers et al, 2011;Withers et al, 2013), but is often overlooked in planning diffuse pollution mitigation. Without complex tracing methods, it is impossible to distinguish between the small point sources and the transfers from land.…”

Nutrient fluxes from domestic wastewater: A national-scale historical perspective for the UK 1800–2010

“…Yet, human-induced eutrophication has been reported in Europe and elsewhere since the early 20 th century (de Jonge et al, 2002;Lewitus et al, 2012;May et al, 2012). The lack of historical data makes establishing reference conditions for surface waters, especially in and downstream of well-populated areas, very difficult.…”

Atmospheric Correction Performance of Hyperspectral Airborne Imagery over a Small Eutrophic Lake under Changing Cloud Cover

“…In the 40-year period from 1970 to 2010, the total phosphorus concentration has decreased from 100 mg/m 3 to <40 mg/m 3 , chlorophyll-a concentration decreased from an annual mean of over 100 mg/m 3 to approximately 40 mg/m 3 , and water clarity improved from a Secchi disk depth of approximately 1.0 m to 1.7 m [26,40]. The high phosphorus load of the lake leads regularly to spring and late summer phytoplankton blooms, particularly with frequent sediment resuspension caused by winds, which cause deep mixing in shallow water [26,39,41]. Also, toxin-producing cyanobacteria are an important part of the Loch Leven phytoplankton community, with cyanobacterial blooms common in late summer and early autumn [41].…”

“…The national nature reserve attracts 230,000 visitors per year. Phytoplankton growth in Loch Leven is primarily phosphorus-limited and has a long and well documented history of eutrophication and recovery [39]. In the 40-year period from 1970 to 2010, the total phosphorus concentration has decreased from 100 mg/m 3 to <40 mg/m 3 , chlorophyll-a concentration decreased from an annual mean of over 100 mg/m 3 to approximately 40 mg/m 3 , and water clarity improved from a Secchi disk depth of approximately 1.0 m to 1.7 m [26,40].…”