Limnology and Oceanography最新文献

Mangroves offer substantial carbon sequestration, acting as nature-based climate solutions. Yet, soil carbon dioxide (CO₂) and methane (CH₄) emissions partially offset these benefits. Despite many studies on emission patterns and drivers, lacking source-specific partitioning hinders deeper mechanistic insights. Here, a 1-yr in situ experiment using deep collar insertion in Kandelia obovata and Avicennia marina forests partitioned soil CO₂ and CH₄ fluxes into heterotrophic and root-affected sources, examining seasonal dynamics, temperature sensitivity (Q₁₀), and soil properties controls. Soil–air carbon fluxes, except for root-affected CH₄, were lowest in winter and peaked in summer or autumn. Soil and root-affected CH₄ fluxes were significantly higher in A. marina forests than in K. obovata forests annually or seasonally. The annual flux ratio of root-affected CO₂ to soil CO₂ averaged 39%, and was relatively 19% higher in A. marina forests than in K. obovata forests. Soil properties collectively explained 64%, 62%, and 36% of variation in soil, heterotrophic, and root-affected CO₂ fluxes, respectively, but only 3%, 22%, and −9% for corresponding CH₄ fluxes. The Q₁₀ of soil CH₄ fluxes was significantly higher in A. marina forests than in K. obovata forests, and root-affected CO₂ fluxes had a higher Q₁₀ than heterotrophic CO₂ fluxes only in A. marina forests. These findings reveal mangrove species-specific differences in the magnitude and Q₁₀ of soil–air carbon fluxes, underscoring mangrove species as key to assessing climate benefits and guiding restoration. We also emphasize the role of soil conditions and flux partitioning in predicting soil CO₂ and CH₄ fluxes, respectively.

Benthic microalgal (BMA) communities contribute significantly to food webs, nutrient cycling, and carbon flows in intertidal habitats. However, the contribution of BMA to saltmarsh carbon stocks (“blue carbon”) is unclear. BMA and sediment total organic carbon (TOC) stocks were measured in an east coast American Atlantic saltmarsh, revealing key relationships between biofilm biomass, carbohydrate, and carbon content. BMA biomass (chlorophyll a) was highest in Sporobolus stands and mudflat habitats, with diatoms the dominant algal group, and cyanobacteria more important in upper saltmarsh sites. Habitat-specific differences in biofilm properties (biomass, carbohydrates, photopigments, near-infrared spectra) corresponded to differences in overall contributions to sediment TOC. Carbohydrates contributed between 8% and 23% of sediment TOC, with the highest levels in Sporobolus and mudflat habitats. BMA biomass and colloidal carbohydrate were significantly correlated, except on lower shore sandflats. The greatest relative contribution of colloidal carbohydrate to %TOC was in upper marsh and tidal channel habitats (1%). Mudflats had the highest %TOC (up to 5% dry weight), but TOC stocks (2000 g C m⁻² to a depth of 10 cm) were highest in Sporobolus habitats. A modeling approach, based on LIDAR and sediment measures, determined a BMA carbon contribution of 1.3–8% of sediment TOC, with the lowest values in Sporobolus and mudflat habitats. Upscaling from m², incorporating habitat heterogeneity, gave median values of 14–16 t TOC ha⁻¹ for the North Inlet Estuary saltmarshes, of which BMA contributed 0.06–0.08 t C ha⁻¹. This approach could permit BMA contributions to blue carbon to be estimated across other saltmarshes.

Marine dissolved organic matter (DOM) represents a primary reservoir in the biogeochemical cycle, and marine microorganisms are essential to the transformation and long-term sequestration of DOM as recalcitrant dissolved organic matter (RDOM). In China's marginal seas, DOM levels are affected by coastal productivity and terrestrial inputs, yet the molecular mechanisms driving the DOM to RDOM transformation remain insufficiently characterized. This study aimed to elucidate the mechanisms behind the DOM transformation mediated by marine microorganisms in the Bohai and Yellow Seas, particularly focusing on molecular-level characterizations of microbial carbon cycling processes. Here, using 16S rDNA amplicon sequencing, we analyzed the bacterial communities across the surface and deep layers. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to molecularly characterize the DOM. Our findings revealed distinct bacterial diversity and functional profiles between the surface and deep layers, with deep layers exhibiting higher microbial diversity. Furthermore, the deep layers were characterized by higher proportions of RDOM, with molecular indicators such as carboxyl-rich alicyclic molecules (CRAM) suggesting enhanced carbon stability. This study highlights the role of microbial processes in shaping the molecular characteristics of DOM across depths, supporting the microbial carbon pump (MCP) framework and characterizing the Bohai and Yellow Seas as significant carbon sinks in the coastal region. These findings advance our mechanistic understanding of oceanic carbon sequestration, particularly in coastal marginal seas.

