Fluorescence measured using the WETStar DOM fluorometer as a proxy for dissolved matter absorption

Dissolved organic matter (DOM) plays a significant role in freshwater and marine aquatic ecosystems including its effects on nutrients and carbon cycling and trace metal and contaminant availability. The colored fraction of DOM, CDOM, directly affects the quantity and spectral quality of available light, thereby impacting both primary production and UV exposure in aquatic ecosystems. Measuring the DOM absorption coefficient in situ is difficult because it requires prefiltration of the sample. From measurements made in inland, riverine, estuarine and coastal environments, we show that using the WETStar fluorometer (WET Labs), good estimates of dissolved absorption can be obtained from DOM fluorescence (DOM-FL) measured in situ on unfiltered samples. DOM-FL measured with the in situ fluorometer compare very well to values obtained on filtered samples using more sophisticated laboratory spectrofluorometers. Acquisition of high frequency, long-term data series or high-resolution profiles is feasible and artifacts resulting from filtration or sample storage can be avoided when measurements are made using the WETStar DOM fluorometer. The utility of high-resolution DOM-FL profiles for biogeochemical studies is illustrated by in situ data obtained in the East Siberian Sea.