Sediment pore-water proteinaceous matter - a proxy of lake palaeoproductivity?

摘要

Fluorescence spectroscopy of pore-water humic substances (HSs) has been proven to be a fast and powerful tool for high-resolution reconstruction of lake trophic history (WOLFE et al. 2002, HEINSALU et al. 2007). In addition to HSs, proteinaceous substances (proteins and amino acids, PSs) absorb and fluo-resce light in the UV-part of the spectrum. Spectrally these substances are clearly discernible: HSs emit light in the spec-tral range 380-480 nm, PSs in the band 300-350 nm. Both carry information about biological material; however, HSs can be considered an indirect indicator of bioproductivity because they are produced from organic matter after biological and chemical transformations, while PSs originate directly from living organisms. They are very sensitive to bacterial degrada-tion, however, and therefore the proteinaceous trace in sedi-ments can be expected to be inflected or lost.We investigated down-core distribution (temporally cover-ing the 20th century) of protein-like fluorescence (PF) in sedi-ment pore water in 4 Estonian lakes with different limnological characteristics. Changes in the distribution of PF were com-pared with the eutrophication history of the lakes and with changes in the sediment composition and the stratigraphy of diatom assemblages. We evaluated the applicability of pore-water PF as a proxy for assessing lake palaeoproductivity.