Abstract. Water quality monitoring programs are often based upon low-frequency regular sampling regimes from which loads are estimated. In this study, stream flow (Q) and phosphorus concentrations (C) were measured at 2-hourly intervals over a 10-week period between October and December 2006 in a tributary of Loch Leven, Scotland. The dataset was deconstructed to emulate different weekly, daily and composite sampling strategies, the aim being to highlight the large amount of uncertainty and imprecision in estimating total (TP) and soluble reactive (SRP) phosphorus loads on the basis of commonly applied sampling strategies and calculation methods. When based on the full dataset, phosphorus (P) loads estimated from the 2-hourly data were 459 kg TP, 351 kg particulate P (PP) and 78 kg SRP. In contrast, P loads estimated from different weekly, daily and composite sampling regimes and determined by applying seven different calculation methods ranged from 22 to 5028 kg TP, 13 to 4588 kg PP and 7 to 286 kg SRP. The results of this study highlight the large amount of uncertainty and imprecision associated with estimating P loads and contributes to the body of evidence that high-frequency monitoring is necessary if P loads to standing water bodies are to be quantified accurately and the effects of nutrient management programs interpreted correctly.

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

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

Article (refereed) -postprint Elliott, J.A.; Defew, L.. 2012 Modelling the response of phytoplankton in a shallow lake (Loch Leven, UK) to changes in lake retention time and water temperature. Hydrobiologia, 681 (1). 105-116. 10.1007/s10750-011-0930-y Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner.1 TitleModelling the response of phytoplankton in a shallow lake (Loch Leven, UK) to changes in lake retention time and water temperature. Keywords:Phytoplankton, retention time, climate change, cyanobacteria, PROTECH This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Hydrobiologia. 2 AbstractThe phytoplankton community of Loch Leven in 2005 was modelled and subjected to a combination of different flushing rates and water temperatures in order to assess the lake's sensitivity to these two climatic drivers. Whilst the simulated annual mean total chlorophyll a proved relatively insensitive to these changes, at the species level marked changes were recorded. Some species responded positively to increased temperature (e.g. Aulacoseira), some negatively (e.g. Asterionella), whilst others were negatively affected by increased flow (e.g. Aphanocapsa) and others enhanced (e.g.Stephanodiscus). However, this relationship with flow was season dependent with, for example, a simulated increase in summer inflows actually benefiting some species through increased nutrient supply, whereas an equivalent increase in flow in wetter seasons would have negatively affected those species (i.e. through flushing loss).Overall, the simulations showed that the range of species types simulated in the community was sufficient for one species to always benefit from the changing niches created by the multiple climatic drivers applied in this study. The level of exploitation by such a species was only constrained by the nutrient carrying capacity of the system, which led to the overall dampened response in the total chlorophyll a measure, both at the annual and season scale. Thus, whilst overall biomass showed relatively little reaction to the two climatic drivers tested, the phytoplankton community composition responded markedly.

Article (refereed) -postprint Elliott, J.A.; Defew, L.. 2012 Modelling the response of phytoplankton in a shallow lake (Loch Leven, UK) to changes in lake retention time and water temperature. Hydrobiologia, 681 (1). 105-116. 10.1007/s10750-011-0930-y Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner.1 TitleModelling the response of phytoplankton in a shallow lake (Loch Leven, UK) to changes in lake retention time and water temperature. Keywords:Phytoplankton, retention time, climate change, cyanobacteria, PROTECH This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to Hydrobiologia. 2 AbstractThe phytoplankton community of Loch Leven in 2005 was modelled and subjected to a combination of different flushing rates and water temperatures in order to assess the lake's sensitivity to these two climatic drivers. Whilst the simulated annual mean total chlorophyll a proved relatively insensitive to these changes, at the species level marked changes were recorded. Some species responded positively to increased temperature (e.g. Aulacoseira), some negatively (e.g. Asterionella), whilst others were negatively affected by increased flow (e.g. Aphanocapsa) and others enhanced (e.g.Stephanodiscus). However, this relationship with flow was season dependent with, for example, a simulated increase in summer inflows actually benefiting some species through increased nutrient supply, whereas an equivalent increase in flow in wetter seasons would have negatively affected those species (i.e. through flushing loss).Overall, the simulations showed that the range of species types simulated in the community was sufficient for one species to always benefit from the changing niches created by the multiple climatic drivers applied in this study. The level of exploitation by such a species was only constrained by the nutrient carrying capacity of the system, which led to the overall dampened response in the total chlorophyll a measure, both at the annual and season scale. Thus, whilst overall biomass showed relatively little reaction to the two climatic drivers tested, the phytoplankton community composition responded markedly.