engleski

Dissolved organic matter in Croatian lakes – the influence of catchment, season and microbes

Dissolved organic matter (DOM) represents one of the largest actively cycled carbon pools on earth. Water is the driving force moving dissolved organic matter through earth reservoirs and across the continuum of the atmosphere, soils, inland waters and oceans. To a significant extent, the DOM in freshwater systems is derived from terrestrial vegetation and soils with varying contributions of autochthonous production. In order to study the interplay of allochthonous versus autochthonous factors driving lake DOM molecular composition, we sampled six lakes of different trophic status across Croatia over the productive season from April to September 2017. We determined pro- and eukaryotic community compositions based on 16S and 18S rRNA genes, respectively, and molecular DOM composition via ultrahigh resolution mass spectrometry. We found that the abundance and average molecular weight of detected molecular formulas decreased with bulk DOC concentration. The influence of terrigenous input declined as lakes became more eutrophic in favor of higher potential lability of the DOM. Lake Vrana on Cres island was an exception regarding most analyzed DOM properties showing exceptionally low terrigenous influence, likely as it represents an isolated cryptodepression without river in- or outflows. Overall, catchment characteristics were the major factor influencing DOM molecular composition. Inter-lake dissimilarity was driven by trophic status while in-lake dissimilarity was not. Seasonal changes were generally small and preliminary results show no significant correlation between the composition and diversity of the eukaryotic community and the DOM molecular composition across lakes.

Bacteria ; Eukaryotes ; DOM ; NGS ; Lakes

nije evidentirano