Announcing the Third Quarter 2027 Limnology and Oceanography Special Collection: Greenhouse Gas Dynamics in Aquatic Ecosystems: Mechanisms, Impacts, and Future Directions

Ecological stoichiometry of aquatic fungi: current knowledge and perspectives

Chapter One - Dissolved Organic Matter: Biogeochemistry, Dynamics, and Environmental Significance in Soils

The Congo Basin, home to the world’s second largest tropical rainforest and river network, plays a crucial role in the global carbon (C) cycle. However, rapid population growth and land-use changes are intensifying geomorphic and biogeochemical disturbances. Consequently, the basin is experiencing accelerated soil redistribution, whose impacts on lateral C transfer along the land–ocean aquatic continuum (LOAC) remain largely unknown. By integrating the most comprehensive observation dataset available with a state-of-the-art land surface model (ORCHIDEE-Clateral), this study quantified the magnitude and temporal evolution of lateral C fluxes in the forms of particulate organic carbon (POC), dissolved organic carbon (DOC), and carbon dioxide (CO₂) over the past five decades, and assessed the impact of these lateral C transfers on the terrestrial C budget. The calibrated ORCHIDEE-Clateral model explains 73%, 84%, 78%, and 84% of the spatial variation in observed river water discharge, sediment discharge, POC concentration, and DOC concentration in the Congo River network, respectively. It also captures well the seasonal variations in riverine water discharge, sediment discharges, water surface extent, and riverine CO₂ partial pressure. Using the calibrated model, we reconstructed the historical evolution of C fluxes and transformations along the LOAC. Since 1970, lateral C (i.e., POC, DOC, and CO2) input from land to river has increased significantly (Mann–Kendall P < 0.001), with POC, DOC, and CO2 rising by 51%, 20%, and 29%, respectively. The increase in POC is primarily driven by land-use change, followed by climate change and rising atmospheric CO₂. Of the terrestrial C entering the Congo River network, 61% of DOC and 67% of POC remain within the river–floodplain complex—approximately two and three times the proportion retained in the Amazon and European river networks, respectively. These results suggest that the majority (> 60%) of the laterally transported terrestrial C is stored or transformed inside the Congo Basin rather than being exported to the ocean or released to the atmosphere. With the projected rapid population growth and land-use expansion in the Congo Basin, lateral C fluxes along the LOAC are expected to intensify further, reinforcing the Congo Basin’s role as a major inland C buffer that reshapes the regional land–ocean C balance.

