This study investigates the interannual variability (IAV) of the Bay of Bengal (BoB) thermohaline structure in terms of mixed layer depth (MLD), isothermal layer depth (ILD), and barrier layer thickness (BLT) over a 65-year period spanning from 1958 to 2022. This study offers a comprehensive understanding of the mentioned IAV and underlying mechanism using the ORAS5 and ERA5 reanalysis data products. Although previous studies have explored seasonal and year-to-year variability in this region, this study delves into unexplored dynamics like differential spatial response to the plausible drivers of the IAV. An empirical orthogonal function (EOF) analysis conducted on monthly anomalies of MLD, ILD, and BLT reveals that the first EOF accounts for 44.5% of the variance in ILD, 23.7% in MLD, and 22.3% in BLT, and the first principal component (PC) shows a good correlation to Niño3.4 index and dipole mode index (DMI). This analysis further reveals that the influence of El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) is restricted to the southern and eastern boundaries of the bay. The composite analysis shows that the ILD exhibits negative (positive) anomalies in the equatorial and the eastern BoB during El Niño (La Niña) years, whereas the MLD does not show a distinct response to the ENSO events. The negative (positive) ILD anomalies are also prominent in the eastern BoB during positive (negative) IOD events. Unlike the ENSO years, negative (positive) MLD anomalies are visible in the Southern BoB during positive (negative) IOD years. The above anomalous variation in the MLD and ILD results in an anomalous decrease (increase) in BLT in the eastern side during El Niño and positive IOD years (La Niña and Negative IOD years). The response mentioned above in the MLD, ILD, and BLT is linked to the interannual response of the Kelvin waves and associated Rossby wave radiation to the ENSO and IOD forcing. In the northern, central, and western BoB, salinity exerts a strong influence on barrier layer formation, likely driven by the freshwater influx through evaporation, precipitation, and river runoff; however, the exact role of river discharge in modulating the IAV of BLT remains poorly understood. Since southern BoB acts as a persistent heat source, meridional heat transport (MHT) via the eastern boundary plays a critical role in enhancing the deepening of ILD, with heat being advected northward by oceanic currents. The role of the East India Coastal Current (EICC) is also evident, with freshwater advection contributing significantly to MLD variability along the east coast of India. The influence of monsoon current is observed in the second EOF of both MLD and ILD, capturing 9% and 8.5% of the variance respectively. A strong monsoon current brings high-saline, relatively cooler Arabian Sea water into the southwest BoB, resulting in deeper MLD and shallow ILD.

How to cite: C T, S. and dey, S. P.: A Long-term Study of Interannual Variability in the Upper Ocean Thermohaline Structure of the Bay of Bengal., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-179, https://doi.org/10.5194/oos2025-179, 2025.

Seaweed plays an important role as a primary producer in the ocean, contributing significantly to the marine environmental problems such as ocean acidification, hypoxia, eutrophication, harmful algal blooms, carbon capture and sequestration. The recent results show that cultivated seaweed such as Gracilaria and wild Sargassum bed can improve DO, pH, decrease N, P concentrations and then purify water quality and improve coastal environment. Based on the seaweed bioremediation technology, resource conservation technology, and ecological enhancement technology, it is possible to increase the resources of both cultivated and wild seaweed, improve marine habitats, conserve fishery resources, and promote the sustainable development of carbon sequestration fisheries. By utilizing seaweed green feed technology, it is able to reduce greenhouse gas (e.g., methane) emissions from livestock animals. Large-scale seaweed cultivation and wild seaweed bed enhancement is an effective approach for developing low-carbon economy, increasing marine C sequestration, solving marine environmental problems and maintaining high quality development of fisheries.

How to cite: Yang, Y. F. and Chung, I. K.: Carbon sequestration effects and bioremediation role of seaweeds , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-234, https://doi.org/10.5194/oos2025-234, 2025.

This study explores the spatiotemporal evolution characteristics of mineralogy, geochemistry, and microbial diversity of sediment cores near the Tianxiu hydrothermal area on the Carlsberg Ridge in the northwestern Indian Ocean. Our research aims to elucidate the variability of hydrothermal activity across temporal scales ranging from tens of millennia to millennia, and how the spatial variation in hydrothermal iron fluxes were deposited. Additionally, we aim to investigate how microbial diversity and authigenic minerals responded to these variations.

Analysis of a distal-vent sediment core retrieved 2.2 km to the venting site of Tianxiu reveals its hydrothermal activity exhibits variability on a 10,000-year scale. Notably, significant enhancements in hydrothermal activity occurred during the deglacial periods and the Last Glacial Maximum (LGM) during the last 30,000 years, both driven by sea-level lowering but through different mechanisms: enhanced magma activity during the deglacial period due to increased partial mantle melting caused by LGM decompression and enhanced crustal permeability during the glacial period. The input of hydrothermal iron flux during the deglacial period was nearly double that of the LGM. 

Further analysis of a near-vent sediment push core TX219 obtained by submersible Jiaolong sheds light on the variability of hydrothermal depositional environments at the millennial scale. The surface 0-6 cm of the sediment core demonstrates signatures of the contribution of low-temperature diffuse flow, enriching the sediment with Fe, Cu and Zn derived from hydrothermal sources. The higher abundances of Fe, and S-oxidizers especially the presence of thermophilic microorganisms and biogenic barite and relatively light Ba isotope composition provide further evidence of the influence of low-temperature hydrothermal fluid.

Our findings contribute to a more comprehensive understanding of the dynamic interplay between hydrothermal activity, mineral precipitation, microbial communities, iron cycling, and the controlling mechanisms of a hydrothermal system.

References:

Li, M., Han, X., Qiu, Z., Fan, W., Wang, Y., Li, H., Chen, H., Hu, H., 2023. Sea‐Level Fall Driving Enhanced Hydrothermal and Tectonic Activities: Evidence From a Sediment Core Near the Tectonic‐Controlled Tianxiu Vent Field, Carlsberg Ridge. Geophys Res Lett 50(7). doi.org/10.1029/2022gl101599.

Qiu, Z., Fan, W., Han, X., Chen, X., Yin, X., 2023. Distribution, speciation and mobility of metals in sediments of the Tianxiu hydrothermal field, Carlsberg Ridge, Northwest Indian Ocean. J Marine Syst 237. doi.org/10.1016/j.jmarsys.2022.103826.

