Tracking changes in the organic matter in a lake palaeoecosystem: A spectrophotometric approach

The applicability of fluorescence spectrophotometry and absorption spectrophotometry of sediment organic matter dissolved in pore water (pDOM) for detecting changes in homogeneous limnic deposits was examined. Testing was performed on sediment cores collected from a shallow hypertrophic lake, Lake Harku, Estonia, in which prolific algal blooms have occurred for the last 60 years. Although the age-resolved profiles of fluorescence and absorbance characteristics of pDOM exhibit minor temporal changes over the last 100 years, the scatter plots of different pairs of the pDOM optical characteristics reveal several decisive periods that temporally accord well with the stratigraphic changes in sub-fossil diatoms and green algae, as well as geochemical proxies.