Lagoons are recognized as significant CO₂ sources in the global carbon cycle. However, the lack of comprehensive measurements capturing simultaneous spatiotemporal variations in partial pressure of CO₂ (pCO₂) limits our understanding of mechanisms driving CO₂ dynamics in lagoons. In this study, autonomous buoys were deployed at five stations across Chiku Lagoon (Taiwan) during the wet season, continuously measuring temperature, salinity, and pCO₂ for over 24 h. Discrete water samples of total alkalinity and dissolved inorganic carbon were collected to establish a freshwater-to-seawater mixing model. Our analysis revealed that biological activity accounted for most of the pCO₂ variability (59%), followed by mixing processes (36%) and the temperature variations effect (5%). These effects contributed to spatial heterogeneity, with the upper lagoon exhibiting stronger emissions (4.8 ± 2.5 mmol m⁻² h⁻¹; mean ± standard deviation) than the middle and lower lagoon (0.6 ± 0.8 to 1.4 ± 1.3 mmol m⁻² h⁻¹). Meanwhile, tidal influences on CO₂ fluxes were evident, with emissions at low tide (1.4 ± 0.5 mmol m⁻² h⁻¹) nearly double those at high tide (0.6 ± 0.3 mmol m⁻² h⁻¹). On average, all stations acted as net sources of atmospheric CO₂ over the sampling period (1.2 ± 1.2 mmol m⁻² h⁻¹). A resampling sensitivity test of the high-resolution buoy data suggests a 3-h interval is optimal in biologically and tidally driven lagoons such as Chiku. These results provide a framework for understanding spatiotemporal CO₂ dynamics and serve as a guide for future monitoring and carbon management strategies in coastal environments.

We assessed responses of Arctic Isochrysis sp. grown under a matrix of temperature (2°C vs. 6°C), light intensity (55 vs. 160 μmol photons m⁻² s⁻¹) and pCO₂ (400 vs. 1000 μatm CO₂). Next to acclimation parameters (growth rates, particulate and dissolved organic C and N, chlorophyll a content), we measured physiological processes in vivo (electron transport rates and net photosynthesis) using fast-repetition rate fluorometry and membrane-inlet mass spectrometry. Within the applied driver ranges, elevated temperature had the most pronounced impacts, significantly increasing growth (~ 40%) and particulate organic carbon production (up to ~ 140%). Light stimulations manifested prominently under high temperature (~ 30–35%), underlining its role as a “master-variable.” pCO₂ was the least effective driver, exerting mostly insignificant effects. The obtained data were used for a simplistic upscaling simulation to investigate potential changes in Isochrysis' bloom dynamics in the Fram Strait with increasing temperatures over the 21^st century. Results suggest that global warming will accelerate bloom dynamics, with earlier onsets of blooms and higher peak biomasses. Despite remaining uncertainties about the magnitude of these effects, data strongly suggest that increasing temperatures over the coming century will affect the phenology of Isochrysis and other Arctic phytoplankton with likely important implications for higher trophic levels.

Besser, A.C., A. L. Robinson, T. F. Turner, C. D. Takacs-Vesbach, and S. D. Newsome. 2025. “Differential Utilization of Submerged Leaf Litter by Microbial Biofilms and Macroinvertebrates in a Large Dryland River.” Limnology and Oceanography 70: 3489–3505. https://doi.org/10.1002/lno.70225.

The article above was originally published with reviewer-only links in the Data Availability Statement. This information has been corrected and the Data Availability Statement now reads:

Amino acid δ¹³C data are archived in the Dryad Digital Repository: https://doi.org/10.5061/dryad.2fqz61326. 16S and 18S rRNA gene sequence data are archived in the NCBI Sequence Read Archive (SRA): https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1289908.

We apologize for this error.

Marine methane emissions are important components of natural methane budgets, but the methane emission contribution derived from the central Arctic is still unclear. Here, we measured the dissolved methane concentration and its stable carbon isotopic signature (δ¹³C-CH₄) while onboard a western Arctic cruise in 2024. In the shelf areas, the methane concentration was found to be 2–3 times higher than that at atmospheric equilibrium, corresponding to a δ¹³C-CH₄ value of less than −56.3‰, which suggests a methanogenic origin. In contrast, the waters in the offshore areas were under or slightly lower than atmospheric equilibrium, corresponding to more positive δ¹³C-CH₄ values (−48.4‰ ± 3.4‰). Persistent excess methane values in the offshore areas were detected in the water column. The mass balance suggested that the in situ production accounted for more than two-thirds of the excess methane. In contrast, microbial oxidation removed over half of the methane pool. Finally, we calculated that the central Arctic can uptake 7.74 ± 11.76 Gg of methane in summer. The combined effect of sea ice melting/freezing and methane removal resulted in a 305% offset of methane diffusion, which provides evidence that the central Arctic, in contrast with the continental shelf region, currently makes a small contribution to atmospheric methane.