Han X., Guo H., Li H et al.,. Evolution of Hydrothermal Activity in Tianxiu Vent Field: Insights from Elemental Geochemistry, Ba Isotopes and Microbiology in Sedimentary Records. (in preparation)

How to cite: Han, X., Qiu, Z., Li, M., Li, H., Fan, W., Wang, Y., and Guo, H.: Spatiotemporal variability of hydrothermal Fe fluxes, authigenic minerals and microbial diversities recorded by sediment cores adjacent to the Tectonic-Controlled Tianxiu vent field, Carlsberg Ridge, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-660, https://doi.org/10.5194/oos2025-660, 2025.

Rivers play a vital role in the global carbon cycle, connecting atmospheric, terrestrial, and oceanic carbon reservoirs. Once viewed merely as conduits transporting carbon from land to sea, rivers are now recognized as "biogeochemical reactors" that actively metabolize organic carbon, resulting in the net emission of carbon dioxide (CO₂) and methane (CH₄). Accurately estimating the carbon budgets of rivers requires accounting for their spatial heterogeneity and diverse physical and biogeochemical characteristics, making extensive data collection a prerequisite. This study compiles a comprehensive dataset for river carbon cycling in China, including the following data: 1) flux data, such as CO₂ and CH₄ fluxes at the water-atmosphere interface and water-sediment interface, as well as the lateral organic or inorganic carbon flux exported by runoff; (2) water attributes, including dissolved and particulate organic carbon contents, partial pressure of CO₂ and CH₄, water temperature, dissolved oxygen, salinity, pH, chlorophyll content, and isotopes; (3) watershed attributes, encompassing watershed area, climate and topographic indices, and land cover/use proportions. Compared to existing dataset, this dataset covers both riverine and watershed-scale variables, making it particularly suited for integrated analysis from a systematic perspective.

How to cite: Liu, J. and Liu, Y.: A comprehensive dataset for river carbon cycling in China, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-702, https://doi.org/10.5194/oos2025-702, 2025.

We are living in a warming world, and the 21st century is warming rapidly compared to preindustrial times, according to the IPCC. Glaciers are a vital component of the Earth system. They not only store water but also vast amounts of microbes, viruses, and nutrients. On the Tibetan Plateau alone, glaciers are estimated to contain around 1023 cells, 2000 Gg of dissolved organic carbon (DOC), and 500 Gg of nitrogen. As temperatures rise, these glaciers are melting at accelerated rates, especially over the past 40–50 years. When glaciers melt, water flows into downstream ecosystems—rivers, proglacial lakes, and foreland areas, and eventually into the sea. Along with water, bioavailable nutrients and microbes are released, which may benefit oligotrophic downstream ecosystems and arid lands. However, glacier meltwater can also release potentially harmful pathogens, posing a risk to human health. This raises an essential question: is glacier melt a benefit or a threat? To address this, we focus on two scientific questions: How does glacier melting impact downstream ecosystems? And, do microbes released from glaciers pose risks to downstream communities?

How to cite: Liu, Y. and Liu, J.: The impact of glacier melting on downstream ecosystem, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-718, https://doi.org/10.5194/oos2025-718, 2025.

The Southern Ocean is a critical component of the global climate system. It controls, to a large extent, the uptake of human-generated heat and carbon into the ocean and the rate of melt of the Antarctic continental ice and consequent sea level rise. We are currently observing critical changes and extreme events in the Southern Ocean including record low levels of sea-ice extent, high temperatures, enhanced ice sheet melt, and dramatic shifts in penguin populations, plankton and benthic communities. Despite a significant growth in Southern Ocean observations over the last decade, observations of this remote and extreme environment are still sparse. This chronic lack of observations is constraining our understanding of the underlying processes of change, ability to predict potential future states and the downstream consequences for the Earth system. It is evident that expanding Southern Ocean observations will require a sustained commitment from the global scientific community, governments and international organizations, and that these efforts are integrated and coordinated into a comprehensive Southern Ocean observing system. These are core objectives of the Southern Ocean Observing System (SOOS), a body whose mission is to facilitate the delivery of a sustained and coordinated Southern Ocean observing system to provide diagnostics and understanding of current conditions, inform predictions of future states, and support policies and regulations for the benefit of society.

How to cite: Hancock, A., Henley, S., Schloss, I., Rack, W., and Meijers, A.: Southern Ocean Observing System for sustained and coordinated observations in a changing world, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-882, https://doi.org/10.5194/oos2025-882, 2025.

The ocean plays a pivotal role as a carbon sink, with microbial processes, particularly the microbial carbon pump, facilitating the transformation of dissolved organic carbon (DOC) into recalcitrant forms that support long-term carbon sequestration. This study explores the effects of nutrient enrichment on DOC utilization and microbial community dynamics through a microcosm incubation experiment using long-term incubated inert waters. We found that nutrient addition, especially in the T-4X treatment group where nutrients were added to reach four times the ambient concentrations, significantly enhanced DOC consumption. This nutrient enrichment also induced microbial community succession, favoring taxa like Bacteroidota that are known for their efficient carbon degradation. While initial increases in microbial diversity were observed, they stabilized over time. Mantel test analysis highlighted strong correlations between environmental factors, such as nitrate and microbial community structure, suggesting complex interactions between nutrient availability and microbial activity. These findings offer insights into how nutrient enrichment influences DOC cycling, microbial ecosystem dynamics, and the potential impacts of eutrophication on marine carbon sequestration processes.

How to cite: Hu, C., Zhang, M., Mu, T., Jiao, N., and Xu, D.: Effects of Nutrient Enrichment on Organic Carbon Utilization: A Microcosm Experiment Using Long-Term Incubated Inert Waters, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1586, https://doi.org/10.5194/oos2025-1586, 2025.

