This session seeks to bring together scientists from multiple disciplines, including biogeochemists, ecologists, geographers, geologists, social scientists, biologists, alongside environmental managers.
By bridging perspectives across the natural and social sciences, the session aims to showcase pioneering research that i) advances understanding processes related to biomass and carbon in blue carbon ecosystems under current and future environmental conditions; and ii) spotlights effective management, conservation, and restoration practices to sustain or enhance carbon sequestration and broader ecosystem services, coupling the ecological functioning with social needs. Through this integration, the session will contribute to the goals of the United Nations Decade for Ocean Sciences, with co-convenorship from the Decade Programme for Blue Carbon in the Global Ocean.
Restoration of coastal wetlands provides climate adaptation and mitigation benefits. However, there is still limited information on the effects of climate change-driven events on restoration projects. We assessed the changes in soil greenhouse gas fluxes (GHG; methane, CH4, carbon dioxide, CO2, and nitrous oxide, N2O) on a site previously used for sugarcane production currently undergoing tidal reinstatement in subtropical Australia. Simultaneously, we sampled two natural reference mangrove sites. Sampling was conducted over three years, encompassing summer and winter seasons, before and after tidal reinstatement, and after the landfall of a cyclone. Before tidal reinstatement, GHG emissions at the restoration site were low and similar to those from the reference sites. After tidal reinstatement, soil conductivity increased from zero to 5.9 ± 2.3 dS m-1, and the soil organic carbon increased by 38%, while GHG emissions remained low. After the tropical storm, a large peak in CH4 was measured at the restoration site (3,661 ± 1,719 µg m-2 hr-1) and at one reference site (7,588 ± 2,193 µg m-2 hr-1); small N2O uptakes were also recorded in the restoration (-2.2 ± 0.5 µg m-2 hr-1) and reference sites ( -0.7 ± 0.1 µg m-2 hr-1). The fluxes were associated with prolonged freshwater flooding and reduced soil conditions (-0.3 ± 12 mV and -151 ± 96 mV, respectively) caused by extreme rainfall. Nevertheless, the emissions from this event did not undermine the carbon sink potential of the restoration project, whose annual emissions (0.8 Mg CO2eq ha-1 yr-1), even for years with cyclones (1.5 Mg CO2eq ha-1 yr-1), remained lower than those from the former agricultural land use (2.6 Mg CO2eq ha-1 yr-1). Climate change will increase the likelihood of extreme rainfall events; however, mangrove restoration projects are likely to remain carbon sinks.
How to cite: Adame, F., Iram, N., Pearse, A., Hall, J., Bennion, V., Lovelock, C., Rummell, A., Marshall, S., Webb, G., Glamore, W., Chalmers, G., Olds, A., Keith, H., and Smart, J.: Restored coastal wetlands emit high levels of methane after a cyclone, but remain carbon sinks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15877, https://doi.org/10.5194/egusphere-egu26-15877, 2026.
Mangroves are among Earth's most carbon-dense ecosystems, yet belowground carbon cycling remains poorly understood compared to aboveground processes. Root exudation, the release of labile organic compounds from live roots, represents a critical pathway for transferring plant-derived carbon to soils. However, exudation has never been quantified in situ in mangroves due to technical challenges. Here, we developed and applied a sealed-cuvette system to quantify root exudation across two dominant species (Avicennia alba and Rhizophora apiculata) and contrasting wet–dry seasons in a deltaic mangrove (Can Gio, Vietnam). Mean root exudation rates were 0.135 ± 0.035 mg C·g⁻¹·h⁻¹ for Avicennia and 0.078 ± 0.017 mg C·g⁻¹·h⁻¹ for Rhizophora, with seasonal rates (pooled across both species) of 0.060 ± 0.013 mg C·g⁻¹·h⁻¹ for the wet season and 0.103 ± 0.031 mg C·g⁻¹·h⁻¹ for the dry season. Gamma GLMs testing for effects of species and season revealed no statistically significant differences in exudation rates (species: p = 0.093; season: p = 0.16), though substantial individual-level variation was observed within each group. Mangrove root exudation rates were comparable to global averages reported across terrestrial ecosystems (~0.058 mg C g⁻¹ h⁻¹), indicating similar root-level carbon release despite contrasting environmental conditions. When multiplied by mangroves' extensive fine-root biomass, and scaled to hectare and annual timescales, preliminary estimates suggest the exudation flux may represent a non-negligible and previously unaccounted-for component of mangrove carbon budgets.
How to cite: Hanemann, L., Maillard, L., Dang, H. T., Huot, H., Rumpel, C., Gunnell, Y., Dahdouh-guebas, F., Le, T., Bui, N. T. K., and Arnaud, M.: Root exudation: meassuring a missing component of carbon flux estimates in mangroves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11818, https://doi.org/10.5194/egusphere-egu26-11818, 2026.
Seagrass ecosystems are major sinks of sedimentary organic carbon (Corg), but the temporal changes of the Corg following the seagrass loss remains limited, particularly across different gradients of disturbance severity. In this study, the temporal changes of the sedimentary Corg across nine intertidal seagrass meadows along Andaman coast and Gulf of Thailand were estimated, by combining historical data sets (2015-2021) with the field re-sapling in 2025 following the same protocols. Sediment properties and Corg stocks were analyzed for the surface sediments (0-20 cm) and whole sediment cores using mixed effect models.
