Do organic matter metrics included in lake surveillance monitoring in Europe provide a broad picture of brownification and enrichment with oxygen consuming substances?

Margot Sepp; Toomas Kõiv; Peeter Nõges; Tiina Nõges

doi:10.1016/j.scitotenv.2017.08.179

Do organic matter metrics included in lake surveillance monitoring in Europe provide a broad picture of brownification and enrichment with oxygen consuming substances?

Sci Total Environ. 2018 Jan 1:610-611:1288-1297. doi: 10.1016/j.scitotenv.2017.08.179. Epub 2017 Aug 30.

Authors

Margot Sepp¹, Toomas Kõiv², Peeter Nõges², Tiina Nõges²

Affiliations

¹ Centre for Limnology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia. Electronic address: margot.sepp@emu.ee.
² Centre for Limnology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia.

PMID: 28851149
DOI: 10.1016/j.scitotenv.2017.08.179

Abstract

Organic matter (OM) has numerous geochemical and ecological functions in inland waters and can affect water quality. Different parameters of aquatic OM are measured with various methods as no single analytical tool can provide definitive structural or functional information about it. In the present paper we review different OM metrics used in the European Union (EU) lake surveillance monitoring programmes and assess their suitability to provide sufficient data about the brownification and enrichment with oxygen consuming substances in European lakes. In the EU Water Framework Directive (WFD), metrics of OM are not mandatory physico-chemical parameters, but only recommended parameters to characterize water transparency, oxygenation conditions or acidification status. Our analysis shows that, as lake OM is monitored under the WFD in only 14 countries, no Europe-wide conclusions on the situation regarding brownification and organic enrichment can be drawn based on these data. Applied parameters in lake surveillance monitoring programmes are biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), dissolved organic carbon (DOC), water colour (WCol), and yellow substance. Different national OM metrics used avoid getting a broad picture of lake OM concentration changes in Europe over the last decades. Furthermore, our results demonstrate that the possibilities to convert different OM parameters to each other are limited because empirical relationships between them are region-specific. OM sensors for continuous measurements and remote sensing surveys could improve the effectiveness of lake OM monitoring, especially its temporal and spatial representativeness. It would be highly suggested to include in lake monitoring programmes also methods (e.g. absorbance or fluorescence spectroscopy) allowing to characterize the composition of OM as it influences strongly the biogeochemical role of OM in lakes.

Keywords: Aquatic organic matter; Dissolved organic carbon (DOC); Lake monitoring; Total organic carbon (TOC); Water Framework Directive (WFD).