Aquatic ecosystems play a crucial role in the global carbon cycle, serving as both significant carbon sinks and as sources of greenhouse gases (GHGs). Dynamic redox fluctuations, driven by factors such as changes in water levels and periodic flooding, facilitate interactions among reduced substances, metal-bearing minerals, and oxygen (Nielsen et al., 2010). These interactions shape microbial communities and influence the dynamics of soil organic carbon (Lalonde et al., 2012;Xiao et al., 2023). While redox fluctuations impact carbon cycling processes driven by microorganisms, further research is needed to elucidate the specific mechanisms through which microbial species, metabolic pathways, and microbial residues affect soil carbon cycling (Hu et al., 2024;Luo et al., 2019). This Special Issue invites research on GHG emissions and carbon sequestration in areas characterized by dry-wet cycling, with a focus on microbial processes and their ecological impact on the carbon cycle. Topics of interest include innovative technologies for GHG mitigation and carbon storage, microbial adaptations to environmental changes affecting GHG emissions, mechanisms of microbial carbon fixation, and interactions between microbes, minerals, and carbon in aquatic ecosystems. The goal is to enhance our understanding of sustainable solutions for managing carbon dynamics in regions with moisture fluctuations.In this Special Issue, the research topics encompass a variety of ecosystems, including wetlands, lakes, agricultural soils, estuarine intertidal zones, grasslands, and saltmarshes. The studies investigate the effects of plants, inorganic substances (e.g., inorganic nitrogen), drought, organic matter (e.g., phenolic compounds), iron-bearing minerals, precipitation, salinity and heavy metals on greenhouse gas (GHG) emissions, microbial metabolism, enzyme activities, and other relevant environmental factors.Li and Ge et al. highlight the importance of soil enzymes in wetland carbon and nutrient cycling and their varied responses to drought. A meta-analysis of 55 studies shows that while most enzyme activities remain stable, phosphorus-related enzyme activity increases by 38% under drought conditions, possibly due to their greater resilience to phenolic biotoxicity. Long-term experiments confirm that drought-driven plant shifts lead to phenolic accumulation, limiting enzyme activity, with phosphorus-related enzymes being an exception. These findings highlight wetland ecosystems' adaptive responses to drought, offering insights for assessing drought impacts and guiding restoration efforts. Jiang et al. demonstrate that the invasive plant Spartina alterniflora significantly affects GHG production in tidal wetland sediments. The presence of this species increases the production rates of CH₄ and CO₂, as well as the levels of organic matter and the abundance of microbial genes in invaded areas. These effects vary with spatial and seasonal dynamics, showing higher GHG production in surface sediments (0-10 cm) during the summer months. This study underscores how the invasion of S. alterniflora modifies GHG dynamics in coastal wetlands, offering valuable insights into emissions and carbon storage potential. Similarly, Zhang et al. examine the impact of varying precipitation levels on soil CO₂ emissions in a saltmarsh within the Yellow River Delta, China. Over a seven-year period, the results indicate that a 40% increase in precipitation enhances soil CO₂ production potential by 66.2%, with the highest soil respiration rates occurring under these conditions. Additionally, the quantity and quality of soil organic carbon positively correlate with CO₂ production, although microbial diversity remains unaffected by changes in precipitation. These findings suggest that moderate increases in precipitation may enhance CO₂ emissions, thereby influencing the carbon sink function of these blue carbon ecosystems. Looking ahead, the importance of aquatic ecosystems in the global carbon cycle is becoming increasingly prominent. As climate change and human activities intensify their impact on the environment, in-depth studies of the dynamics of microbial processes in ecosystems such as wetlands, lakes, and paddy fields will become crucial. Future research should focus on the effects of dynamic redox fluctuations on microbial communities and soil organic carbon, exploring the specific mechanisms through which different microbial species, metabolic pathways, and microbial residues influence soil carbon cycling. Additionally, developing innovative technologies to reduce GHG emissions and promote carbon storage will be key to achieving sustainable development.Research should also examine biological adaptations to environmental changes, particularly in regions characterized by dry-wet cycles, to enhance the functionality of carbon sinks. As our understanding of heavy metals in soil environments and their effects on microbial metabolism deepens, future management strategies will become more targeted to address the challenges posed by metal pollution. In summary, future research will contribute valuable scientific knowledge for combating climate change and provide feasible solutions for the conservation and restoration of aquatic ecosystems.

Wetlands and aquatic ecosystems are an important part of the ecological system and national resources, but their contamination poses a major environmental threat to human health that needs an effective and affordable solution for its management now and the future. Pollution of our freshwater environments with toxic materials from man-initiated activities such as mining and smelting of metalliferous ores, use of agricultural chemicals such as fertilizers, pesticides, and fossil burning, have dramatically increased since the onset of industrial revolution, and now requires the taking of immediate steps to restore derelict land and water environments. Waterlogging-tolerant vetiver grass, Chrysopogon zizanioides roots secrete phytochelating nano-molecules in their rhizospheres which translocate HMs from the HM-contaminated waters into their cortices, and the extraradical mycelium (ERM) of their root-associated indigenous arbuscular mycorrhizal fungi (AMF) also secrete HM-affinity-transporters-nano-molecules in the rhizospheres of the host plant. AMF also secrete Glomalin-nano-molecules which help bind the rhizosphere soil. Vetiver grass and its AMF associations can be used as potential bio-tools for decontaminating polluted aquatic ecosystems and wetlands and exploited by using them in planted-constructed wetlands (CWs) to remove heavy metals from wetlands and aquatic ecosystems in a process termed as Nano-Mycorrhizo-Phyto-Remediation (NMPR). The mycorrhiza is one of the most important symbioses on earth, linking the rhizosphere (and its microbiota and the root systems of aquatic macrophytes and they play an important role in the growth of plants by increasing their tolerance to biotic and abiotic stresses on contaminated soils and waters. AM fungi should be considered as ideal participants of CW systems for the phytoremediation of HM-contaminated waters.