Methane is a short-lived greenhouse gas but has a far greater warming effect than carbon dioxide. At the same time, the livestock sector serves as a large contributor to global emissions of anthropogenic methane. Herein, this work aimed to use cultivated seaweed supplementation to reduce methane emissions and investigate the potential influencing mechanism. To evaluate the feasibility, two cultivated seaweeds, Laminaria japonica Aresch, and Porphyra tenera, along with the enzymatic hydrolysates derived from L. japonica, underwent in vitro trials, and they were both added into corn silage feed (CSF) with different concentrations (1%, 5%, and 10% of CSF) for methane reduction evaluation. The results indicated that >75% and 50% reductions in methane production were observed for the seaweeds and seaweed enzymatic hydrolysates in 9- and 30-day, respectively. Combined high-throughput sequencing and multivariate analysis revealed that supplementation with seaweed and seaweed enzymatic hydrolysates had a notable impact on the prokaryotic community structure. Mantel tests further revealed that significant correlations between the prokaryotic community and methane accumulation (P < 0.05), implying the prokaryotic community plays a role in reducing methane emissions within the rumen. Correspondingly, the networks within the prokaryotic community unveiled the crucial role of propionate/butyrate-producing bacteria in regulating methane emissions through microbial interactions. The predicted function of the prokaryotic community exhibited a significant reduction in the presence of the narB gene in seaweed-supplemented treatments. This reduction may facilitate an increased rate of electron flow toward the nitrate reduction pathway while decreasing the conversion of H₂ to methane. These results indicated the supplementation of cultivated seaweeds and the enzymatic hydrolysates has the potential to reshape the community structure of rumen microbial communities, and this alteration appears to be a key factor contributing to their methane production-reduction capability.

How to cite: Liu, J., Liu, Q., and Zheng, L.: Feeding Algae to Ruminants for Methane Reduction, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-238, https://doi.org/10.5194/oos2025-238, 2025.

The chemical oxygen demand (COD) is an essential indicator of organic pollution that represents the amount of bulk carbon in water. COD is strongly correlated with nutrient cycles and other pollutants in the environment, but it has a limited ability to quantify the amount of organic carbon (OC), of which a large proportion is made up of refractory dissolved organic carbon (RDOC) and is a potential carbon sink. Moreover, the biodegradability of OC in terms of its fate and destination should be explored, as well as how this is reflected by COD. Methods based on particle size, spectroscopy, and isotopic tracing are expected to help with deciphering the bioavailability of COD-responsive OC and explore the processes of biogeochemical cycles. As the pressure on the environment from anthropogenic inputs increases, understanding the bioavailability of OC associated with COD will help with developing more precise scientific indicators for environmental monitoring and identifying how new tools will increase knowledge of the carbon cycle. In this review, we discuss the application, scope, means, and advances of COD measurement. Based on data in the literature, we estimate the global RDOC stock and assess the impact of anthropogenic RDOC on the carbon cycle in offshore bays. This review presents new insights into the behavior of OC in aquatic environments and a potential pathway for ocean negative carbon emissions by expanding the role of RDOC as a carbon sink to offset the effect of anthropogenic carbon emissions.

How to cite: Lv, Z., Ran, X., Liu, J., Feng, Y., Zhong, X., and Jiao, N.: Effectiveness of Chemical Oxygen Demand as an Indicator of Organic Pollution in Aquatic Environments, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-295, https://doi.org/10.5194/oos2025-295, 2025.

    The efficacy of ocean iron fertilization (OIF) is limited, with the dissolution of diatom biological silica (BSi) representing a significant impediment, which results in the slow sinking and rapid remineralization of organic carbon in surface seawater. A mineral-enhanced biological pump (MeBP) strategy has been proposed, based on the use of clay minerals that agglomerate with BSi and inhibit BSi dissolution. This approach is presumed to facilitate an increase in the amount of BSi deposited and a decrease in organic carbon loss. In order to evaluate the efficacy of the MeBP strategy, montmorillonite was selected as the model clay mineral, and Chaetoceros as the model diatom in this study. A verification test was conducted in a 5-tonne water column with varying concentrations of montmorillonite. The findings demonstrated that diatoms disintegrated montmorillonite, releasing Si and Al, which were subsequently incorporated by the diatoms as framework elements to construct BSi. Al inhibits the dissolution of BSi and facilitates the aggregation of BSi with residual montmorillonite, thereby promoting the deposition of organic carbon and protecting it from degradation. The quantity of BSi present in the deposit increased by more than 18 when montmorillonite was introduced, compared to the amount observed in the absence of montmorillonite. The organic storage rate increased by more than one order of magnitude. Furthermore, montmorillonite has been observed to promote diatom blooms and delay diatom decay by modifying the diatom growth environment. Consequently, MeBP is demonstrated to be an effective approach for significantly improving the efficiency of the vertical carbon export of OIF, which represents a promising strategy for enhancing the oceanic biological pump using clay minerals.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant Nos. 42172047, 42188102), Guang-dong Basic and Applied Basic Research Foundation (Grant Nos. 2022A1515010824, 2024B1515040003), and the ONCE project.

How to cite: Liu, D., Shen, Y., Yu, R., Li, M., and Jiao, N.: Mineral-enhanced biological pump (MeBP): a promising strategy for the effective supplementation of ocean iron fertilization (OIF), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-404, https://doi.org/10.5194/oos2025-404, 2025.