Sites that were affected by the long-term or complete seagrass loss had substantial decline in sedimentary Corg stocks, with annual losses up to 17 Mg C ha⁻¹ yr⁻¹ and associated potential CO2 emissions over 60 Mg CO₂ ha⁻¹ yr⁻¹. These Corg losses are accompanied by decreases in dry bulk density and Corg content, indicating sediment softening and destabilization and reduced organic inputs. On the other hand, sites with partial loss and intact seagrass meadows showed different trajectories: some meadows retained long term Corg stocks with some surface losses, while others exhibited net declines in both surface and long term Corg stocks despite low changes of Corg content. This indicates that Corg enrichment does not ensure long-term carbon retention where physical sediment reorganization and lateral redistribution dominate.
Our results demonstrate that seagrass loss severity and sediment physical dynamics jointly regulate sedimentary carbon stability and CO₂ release. Distinguishing between surface reworking and whole-core carbon loss is therefore essential for accurately assessing blue carbon vulnerability and for integrating seagrass degradation into coastal carbon budgets, greenhouse-gas inventories, and climate mitigation strategies.
How to cite: Stankovic, M., Hayeewachi, L., Halim, M., and Prathep, A.: Blue carbon dynamics following widespread seagrass loss across tropical coastal sediments in Thailand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3244, https://doi.org/10.5194/egusphere-egu26-3244, 2026.
The mangrove wetlands are recognized as very important in the process of carbon sequestration, but the fluctuation in salinity, the development of the aquaculture, and deforestation pose a threat to the ecological balance and the welfare of the local society. Our long term study at the Indian Sundarbans on restoration model of mangrove ecosystems revealed interconnectivity of community participation and multispecies mangrove restoration on blue carbon pool. In this study, five mangrove species (Avicennia marina, Bruguiera sexangula, Ceriops tagal, Rhizophora mucronata and Xylocarpus moluccensis) were investigated in a degraded mudflats area of 102 hectares located on Satjelia Island on how they can be restored. The analysis of geochemical indicators of soil, including organic carbon (SOC) and organic carbon density (OCD), humic and fulvic acids, and the evaluation of community participation contribute to creating a comprehensive picture of what the ecosystem recovery process is all about.
It can be seen that introduction of Avicennia marina as a propagule, using a dibbling technique has been a notably successful one, as there is low cost per survivor and a notable growth rate in OCD of more than 90 per cent over a five-year time. An analysis of chronosequence suggests that the mangrove plantations have significantly increased the sequestration of carbon in the uppermost soils layers which provides a stark difference to the insignificant increases in the natural Proteresia coarctata mudflats. Local communities involvement through forest committees has also played a big role in the survival of saplings, reduction of grazing pressures as well as the overall success of the restoration efforts. Study indicates a better blue carbon pool and survival rate of species (R. mucronata, S. caseolaris and A. marina) for community managed restoration site. This research highlights the need to integrate the ecological and community level interventions by means of a multisided approach for an effective mangrove restoration. The findings show that the recovery of the mangrove ecosystems can result in desirable modifications on the soil geochemistry, as indicates by geochemical carbon indicators such as humic acid, fulvic acid and blue carbon pool, which can contribute to the increase of the coastal resilience. Furthermore, the combination of these activities with participatory governance models is a scalable and powerful approach to a contribution to the global climate change mitigation agenda including REDD+ and SDG14 targets. The example of the Indian Sundarbans is the way in which mangrove can be restored as a two-fold solution to serve dual objectives, both environmental and community development, and be a precursor to community-based climate action projects.
How to cite: Chowdhury, A., Naz, A., and Bhattacharyya, S.: Geochemistry Meets Community: Multispecies Mangrove Restoration Driving Blue Carbon Sequestration in the Indian Sundarbans, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1867, https://doi.org/10.5194/egusphere-egu26-1867, 2026.
Saltmarshes accumulate and store organic carbon through the drawdown of atmospheric CO2 by photosynthesising vegetation (autochthonous carbon), and the deposition of externally derived carbon (allochthonous) during tidal inundation. These organic carbon sources can be different ages and remain stored in the soil for variable lengths of time, from minutes to millennia. International policy frameworks recognise that the management of saltmarshes can provide a climate mitigation service, yet uncertainties remain regarding the inclusion of allochthonous organic carbon in saltmarsh projects.
We employed a novel methodology to compare the radiocarbon (14C) contents of saltmarsh soils and CO2 evolved from aerobic laboratory incubations to show that young (14C-enriched) organic carbon is preferentially respired over old (14C-depleted) organic carbon. The 14C contents of the respired CO2 were compared to the 14C content of carbon pools defined by their thermal reactivity, measured by ramped oxidation. In most cases, the 14C content of the most thermally labile carbon pool was closest to the 14C content of the CO2 evolved from aerobic incubations of the same soils, suggesting the thermal and biological lability of saltmarsh soil carbon in oxic conditions is closely related. These results highlight the role of saltmarshes as stores of both old, thermally recalcitrant organic carbon, as well as younger, thermally labile organic carbon. Management interventions, such as restoration, may help mitigate CO2 emissions by limiting oxygen exposure and preserving these stores of thermally labile carbon.
We also highlight inconsistencies in the treatment of allochthonous carbon across blue carbon (saltmarsh, seagrass and mangrove) accounting methodologies. A review of these frameworks and their scientific basis reveals a lack of standardized, evidence-based approaches for determining the proportion of allochthonous carbon that should be discounted in additionality calculations. This research provides crucial evidence towards addressing these gaps and improving the robustness of blue carbon policy and accounting.
How to cite: Houston, A., Garnett, M. H., and Austin, W. E. N.: Sources, Sinks and Subsidies of Organic Carbon in Saltmarsh Habitats , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5773, https://doi.org/10.5194/egusphere-egu26-5773, 2026.
