A survey of the lakes of the English Lake District: the Lakes Tour 2010

Maberly, S.C.; De Ville, M.M.; Thackeray, S.J. ORCID: https://orcid.org/0000-0003-3274-2706; Feuchtmayr, H.; Fletcher, J.M.; James, J.B.; Kelly, J.L.; Vincent, C.D.; Winfield, I.J.; Newton, A.; Atkinson, D.; Croft, A.; Drew, H.; Saag, M.; Taylor, S.; Titterington, H.. 2011 A survey of the lakes of the English Lake District: the Lakes Tour 2010. NERC/Centre for Ecology & Hydrology, 148pp. (CEH Project Number: C04357, LA/NEC04357/1) (Unpublished)

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Abstract/Summary

1. This report presents information resulting from a survey of the limnology of the 20 major lakes and tarns in the English Lake District based on samples taken in January, April, July and October 2010. This ‘Lakes Tour’ supplements similar tours in 1984, 1991, 1995, 2000 and 2005. 2. On each sampling occasion depth-profiles were collected of water temperature and oxygen concentration and Secchi depth was measured. An integrated water sample was analysed for pH and alkalinity, major cations and anions, plant nutrients, phytoplankton chlorophyll a and species composition and zooplankton abundance and species composition. Some of the field work and chemical analyses were carried out collaboratively between staff from CEH and the Environment Agency. 3. The lakes had a range in tendency to stratify in summer with the weakest stratification in large, relatively shallow and exposed lakes such as Bassenthwaite Lake. During summer stratification oxygen-depletion at depth was only found in the more productive lakes. 4. Water clarity, assessed by Secchi disc, varied between about 13 m in clear unproductive lakes such as Wastwater to less than 2 m in the more productive lakes during summer such as Esthwaite Water. 5. Major ion composition varied with geology and altitude. Lakes on the Silurian slates (those in the Windermere and Coniston Water catchments) tended to have anions dominated by alkalinity (bicarbonate) and cations dominated by calcium whereas the other lakes tended to have anions dominated by chloride and cations dominated by sodium. 6. Availability of phosphorus is the main factor that affects lake productivity. Concentrations were lowest in Wastwater and Ennerdale Water and highest in Elterwater and Esthwaite Water. Nitrate was the dominant form of nitrogen. Nitrate concentrations tended to be lowest in July because of biological uptake and seasonal fluctuations were most marked in the productive lakes. Silica, an essential nutrient for diatoms, showed a similar seasonal pattern to nitrate but the depletion was more marked in April because the spring bloom is typically dominated by diatoms. In unproductive lakes such as Wastwater and Ennerdale Water concentrations of silica did not vary seasonally. 7. The concentration of chlorophyll a was used as a measure of phytoplankton abundance. Comparisons across lakes showed low concentrations all the year in the unproductive lakes and seasonally high concentrations in the more productive lakes. Loughrigg Tarn had the highest annual average concentration of chlorophyll a. 8. The species composition varied seasonally in all the lakes, even unproductive ones with limited seasonal changes in nutrient concentrations, underlying the sensitivity of phytoplankton to environmental conditions. Overall, diatoms dominated in January and particularly, April, but in .July and October a range of different groups dominated depending on the lake. 9. Zooplankton abundance was very variable and greatest in the productive lakes and seasonally, abundance tended to be greatest in July and October. Seventeen genera of zooplankton were recorded in total. The unproductive lakes tended to be dominated by Eudiaptomus gracilis and this species dominated most of the lakes in January. Daphnia spp. were often important in the summer in the more productive lakes. Another cladoceran, Bosmina spp. was in appreciable numbers in January in some lakes. Ceriodaphnia and Mesocyclops were an important part of the zooplankton community in some lakes. 10. The known status of fish populations, although not undertaken in the project, was summarised. Eighteen species have been recorded in these lakes, but of these six are probably introduced. Some lakes have very little fish-data and require more research. 11. Heavy metals were measured for the first time. Although many samples were below the limit of detection, copper concentrations were elevated in Coniston Water and Haweswater, lead was elevated in Haweswater and zinc was elevated in Bassenthwaite Lake, Brothers Water, Buttermere and Haweswater. 12. Micro-organic pollutants were measured for the first time and most samples were below current detection limits. Of the 128 compounds analysed, 16 gave values above the detection limit but only five exceeded the limit more than once. Of these, Diazinon, an organophosphorus insecticide, had concentrations that exceeded Environmental Quality Standards in Buttermere and was high in a number of other lakes; this merits further investigation. 13. The current state of each lake was summarised in terms of key limnological variables, trophic state and ecological status under the current definitions of the Water Framework Directive. 14. Only Buttermere and Wastwater were at High ecological status for both total phosphorus and chlorophyll a. Brothers Water, Coniston Water, Crummock Water, Derwent Water, Ennerdale Water and Haweswater were at Good ecological status. Bassenthwaite Lake, Blelham Tarn, Elterwater, Esthwaite Water, Grasmere, Loweswater, Rydal Water, Thirlmere, Ullswater and the North and South Basins of Windermere were at Moderate ecological status, although Ullswater was close to Good status. Loughrigg Tarn was at Poor status because of high phytoplankton chlorophyll a. Lakes at Moderate or Poor ecological status will require further work to bring them to Good ecological status by 2015 under the Water Framework Directive (WFD), although Rydal Water and Loughrigg Tarn are not on the UK –list of WFD lakes. 15. Long-term change from 1984 to 2010 (1991 to 2010 for some variables) were analysed. There have been changes in the concentration of major ions in many sites. This has largely been caused by reduction in sulphate deposition from acid rain, causing widespread increases in alkalinity and pH and reductions in concentration of calcium, magnesium, sodium and potassium because of reduced cation-exchange in the soil. Reducing concentrations of sodium and chloride are probably related to reductions in stormy weather since the mid 1990s and hence reduced input of sea-salt in rain. On average, in comparison to the 2005 Lakes Tour, there has been a reduction in concentration of TP and phytoplankton chlorophyll a and an increase in Secchi depth. While the magnitude of change is small, it is, encouragingly in the right direction. 16. The lakes in the English Lake District are extremely valuable scientifically as they are highly diverse. This was illustrated by showing the link between catchment altitude (as a proxy for land use and soil type) and a range of water chemistry variables and the relationship between phytoplankton chlorophyll a and total phosphorus which shows that the productivity of these lakes is controlled by phosphorus. The magnitude of the seasonal changes in silica and nitrate is positively linked to lake productivity. Secchi depth is negatively correlated with phytoplankton, but in January Secchi depth is less for a given chlorophyll a concentration, probably because of attenuation by dissolved organic carbon and particulate material brought in to the lakes by winter rains. Minimum oxygen concentration at depth is also negatively related to phytoplankton chlorophyll a. 17. It is suggested that more work is needed at lakes which have failed Good ecological status, and at Ennerdale Water in particular where there has been a dramtic decrease in Secchi depth that appears to be linked to increased productivity. The fish populations in many lakes need to be studied in more detail. 18. The joint-manning of the Lakes Tour by CEH and the EA worked well and could be a model for other work in the future.

Item Type:	Publication - Report
Programmes:	CEH Topics & Objectives 2009 - 2012 > Water > WA Topic 2 - Ecohydrological Processes > WA - 2.3 - Assess the responses of river, lake and wetland ecosystems to ecohydrological drivers
UKCEH and CEH Sections/Science Areas:	Parr
Additional Pages:	86
Funders/Sponsors:	Environment Agency, Lake District National Park Authority
NORA Subject Terms:	Ecology and Environment
Date made live:	28 Jun 2011 14:05 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/14563

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