In recent years, the contribution of ammonia-oxidizing archaea (AOA) to N₂O in marine nitrification processes and its coupling with carbon cycling has become a hot topic under global climate change conditions. To mitigate the greenhouse effect of N₂O, significant efforts have been made to better understand the mechanism of archaeal N₂O production. Reviewing the latest progress of archaeal N₂O production leads to the following implications: (1) Changes in the abundance of AOA under different conditions do not necessarily parallel the accompanying production of archaeal N₂O. (2) With the development of selective inhibitors, isotope techniques, and molecular technologies, the important role of AOA in global nitrogen cycling and N₂O emissions is gradually being confirmed. The expansion of global ocean acidification further alters the marine ecological environment, restricting ammonia oxidation. The expansion of oceanic oxygen minimum zones will change the vertical and horizontal distribution of dissolved oxygen (DO) in the ocean, thereby altering the N₂O metabolic processes of AOA. Given the current state of research on marine AOA production of N₂O, the study of N₂O production mechanisms and ammonia-oxidizing microorganisms is still in its infancy. It is necessary to conduct further research in the following areas: (1) Previous studies on N₂O generation mechanisms in the ocean have mainly focused on nitrifying bacteria and denitrifying bacteria, with insufficient understanding of marine AOA and a lack of sufficient AOA and N₂O distribution data to quantify AOA's contribution to N₂O generation. (2) There are very few pure strains of marine AOA that can be cultured, which makes it impossible to reproduce the nitrogen metabolic processes of marine AOA in the laboratory, representing a current challenge in N₂O generation mechanisms and AOA research. Future research needs to improve the culture medium based on the nutritional deficiencies of AOA and guide the configuration of culture media for different AOA groups by combining metagenomics. (3) The genomics of key enzymes in the aerobic/anaerobic ammonia oxidation metabolism of archaea and the electron transfer process in the ammonia oxidation process are still uncertain, requiring further exploration using isotope techniques and metagenomics. (4) There is little understanding of the in situ ecological function of marine AOA, necessitating in situ incubation experiments to discuss the contribution of AOA to the N₂O generation mechanism from the perspective of in situ ecological function. (5) Existing studies have used double 15N-18O labeling technology to determine the significant contribution of NH2OH oxidation to archaeal N₂O production and have clearly described the pathways and kinetic processes of N₂O production in AOA. This research has improved our understanding of marine N₂O production, and the multiple sources of N and O atoms in N₂O determined here should provide information for biogeochemical models aimed at solving marine nitrogen and carbon cycling. Dual isotope labeling technology can be combined with manipulation experiments of temperature, pH, DO, etc., to explore the response rate and pathways of archaeal N₂O production to ocean warming, acidification, and deoxygenation. In summary, AOA, as a major driver of marine nitrogen and carbon cycling, has become a new field in the effect of N₂O on global climate change.

How to cite: Xie, W. and Guo, Y.: Research Progresses on Mechanism of N2O Production and its coupling with carbon cycling by Marine Ammonia-Oxidizing Archaea, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-304, https://doi.org/10.5194/oos2025-304, 2025.

Heterotrophic bacteria are fundamental components of marine ecosystems and play vital ecological roles in affecting energy flowing and carbon cycling. Previous studies of microbial carbon pump (MCP) have shown that heterotrophic bacteria can mediate the transformation of marine labile dissolved organic carbon (DOC) to refractory DOC (RDOC). The RDOC and other byproducts produced by bacterial metabolism can act as nucleation sites of calcium carbonate crystals, meanwhile alkalinity of the seawater can increase due to bacterial metabolism, both of which promote the precipitation of calcium carbonate in the ocean. However, the understanding of mechanism of microbial biomineralization is still constrained. To fill the gap, we isolated several mineralizing bacteria from coral ecosystems and illustrated that arginine maybe the important regulator of microbial biomineralization although the deeper learning was needed. Our study could potentially advance the understanding of microbial biomineralization and reveal the synergistic mechanism of MCP and carbonate counter pump (CCP).

How to cite: Wang, X., Zhang, L., Tang, K., Fei, X., Yan, J., and Weng, J.: Regulation of carbon cycling by microbial biomineralization processes in the ocean, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-543, https://doi.org/10.5194/oos2025-543, 2025.

Climate change is driving unprecedented changes in both terrestrial and marine environments. The Southern Ocean, with its proximity to Antarctica, is a unique and ecologically critical region. While several studies have shed light on the ecology of macrofauna, comparative insights into microbial communities remain limited. In this presentation, I will discuss our recent work on Southern Ocean microbial communities using both amplicon and shotgun sequencing approaches. Our findings indicate that environmental factors such as temperature, salinity, depth, and water masses play a major role in shaping the diversity and functionality of these microbial communities, including viruses. I will highlight new insights into the biogeography of these communities and the impact of spatial variability on their composition. Using Marine Snow Catchers and our latest metagenomic data, we demonstrate the direct role of microbial communities in mediating carbon and nitrogen cycling. Our comprehensive gene and genome catalogue from the Southern Ocean reveals diverse consortia of microbial assemblages, including those with chemolithoautotrophic lifestyles. Collectively, these results underscore the central role of microbial communities in providing essential ecosystem services in the Southern Ocean.

How to cite: Makhalanyane, T.: Disentangling the drivers of bacterial and viral communities in the Southern Ocean , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-315, https://doi.org/10.5194/oos2025-315, 2025.

Macroalgae widely distribute in intertidal zones, one of blue carbon organisms. However, the regulatory mechanisms of tide on the carbon sequestration of macroalgae are still unclear. This study explored the effects of desiccation-rewetting cycles induced by tide on dissolved organic carbon (DOC) release from Ulva pertusa, which is prevalent from high to low tidal zones. Results showed that the DOC release of U. pertusa varied with desiccation levels, releasing 0.082, 0.22, and 0.35 mg g^-1 at 0%, 40%, and 80% water loss, respectively. During desiccation stage, DOC accumulated on the surface of U. pertusa at a rate of about 0.52 mg g^-1h^-1. Following 4 h of rewetting, DOC released surges to 3.95, 10.05, and 8.41 mg g^-1. Using a stable isotope (¹³C) tracer method, we found that most DOC released by U. pertusa come from early fixed carbon. At 40% water loss, partial DOC stemmed from newly fixed carbon. DOC composition varied with desiccation level, affecting its bioavailability. After 16 days of degradation, DOC concentrations from U. pertusa at 0%, 40%, and 80% desiccation were 1.99, 3.22, and 2.54 mg g^-1, respectively. The 80% water loss showed the highest degradation rate, while the non-water-loss treatment group had the most potential to form refractory DOC. This study underlines the complex relationship between tide and the dynamics of DOC release in U. pertusa, highlighting their role in coastal carbon cycling.

How to cite: zhihai, Z., song, Q., and zhengyi, L.: Regulation of desiccation-immersion cycle on the rate and fate of dissolved organic carbon release by intertidal macroalgae, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-400, https://doi.org/10.5194/oos2025-400, 2025.