Methane is a potent greenhouse gas, and aquatic environments such as wetlands, lakes, rivers, and estuaries are recognized as significant natural sources of methane emissions. However, a major gap in current methane budgets is the limited understanding of methane contributions from groundwater–surface water interactions. Groundwater discharge has often been overlooked in methane budgets due to the difficulty of detecting and quantifying both discharge rates and the associated methane fluxes. This study addresses this gap by synthesizing global literature to estimate groundwater methane concentrations and fluxes across various aquatic environments. A systematic review of peer-reviewed literature from 2011 to 2023 was conducted, synthesizing data on groundwater methane concentrations, discharge rates, and environmental factors across diverse aquatic environments. These data were subsequently integrated with global groundwater discharge estimates to quantify methane fluxes, thereby advancing current understanding of groundwater contributions to aquatic methane emissions and their potential role in the global carbon cycle. The main findings are as follows: (1) The average global groundwater methane concentration was 0.31 ± 0.47 mmol/L. (2) The global average groundwater-driven methane flux was estimated to be 3.9 ± 6.2 mmol/m²/day. (3) When extrapolated globally using existing estimates of groundwater discharge, these fluxes suggest that groundwater may account for up to 70% of methane emissions from surface waters in aquatic systems. (4) In some environments, groundwater-driven methane fluxes exceed direct surface water–atmosphere methane emissions by several fold, particularly in subarctic and temperate regions. This significant groundwater contribution has been largely unrecognized in global methane budgets and climate models. Findings indicate a lack of studies quantifying groundwater-driven methane fluxes (or providing concurrent data on groundwater methane concentrations and groundwater discharge), particularly in streams. Incorporating groundwater-driven methane into carbon accounting frameworks is essential for improving the accuracy of methane emission estimates and for better informing climate mitigation strategies. Further empirical studies are needed to reduce uncertainty and address current data gaps across geographic regions and aquifer types. Graphical Abstract Methane, a potent greenhouse gas, is emitted directly to the atmosphere from aquatic environments like wetlands, lakes, rivers, and estuaries, yet the contribution from groundwater discharge to these emissions remain poorly understood, a gap this study addresses. The graphical abstract illustrates the formation of methane in anaerobic groundwater systems, followed by its discharge into aquatic environments, and release to the atmosphere. Arrows link these hydrogeological and biogeochemical processes. This study, synthesizing global literature from 2011 to 2023, estimates groundwater methane concentrations and fluxes, revealing a global average groundwater methane concentration of 0.31 ± 0.47 mmol/L and a global groundwater driven methane flux of 3.9 ± 6.2 mmol/m²/day. A key finding is that groundwater discharge may contribute up to 70% of methane emissions from aquatic environments, with fluxes exceeding surface water emissions by up to 6 times, especially in subarctic and temperate regions. The role of groundwater discharge in methane budgets has been largely unrecognized, while this study clearly shows the need for its integration into carbon accounting frameworks.

