Limnology and Oceanography Letters最新文献

By disturbing the upper ocean, typhoons may play a crucial role in marine ecosystems. Previous studies mostly demonstrated surface chlorophyll a (Chl a) increase under typhoon conditions. By using satellite data and a physical–biogeochemical model, however, we show that approximately 49% of typhoons crossing the northern shelf of the South China Sea induced surface Chl a decline. Cases with Chl a decline were typically associated with high pre-typhoon Chl a from the Pearl River plume. During and after typhoon, advection (vertical mixing) drove the Chl a decline on the shallow shelf, < 50 m (deep shelf, > 50 m). For depth-averaged Chl a, it still decreased in the shallow shelf due to the typhoon-induced onshore advection, while it increased in the deep shelf attributable to the mixing-induced nutrient supply. This study demonstrates diverse responses of Chl a to typhoons in shelf areas, underscoring the importance of fully understanding both physical and biogeochemical dynamics when evaluating typhoon impact on marine ecosystem.

Partial migration of organisms, in which only a subset of a population migrates, plays an important role in life-history strategies and population resilience in many taxa, yet the mechanisms shaping it under changing environments need further investigation. Otolith element profiles of fishes can reveal detailed patterns of their migration. Temperate eels have a wide latitudinal distribution and show remarkable partial migration life-histories that use both freshwater and marine habitats in the sub-adult stages. We analyzed the otolith Sr/Ca ratios of 355 silver-phase Japanese eels collected in Japan to evaluate their migration patterns. For the first time, our results demonstrate female dominance in both lower-estuarine/marine and freshwater habitats, and male dominance in habitats of intermediate salinity. Our study also reveals a latitudinal cline of migratory contingents, with higher use of saline habitats at northern sites. Interannual comparisons suggested relative stability in migratory contingents, although one study system showed temporal changes.

Estuaries are critical for land-ocean carbon exchange, but coupling mechanisms between air–sea CO₂ fluxes (FCO₂) and phytoplankton gross primary productivity (GPP) remain poorly understood. This study used high-frequency underway monitoring in the Lingdingyang Estuary to resolve spatiotemporal interplays between FCO₂ and GPP. Annual mean FCO₂ was 20.29 ± 23.34 mol C m⁻² yr⁻¹, with flooding season (82.97 ± 80.49 mmol C m⁻² d⁻¹) an order of magnitude higher than dry season. Gross primary productivity averaged 2.23 ± 2.07 mol C m⁻² yr⁻¹, increasing significantly during flooding. The results revealed a distinct “source-to-sink” FCO₂ gradient, with a 116% reduction over ∼40 km, primarily driven by phytoplankton activity. Biological processes explained 30–50% of FCO₂ variability. While net autotrophy in the mid-estuary reduced FCO₂ by 48.6 mmol C m⁻² d⁻¹ during flooding, heterotrophic activity downstream offset 40–60% of GPP-driven uptakes. This study quantifies how urban estuary oscillate between carbon source and sink states, providing parameters for blue carbon frameworks and demonstrating that eutrophication-driven loads reduce overall carbon sequestration efficiency through enhanced heterotrophic activities.

The flux of carbon through the labile dissolved organic matter (DOM) pool supports marine microbial communities and represents the fate of approximately half of marine net primary production (NPP). However, the behavior of individual chemical structures that make up labile DOM remain largely unknown. We performed 12 uptake kinetics and two uptake competition experiments on the abundant betaine osmolytes glycine betaine (GBT) and homarine. Combining uptake kinetics with dissolved metabolite measurements, we quantified fluxes through the DOM pool. Fluxes were correlated with particulate concentrations and ranged from 0.53 to 41 and 0.003 to 0.54 nmol L⁻¹ d⁻¹ for GBT and homarine, respectively, equivalent to up to 1.2% of NPP. Turnover times of dissolved GBT and homarine ranged from 1 to 57 d. Betaines and sulfoniums such as dimethylsulfoniopropionate competitively inhibited homarine uptake. Our results quantify GBT and homarine cycling and suggest an important role for uptake competition in regulating dissolved metabolite concentrations and fluxes.

