Physicochemical Characteristics

Alcocer, Javier; Merino–Ibarra, Martín; Ramírez-Zierold, Jorge A.; Oseguera, Luis A.; Cortés‐Guzmán, Daniela; Castillo-Sandoval, Fermín S.; Guzmán-Arias, Andrea P.; Pérez-Ramírez, María Guadalupe

doi:10.1007/978-3-030-79096-7_7

Cited by 2 publications

(1 citation statement)

References 46 publications

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“…If Alchichica's DOC actually represents a long-term reservoir, its presence might favor the development of bacterial populations growing on it. A shift of the cyanobacterial DOC toward the hypolimnion of Lake Alchichica was described at the end of the spring (Alcocer et al, 2014a;2022). Thus, deeper and darker anoxic waters in Alchichica could better preserve DOC from intense microbial and light degradation, hence allowing its accumulation over time.…”

Section: Doc Accumulation In (The Bottom Water Of) Lake Alchichicamentioning

confidence: 99%

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

Havas

Thomazo

Iniesto

et al. 2023

Preprint

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Abstract. The dissolved organic carbon (DOC) reservoir holds a critical role in the C cycle of marine and fresh water environments because of its large size and involvement in many biogeochemical reactions. Despite poor constraints, its importance in ancient Earth’s C cycles is also commonly invoked. However, DOC remains rarely quantified and characterized in modern stratified analogs. Here, we investigated the DOC reservoirs of four redox-stratified alkaline crater lakes from Mexico. To achieve this, we analyzed the concentrations and isotopic compositions of DOC throughout the four water columns and compared them with existing data on dissolved inorganic and particulate organic C reservoirs (DIC and POC). The four lakes have high DOC concentrations with important variability between and within the lakes (averaging 2 ± 4 mM; 1SD, n=28; representing from ~ 15 to 160 times the amount of POC). δ13CDOC signatures also span a broad range of values from -29.3 to -8.7 ‰ (with as much as 12.5 ‰ variation within a single lake). The prominent DOC peaks (up to 21 mM), together with their associated isotopic variability, are interpreted to reflect oxygenic and/or anoxygenic primary productivity through the release of excess fixed-carbon in three of the lakes (Atexcac, La Preciosa and La Alberca de los Espinos). By contrast, the variability of [DOC] and δ13CDOC in Lake Alchichica was mainly explained by partial degradation of organic matter and accumulation of DOC in anoxic waters. Overall, DOC records detailed metabolic functioning such as active DIC-uptake and DIC-concentrating mechanism that cannot be inferred from DIC and POC analyses alone but that are critical to understand carbon fluxes from the environment to the biomass. Extrapolating our results to the geological record, we suggest that anaerobic oxidation of DOC may have caused the very negative C isotope excursions in the Neoproterozoic, but it is unlikely that a large oceanic DOC reservoir overweight the associated DIC reservoir. Overall, this study shows how the analysis of DOC in modern lakes deepens our understanding of the C cycle in stratified environments and how it can help to size boundary conditions to the Earth’s past oceans.

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Section: Doc Accumulation In (The Bottom Water Of) Lake Alchichicamentioning

confidence: 99%

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

Havas

Thomazo

Iniesto

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

Havas¹,

Thomazo²,

Iniesto³

et al. 2023

Biogeosciences

View full text Add to dashboard Cite

Abstract. The dissolved organic carbon (DOC) reservoir plays a critical role in the C cycle of marine and freshwater environments because of its size and implication in many biogeochemical reactions. Although it is poorly constrained, its importance in ancient Earth's C cycles is also commonly invoked. Yet DOC is rarely quantified and characterized in modern stratified analogues. In this study, we investigated the DOC reservoirs of four redox-stratified alkaline crater lakes in Mexico. We analyzed the concentrations and isotopic compositions of DOC throughout the four water columns and compared them with existing data on dissolved inorganic and particulate organic C reservoirs (DIC and POC). The four lakes have high DOC concentrations with great variability between and within the lakes (averaging 2 ± 4 mM; 1 SD, n=28; i.e., from ∼ 15 to 160 times the amount of POC). The δ13CDOC signatures also span a broad range of values from −29.3 ‰ to −8.7 ‰ (with as much as 12.5 ‰ variation within a single lake). The prominent DOC peaks (up to 21 mM), together with their associated isotopic variability, are interpreted as reflecting oxygenic and/or anoxygenic primary productivity through the release of excess fixed carbon in three of the lakes (Alberca de los Espinos, La Preciosa, and Atexcac). By contrast, the variability of [DOC] and δ13CDOC in the case of Lake Alchichica is mainly explained by the partial degradation of organic matter and the accumulation of DOC in anoxic waters. The DOC records detailed metabolic functions such as active DIC-uptake and DIC-concentrating mechanisms, which cannot be inferred from DIC and POC analyses alone but which are critical to the understanding of carbon fluxes from the environment to the biomass. Extrapolating our results to the geological record, we suggest that anaerobic oxidation of DOC may have caused the very negative C isotope excursions in the Neoproterozoic. It is, however, unlikely that a large oceanic DOC reservoir could overweigh the entire oceanic DIC reservoir. This study demonstrates how the analysis of DOC in modern systems deepens our understanding of the C cycle in stratified environments and helps to set boundary conditions for the Earth's past oceans.

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Physicochemical Characteristics

Cited by 2 publications

References 46 publications

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes

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