Effects on aquatic ecosystems

Abstract. As the second largest area of contiguous tropical rainforest and second largest river basin in the world, the Congo Basin has a significant role to play in the global carbon (C) cycle. For the present day, it has been shown that a significant proportion of global terrestrial net primary productivity (NPP) is transferred laterally to the land–ocean aquatic continuum (LOAC) as dissolved CO2, dissolved organic carbon (DOC), and particulate organic carbon (POC). Whilst the importance of LOAC fluxes in the Congo Basin has been demonstrated for the present day, it is not known to what extent these fluxes have been perturbed historically, how they are likely to change under future climate change and land use scenarios, and in turn what impact these changes might have on the overall C cycle of the basin. Here we apply the ORCHILEAK model to the Congo Basin and estimate that 4 % of terrestrial NPP (NPP = 5800±166 Tg C yr−1) is currently exported from soils and vegetation to inland waters. Further, our results suggest that aquatic C fluxes may have undergone considerable perturbation since 1861 to the present day, with aquatic CO2 evasion and C export to the coast increasing by 26 % (186±41 to 235±54 Tg C yr−1) and 25 % (12±3 to 15±4 Tg C yr−1), respectively, largely because of rising atmospheric CO2 concentrations. Moreover, under climate scenario RCP6.0 we predict that this perturbation could continue; over the full simulation period (1861–2099), we estimate that aquatic CO2 evasion and C export to the coast could increase by 79 % and 67 %, respectively. Finally, we show that the proportion of terrestrial NPP lost to the LOAC could increase from approximately 3 % to 5 % from 1861–2099 as a result of increasing atmospheric CO2 concentrations and climate change. However, our future projections of the Congo Basin C fluxes in particular need to be interpreted with some caution due to model limitations. We discuss these limitations, including the wider challenges associated with applying the current generation of land surface models which ignore nutrient dynamics to make future projections of the tropical C cycle, along with potential next steps.

The frequency and intensity of extreme weather events (EWEs) have increased in recent decades and are projected to continue rising globally. The impact of EWE on boreal ecosystems can be disproportionate. In forests, the exchange of CO2 is affected by droughts depending on their timing and severity. In lakes, heatwaves might strengthen stratification and trigger oxygen depletion, with consequences on greenhouse gas (GHG) dynamics. Excessive heat and winds can also increase GHG emissions from peatlands and lakes. The driving mechanisms of GHG exchange in these three ecosystems differ, and their responses to EWE also vary. Long-term flux data, obtained with the Eddy covariance (EC) technique, enable us to establish a baseline response and analyse how these different ecosystems react to EWE. The EC technique measures the vertical exchange of gases, particles, and energy at an ecosystem scale, with a 30-minute interval, demonstrating the instantaneous response of the ecosystem.Here, we analysed the effect of EWE on GHG dynamics from adjacent forest (Hyytiälä), lake (Kuivajärvi) and peatland (Siikaneva) ecosystems, where long-term EC flux measurements are available. EWE, such as heatwaves, dry spells, excessive rainfall, prolonged high wind spells, and compound events, have been identified in the last decade using both in situ and ERA5 reanalysis Land hourly datasets. The ecosystems exhibit contrasting responses to the EWEs. For instance, during the 2018 heatwave, the forest exhibited enhanced CO2 uptake, while both the lake and the peatland showed increased emissions relative to the reference period (2013-17).

Aquatic ecosystems in eastern China are suffering threats from heavy metal pollution because of rapid economic development and urbanization. Heavy metals in surface sediments were determined in five different aquatic ecosystems (river, reservoir, estuary, lake, and wetland ecosystems). The average Cd, Cr, Cu, Ni, Pb, and Zn concentrations were 0.716, 118, 37.3, 32.7, 56.6, and 204 mg/kg, respectively, and the higher concentrations were mainly found in sediment samples from river ecosystems. Cd was the most anthropogenically enriched pollutant, followed by Zn and Pb, indicated by enrichment factors >1.5. According to consensus-based sediment quality guidelines, potential ecological risk indices, and risk assessment codes, all five types of aquatic ecosystems were found to be polluted with heavy metals, and the most polluted ecosystems were mainly rivers. Cd was the most serious pollutant in all five aquatic ecosystems, and it was mainly found in the exchangeable fraction (about 30% of the total Cd concentration, on average). The results indicate that heavy metal contamination, especially of Cd, in aquatic ecosystems in eastern China should be taken into account in the development of management strategies for protecting the aquatic environment.

