Cycling of calcite in hard water lakes of different trophic states

Abstract

Based on oxygen (O 2 ), pH, calcium (Ca 2+ ), and carbonate (CO 22 3 ) sediment pore-water concentration profiles, we compare the benthic dissolution of autochthonous calcite in oligotrophic Lake Lucerne and eutrophic Lake Sempach. Despite their difference in trophic state, the two lakes have similar benthic O 2 regimes because L. Sempach is artificially oxygenated. This peculiarity enabled the study of the direct effect of trophic state on benthic calcite dissolution. Although areal benthic O 2 fluxes did not differ, O 2 penetrated deeper into the sediment of the oligotrophic L. Lucerne, where most organic matter (OM, 96%) was degraded aerobically, whereas in L. Sempach, aerobic and anaerobic decomposition contributed about equal amounts to the biogenic carbon dioxide production. Release rates of bicarbonate from L. Sempach sediments exceeded those of L. Lucerne nearly twofold. The HCO 2 3 : Ca 2+ ratio of benthic fluxes was 3.7 in L. Lucerne compared to 10.3 in L. Sempach, suggesting that in L. Sempach most of the released HCO 2 3 did not originate from calcite dissolution. Furthermore, benthic calcite dissolution in L. Lucerne exceeded that in L. Sempach by two-fold, despite lower pH values in the pore water of L. Sempach. Differences in benthic microbial decomposition of OM and redissolution of calcite crystals are explained by the longer residence time of OM and calcite in the oxic sediment layer of the oligotrophic lake and the larger weight-specific surface area of its smaller autochthonous calcite crystals. We suggest that trophic state and O 2 supply to the sediment are key parameters controlling the cycling of calcite and organic carbon in lakes.

A key continental archive for the last 2 Ma of climatic history of the central Mediterranean region: A pilot drilling in the Fucino Basin, central Italy

“…Gierlowsky-Kordesh, 2010;Vogel et al, 2010), and the preservation of calcite as a function of organic matter (OM) decomposition and bacterial CO 2 release in the bottom waters (e.g. Müller et al, 2006). Also, TOC is mainly a function of changes in organic production in the lake and of changes in catchment vegetation (Leng et al, 2013), and, along with TIC, it tends to be higher during warmer and wetter periods (i.e.…”

Regulation of spatial and temporal variability of carbon flux in six hard‐water lakes of the northern Great Plains

“…For example, freshwater lakes with pH .8 have low concentrations of dissolved CO 2 relative to HCO { 3 and CO 2{ 3 and are often sites of in-gassing of atmospheric carbon (Schindler et al 1997;Bade and Cole 2006). Reactions can be more complex in lakes with elevated concentrations of DIC or intense primary production, since thermal or biotic initiation of CaCO 3 precipitation (Brunskill 1969;Mü ller et al 2006) can result in net increases in dissolved CO 2 concentrations while reducing total DIC content (McConnaughey et al 1994). Similarly, because climatic variability can alter influx of DIC and DOC from catchments (Kelly et al 2001;Rantakari and Kortelainen 2005), and because the magnitude and character of these inputs will also depend on local vegetation, soils, and geology (Dean 1999), it has proven difficult to evaluate the hierarchical relationships among potential mechanisms (metabolism, chemistry, climate) as controls of CO 2 fluxes.…”

Précipitation de carbonates de cations divalents dans les systèmes lacustres : intérêt, état des connaissances des mécanismes et suggestions (Revue critique de la littérature)

“…La production biogénique de HCO 3 − en milieu anoxique s'explique mieux si on le considère comme étant un produit d'oxydation anaérobie de la matière organique constituée de carbone d'azote et de phosphore (MÜLLER et al, 2006) : …”

“…Des essais menés à 25 °C à partir d'échantillons d'eau synthétisée selon la méthode décrite plus avant et sans précaution aucune (milieu aéré ou désaéré) ont conduit à la précipitation de CaCO 3 d'après les analyses chimiques. Ces expériences aux résultats prévisibles (non présentés ici) n'ont rien d'attrayant en elles-mêmes, cependant permettent tout au moins de comprendre que seuls les lacs durs alcalins (pH supérieur à 8) précipitent le carbonate de calcium dans la colonne d'eau lorsque les conditions qui favorisent leur saturation en ce carbonate sont réunies (DEAN et SCHWALB, 2002;MÜLLER et al, 2006). (DEAN, 1999;QUERALT et al, 1997 , la structure cristalline identique de leur carbonate (rhomboédrique), leurs charges et leurs électronégativités similaires sont autant de facteurs favorables à la formation de solution solide Ca 1-x Mg x CO 3 tant décrites dans la littérature (DEAN, 2009;LAST et De DECKKER, 1990;MORSE et al, 2007;MÜLLER et al,1972;QUERALT et al,1997).…”

“…La dissolution de la calcite dans la colonne d'eau ou dans les sédiments dépend de la production de protons que génère la décomposition aérobie de la matière organique (MÜLLER et al, 2006). L'équilibre (22) Alors que la production de la matière organique (eutrophisation par exemple) élève le pH de l'eau et provoque la précipitation du carbonate de calcium, la décomposition de la matière organique augmente l'acidité de l'hypolimnion propice à la dissolution de ce carbonate (DEAN, 1999).…”