The Paris Agreement aims to keep the global temperature rise under 2°C, which is implemented through National Greenhouse Gas Inventory Reports (NIRs) and Nationally Determined Contributions (NDCs). Blue carbon ecosystems, despite substantive climate change mitigation potential, remain underutilised in the Paris Agreement. We analysed over 1700 NDCs and NIRs submitted since 2015 to identify inclusion and quantify mitigation gaps in the utilisation of blue carbon ecosystems (mangroves, seagrasses, tidal marshes, and tidal flats) in the context of the Paris Agreement. 33% of the blue carbon-holding countries have incorporated them into NIRs, and 19% have set quantifiable NDC targets, with Non-Annex I Parties making much of this contribution. Only 13.4 Gt CO₂ eq of blue-carbon mitigation is currently pledged, yet Non-Annex I Parties hold nearly twice the untapped potential (68.7 Gt CO₂ eq) compared to Annex I Parties (35.5 Gt CO₂ eq), highlighting both the opportunity and the imbalance. Full protection and restoration of blue-carbon ecosystems could sequester 122.3 Gt CO₂ eq by 2050—roughly 2.5 years of global emissions from all sectors. Closing this gap would elevate blue carbon from a marginal opportunity to a core component of global mitigation, while enhancing the resilience and improving the livelihoods of coastal communities.
How to cite: Bhargava, R., Kadri, A., Adame, M. F., Bhatia, N., Macreadie, P. I., van Breugel, M., Qu, S., Bukoski, J., Baez, S., Cifuentes-Jara, M., Tang, H., and Friess, D. A.: Ambition Disparity Reveals Unlocked Mitigation Potential for Blue Carbon in the Paris Agreement , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-165, https://doi.org/10.5194/egusphere-egu26-165, 2026.
The Voluntary Carbon Market (VCM) relies on a handful of validated standards, each one counting with a suite of methodologies, tools, and templates. In the past few years, Blue Carbon Ecosystems (BCEs), most prominently mangrove ecosystems, have gained a lot of attention due to their remarkable capacity to store much higher amounts of carbon than terrestrial forests. Nevertheless, mangroves may offer more complexities to conservation and restoration that range from sea-level rise to human-induced encroachment. Carbon standards have much improved their thoroughness so the attend to those complexities, especially regarding the contribution of and impact on communities and the hydrological and sedimentological requirements for a healthy ecosystem. The higher level of demands for a responsibly established project usually represents higher initial costs, e.g., feasibility study (FS) and project development document (PDD), and a longer period for revenue from the investor’s perspective. This is perceived as a negative scenario due to the market’s nature of rapid profit and revenue, thus, pushing blue carbon projects to a halt even before implementation. Here, we discuss what are the key-factors representing a conflict of interest between conservation, restoration, and VCM implementors, and make recommendations on how to overcome such dispute to achieve the promotion of BCEs around the globe.
How to cite: Abuchahla, G., Nasution, M., Pradana, H., Ramadhana, F., and Saavedra-Hortua, D.: How the Current Blue Carbon Project Standards hinder Mangrove Conservation and Restoration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10656, https://doi.org/10.5194/egusphere-egu26-10656, 2026.
The proliferation of invasive alien species (IAS) is one of the main threats to the conservation of estuarine habitats, including saltmarshes. Differences between IAS and their native counterparts in structural traits (e.g. plant size, biomass allocation, shoot stiffness) and chemical composition (e.g. nutrient and lignin content) can affect the accumulation and long-term storage of organic carbon (OC) in saltmarsh sediments. However, the impact of IAS colonization on sedimentary carbon sinks in saltmarshes remain largely unexplored, particularly in Europe. Existing studies are scarce and focus primarily on the herbaceous species Spartina alterniflora, while no research has yet assessed the impact of the spread of woody shrub species such as Baccharis halimifolia, one of the main IAS in European estuaries. This study examines organic carbon (OC) stocks, 210Pb-derived accumulation rates and the molecular composition of the organic matter (i.e. through pyrolysis techniques) in 12 sediment cores sampled across native saltmarsh (i.e. Juncus maritimus and Spartina maritima) and invasive saltmarsh communities (i.e. Spartina alterniflora, Spartina anglica and Baccharis halimifolia) in the Gulf of Biscay. The results of this study serve as a basis for the implementation of conservation and restoration actions in saltmarsh environments that address both biodiversity and climate change mitigation goals.
How to cite: Mazarrasa, I., Arias-Ortiz, A., Kaal, J., Morán, S., Juanes, J. A., and Ondiviela, B.: Impact of the spread of invasive alien species in saltmarshes sedimentary carbon sinks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10706, https://doi.org/10.5194/egusphere-egu26-10706, 2026.
Salt marshes are among the most carbon-dense ecosystems on Earth, yet their net climate benefit depends on carbon exchanges across the atmosphere-soil-water continuum, including lateral export to adjacent coastal waters. Most mechanistic understanding of lateral exchanges is derived from warm-season observations, leaving uncertainties about how cold-season conditions regulate soil-water connectivity and associated solute and carbon transport. We address this gap using year-round, high-frequency measurements of soil temperature, groundwater and surface-water elevations, and tidal creek discharge across multiple New England salt marshes (Gouldsboro, northern Maine; Wells, southern Maine; and Chatham, Cape Cod, Massachusetts). Soil temperatures decreased with latitude, and sustained freezing occurred at both Maine sites from December through mid-March. Within marshes, freezing was strongly elevation-dependent: creek beds remained unfrozen due to persistent exposure to relatively warm, saline seawater, whereas higher-elevation platforms that were inundated less frequently froze to depths of 25-30 cm. Despite frozen ground, we observed minimal seasonal changes in water-table fluctuations. However, reduced hydraulic conductivity during winter suggests diminished but ongoing water and solute exchange between marsh sediments and tidal creeks. Together, these observations indicate that cold-season freeze-thaw alters marsh-creek exchange but does not eliminate lateral water and solute export to tidal channels. Incorporating cold-season controls on marsh-creek exchange and lateral export into marsh carbon assessments is essential for closing year-round carbon budgets and evaluating blue carbon under changing winter conditions and inundation regimes.