Review on the Role of Terrestrial Aquatic Photosynthesis in the Global Carbon Cycle

PDF HTML阅读 XML下载 导出引用 引用提醒 鄱阳湖湿地不同土地利用方式下土壤微生物群落功能多样性 DOI: 10.5846/stxb201306121688 作者: 作者单位: 江西省分子生物学与基因工程重点实验室,江西省分子生物学与基因工程重点实验室,江西省分子生物学与基因工程重点实验室,江西省分子生物学与基因工程重点实验室;鄱阳湖环境与资源利用教育部重点实验室,江西省分子生物学与基因工程重点实验室;鄱阳湖环境与资源利用教育部重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31360127,31260110) Response of soil microbial functional diversity to different land-use types in wetland of Poyang Lake, China Author: Affiliation: Key Laboratory of Molecular Biology and Genetic Engineering in Jiangxi Province,Nanchang University,Key Laboratory of Molecular Biology and Genetic Engineering in Jiangxi Province,Nanchang University,Key Laboratory of Molecular Biology and Genetic Engineering in Jiangxi Province,Nanchang University,Key Laboratory of Molecular Biology and Genetic Engineering in Jiangxi Province,Nanchang University; Key Laboratory of Environment and Resource Utilization of Poyang Lake, Ministry of Education,Key Laboratory of Molecular Biology and Genetic Engineering in Jiangxi Province,Nanchang University; Key Laboratory of Environment and Resource Utilization of Poyang Lake, Ministry of Education Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:于2011年5月分别采集鄱阳湖围垦92、48a和38a的水稻田,退田还湖25a的退耕地以及自然湿地共5个样地的表层土壤,利用Biolog-ECO板技术对土壤微生物群落的单一碳源利用情况进行了测定,并结合群落指数和主成分分析(PCA)对培养72 h土壤微生物群落功能多样性变化进行了分析。结果表明:退耕地和自然湿地土壤微生物群落利用31种碳源的能力较强,来自不同围垦年限的土壤微生物群落利用碳源能力均较弱;且随围垦时间的增长,土壤微生物对碳源的利用能力呈降低的趋势。自然湿地、退耕地与围垦92、38a样地土壤之间存在显著的微生物功能多样性差异;围垦对土壤微生物代谢糖类、羧酸类、氨基酸类物质的影响最为明显。结果提示,围垦改变了湿地土壤微生物群落结构,退田还湖有助于湿地土壤微生物群落结构的恢复。 Abstract:Wetland ecosystem, the transitional region between terrestrial ecosystem and aquatic ecosystem, plays a crucial role in global carbon and nitrogen cycle, flood constraint, runoff regulation, climate improvement, pollution prevention and organismal habitats supply. However, as a consequence of human beings' reclamation and contamination in the past centuries, wetland ecosystems around the world have been destructed and their total area has being declining. Hence, it is urgent to restore wetland ecosystem resources and its ecological function. Microorganisms are one of the predominant participants associated with the function of wetlands. To accomplish wetland restoration scientifically and efficiently, it is indispensable to reveal the responding mechanism of microbial variation due to wetlands' reclamation and restoration. In this study, a series of lands under different utilized types were selected as sampling sites in Nanjishan Wetland National Nature Reserve of Poyang Lake, which located in Jiangxi Province, China. The sites were 38, 48 and 92 year-old reclaimed lands (named RL38, RL48 and RL92, all were paddy fields), 25-year-old retired cropland (RC25) and native wetland (NW). In May 2011, surface soil samples (0-20 cm depth) were collected using earth boring auger in these sampling sites. Biolog-ECO plates were performed to survey the sole-carbon-source utilization of soil microbial communities. Average well colour development (AWCD) of all 31 carbon sources and the 6 kinds of carbon sources were calculated respectively. Microbial community indices calculation and principal components analysis (PCA) were carried out to analyze the variations of functional diversity of soil microbial community in exponential phase. It aimed to preliminarily reveal: 1) the effects of reclamation on the functional diversity of soil microbial community; 2) whether it was efficient at microbial level for wetland restoration by returning farmland to lake wetland. In consequence, 1) the average well colour development (AWCD) of all the soil samples was at a low level during the initial 48 hours. Subsequently, all the AWCDs presented a rapid rising in addition to the 92-year reclaimed land. 2) Generally, the order of AWCD of soil microorganisms was as follows: RC25 > NW > RL38 > RL48 > RL92. Notably, it was significantly higher in retired cropland and native wetland than in reclaimed lands (P<0.01). 3) The AWCD variation of carbohydrates, carboxylic acids and amino acids among sampling sites accorded with the total AWCD of all the 31 sole-carbon sources. 4) According to the microbial functional Richness index and the comprehensive loading scores of PCA, the utilization ability order in exponential phase among sampling sites was RC25 > NW > RL48 > RL38 > RL92. On the first two axes, a total 53.22% variation of functional diversity was explained. The results indicated that 1) the functional diversity of soil microbial community was significantly lower in reclaimed lands than in native wetland and decreased with the extension of reclamation age; 2) soil microorganisms associated with metabolism of carbohydrates, carboxylic acids and amino acids were most apparently affected by reclamation. 3) it was efficient, to some extent, to recover the soil microbial metabolic activity by returning the farmland to lake wetland. 参考文献 相似文献 引证文献