Salt marsh wetlands exhibit high carbon capture and storage capabilities, which are crucial for mitigating climate change. However, the mechanisms of soil organic carbon (SOC) sequestration in coastal deltaic salt marsh wetlands are not well understood. To bridge this gap, we present new findings on the distribution, sources, and decomposition of SOC in the Yellow River Delta wetland, focusing on four vegetation types along a salinity gradient: Phragmites australis, Tamarix chinensis, Suaeda salsa, and Spartina alterniflora. The input of litter was found to be the primary factor affecting SOC at the depth from 20 to 100 cm, while microbial degradation and clay content were the main factors in the deeper soil layers between 20 and 100 cm. The SOC in all four communities was predominantly derived from recalcitrant organic carbon (81%–99%). A Monte Carlo model revealed that terrestrial sources accounted for 61% of SOC, plant sources for 31%, and marine sources for 8%. The vertical distribution of δ¹³C profiles in Phragmites australis and Spartina alterniflora communities was influenced by preferential utilization of ¹²C and substrate, with SOC degradation rate constants of 0.28 and 1.02 per annum (a⁻¹), respectively. The invasion of Spartina alterniflora has led to a significant increase in the easily oxidizable carbon (EOC) to SOC ratio, thus reducing SOC stability, which underscores the importance of mitigating Spartina alterniflora invasion. SOC stability was increased by evaluated salinity in the Yellow River Delta wetland, which was higher than that in Chinese coastal wetlands. 

How to cite: Zhao, G., Ni, X., and Ye, S.: Source and degradation characteristics of wetland soil organic matter along a salinity gradient in Yellow River Delta, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-410, https://doi.org/10.5194/oos2025-410, 2025.

The biogeochemical processes of organic matter exhibit notable variability and unpredictability in marginal seas. In this study, the abiologically and biologically driving effects of particulate organic matter (POM) and dissolved organic matter (DOM) were investigated in the Yellow Sea and Bohai Sea of China, by introducing the cutting-edge network inference tool of deep learning. The concentration of particulate organic carbon (POC) was determined to characterize the status of POM, and the fractions and fluorescent properties of DOM were identified through 3D excitation-emission-matrix spectra (3D-EEM) combined parallel factor analysis (PARAFAC). The results indicated that the distribution of POM and DOM exhibited regional disparity across the studied sea regions. POM demonstrated greater heterogeneity in the South Yellow Sea (p < 0.05), and in contrast, all three fluorescent components of DOM displayed a higher degree of heterogeneity in the Bohai Sea (p < 0.05). To delve into the drivers of the discrepancy, artificial neural network (ANN) models were constructed, incorporating 15 extra abiotic and biotic parameters. Under optimal parameter setting, ANNs achieved a maximum Pearson correlation coefficient (PCC) of 0.87 and a minimum Root Mean Squared Error (RMSE) of 0.23, indicative of robust fitting performance. The model identified turbidity and temperature as the most influential factors, accounting for the variation in the heterogeneity of POM and DOM across different sea regions, respectively. Additionally, the result highlighted the significant role of pico-size photosynthetic organisms among biological predictors, which may suggest their pivotal, yet often underappreciated, role in blue carbon cycles. In conclusion, this research introduces advanced deep-learning modeling techniques, providing novel insights into the biogeochemical processes of organic matter in marginal seas.

How to cite: Wang, T., Li, J., Nadarajah, S., Gao, M., Chen, J., and Qin, S.: The Abiologically and Biologically Driving Effects on Carbon Transformation in Marginal Seas Revealed by Deep Learning-Assisted Model Analysis, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-416, https://doi.org/10.5194/oos2025-416, 2025.

Ocean microalgae is the unicellular algae with 5-50 µm, absorbing CO₂ efficiency is 10-50 times that of land plant, and fixing CO₂ is more than 40% of globe. Dried microalgae contain 50% C, and 1 kg microalgae could fix about 1.83 kg CO₂. Red tide explosion has the negative effect on ocean carbon storage. Red tide cause CO₂ release to atmosphere, Ocean become the “carbon source” not the carbon sink of atmosphere CO₂; Furthermore, red tide as well as eutrophication damage the coastal eco-environment, reducing the efficiency of carbon fixation and weaking the function of carbon sink greatly. Therefore, an emergency response technology system employing hydroxyl radicals (•OH) has been developed for the red tides treatment in ship. In the system, microalgae with density ranging from 10⁵~10⁶ cells/L is pumped from the ocean surface into a primary pipeline in ship, and concentrated to densities of 10⁷~10⁸ cells/L by algal concentrator. In the main pipeline, the •OH at low concentration of 1mg/L could inactivate microalgae with the efficiency of ~100% and short time of 6~10s. The microscopic examination results showed that the algal cell integrity was maintained with •OH inactivation without the release of internal organic matters. Finally, flocculants are applied to the main pipeline to facilitate the flocculation of the dead algae. Inactivated microalgae combined with flocculant were pumped to 5 m below the surface, and subsequently sedimented to seabed. Under the conditions of low-temperature, high-salinity and high-density, the dead microalgae were forced in the deep ocean, and then enter the millennial scale carbon cycle, realizing carbon fixation and carbon storage.

How to cite: Bai, M., Zhang, Y., Liu, J., Bian, Y., Liu, Y., Long, X., and Liu, Y.: Studies on Carbon Fixation and Carbon Storage in seabed for Hydroxyl Radical-inactivated Red Tide Algae Rapidly, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-422, https://doi.org/10.5194/oos2025-422, 2025.

Most marine algae preferentially assimilate CO₂ via the Calvin-Benson Cycle (C₃) and catalyze HCO₃⁻ dehydration via carbonic anhydrase (CA) as a CO₂-compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C₄) to enhance photosynthesis. The occurrence and importance of the C₄ pathway remains uncertain, however. Here, we demonstrate that carbon fixation in Ulva prolifera, a species responsible for massive green tides, involves a combination of C₃ and C₄ pathways_, and a CA-supported HCO₃⁻ mechanism. Analysis of CA and key C₃ and C₄ enzymes, and subsequent analysis of δ¹³C photosynthetic products showed that the species assimilates CO₂ predominately via the C₃ pathway, uses HCO₃⁻ via the CA mechanism at low CO₂ levels, and takes advantage of high irradiance using the C₄ pathway. This active and multi-faceted carbon acquisition strategy is advantageous for the formation of massive blooms, as thick floating mats are subject to intense surface irradiance and CO₂ limitation.

How to cite: Liu, D.: Massive macroalgal blooms in the Yellow Sea, China: Formation and implications, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-488, https://doi.org/10.5194/oos2025-488, 2025.