Antarctica is a seasonally active region for marine organic sulfur cycling and ocean-atmospheric sulfur fluxes. Organic sulfur compounds, such as dimethylsulfoniopropionate and dimethylsulfide, produced by microbes are key chemical currencies in interspecies interactions, which in turn, underpin marine sulfur dynamics. This study examined Antarctic phytoplankton-bacteria associations and their influence on marine sulfur cycling along a coastal gradient from an inner fjord of the Sørsdal glacier to the open ocean (six sites). Phytoplankton abundance increased with distance from the glacier, corresponding with an increase in dimethylsulfoniopropionate concentrations (dissolved 13–28 nM; total 73–140 nM) and phytoplankton dimethylsulfoniopropionate lyase activity. Microbial community composition varied with glacial-influence, and overall abundance declined with distance from the glacier. We identified strong associations between dominant phytoplankton genera (Cylindrotheca, Corethron, Chaetoceros, Fragilariopsis, Leptocylindrus/Dactyliosolen, and Phaeocystis) and bacteria from the Rhodobacteraceae (i.e., Roseobacter group), highlighting the prevalence of these species' complexes in Antarctic waters. Specifically, pigment markers of Phaeocystis sp. and amplicon sequence variants (ASVs) belonging to Octadecabacter and Sulfitobacter correlated positively with dissolved dimethylsulfoniopropionate concentrations and phytoplankton dimethylsulfoniopropionate lyase activity, supporting their role in marine sulfur metabolism and extending the known geographical range of sulfur-mediated phytoplankton associations with the Roseobacter group. In broadening the reported range of these interorganism interactions to Antarctic waters, these results extend the prevalence and weight of the role of sulfur-based dependencies in structuring marine microbial communities.

Human pressures are leading to the replacement of macroalgal forests by alternative opportunistic species on shallow temperate reefs. Nonetheless, the ecological consequences of habitat reconfiguration for coastal biodiversity and ecosystem functioning remain poorly quantified. By means of a field study, we compared the metabolic functioning and biodiversity of macroalgal forests dominated by the fucoid Ericaria brachycarpa at pristine sites with that of assemblages formed by a shrub-like rhodophyte (i.e., Halopithys incurva) at urban sites. Dominant macroalgae at pristine and urban sites supported similar abundance and species richness of vagile invertebrates, but macroalgal forests supported higher invertebrate biomass. Shrub-like assemblages at urban sites sustained an autotrophic metabolism with a net diel O₂ production throughout the year, whereas macroalgal forests tended to be heterotrophic during warmer months. Diel fluxes of total dissolved inorganic carbon, as well as the contribution of production/respiration, were consistent with O₂ fluxes, with E. brachycarpa forests functioning as a heterotrophic carbon source in summer. This could be the result of reduced photosynthetic performance of the dominant brown macroalga and/or increased community respiration in warmer seawater. Our findings suggest that benthic assemblages in urban areas, formed by large and architecturally complex macroalgae, do not markedly differ from those found in pristine areas in terms of supported biodiversity and may sustain a more stable autotrophic balance under varying environmental conditions. Avoiding further degradation of these urban habitats (i.e., shift from shrub-like to mat-like turfs) could be a viable strategy for sustaining ecosystem functioning along peri-urban and urban Mediterranean coasts.

There is a global increase in the decommissioning of offshore oil and gas (O&G) infrastructure at the end of its operating lifetime. However, there is strikingly limited empirical evidence for the environmental and ecological impacts of decommissioning. Here, we employed a meta-analytical approach on an industry benthic monitoring database to investigate the benthic biodiversity and food web properties of structures sampled in the short term (< 1 yr; scenario 1), medium term (1–5 yr; scenario 2), and long term (> 5 yr; scenario 3) after decommissioning. We found reduced species richness and simplified food webs in scenario 1, followed by the first signs of recovery in scenario 2, with a slightly higher proportion of intermediate species and density of food web connections. Food webs recovered further in scenario 3, with a much greater density of interactions, but also more links and longer food chains, while a reduction in generalism and connectance indicated an increased prevalence of specialist species. Our findings demonstrate disturbance risks associated with the decommissioning process in the short term, but a positive recovery trajectory over longer timescales. We highlight the importance of industry collecting more extensive and long-term data at multiple time points and covering different decommissioning types, establishing a standardized data workflow for integrating with available monitoring efforts, and improving stakeholder participation and data accessibility to support an environmentally sound decommissioning process.