Denitrification and anammox collectively drive nitrogen loss from aquatic ecosystems, yet their global patterns and interactions remain unclear. To fill this gap in knowledge, we compiled a global dataset on anammox and denitrification, encompassing river, lake, wetland, and estuary ecosystems and comprising 2539 observations from 136 peer-reviewed papers. Here, we show that aquatic ecosystems with abundant denitrifying bacteria tend to have abundant anammox bacteria, but the abundance of anammox bacteria is lower than that of denitrifying bacteria. Importantly, we observed that hotspots for denitrification in aquatic ecosystems were also hotspots for anammox, and we explained the variation in anammox (21.55 (95% CI: 8.21–58.90) nmol-N g-1 day-1) and denitrification rates (171.76 (95% CI: 65.40–519.25) nmol-N g-1 day-1) across aquatic ecosystems. These results highlight that anammox should be included in models for accurate nitrogen budget assessment in aquatic ecosystems on a global scale, especially in the context of future climate warming.

&amp;lt;p&amp;gt;Peatlands are vital to the global carbon (C) cycle as they act as a significant C store and these systems in Ireland store between 1064 &amp;amp;#8211;1503 Gt C on ~20% of the land area. However, around 90% of this area has been drained and degraded by various anthropogenic activities and the emissions from these activities are approximately 3 million t C per year. A better understanding of the land-atmosphere C and greenhouse gas (GHG) dynamics is vital to halt these emissions and enhance the C sink strength of these ecosystems. Gross Primary Productivity (GPP) is a major part of the peatland carbon cycle and detailed knowledge of the spatial and temporal extent of GPP is imperative for improving our predictions of peatland ecology, biogeochemistry and carbon balance in response to global change. Eddy covariance (EC) techniques are widely used to measure carbon fluxes but can only account for fluxes within the flux footprint of the tower, and it is challenging to scale up data from EC towers to regional and global scales due to the limited number of towers and their geographic locations. This research assesses the relationship between remote sensing and ground-based measurements for a near-natural raised bog in Ireland using EC techniques and high-resolution Sentinel 2A satellite imagery. Vegetation indices (VIs) are one of the key input parameters for satellite-based GPP and most of the existing VIs have been developed for grassland, agriculture, and forest ecosystems. This study developed a hybrid index for raised bogs using multiple linear regression and six widely practiced conventional vegetation indices. Two approaches have been used in this study for estimating GPP using the LUE model. Initially, all the individual indices have been used to model the GPP, which was subsequently compared with the EC GPP to determine the performance of each index against the EC data. The model was run with meteorological data and satellite-derived vegetation indices. During the 2018 study period, the weather was exceptionally dry which made it challenging and rewarding at the same time as the hybrid index was developed for an exceptional year. It was crucial to test the performance of the hybrid index under more normal weather conditions with limited clear sky satellite imagery. Therefore, the hybrid index was validated for the year 2019 which had normal weather conditions. The hybrid index based modelled GPP showed a significant correlation with the EC GPP for both the years with an R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt; &amp;gt; 0.95. Overall, this research has demonstrated the potential of combining EC techniques and the hybrid index along with satellite-derived models to better understand and monitor key drivers and patterns of GPP of raised bog ecosystems under different climate scenarios.&amp;lt;/p&amp;gt;

Water quality and periphyton functional response to input of dissolved manure-derived hydrochars (DHCs).