The frequency of riverine floods is predicted to increase in East Asia. However, the response of coastal hypoxia (<63 μmol L⁻¹) to floods has not been well understood. In the summer of 2020, characterized by one of the most significant Changjiang water fluxes in three decades, we conducted a cruise during the flood period on the East China Sea inner shelf. Our observations n revealed severe bottom hypoxia with a maximum spatial coverage of ~11,600 km² and a minimum dissolved oxygen concentration (DO) of 21 μmol L⁻¹. In the surface layer, the relationships between salinity and nitrate, dissolved inorganic carbon (DIC) indicated significant organic matter production, validated by a high-Chlorophyll-a (Chl a) patch (>5 μg L⁻¹). Furthermore, the significant relationship between apparent oxygen utilization and DIC of deep waters reveals that the organic matter decomposition primarily drove the hypoxia during the flood period. Episodic wind events also influenced bottom DO and DIC, by transporting surface waters to the deep. Multiple-years dataset shows that the average Changjiang nitrate flux during flood years is about 1.4 times that during non-flood years. The flood waters mix with estuarine waters, forming the high-nutrient plume waters, which expanded farther offshore during the flood period. While high turbidity remained confined to the inner estuary. Consequently, the high-Chl a area significantly expanded, which significantly exacerbated the hypoxia.

How to cite: Li, D., Chen, J., Wang, B., Jin, H., Shou, L., Lin, H., Miao, Y., Sun, Q., Jiang, Z., Meng, Q., Zeng, J., Zhou, F., and Cai, W.-J.: Hypoxia triggered by expanding river plume on the East China Sea inner shelf during flood years, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-552, https://doi.org/10.5194/oos2025-552, 2025.

Mini Marine Environment Chamber System (Mini-MECS) is a mesoscale marine climate and environment simulation experimental device with the parameter control function. Its main equipment is three large experiment chambers with a diameter of 3.2m and a height of 12.5m. It can be used to carry out large-scale marine environmental ecology scientific experiments, which can not only meet the huge demand for the marine mesoscale vertical process simulation, but also ensure the number of parallel comparisons required for scientific verification. Lots of engineering techniques have been applied to construct this large-scale experiment equipment, for example structural design, ocean temperature field simulation and control and multi-parameter joint measurement. This paper introduces its construction process, technologies and experiment applications.

How to cite: Liu, Y., Huang, S., and Xue, G.: Construction and Application of Mini Marine Environment Chamber System (Mini-MECS), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-569, https://doi.org/10.5194/oos2025-569, 2025.

Geologic evidence reveals that the Earth's orbit change has significant impact on the global carbon cycle. However, the mechanism is still not fully understood. In this study, we present numerical experiment and geologic records to show that the low-latitude hydrological cycle and weathering are affected by moving perihelion. More specifically, precession of the Earth’s rotation axis alters the occurrence season and latitude of perihelion. When perihelion occurs, increasing insolation raises the moist static energy over land faster than over ocean due to differing thermal inertia. This thermodynamically moves the tropical convergence precipitation from the ocean to the land, contributing to enhancing the terrestrial precipitation and weathering over the latitudinal rain belt. Our results suggests that the insolation in individual seasons is equally important in shaping the orbital scale climate changes at low-latitude. This provides new insight on the Milankovitch theory which highlights the role of summer isolation in driving the astronomical climate change.

How to cite: Yang, H., Shi, X., Wang, X., Lohmann, G., Jian, Z., Liu, J., and Chen, D.: Moving perihelion reshape the low-latitude hydrological cycle and weathering, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-579, https://doi.org/10.5194/oos2025-579, 2025.

Human-induced nutrient input into the world's coastal waters is leading to an increase in nutrients and increasing eutrophication. However, how the functioning of aquatic ecosystems responds to these changes is still poorly understood. In this study we report on the long-term changes in nutrient regime and planktonic ecosystem function in the Daya Bay, a typical subtropical semi-enclosed bay that has experienced rapid economic and social development for several decades. Time-series data (from 1991 to 2018) were collected at a mostly quarterly resolution to visualize the long-term changes in dissolved inorganic nutrients and plankton abundances, based on which we constructed a simplified abundance size spectra (SASS) and plankton abundance ratio to describe the functioning of the planktonic ecosystem. The results showed a long-term increase in the system productivity but a decrease in integrated energy transfer efficiency of the planktonic ecosystem with increasing dissolved inorganic nitrogen (DIN) contents. Changes in the nutrient regime and functioning of the planktonic ecosystem were detected at a tipping point or threshold around 2006–2007, the shifts of which were characterized by abrupt changes in the trends of nutrient contents (phosphate, ammonia and nitrite), nutrient ratios (DIN/phosphate and silicate/phosphate), plankton abundance and total plankton biomass. Compared to the nutrient regime, the functioning of the planktonic ecosystem shifted a few years later. Overall, our findings suggest that the pelagic ecosystem in coastal waters such as Daya Bay may change significantly in response to long-term increases in human nutrient inputs. These shifts may have profound implications for fisheries production and ecosystem management in the bay.

How to cite: Gang, L., Linbin, Z., Kaizhi, L., and Yu, Z.: Increasing nutrient inputs shift the regime of marine ecosystem over decades in Daya Bay, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-820, https://doi.org/10.5194/oos2025-820, 2025.

Microorganisms consume and transform dissolved organic matter (DOM) into various forms. However, it remains unclear whether the ecological patterns and drivers of DOM chemodiversity are analogous to those of microbial communities. Here, a large-scale investigation is conducted along the Chinese coasts to resolve the intrinsic linkages among the complex intertidal DOM pools, microbial communities and environmental heterogeneity. The abundance of DOM molecular formulae best fits log-normal distribution and follows Taylor’s Law. Distance-decay relationships are observed for labile molecular formulae, while latitudinal diversity gradients are noted for recalcitrant molecular formulae. Latitudinal patterns are also observed for DOM molecular features. Negative cohesion, bacterial diversity, and molecular traits are the main drivers of DOM chemodiversity. Stochasticity analyses demonstrate that determinism dominantly shapes the DOM compositional variations. This study unveils the intrinsic mechanisms underlying the intertidal DOM chemodiversity and microbial communities from ecological perspectives, deepening our understanding of microbially driven chemical ecology.