How to cite: Guimond, J., Boles, E., Cartafalsa, T., Eagle, M., and Tamborski, J.: Accounting for winter: freeze-thaw controls on salt marsh-creek water and carbon exchange, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2336, https://doi.org/10.5194/egusphere-egu26-2336, 2026.
Saltmarshes trap and store organic matter from different sources with different soil turnover times. Constraining drivers of variability in soil organic matter turnover are crucial for quantifying the potential climate mitigation achieved through targeted management interventions on saltmarsh habitats (e.g., restoration). Better constraining saltmarsh soil organic matter turnover on a continental scale would improve the scientific evidence base for the integration of these important carbon stores into policy frameworks and guide priority actions and decision making.
We undertook thermogravimetric analysis of newly collected and archived samples to measure the thermal reactivity of saltmarsh soil organic matter across Europe. Here, we present the first estimate of saltmarsh soil organic matter reactivity on a pan-European scale. We present preliminary evidence to suggest that saltmarsh soils which have larger stores of thermally labile organic matter generate higher greenhouse gas fluxes under exposure to aerobic conditions. We propose that measuring the thermal lability of soil organic matter could be useful when targeting management actions on saltmarsh habitats to achieve emissions reductions.
If you would be interested in contributing samples (these can be cold-stored or dried archival material, or potentially new collections) and being part of a collaborative effort to understand the reactivity of the organic matter stored in pan-European saltmarshes, please visit this poster.
How to cite: Austin, W. and Houston, A.: Pan-European Assessment of Saltmarsh Soil Organic Matter Reactivity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8226, https://doi.org/10.5194/egusphere-egu26-8226, 2026.
Vegetated coastal communities are main sources of the marine dissolved organic matter (DOM), which may enter into the food chain (i.e. labile DOM) or remain stored in the ocean for longer periods (i.e. recalcitrant DOM), contributing to the blue carbon pool [1]. In particular, microbial utilization and processing of labile molecules of DOM is a key process that modifies the chemical composition and reactivity of DOM, ultimately resulting in the accumulation of resistant molecules [2]. In recent years, a growing number of studies have shown that the chemical characterization of DOM at molecular level using ultra-high resolution mass spectrometry (UHRMS) can provide key information on the sources, transformations, and fate of marine DOM [3]. This study was aimed to characterize at molecular level the labile, bacterial metabolism-derived, and recalcitrant fractions of DOM associated to three blue-carbon communities: the seagrasses Cymodocea nodosa and Zostera noltei, and the macroalga Caulerpa prolifera. For this purpose, a bioavailability experiment was conducted using seawater (free of microorganisms) from each community and a coastal bacterial inoculum. The viability of the cultures was confirmed by the decrease of dissolved organic carbon concentration and the increase of bacterial abundance observed in all communities at the end of the experiment. The solid-phase extraction of DOM followed by UHRMS analyses allowed the assignment of molecular formulas to compounds present in DOM at the beginning and at the end of experiment. The results showed that the percentage of molecular formulae that disappeared during bacterial cultivation (i.e., labile compounds) varied among communities, with the following trend: C. prolifera (55%) > C. nodosa (50%) > Z. noltei (38%). Representation of these molecular formulae in a van Krevelen diagram showed that a significant number of them were in the regions of compounds considered to be easily bioavailable, such as lipid-, peptide-, amino sugar- and carbohydrate-like compounds. On the other hand, the molecular formulae that were detected at the beginning and at the end of the culture (9-12%) were assigned to compounds resistant to degradation, and most of them fell in the diagram within the chemical classes expected for recalcitrant molecules (lignin- and tannin-like regions). These results provide insights into the molecular composition of DOM in blue carbon ecosystems, showing that the lability/recalcitrance of DOM, and hence the potential contribution to the blue carbon pool, seems to depend on the dominant species.
[1] Carlson, C. A. and Hansell, D. A. 2015. “DOM sources, sinks, reactivity, and budgets” In Biogeochemistry of marine dissolved organic matter (second edition), edited by D. A. Hansell and C. A. Carlson. Academic Press, Boston, MA, 65-126 pp.
[2] Li, H., Zhang Z., Xiong, T., Tang, K., He, C., Shi, Q., Jiao, N., Zhang, Y. 2022. Carbon sequestration on the form of recalcitrant dissolved organic carbon in a seaweed (kelp) farming environment. Environ. Sci. Technol. 56: 9112-9122.
[3] Qi, Y., Q. Xie, J. J. Wang, et al. 2022. “Deciphering dissolved organic matter by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS): from bulk to fractions and individuals.” Carbon Res. 1: 3.
