| Title | Manganese-mediated hydrochemistry and microbiology in a meromictic subalpine lake (Lake Idro, Northern Italy) - A biogeochemical approach |
| Abstract | This study presents the findings from several field campaigns carried out in Lake Idro (Northern Italy), a deep (124 m) meromictic-subalpine lake, whose water column is subdivided in a mixolimnion (~0-40 m) and a monimolimnion (~40-124 m). Hydrochemical data highlight two main peculiarities characterizing the Lake Idro meromixis: a) presence of a high manganese/iron ratio (up to 20 mol/mol), b) absence of a clear chemocline between the two main layers. The high manganese content contributed to the formation of a stable manganese dominated deep turbid stratum (40-65 m), enveloping the redoxcline (~45-55 m) in the upper monimolimnion. The presence of this turbid stratum in Lake Idro is described for the first time in this study. The paper examines the distribution of dissolved and particulate forms of transition metals (Mn and Fe), alkaline earth metals (Ca and Mg), and other macro-constituents or nutrients (S, P, NO3-N, NH4-N), discussing their behavior over the redoxcline, where the main transition processes occur. Field measurements and theoretical considerations suggest that the deep turbid stratum is formed by a complex mixture of manganese and iron compounds with a prevalence of Mn(II)/Mn(III) in different forms including dissolved, colloidal, and fine particles, that give to the turbid stratum a white-pink opalescent coloration. The bacteria populations show a clear stratification with the upper aerobic layer dominated by the heterotrophic Flavobacterium sp., the turbid stratum hosting a specific microbiological pool, dominated by Caldimonas sp., and the deeper anaerobic layer dominated by the sulfur-oxidizing and denitrifier Sulfuricurvum sp. The occurrence in August 2010 of an anomalous lake surface coloration lasting about four weeks and developing from milky white-green to red-brown suggests that the upper zone of the turbid stratum could be eroded during intense weather-hydrological conditions with the final red-brown coloration resulting from the oxidation of Mn(II)/Mn(III) to Mn(IV) compounds. |
| Source | Science of the total environment 795–148743 |
| Keywords | RedoxclineMicrobial activityChemoclineManganese/iron cycleMeromictic lakesTurbid stratum |
| Journal | Science of the total environment |
| Editor | Elsevier, Lausanne ;, Paesi Bassi |
| Year | 2021 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.scitotenv.2021.148743 |
| Authors | Tartari, Gianni and Copetti, Diego and Franzetti, Andrea and Balordi, Marcella and Salerno, Franco and Thakuri, Sudeep and Leoni, Barbara and Chiarello, Gianluca and Cristiani, Pierangela |
| Text | 455449 2021 10.1016/j.scitotenv.2021.148743 Redoxcline Microbial activity Chemocline Manganese/iron cycle Meromictic lakes Turbid stratum Manganese mediated hydrochemistry and microbiology in a meromictic subalpine lake Lake Idro, Northern Italy A biogeochemical approach Tartari, Gianni and Copetti, Diego and Franzetti, Andrea and Balordi, Marcella and Salerno, Franco and Thakuri, Sudeep and Leoni, Barbara and Chiarello, Gianluca and Cristiani, Pierangela Tartari Gianni IRSA CNR; Copetti Diego IRSA CNR; Franzetti Andrea Uni Bicocca; Balordi MArcella RSE; Salerno Franco IRSA CNR; Thakuri Sudeep Kathmandu University; Leoni Barbara Uni Bicocca; Chairello Gianluca Uni Milano, Cristiani Pierangela RSE This study presents the findings from several field campaigns carried out in Lake Idro Northern Italy , a deep 124 m meromictic subalpine lake, whose water column is subdivided in a mixolimnion 0 40 m and a monimolimnion 40 124 m . Hydrochemical data highlight two main peculiarities characterizing the Lake Idro meromixis a presence of a high manganese/iron ratio up to 20 mol/mol , b absence of a clear chemocline between the two main layers. The high manganese content contributed to the formation of a stable manganese dominated deep turbid stratum 40 65 m , enveloping the redoxcline 45 55 m in the upper monimolimnion. The presence of this turbid stratum in Lake Idro is described for the first time in this study. The paper examines the distribution of dissolved and particulate forms of transition metals Mn and Fe , alkaline earth metals Ca and Mg , and other macro constituents or nutrients S, P, NO3 N, NH4 N , discussing their behavior over the redoxcline, where the main transition processes occur. Field measurements and theoretical considerations suggest that the deep turbid stratum is formed by a complex mixture of manganese and iron compounds with a prevalence of Mn II /Mn III in different forms including dissolved, colloidal, and fine particles, that give to the turbid stratum a white pink opalescent coloration. The bacteria populations show a clear stratification with the upper aerobic layer dominated by the heterotrophic Flavobacterium sp., the turbid stratum hosting a specific microbiological pool, dominated by Caldimonas sp., and the deeper anaerobic layer dominated by the sulfur oxidizing and denitrifier Sulfuricurvum sp. The occurrence in August 2010 of an anomalous lake surface coloration lasting about four weeks and developing from milky white green to red brown suggests that the upper zone of the turbid stratum could be eroded during intense weather hydrological conditions with the final red brown coloration resulting from the oxidation of Mn II /Mn III to Mn IV compounds. 795 Published version https //www.sciencedirect.com/science/article/pii/S0048969721038158 Manganese mediated hydrochemistry and microbiology in a meromictic subalpine lake Lake Idro, Northern Italy A biogeochemical approach Ciclo del manganese in un ambiente lacustre e meromittico, le cui acque sono quindi sempre stratificate. Il caso di studio si caratterizza per un rapporto stechiometrico manganese/ferro particolarmente alto. Tartari_2021_STOTEN.pdf Articolo in rivista Elsevier 0048 9697 Science of the total environment Science of the total environment Sci. total environ. gianni.tartari TARTARI GIANNI diego.copetti COPETTI DIEGO franco.salerno SALERNO FRANCO |
