Variability of benthic methane‐derived carbon along seasonal, biological, and sedimentary gradients in a polymictic lake

Tsuchiya, Kenji; Komatsu, Kazuhiro; Shinohara, Ryuichiro; Imai, Akio; Matsuzaki, Shin‐ichiro S.; Ueno, Ryuhei; Kuwahara, Victor S.; Kohzu, Ayato

doi:10.1002/lno.11571

Cited by 7 publications

(6 citation statements)

References 44 publications

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“…The measurement of the stable isotope ratio of 13 C to 12 C in different compartments of the C cycle in lakes has been a powerful tool in the past decades to study the fate of C derived from methanogenesis (e.g., Kankaala et al, 2006;Tsuchiya et al, 2020). The 13 C: 12 C ratio is often expressed relative to a standard (Vienna Peedee belemnite with a 13 C: 12 C ratio of 0.0112372) according to…”

Section: Introductionmentioning

confidence: 99%

Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input

et al. 2021

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Methane (CH4) is an important component of the carbon (C) cycling in lakes. CH4 production enables carbon in sediments to be either reintroduced to the food web via CH4 oxidation or emitted as a greenhouse gas making lakes one of the largest natural sources of atmospheric CH4. Large stable carbon isotopic fractionation during CH4 oxidation makes changes in 13C:12C ratio (δ13C) a powerful and widely used tool to determine the extent to which lake CH4 is oxidized, rather than emitted. This relies on correct δ13C values of original CH4 sources, the variability of which has rarely been investigated systematically in lakes. In this study, we measured δ13C in CH4 bubbles in littoral sediments and in CH4 dissolved in the anoxic hypolimnion of six boreal lakes with different characteristics. The results indicate that δ13C of CH4 sources is consistently higher (less 13C depletion) in littoral sediments than in deep waters across boreal and subarctic lakes. Variability in organic matter substrates across depths is a potential explanation. In one of the studied lakes available data from nearby soils showed correspondence between δ13C-CH4 in groundwater and deep lake water, and input from the catchment of CH4via groundwater exceeded atmospheric CH4 emissions tenfold over a period of 1 month. It indicates that lateral hydrological transport of CH4 can explain the observed δ13C-CH4 patterns and be important for lake CH4 cycling. Our results have important consequences for modelling and process assessments relative to lake CH4 using δ13C, including for CH4 oxidation, which is a key regulator of lake CH4 emissions.

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Section: Introductionmentioning

confidence: 99%

Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input

et al. 2021

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“…At Stn. B, water depth 2.0 m, the sediments include coarser particles derived from dredging (Tsuchiya et al 2020). At Stn.…”

Section: Methods Lake Kasumigauramentioning

confidence: 99%

“…For example, the sandy sediment at Stn. B had a lower organic matter content than the sediment at the other stations (Tsuchiya et al 2020 should be addressed in the future work because they could be involved in the P release from the bottom sediments (Sinkko et al 2011).…”

Section: àmentioning

confidence: 99%

Warming of water temperature in spring and nutrient release from sediment in a shallow eutrophic lake

Shinohara

Tsuchiya

Kohzu

2021

Journal of Water and Climate Change

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We investigated whether recent springtime water temperature increases in a shallow eutrophic lake affected bottom sediment temperature and fluxes of ammonia (NH4+) and phosphate (PO43−) from the sediment. We conducted a lake-wide survey of Lake Kasumigaura, Japan, and analyzed the relationship between water temperature increases in spring and NH4+ and PO43− release fluxes. We also developed a numerical model to analyze how water temperature increase affects sediment temperature. Water temperature in May increased during 2010–2019 at a rate of 1.8–3.2 °C decade−1. The numerical simulation results showed that the water temperature increase was accompanied by a sediment temperature increase from a minimum of 18.3 °C in 2011 to a maximum of 21.6 °C in 2015. Despite the substantial difference in the observed sediment temperature (2.9 °C), no significant differences in NH4+ and PO43− fluxes in May between 2013/2014 and 2015 were found. These results suggest that both water and sediment temperatures are increasing in Lake Kasumigaura in spring, but it is unclear whether this warming has affected NH4+ and PO43− releases from the sediment. However, because a nonlinear response to sediment temperature was observed, future springtime warming may accelerate NH4+ and PO43− releases.

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“…To estimate the contribution of sulfide-S to animals, a simple twoendmember (assuming SOB and POM) isotope mixing model was used (Phillips & Gregg, 2001). This model was often applied to estimate the contribution of methane-derived carbon in a freshwater lake (e.g., Tsuchiya et al, 2020). We modified the model to estimate the contribution of sulfide-S. Because the S isotope discrimination between animal and diet resource is negligible (Fry et al, 1983), the isotope mixing model can be represented simply as shown below:…”

Section: Estimation Of Sulfide-s Contributionmentioning

confidence: 99%

Major contribution of sulfide‐derived sulfur to the benthic food web in a large freshwater lake

2023

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In freshwater systems, contributions of chemosynthetic products by sulfur‐oxidizing bacteria in sediments as nutritional resources in benthic food webs remain unclear, even though chemosynthetic products might be an important nutritional resource for benthic food webs in deep‐sea hydrothermal vents and shallow marine systems. To study geochemical aspects of this trophic pathway, we sampled sediment cores and benthic animals at two sites (90 and 50 m water depths) in the largest freshwater (mesotrophic) lake in Japan: Lake Biwa. Stable carbon, nitrogen, and sulfur isotopes of the sediments and animals were measured to elucidate the sulfur nutritional resources for the benthic food web precisely by calculating the contributions of the incorporation of sulfide‐derived sulfur to the biomass and of the biogeochemical sulfur cycle supporting the sulfur nutritional resource. The recovered sediment cores showed increases in 34S‐depleted sulfide at 5 cm sediment depth and showed low sulfide concentration with high δ34S in deeper layers, suggesting an association of microbial activities with sulfate reduction and sulfide oxidation in the sediments. The sulfur‐oxidizing bacteria may contribute to benthic animal biomass. Calculations based on the biomass, sulfur content, and contribution to sulfide‐derived sulfur of each animal comprising the benthic food web revealed that 58%–67% of the total biomass sulfur in the benthic food web of Lake Biwa is occupied by sulfide‐derived sulfur. Such a large contribution implies that the chemosynthetic products of sulfur‐oxidizing bacteria are important nutritional resources supporting benthic food webs in the lake ecosystems, at least in terms of sulfur. The results present a new trophic pathway for sulfur that has been overlooked in lake ecosystems with low‐sulfate concentrations.

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Variability of benthic methane‐derived carbon along seasonal, biological, and sedimentary gradients in a polymictic lake

Cited by 7 publications

References 44 publications

Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input

Methane in Lakes: Variability in Stable Carbon Isotopic Composition and the Potential Importance of Groundwater Input

Warming of water temperature in spring and nutrient release from sediment in a shallow eutrophic lake

Major contribution of sulfide‐derived sulfur to the benthic food web in a large freshwater lake

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