How to cite: Casal Porras, I., Brun, F. G., Pérez Lloréns, J. L., and Zubía, E.: Molecular profile of labile and recalcitrant dissolved organic matter in coastal vegetated communities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13763, https://doi.org/10.5194/egusphere-egu26-13763, 2026.
email-charukasadanruwan@gmail.com
Abstract
Seagrass leaves provide microhabitat for epiphytic organisms but knowledge on epiphytic fauna and associated bionts in seagrass are limited. In addition, seasonal changes in population structure of epiphytic communities have not been studied widely under Sri Lankan context. This abstract presents the diversity and abundance of filamentous epiphytic algal communities on the leaves of Oceana serrulata in Kayankerni Marine Sanctuary in Eastern coast of Sri Lanka. Leaves of Oceana serrulata were collected once a month from August 2024 to January 2025 and preserved with 5% formaldehyde. Leaves were measured and divided into three similar sections and labelled as tip, middle, basal parts. Ten randomly selected leaves per month were subjected to identify the filamentous epiphytes and their abundance. Epiphyte species were identified up to genus level using guide, key and published literature. Percentage epiphytic cover of each section of leaves was estimated using the microscopic field as the sample unit under 10*10 magnification. Shanon-Wiener diversity index, Pielou’s evenness index and Dominance index for each month calculated. Arcsine converted data of epiphytic cover on entire leaf-blades among different months were compared using ANOVA to identify the temporal variations. In addition, the percentage epiphytic cover of each species among sampling occasions were compared using ANOVA. Six genera of filamentous epiphytes were reported from leaf blades and were Ulva, Gayliella, Hydrolithon, Myrionema, Herposiphonia and Calaconema. Genus Ulva reported three (03) distinct species while others reporting single species each accounting the species richness of filamentous algae up to eight (08). Percentage epiphytic cover on the leaf blades was ranged from 11.25% to 1.18% reporting the highest epiphytic cover in August and lowest in January. Contribution of different genera to total epiphytic cover was reported as follows: Ulva spp. (27.87%), Gayliella sp. (26.63%), Hydrolithon sp. (22.04%), Myrionema sp. (12.03%), Herposiphonia sp. (11.04%), and Calaconema sp. (0.38%). The abundance of Gayliella sp., Herposiphonia sp., Ulva sp.1, and Ulva sp.2 have been reducing gradually from August to January, while Myrionema sp. and Ulva sp.3 were reported throughout the sampling period in low abundance. Calaconema sp.was reported varying levels in low abundance during the sampling period. Abundance of Gayliella sp. and Herposiphonia sp. was significantly higher (p<0.05) in November compared to other months. Ulva sp.1 was significantly higher in September and November (p<0.05) than other months. Hydrolithon sp. was significantly higher (p<0.05) in November than other months. Abundance of Ulva sp.2, Calaconema sp., Myrionema sp., and Ulva sp.3 have no significant differences (p<0.05) among the months. Shanon-Wiener diversity index has been gradually reduced from August (1.66) to January (0.48). Shanon-Wiener diversity index change in different parts with following pattern tip<middle<base in each month respectively. Pielou’s evenness index was reported 0.80,0.81,0.69,0.77,0.91 from August to December and significant reduction in January (0.35). The dominance index was highest in January (0.76) and ranged from 0.23 to 0.32 from August to November respectively. These results indicate the changes of epiphytic diversity on Oceana serrulata during the Sampling period and their abundances.
Keywords: Seagrass, Filamentous marine algae, Diversity indices, Temporal changes in marine epiphytes
How to cite: Sandaruwan, C., Kelum Wijenayake, H., Jayakody, S., De Silva, S., Van Keulen, M., and Udagedara, S.: Filamentous epiphyte diversity and abundance on the leaves of Oceana serrulata in Kayankerni Marine Sanctuary of Sri Lanka, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-344, https://doi.org/10.5194/egusphere-egu26-344, 2026.
Marine macrophytes play a significant role in the marine carbon cycle by releasing dissolved organic carbon (DOC), including a recalcitrant fraction with potential for long-term carbon sequestration. Here, we investigated how warming and the presence of an invasive species affect DOC dynamics in different native temperate macrophyte communities (Zostera noltei, Cymodocea nodosa and Caulerpa prolifera) from the south of the Iberian Peninsula, a transitional habitat between Atlantic and Mediterranean marine regimes. Additionally, we introduced a standardized framework to link DOC release to internal carbon content, facilitating comparisons of blue carbon pathways among macrophyte communities across diverse ecosystems. Controlled mesocosm experiments across three temperatures (24, 26 and 28 °C) revealed that the presence of the invasive seagrass Halophila stipulacea did not significantly alter the carbon metabolism or DOC fluxes of native macrophytes. However, temperature significantly affected both the quantity and composition of the released DOC. In particular, recalcitrant DOC decreased by 28%, while labile DOC increased by a similar proportion as temperature rose, and bioavailable DOC decay rates also declined significantly at higher incubation temperatures of the tested macrophytes. These results suggest that warming may enhance both net and labile DOC production, while the remaining DOC is less bioavailable than that produced at lower temperatures. This clearly indicates that warming restructures DOC composition, potentially reducing coastal carbon storage capacity and the role of recalcitrant DOC. By applying our proposed standardization, we estimate that the recalcitrant fraction produced in the tested macrophyte communities was comparable in magnitude, although 1.41 higher, to the carbon burial rates in the sediment measured in the same communities, which underscores the potential contribution of recalcitrant DOC produced by macrophyte communities to the long-term carbon storage. This standardized approach positions recalcitrant DOC as a crucial climate-sensitive blue carbon pathway that should be integrated into global carbon budget estimates.