How to cite: Tu, Q., Ji, M., and Ma, K.: Disentangling drivers of mudflat intertidal DOM chemodiversity and its relationship with microbiomes, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-829, https://doi.org/10.5194/oos2025-829, 2025.

Recent studies investigating the biological responses to ocean alkalinity enhancement (OAE) have produced varying results. Some research suggests that the impact on microbial communities is overall insignificant, while other studies indicate that certain phytoplankton, such as diatoms and nitrogen-fixing species, can benefit from OAE due to the release of biominerals. Factors including the method of OAE and especially whether it constitutes an equilibrated or unequilibrated addition of alkalinity to the ocean may be critical in determining biological responses.

Two mesocosms experiments in Guangdong to date suggested no significant microbial effects to an unequilibrated alkalinity addition of 100-200 µmol kg^-1. However, these experiments were short in duration (<1 month) in lined ponds with no benthic interactions or higher trophic levels (e.g. fish). In our forthcoming project, we will conduct longer-term (months to over a year) mesocosm experiments at million litre scale to monitor the responses of microbial and planktonic communities to an ocean alkalinity gradients under more environmentally realistic conditions than is possible in smaller incubations. Our main focus will be on prokaryotes, eukaryotes, and viruses, which encompass primary producers, grazers, decomposers, and parasites—essentially the main functional groups that mediate elemental cycles within the microbial and biological carbon pump.

We plan to sample and analyze crucial ecological parameters, including primary production, carbon fixation rates, trophic strategies, particle production and transportation rates, as well as aggregation and disaggregation processes. Additionally, we will examine community composition and biodiversity indices, while also conducting chemical measurements of inorganic carbon and biominerals, such as calcium carbonate and biogenic silica to close carbon and nutrient budgets. Finally, data collected by our collaborators will be synthesized and analyzed to address two main questions: whether OAE can lead to significant biological effects and whether side-effects alter the overall efficiency of the OAE concept with respect to altering the carbon budget.

How to cite: Li, Q., Hopwood, M., Wang, X., and Wang, Y.: Assessing the Benefits and Risks of Ocean Alkalinity Enhancement for Carbon Sequestration: Biological and Microbial Impacts, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-840, https://doi.org/10.5194/oos2025-840, 2025.

It is expected that about 600-GT CO₂ is expected to be emitted by the industrial sector for the next 50 years. In order to achieve the goal to reduce the industrial CO₂ emission by 75%, an innovative carbon capture and utilization technology should be urgently developed and implemented.  From 2050, all the flights taking off from any airport in the Europe should be fueled with jet-oils more than 70% of which should be sustainable aviation fuel (SAF). By the same year, all the petrol-based jet-fuel consumed in the US will be replaced with SAF. Therefore, 190 private companies located in 330 cities, 73% of which are in the EU or the US, are planning to produce SAF. As one of the most important jet-fuel providers in the world, Korea is finding a stable biomass source for producing SAF. Growing algae for oil extraction has attracted interest from engineers, since its lipid content is 40-60%. If CO₂ is supplemented to the algae-growing farm, a higher yield is expected.  Moreover, CO₂ is supplied to the farm as HCO₃^-, the yield can double. In this presentation, an innovative and economical strategy to produce SAF via utilizing CO₂ from industry will be presented. The feasibility of the strategy will evaluated in a holistic way.   

How to cite: Jung, N.-J. and Kim, H.: Production of Sustainable Aviation Fuel from CO2-fed Algae Farm: A beneficial way of achieving both green-energy production and CO2 reduction simultaneously, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-848, https://doi.org/10.5194/oos2025-848, 2025.

Lignin is the most abundant aromatic carbon polymer on earth. Its bioconversion is essential for the global carbon cycle and bioenergy production. Microbial communities, with their versatile enzymes and pathways, play a vital role in lignin biodegradation. The interactions among the members of a community greatly affect the performance outcome, yet it is a significant challenge to mechanistically unravel such complex interactions. Here, we developed a marine lignin degrading bacterial consortium (LD), through “top-down” enrichment. High-throughput sequencing revealed that LD is dominated by Pluralibacter gergoviae (>98%), an only identified lignin degrader, with additional rare non-degraders, e.g., Vibrio alginolyticus, Aeromonas hydrophila and Shewanella putrefaciens. Interestingly, physiological analyses suggested that the LD consortium significantly enhanced growth/degradation than the P. gergoviae alone. Thus, the additional outliers, overshadowed by P. gergoviae, are considered to be microbial “dark matter” without definitely roles in lignin degradation. Genome-scale metabolic models were constructed for P. gergoviae and three non-lignin degrading species. An integrated in silico simulation predicted that growth/degradation is boosted by metabolic exchanges between members. The metabolic profiling and culture experiments validated the predication and revealed that the non-degraders survived on metabolic intermediates from P. gergoviae, including succinate, malate, serine and PCA derivates. In return, the non-degraders fed back glycerol, aspartate, alanine, fumarate to P. gergoviae to stimulate its growth and further enhance lignin degradation. Our study revealed the inner workings of the black-box of the LD consortium, in which the microbial dark matter interacts to form a syntrophic community with P. gergoviae for lignin catabolism. Our study highlights the unrecognized role of outliers in lignin degradation, providing a valuable step forward in manipulating microbiomes for biotechnology development.

How to cite: Lin, L.: Modeling cross-feeding interactions reveals the roles of microbial dark matter in coastal terrestrial organic carbon coversion , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-850, https://doi.org/10.5194/oos2025-850, 2025.

Under climate change scenarios, seaweed (also called macroalgae) have attracted wide attention due to their significant carbon sequestration capabilities through various pathways, such as the burial of macroalgal debris or particulate organic carbon in local sediments, export to the deep ocean, and contribution of recalcitrant DOC (RDOC) to seawater. Since farmed macroalgae are harvested and removed from the ocean after maturity for various uses such as food or materials, their carbon sequestration primarily occurs during the macroalgal growth period. We revealed that the total RDOC contributed by kelp over its growth cycle equals the carbon content of the harvested kelp biomass, and a considerable portion of kelp-derived RDOC molecules can be transported over long distances and reach the deep sea. In addition, deep-sea macroalgae sinking for carbon sequestration is gaining global attention recently as a potential carbon dioxide removal (CDR) strategy. However, this strategy has faced criticism for limited understanding of its actual carbon sequestration effects and environmental impacts, as well as the ethical concerns. While, in the Yellow Sea, millions of tons of macroalg Ulva prolifera sink to seafloor annually following green tides, yet their fate and carbon sequestration capacity remain unclear. Our simulated two-year degradation of U. prolifera revealed that approximately 38% of the carbon in sunken macroalgal biomass was not respired back into CO₂, indicating significant potential for long-term carbon retention, despite its ethical and environmental impacts.