Climate change increases the magnitude and frequency of extreme weather events. This includes severe summer storms altering lake physical structure, biodiversity and ecosystem processes. However, insights into lake responses to extreme storms and the underlying mechanisms primarily rest on unreplicated and observational case studies, without separating effects of physical forcing from secondary drivers such as external nutrient and dissolved organic matter inputs. In a large-scale replicated experiment conducted in a unique enclosure facility mimicking realistic environmental conditions, we tested how storm-induced mixing entails changes in lake ecosystems. Consequences include altered phytoplankton composition, nutrient, oxygen and carbon dynamics, with potential negative feedbacks on climate through organic matter sequestration. These experimental results are reflected in a minimal dynamical model and are also supported by observations made during a natural severe storm. An important practical implication is that efforts to abate lake eutrophication needs to accommodate the projected increases in extreme weather situations.

Rewetting of drained wetlands is promoted as an efficient nature-based solution to combat multiple environmental challenges. Yet, how rewetting influences the total lateral carbon export via runoff across diverse landscapes is rarely studied. Here we show by paired (rewetted/drained) sampling of 66 wetlands along a large geographical- and climatic range of boreal and hemi-boreal Sweden that rewetted sites had higher (on average 1.5–5.5 times) runoff concentrations of all major carbon forms (total organic carbon [TOC], carbon dioxide [CO₂], and methane [CH₄]) than drained sites. While the rewetting effect varied considerably across site pairs, the effects on TOC and CO₂ were weakly related (negatively) to aquatic carbon to nitrogen ratio (C/N) and latitude, though only during autumn season. No such relationship was observed for CH₄, regardless of season. These findings suggest that rewetting enhances lateral carbon export, with potential implications for climate benefit assessments and downstream water quality.

The oceans play the dual role of carbon sinks and greenhouse gases (GHGs) sources in global climate change, but there are still gaps in understanding the GHG fluxes and regulation mechanisms across ecosystem scales. We conducted five cruises across a coastal-to-oligotrophic ocean continuum to evaluate the distributions and air-sea exchange of carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄). The results show that GHGs exhibit significant positive fluxes in the coastal zone, with N₂O and CH₄ (CO₂ equivalent) accounting for 30–50% of the total flux. In contrast, about 40% of the CO₂ uptake is offset in the pelagic ocean, suggesting a spatial gradient pattern of “coastal enhancement–pelagic compensation.” In addition, we identified critical drivers and causal pathways for temperature, oxygen and nutrients. The study shows that oceanic non-CO₂ gases have significant positive climate effects, which highlights the importance of the multi-gas synergistic framework in assessing regional climate feedback.

Blue carbon sequestration in coastal ecosystems is only relevant to climate change mitigation and carbon offset crediting if the carbon is taken out of circulation for at least a century. Here, we examined sediment cores, up to 2.2 m deep, collected in modern Zostera marina seagrass meadows in Mid-Atlantic lagoons in Virginia, USA. Seagrass was widely abundant here until disease caused regional extinction in 1933. In 1998, 65 yr later, a small naturally seeded seagrass patch was found and spurred a large-scale seagrass restoration project, now covering more than 40 km². Integrated data on ²¹⁰Pb and ¹⁴C dating, sediment organic matter and carbon content, and stable isotopic and DNA analysis revealed that a large part of the seagrass organic carbon persisted for centuries despite the absence of seagrass for many decades. In some cases, this legacy blue carbon was double the amount buried in sediments of the restored seagrass meadows.

López-Rojo, N., T. Datry, F. J. Peñas, et al. 2024. “Carbon Emissions From Inland Waters May Be Underestimated: Evidence From European River Networks Fragmented by Drying.” Limnology and Oceanography Letters 9, no. 5: 553–562. https://doi.org/10.1002/lol2.10408.

In Fig. 4 of the main text, and Table 3 of Supporting Information 4, units of C emissions (“Tg C-CO₂ d⁻¹” and “Tg C-CO₂ yr⁻¹”) were incorrect. In the figure, units in y-axis and in the legend should have been “t C-CO₂ d⁻¹” (tons of C-CO₂ per day) and in table, “t C-CO₂ yr⁻¹” (tons of C-CO₂ per year).

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