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Lakes provide essential ecosystem goods and services on which humans depend, and are integral to many global biogeochemical cycles, yet are sensitive to environmental perturbation operating at global, regional and local scales, many resulting from human influence. Such pressures from human activity and long-term background changes can degrade ecological status, a loss that arisen in part due to the underestimation of ecosystem goods and services that are not fully accounted for. The complex web of external pressures and internal interactions that control the biological structure and ecological function of lakes requires a ‘systems approach’, where different trophic levels are studied and different approaches including long-term monitoring are taken (Maberly and Elliott 2012). This complexity can result in dramatic shifts in the functioning and structure of such systems. Long term monitoring is key to understanding and developing insights into how systems react to change in the environment and external stressors.

Figure 3.7 Views over the Windermere lake system and catchment

Copyright photos: CEH

Long term monitoring of Windermere since 1945 has revealed that eutrophication of the lake started before monitoring and was driven by nutrient enrichment from population increases, sewage disposal and agricultural intensification. Since then nutrient enrichment has enhanced the lake response to meteorological change (McGowan et al. 2012). Climate change impacts have been picked up in Blelham Tarn (Foley et al. 2012) showing that over 40 years the duration of stratification had increased by nearly 40 days, as had the hypolimnetic anoxia period. Another study of Daphnia galeata (Thackeray et al. 2012) data collected over 80 years indicated change in nine of ten phonological metrics, primarily driven by phytoplankton phenology and spring water temperature, both linked to climate change.