Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 10

Report on DOC quantity and quality data collected for Euro-limpacs at a previously established EU-VULCAN climate manipulation experiment

This report provides an interim summary of results from a plot−scale manipulation experiment, which is being used to assess the potential impact of climate change on the release of dissolved organic carbon (DOC) from soils to surface waters. Surface water DOC concentrations have undergone dramatic increases since the 1980s, most clearly in the 22 lakes and streams of the UK Acid Waters Monitoring Network but also in other UK upland waters and other areas of Europe and North America. The potential implications of rising DOC are wide−ranging, from local ecosystem impacts on freshwater acidity, light regime and energy supply, through increased water treatment costs and health risks, to issues relating to increased fluxes of carbon and heavy metals from terrestrial stores into more reactive, mobile aquatic reservoirs. At present, there is no consensus on the likely drivers of rising DOC concentrations, but a number of processes linked to climate change have been suggested including rising temperatures, increased soil aeration, changes in water flowpath due to increased rainfall and increases in primary production linked to rising atmospheric CO2 levels. Other proposed drivers are linked to atmospheric deposition, notably to the major reduction in atmospheric S deposition that has occurred since the 1980s, and the recovery from acidification that this has led to in soils and waters. These and other possible drivers of rising DOC have been considered in detail in a recent review supported by Euro−limpacs. It is clearly essential that the main drivers of rising DOC be identified, before their wider significance, and future trajectory, can be established. The experimental work described in this report is intended to assess the validity and significance of two key proposed climatic influences on DOC, rising temperature and increased drought frequency.

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