Changing nutrient levels in Grasmere, English Lake District, during recent centuries

Abstract

1. Historical nutrient changes in Grasmere were investigated using a 300-year record derived from six sediment cores. One core was investigated at high resolution for diatoms, total sedimentary phosphorus, and loss-on-ignition (LOI), and was dated using 210 Pb and 137 Cs. Six other cores were scanned for magnetic susceptibility, diatoms and LOI to confirm the stratigraphic integrity of the primary record. 2. A rise in nutrient levels occurred after 1855 AD. This event was marked by a shift away from benthic diatom assemblages and a rise in Asterionella formosa. The onset of eutrophication from 1855 corresponds to the expansion of the local and tourist population in the area. 3. The replacement of A. formosa with Cyclotella spp. ca 1945-65 indicates reduced nutrient loads, possibly because of enhanced flushing brought about by the seasonal rainfall distribution. 4. After 1965 a step-wise increase in both absolute and relative amounts of Asterionella was found. High sedimentary P and diatom inferred TP confirmed the high nutrient loading of the lake. Nutrient increase is attributable to problems with the Grasmere village sewage system and the installation of a wastewater treatment works (WwTW) on the River Rothay in 1971. Modifications to the WwTW in 1982 caused an initial improvement, but have not led to a full recovery to pre-1965 ecological conditions. 5. The diatom record indicates a further improvement after 1990 by a return toward Achnanthes minutissima. 6. The sedimentary archive of sensitive sites provides important benchmarks against which to judge the attainment of water quality targets.

Modern Pollution Signals in Sediments from Windermere, NW England, Determined by Micro-XRF and Lead Isotope Analysis

“…In 1992, the introduction of a "phosphate stripping" treatment at Tower Wood and Ambleside STW led to a reduction in phosphate loading, particularly in the South Basin (Talling, 1999;Parker and Maberley, 2000). Similar findings were observed further north at Grasmere, where the onset of eutrophication is dated to 1855, analogous with the expansion of human settlement (Barker et al, 2005;Sabater and Haworth, 1995).…”

“…A number of studies have dated recent sediments in Windermere and other lakes in the catchment (Aston et al, 1973;Pennington et al, 1973;Pennington et al, 1976;Appleby et al, 1991;Appleby et al, 2003;Barker et al, 2005). In the North Basin, 210 Pb dates from a 1997 mini-core (located c. 600 m SW of core +54-03/68 PC)…”

Recent histories of six productive lakes in the Irish Ecoregion based on multiproxy palaeolimnological evidence

“…Second, how have the trajectories of changes in trophic status of such lakes varied over the last c. 100-200 years? Eutrophication is most commonly associated with increased availability of phosphorus (P) (Ule´n & Kalisky, 2005;Smith et al, 2005) or nitrogen (Bergstrom et al, 2005) and is considered the principal pressure on lake water quality in the Irish Ecoregion (EHS, 2000;Jennings et al, 2003). Increased loadings of P to lakes (e.g., Battarbee, 1978;Anderson, 1990Anderson, , 1997Anderson & Rippey, 1994;Gibson et al, 1995;Bowman & Clabby, 1998;Linnane & Murray, 2002;Foy et al, 2003;Jordan & Rippey, 2003;Barker et al, 2005;Davies et al, 2005;Miettinen et al, 2005;Reid, 2005;Reavie et al, 2006;Leira et al, in press) are commonly attributed to discharges of municipal and industrial waste (Smith et al, 1999) and agricultural intensification, with diffuse agricultural sources often considered the main contributor (Lucey et al, 1999;EHS, 2000;Jennings et al, 2003;Smith et al, 2005). Eighteen percent of a total of 492 lakes in the Republic of Ireland surveyed during the period 2001-2003 were assigned a eutrophic or hypertrophic status (Toner et al, 2005), while more than 50% of c. 600 lakes in Northern Ireland surveyed in the 1980s and 1990s were classed as eutrophic (HMSO, 1990;Gibson et al, 1995).…”

Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

“…In general, the deepest area of a lake receives most sediment mass through the process of sediment focusing and often sediment accumulation rates tend to be higher than found in littoral regions (Hå kanson and Jansson, 1983;Cohen, 2003;Smol, 2008). Despite differences in sediment accumulation rates across cores, even in small lakes, it is usually possible to match profiles for various sediment signatures (e.g., LOI, diatom community shifts) so that chronologies can be transferred between cores (Anderson et al, 1994;Barker et al, 2005). Indeed, in Esthwaite Water, existing palaeolimnological data from several cores (ESTH1-ESTH8) taken over the last 15 years exhibit close matches in LOI and diatom stratigraphies (Bennion, unpublished data).…”