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

May, Linda; Defew, L. H.; Bennion, H; Kirika, A.

doi:10.1007/s10750-011-0922-y

Cited by 48 publications

(21 citation statements)

References 49 publications

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“…These results suggest that diffuse losses from both land use and livestock, particularly cattle, were the dominant contributor to the overall P load in the last two decades. Similar relative changes in loading, with similar time lines, have been reported from other catchments in Ireland (Foy and Lennox 2006) and Europe (Jeppesen et al 2005;May et al 2012). These coincidental patterns most likely reflect regional scale drivers of policy and management, particularly a reduction in P loads from WWTPs due to implementation of EU directives on wastewater treatment, together with intensification of agriculture due to implementation of the EU Common Agriculture Policy in the 1980s and 1990s.…”

supporting

confidence: 75%

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Drivers of long-term trends and seasonal changes in total phosphorus loads to a mesotrophic lake in the west of Ireland

Jennings

Allott

Lenihan³

et al. 2013

Mar. Freshwater Res.

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Abstract. Excess phosphorus (P) loading is a major cause of deterioration in surface water quality. In Ireland, regulation has focussed on control of P losses from agriculture and wastewater treatment plants (WWTPs): the two main sources of excess P. Hindcast modelling for Lough Leane, south-west Ireland, indicated that, while the only municipal (point) source contributed up to 41% of the annual TP loading until the mid 1980s, over 90% of the TP load was from diffuse sources following upgrading of the WWTP. Field data from [2000][2001][2002][2003][2004][2005][2006] confirmed that most of the TP load came from agriculture, with 73% being exported between September and February, generally the wettest months in the region. However, the WWTP contributed up to 60% of daily loads during summer. Short lake residence times (two to four months) between October and February indicated that external loadings during these months were unlikely to make a significant contribution to summer phytoplankton growth in the lake. In contrast, the potential effects of point sources during low flows were maximised by longer residence times between April and September. The results highlight the importance to aquatic pollution impacts of, and therefore the need for regulatory responses to respect, seasonal variations in loading and residence time.

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confidence: 75%

“…Jeppesen et al 2005) and on palaeolimnological studies (e.g. May et al 2012). However, while the loading from point sources has decreased in many catchments owing to tighter controls on effluent P levels, lake trophic status has not always shown a concurrent improvement, often attributed to loading from diffuse sources.…”

mentioning

confidence: 99%

Drivers of long-term trends and seasonal changes in total phosphorus loads to a mesotrophic lake in the west of Ireland

Jennings

Allott

Lenihan³

et al. 2013

Mar. Freshwater Res.

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“…Long term datasets for the loch show that P concentrations have declined markedly but the trend was non-linear with a slight increase in the early 1990s caused by P recycling from the sediments . Additionally agriculture in the Leven catchment remains a significant diffuse source of nutrients to the loch as much of the land is used for arable farming, and rural septic tanks also contribute to the P load (May et al, 2012). The sediment record suggests that those diatom taxa lost during enrichment have not yet returned, most likely because nutrient concentrations remain too high .…”

Section: Cyclotella Radiosa Cyclostephanos Dubiusmentioning

confidence: 99%

Assessing degradation and recovery pathways in lakes impacted by eutrophication using the sediment record

2015

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Efforts to restore enriched lakes have increased yet there remains uncertainty about whether restoration targets can be achieved and over what timescale. Paleoecological techniques, principally diatom analyses, were used to examine the degree of impact and recovery in 12 European lakes subject to eutrophication and subsequent reduction in nutrient loading. Dissimilarity scores showed that all sites experienced progressive deviation from the reference sample (core bottom) prior to nutrient reduction, and principal curves indicated gradual compositional change with enrichment. When additive models were applied to the latter, the changes were statistically significant in 9 of the 12 sites. Shifts in diatom composition following reduction in nutrient loading were more equivocal, with a reversal toward the reference flora seen only in four of the deep lakes and one of the shallow lakes. Of these, only two were significant (Lake Bled and Mjøsa). Alternative nutrient sources seem to explain the lack of apparent recovery in the other deep lakes. In three shallow lakes diatom assemblages were replaced by a community associated with lower productivity but not the one seen prior to enrichment. Internal loading and top down control may influence recovery in shallow lakes and climate change may have confounded recovery in several of the study sites. Hence, ecosystem recovery is not simply a reversal of the degradation pathway and may take several decades to complete or, for some lakes, may not take place at all. By assessing ecological change over a decadal to centennial timescale, the study highlights the important role that paleolimnology can play in establishing a benchmark against which managers can evaluate the degree to which their restoration efforts are successful.

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“…3) is a large (13.3 km 2 surface area) shallow (mean depth 3.9 m) eutrophic loch in east central Scotland (latitude 56 o 10 0 N, longitude 3 o 30 0 W). The loch has a long and well documented history of eutrophication problems, with catchment management during 1970s-1990s resulting in a significant reduction in external P loading (Bailey-Watts & Kirika, 1999;D'Arcy et al, 2006;May et al, 2011). The period of high external loading was characterised by high baseline TP concentrations apparently masking any seasonal TP trends (Fig.…”

Section: Study Sitementioning

confidence: 99%

“…In an attempt to improve water quality, external P inputs to the loch were reduced by more than 60% between the 1970s and 1990s (BaileyWatts & Kirika, 1999;May et al, 2011). The lake responded slowly and significant improvements in water quality as a result of this management activity have been observed only recently (D'Arcy et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Long-term variation and regulation of internal phosphorus loading in Loch Leven

et al. 2011

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Long-term monitoring data (1968Long-term monitoring data ( -2008 were used to investigate internal phosphorus (P) loading following external P loading reduction in shallow Loch Leven, Scotland. A whole-lake sediment P inventory (upper 3 cm of sediment; 2005) suggested a release-potential of 29.7 tonnes (t) from the release sensitive sediment P pools. 18.5 t was contained within shallow water sediments (\4.5 m water depth) with 7.6 t in deeper water sediments below the photic zone ([5 m water depth). The ''observed'' release (\5.1 t), estimated using a water column P mass balance approach (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008), was\5.1 t, indicating the presence of regulating mechanisms. Observed P release declined between 1989 and 2008, with the exception of 2003-2006. Observed P release estimates were positively correlated with annual average water column P concentration after 1989, highlighting the role of internal loading in maintaining poor water quality conditions after management intervention. Multiple regression analysis suggested that internal loading was driven by the wave mixed depth in spring (positive driver), summer water temperature (positive driver) and spring water clarity transparency (negative driver). The potential importance of biological and physico-chemical feedback mechanisms in the regulation of benthic-pelagic coupling and water quality in Loch Leven are discussed.

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

Cited by 48 publications

References 49 publications

Drivers of long-term trends and seasonal changes in total phosphorus loads to a mesotrophic lake in the west of Ireland

Drivers of long-term trends and seasonal changes in total phosphorus loads to a mesotrophic lake in the west of Ireland

Assessing degradation and recovery pathways in lakes impacted by eutrophication using the sediment record

Long-term variation and regulation of internal phosphorus loading in Loch Leven

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