How to cite: Yamuza Magdaleno, A., Azcárate-García, T., Egea, L. G., Álvarez-Salgado, X. A., Reuter, H., Brun, F. G., and Beca-Carretero, P.: Temperature Modulates Recalcitrant Dissolved Organic Carbon Production by Coastal Macrophytes: An Underestimated Blue Carbon Pathway, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1285, https://doi.org/10.5194/egusphere-egu26-1285, 2026.
Mangroves are increasingly positioned at the centre of “blue carbon” strategies, yet carbon-centric planning can obscure the broader ecosystem service (ES) bundle that underpins coastal resilience, biodiversity outcomes, and social legitimacy. We synthesize how multiple mangrove ES are studied alongside carbon sequestration and discuss implications for regions that may become suitable for mangroves under climate change, with a brief connection to ongoing coastal forest research on Jeju Island, Republic of Korea.
We searched Web of Science using “mangrove*”, “blue carbon”, and “carbon”, screened 813 records, and analysed 423 site-based studies. Each study was coded by country, research approach (experiment, observation, modelling, remote sensing, secondary synthesis, survey/interview, and policy analysis), and ES classes using the Common International Classification of Ecosystem Services (CICES v4.3). Research effort was geographically uneven across 59 countries (plus global multi-region studies), and study effort increased with national mangrove extent (Spearman ρ = 0.53, p < 0.0001), indicating that evidence is concentrated where mangroves already dominate coastal landscapes.
Multi-service integration was limited: only ~22% of studies investigated more than one ES, restricting insight into synergies and trade-offs required for robust management and safeguards. Regulating services dominated the co-assessments with carbon sequestration, most commonly nutrient cycling, soil formation, and coastal protection. Provisioning services (e.g., fishing and biomass) and cultural services (e.g., recreation) were studied less frequently. Critically, stakeholder engagement remained minimal, only ~5% of studies incorporated perspectives from local communities, policymakers, or other relevant groups, highlighting a gap between biophysical evidence and decision pathways that govern implementation, equity, and long-term maintenance.
These evidence gaps are increasingly consequential under climate-driven poleward expansion. Jeju Island is a subtropical - temperate transition zone where true mangroves are not yet established, but semi-mangrove species (e.g., *Hibiscus hamabo* and *Paliurus ramosissimus*) occur within coastal shrub, forest mosaics and provide regulating and habitat functions comparable to widely cited mangrove co-benefits. Current monitoring by the National Institute of Forest Science is structuring protocols that jointly quantify vegetation structure and composition, plant physiological performance, and carbon pools (aboveground biomass and soil carbon), while also documenting co-benefits relevant to coastal hazard buffering and biodiversity conservation.
We conclude that mangrove planning, especially in future-suitable regions, should shift from single-metric carbon optimisation to a multifunctional ES framework supported by harmonised monitoring and early stakeholder integration to anticipate trade-offs and maximise durable climate, biodiversity, and livelihood outcomes.
This research was conducted at the Warm-Temperate and Subtropical Forest Research Center, National Institute of Forest Science (Project No. FE-2022-04-2025).
How to cite: Lee, B., Lee, H., Kim, H., and Park, E.: Integrating Multiple Ecosystem Services into Mangrove Management: Evidence Synthesis and Insights from Emerging Habitats in Jeju Island (Korea), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6286, https://doi.org/10.5194/egusphere-egu26-6286, 2026.
Mangrove forests provide critical ecosystem services, including carbon sequestration, coastal protection, and support for local livelihoods. Although global conservation efforts have slowed the rate of mangrove area loss, degradation remains a persistent challenge, particularly in rapidly urbanizing coastal regions.
In megacities such as Mumbai, India, mangrove conservation policies are in place. However, intense urban development, population growth, and pollution pressures continue to undermine ecosystem functioning. Nutrient influx from urban sewage has caused pronounced eutrophication, potentially constraining mangrove productivity and carbon storage capacity. At the same time, conservation policies have often been implemented with limited participatory engagement, restricting traditional access to mangrove resources by the indigenous fishing community known as the Kolis. As a result, the perceptions and knowledge of the Koli community remain weakly integrated into mangrove conservation in Mumbai.
This study aims to elucidate the temporal progression of mangrove degradation accompanying Mumbai’s urbanization and to examine how the life experiences and environmental perceptions of the Kolis have transformed over this period. We adopted an interdisciplinary approach integrating ecological and social data. Ecological assessments included water quality measurements and nitrogen stable isotope (δ¹⁵N) analysis of tree rings of Avicennia marina, used as a time-integrated indicator of anthropogenic nitrogen. These data were complemented by semi-structured and group interviews with the Kolis, focusing on changes in mangrove use, livelihoods, and environmental conditions.
The results show elevated δ¹⁵N values recorded in the tree rings of mangroves growing in close proximity to sewage sources, indicating sustained anthropogenic nitrogen inputs over time. Meanwhile, the Koli communities demonstrated a clear awareness of environmental changes in mangrove forests and reported that fisheries commercialization, urbanization, and environmental policies have substantially altered their relationships with mangrove ecosystems. Importantly, local perceptions of environmental change were found to be largely consistent with the ecological evidence. These results underscore that the local communities, such as the Kolis, play a frontline role in perceiving environmental change, and that their knowledge is essential for effective mangrove conservation in urban coastal areas.
This study demonstrates that mangrove degradation in urban coastal areas is reflected in both ecological indicators and local environmental perceptions, highlighting the importance of integrating local knowledge into mangrove degradation assessment and conservation strategies.
How to cite: Uruma, K., Ohte, N., and Srivastava, S.: Mangrove Degradation in a Megacity: Linking Tree-Ring δ¹⁵N with Local Ecological Perceptions in Mumbai, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8199, https://doi.org/10.5194/egusphere-egu26-8199, 2026.