How to cite: Zhang, Y., Li, H., and Feng, X.: Underestimated carbon sequestration effects of seaweed farming  and carbon sequestration capability of sunken wild macroalgae in coastal oceans, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-959, https://doi.org/10.5194/oos2025-959, 2025.

Various mCDR activities have been proposed to reduce the atmospheric CO₂ concentration to curtail global warming and mitigate surface ocean acidification, such as coastal blue carbon, sinking crop residue, sinking macroalgae, sediment trapping, ocean fertilization, and ocean alkalinity enhancement, in recent decades. More than one hundred coastal states can technically carry out one or more such CDR activities. The efficacy and environmental impacts of significant scale of mCDR activities are not understood fully due to the absence of field scientific experiments. mCDR activities aim to modify the global atmospheric greenhouse gas composition, and the global ocean environment changes subsequently because the ocean and atmosphere are coupled. The international community, therefore, has waited for a globally transparent regulatory mechanism, such as the 2013 amendments to the London Protocol, to be universally accepted. Introducing substances or energy into the marine environment is much less costly than the efforts to assess the efficacy and environmental impact arising from such an introduction, commonly known as monitoring, reporting, and verification (MRV). Developing economies may introduce the material or energy needed, and the developed economies may transfer the required MRV technologies as a part of joint scientific research, which aligns with the Common But Differentiated Responsibilities (CBDR) formalized in the UNFCCC. Authors call for internationally coordinated scientific research for marine Carbon Dioxide Removal (mCDR) activities to meet the goals of the 2015 Paris Agreement. A more robust international governance regime will emerge by learning scientific facts through international joint scientific research.

How to cite: Hong, G. and Zuo, F.: A call for internationally coordinated scientific research for marine Carbon Dioxide Removal (mCDR) activities, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1058, https://doi.org/10.5194/oos2025-1058, 2025.

The built environment sector plays a pivotal role in providing services for people around the world and fostering economic development. Yet, it is also a major contributor to climate and ecological damage, with up to 79% of carbon emissions globally being linked to infrastructure. The built environment and infrastructure also contribute considerably to biodiversity loss and ecosystem degradation by taking up space from various native species without consideration of mitigation, restoration, or coexistence with ecology. 

The need is clear: we must prioritise solutions that protect and restore nature and biodiversity – this is where Nature-positive Engineering (NPE) comes in. By rethinking how we engineer our cities and towns, infrastructure, and energy systems, we can transform these sectors into powerful forces for ecological restoration and resilience, whilst also mitigating carbon emissions.

Nature-positive Engineering has the potential to tackle the complex and interrelated planetary crises, while simultaneously contributing to the resilience of communities and minimising the impact of engineering interventions on nature and people. Examples of nature-positive solutions include environmental protection, creation, restoration, and sustainable management of natural ecosystems, ultimately leading to an overall biodiversity net gain and to healthier, functioning ecosystems. These solutions are ecology-minded from outset, while safely delivering outcomes for people and community. 

At the One Ocean Science Congress, ICSI will launch their new publication: Foresight Review on Nature-positive Engineering (NPE). Funded by Lloyds Register Foundation and published in Q2 2025, the interactive report will bring clarity on what makes an intervention “nature-positive”, and a clear definition of NPE to support this. It will outline the progress that different organisations are currently making, how NPE approaches and solutions are implemented, and identify new and emerging trends. Finally, it will provide a framework to ensure future approaches to engineering help protect, restore and enhance natural ecosystems.

The publication will have a clear objective to mobilise the engineering profession and a particular focus on coastal and marine environments, including deep dives into: 

• Coastal protection and adaptation
• Offshore renewable energy (ORE) 
• Ports and shipping (focusing on port cities) 

The research methods for the project include extensive desk-based research and consultation with key experts and stakeholders across the engineering value chain. This includes 1:1 interviews, a global call for input (survey) and a series of regional roundtables to take place in Rio de Janeiro, Brussels, London, Nairobi, and Singapore. The roundtables will help to gather case studies of nature positive engineering in action to inform the publication, and engage a wide range of stakeholders in foresighting exercises. 

Emphasis will be placed on the value creation and scalability of NPE solutions throughout their full life cycle, ensuring safe practice and attention to biodiversity and ecosystem health and functionality are embedded at every stage from design to decommissioning. There will be a clear focus on implementation of NPE solutions and the pathway to accelerate these.

How to cite: Carluccio, S.: Nature-positive Engineering in Marine and Coastal Environments , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1205, https://doi.org/10.5194/oos2025-1205, 2025.

The application of artificial upwelling (AU) has garnered increasing scientific interest for its potential to enhance the transport of nutrient-rich bottom waters to the surface, thereby stimulating seaweed growth and increasing organic carbon removal from coastal environments. However, field experiments validating this hypothesis remain scarce. To address this issue, we developed a robust, solar-powered, air-lifted AU system to withstand harsh weather conditions while effectively fertilizing the surface ocean. This study was conducted in the oligotrophic Aoshan Bay, Shandong Province, China, to assess the impact of the AU system on regional carbon removal. Comparative analysis of temperature and nutrient profiles between AU-affected sites and reference locations indicated successful lifting of nutrient-rich waters to the surface. Our findings demonstrate that AU significantly stimulated seaweed growth, with the average weight of individual plants increasing by 8.98 grams. This approach could potentially lead to an additional carbon removal capacity of approximately 14.8 thousand tons in coastal waters, if implemented along the Chinese coastline.

How to cite: Fan, W., Liu, J., Qu, M., Zhang, Y., Zou, Z., and Chen, Y.: Utilizing Artificial Upwelling to Enhance Carbon Removal by Stimulating Seaweed Cultivation, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1582, https://doi.org/10.5194/oos2025-1582, 2025.