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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. [ABSTRACT FROM AUTHOR]

Abstract: The accumulation of anthropogenic CO2 in the oceans is altering seawater carbonate chemistry. Investigation and monitoring of the carbonate parameters is therefore necessary to understand potential impacts on ocean ecosystems. Total alkalinity (AT) and dissolved inorganic carbon (CT) were sampled across the Rockall Trough in Feb 2009 (CE0903) and Feb 2010 (CE10002) as part of a baseline study of inorganic carbon chemistry in Irish shelf waters. The results have been compared with data from WOCE surveys A01E (Sept 1991), A01 (Dec 1994), AR24 (Nov 1996) and A24 (June 1997). The 2009 and 2010 datasets provide a snapshot of the biogeochemical parameters which can act as a baseline of inorganic carbon and acidity levels in surface waters of the Rockall Trough in late winter for future comparison since previous surveys in the area have been affected by biological activity. The dataset also offers the possibility to compare decadal changes in subsurface waters. The temporal evolution of anthropogenic carbon (ΔCant) between the 1990s and 2010 was evaluated using two separate methods; (i) a comparison of the concentrations of C T between surveys, after correcting it for remineralisation of organic material and formation and dissolution of calcium carbonate (ΔC T-abio) and (ii) an extended Multiple Linear Regression was used to calculate the ΔCant (). There was an increase in ΔC T-abio and of 18±4μmolkg−1 and 19±4μmolkg−1, respectively, in the subsurface waters between 1991 and 2010, equivalent to a decrease of 0.040±0.003 pH units over the 19 year period. There was an increase in both ΔC T-abio and of 8±4μmolkg−1 in Labrador Sea Water (LSW) in the Trough between 1991 and 2010, and LSW has acidified by 0.029±0.002 pH units over the same time period. A reduction in calcite and aragonite saturation states was observed, which may have implications for calcifying organisms in the region. [Copyright &y& Elsevier]