Lagoons are recognized as net sources of carbon dioxide (CO2) to the atmosphere, with pronounced spatial and diurnal variability in partial pressure of CO2 (pCO2) and air–water CO2 fluxes. Furthermore, these spatiotemporal variabilities are affected by seasonal weather changes associated with the terrestrial inputs from nearby human activities on land. Such dynamic pCO2 variations rely on a high-density sampling strategy, with five to six lab-made CO2 buoys deployed for over 24 hours across Chiku Lagoon, Tainan, Taiwan, measuring water temperature, salinity, and pCO2 every minute. Four field campaigns were conducted during January 2022, April 2023, August 2020, and September 2021 to investigate the seasonal variability. This high-density sampling strategy has revealed pronounced pCO2 changes among four campaigns, with the highest average pCO2 value in August 2020 (1931±980 μatm) and the lowest average value in April 2023 (732±228 μatm). Across all sampling periods, the lagoon acted as a net source of atmospheric CO2 (1.3±1.4 mmol m–2 h–1), with the strongest average emission in August 2020 (1.9±3.2 mmol m–2 h–1), which was twice higher than the average emission in April 2023 (0.9±1.2 mmol m–2 h–1). Through analyzing pCO2 deviations from a two end-member mixing model, shifting between biological activity (photosynthesis and respiration) and tidal-induced mixing processes were revealed across seasons. In August 2020, biological activity was the dominant factor on pCO2 changes, while the mixing effect and biological activity both controlled pCO2 changes in January 2022 and April 2023. Additionally, Chiku Lagoon was found to act as a CO2 source while functioning as a net autotrophic system in August 2020. These findings underscore the necessity of high-density sampling to resolve rapid and dynamic carbon cycling in tropical lagoons across diurnal, spatial, and seasonal scales, thereby providing a foundation for regional environmental management and offering strategies to assess the carbon footprint and enhance carbon neutrality in local industries.
How to cite: Yuan, F.-L., Huang, W.-J., Weerathunga, V., Kao, K.-J., Lai, C.-Y., Wang, C.-Y., Lin, T.-H., Liu, J. T., Chen, J.-J., and Chou, W.-C.: High-Density Sampling Reveals Seasonal Spatiotemporal Variations in Partial Pressure of Carbon Dioxide in a Tropical Lagoon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8684, https://doi.org/10.5194/egusphere-egu26-8684, 2026.
Mangroves are carbon dense ecosystems. Their root exudates could remobilise buried soil organic matter in the form of CO2 emission, notably by stimulating organic matter decay indirectly via an exudate sugar-driven and microbially mediated pathway, or directly by the breakage of organo-mineral bonds. Here, we used a manipulative laboratory incubation to test the effect of root exudate type on CO2 emission in two contrasting mangrove soils: a peat soil with mostly particulate organic matter (Dumbea, New Caledonia, France) and a mineral soil dominated by organo-mineral associations (Can Gio, Vietnam). Using a custom-made 20 cm long needle with a side-port near the tip,we spiked two exudates types, oxalic acid and glucose, into the mineral and organic mangrove soils. The soil CO2 emission was quantified with a gas analyser over time. Iron and pH were mapped at high spatial resolution using two-dimensional Diffusive Equilibrium Thin-films (2D-DET) gels. The root exudate inputs significantly increased the CO2 emission in both mangroves (by an order of magnitude; p< 0.01). The organic rich and mineral mangrove soil CO2 emission responded similarly to both root exudate types. There was no difference in soil CO2 emission between glucose and oxalic acid treatment. Oxalic acid reduced the soil pH consistently across the vertical soil profile in the mineral mangrove soil, while in the peat soil there was a sharp pH decrease in the few top millimetres of soil. For both soil types, the iron concentration was multiplied by an order of magnitude under oxalic acid treatment with a peak in the soil surface, and was slightly increased under glucose treatment. Our results reveal that root exudation could be a major driver of carbon, pH, and iron dynamics in mangrove soils. These findings highlight the importance of understanding root-soil interaction to constrain mangrove carbon budgets.
How to cite: Arnaud, M., Lovelock, C. E., Mouret, A., Huyen, D. T., Robin, S. L., Abiven, S., Kumar Mishra, A., Hilal Farooq, S., Bhadra, T., Felbacq, A., Marchand, C., Bottinelli, N., AlAldrie Amir, A., Pihlblad, J., Ullah, S., and Rumpel, C.: Root exudate analogues increase soil CO2 emission, iron concentration, and acidity in mangroves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9677, https://doi.org/10.5194/egusphere-egu26-9677, 2026.
Mangrove ecosystems are among the most productive and valuable environments on Earth, delivering essential ecological and socio-economic benefits including carbon sequestration, coastal protection, and habitat provision for diverse marine species. However, mangroves face increasing pressures from human activities, with rapid expansion of pond aquaculture emerging as a main driver of mangrove deforestation, especially in Asia, which hosts nearly 40% of the world’s mangroves.
This study presents a comprehensive continental-scale assessment of mangrove loss attributable to aquaculture pond expansion across Asia’s coastal zones, with a focus on Southeast Asia, where mangrove conversion is most severe. Utilizing satellite-based Earth observation data, including an object-based, single-feature inventory of aquaculture pond dynamics derived from Sentinel-1/-2 optical and radar time series and Landsat archive imagery, alongside the Global Mangrove Watch (GMW) dataset, we quantified spatial and temporal relationships between pond presence and mangrove forest decline.
By integrating these datasets within a harmonized time-indexing framework, we directly associate pond activation events with subsequent mangrove decline to attribute deforestation to aquaculture expansion. Our results reveal strong spatial-temporal correlations: aquaculture ponds predominantly cluster in coastal river deltas, overlapping with mangrove loss hotspots, while pond activation frequently coinciding with or directly following significant mangrove loss. Across Asia, mangrove cover declined by approximately 7.2 percent (2,284 km²) in Indonesia and up to 22.2 percent in Pakistan over the study period from 1996-2019. Key hotspots of aquaculture-driven mangrove degradation were identified primarily in Indonesia, Myanmar, and Vietnam, with Indonesia alone accounting for over 13,000 hectares of mangrove loss between 1996 and 2007 due to pond expansion.
Overall, this study underscores the substantial environmental footprint of pond aquaculture on Asia’s coastal ecosystems, demonstrating that aquaculture expansion is a principal driver of mangrove loss in critical regions. By leveraging advanced satellite Earth observation technologies, this research demonstrates the potential of remote sensing data to accurately quantify and monitor mangrove loss at large scales, providing timely, spatially detailed insights into ecosystem changes. Such capabilities are essential for deepening our understanding of the increasing pressures blue carbon ecosystems face from anthropogenic and climatic changes.
How to cite: Ottinger, M., Almeida Famada, L. D., Huth, J., and Bachofer, F.: Monitoring Mangrove Loss from Pond Aquaculture Expansion in Asia Using Satellite Earth Observation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10584, https://doi.org/10.5194/egusphere-egu26-10584, 2026.
Over the past decade, rapid advances in modelling techniques—from process-based and empirical approaches to ecosystem service tools and risk frameworks—have greatly expanded the ability to quantify the benefits provided by blue carbon ecosystems (mangroves, tidal marshes, and seagrasses), including carbon sequestration, coastal protection, habitat provision, and water quality regulation. However, models vary widely in assumptions, data needs, scales, and documentation, leaving numerous actors (managers, researchers, policy makers) with a confusing number of tools but little guidance on how to choose among them. This gap has major consequences for climate policy and nature based solutions, leading to inconsistent assessments, limited uptake by practitioners, and underuse of robust existing models.
Addressing these challenges, we are currently working on a novel project aiming to develop a guideline of the different modelling techniques available to support the quantification of ecosystem services provided by blue carbon ecosystems (e.g., mangroves, tidal marshes, seagrasses). More specifically, we are reviewing the modelling techniques and algorithms available in the scientific literature used to quantify ecosystem services (e.g., coastal protection, resilience, carbon, water quality, etc.) provided by blue carbon ecosystems. We plan to produce a guide to support a variety of actors (e.g., managers, researchers, policy makers, etc.) to apply these models in their work using different case studies. We will develop an online platform that supports coherent, comparable, and policy relevant blue carbon assessments worldwide.
How to cite: Maxwell, T., Carnell, P., Perera, N., and Duarte de Paula Costa, M.: Reviewing models of ecosystem services provided by Blue Carbon ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11737, https://doi.org/10.5194/egusphere-egu26-11737, 2026.
Seagrass meadows are vital coastal ecosystems that provide significant ecological services, including shoreline stabilization, wave energy attenuation, carbon sequestration, and enhancement of marine biodiversity. However, their global decline due to natural and anthropogenic stressors necessitates systematic identification of suitable regions for sustainable seagrass cultivation and restoration. This study aims to assess the potential sites for seagrass cultivation and restoration along the east coast of India, encompassing the coastal regions of Tamil Nadu, Andhra Pradesh, Odisha, and West Bengal, by evaluating key physical and biogeochemical parameters within established seagrass tolerance thresholds.
The bathymetry, significant wave height, potential surface temperature, sea surface salinity, photosynthetically available radiation (PAR) and chlorophyll-a concentration data are used to identify potential sites along the east coast of India. Our analysis indicates a pronounced seasonal cycle across the study area, up to 30 m depth which is suitable for seagrass photosynthesis, driven primarily by monsoon dynamics and regional freshwater inputs. Certain coastal stretches exhibit persistently moderate wave energy, favorable thermal and salinity regimes, and sufficient primary productivity, suggesting high potential for sustainable seagrass establishment. This study provides a data-driven framework and a machine learning technique for identifying suitable potential seagrass restoration/ cultivation sites all along the east coast of India.
Keywords: Seagrass Restoration, Seagrass in east Indian coast, Seagrass Datasets
How to cite: Amit, A. and Dash, M. K.: Potential Site Selection for Seagrass Cultivation/ Restoration in the East Coast of India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16096, https://doi.org/10.5194/egusphere-egu26-16096, 2026.
Mangrove forests are among the most carbon-rich coastal ecosystems, yet their aboveground biomass (AGB) remains poorly quantified in arid regions where structural complexity, closed canopies, and logistical constraints limit conventional field surveys. Improving AGB estimation in these understudied ecosystems is essential for advancing blue-carbon inventories, understanding ecological functioning under extreme environmental conditions, and supporting conservation and restoration initiatives. To address this gap, we present a UAV-based framework designed to generate high-resolution, non-destructive AGB estimates for Avicennia marina mangroves along the Saudi Arabian Red Sea coast, where data on AGB and carbon stocks remain scarce. The proposed approach implements a crown-to-grid framework that simulates quadrat-based AGB sampling at the site-scale using UAV-LiDAR and multispectral data. Field-measured trees are used exclusively to provide reference AGB values derived from an existing allometric relationship for Middle Eastern Avicennia marina. For model training, the crowns of these reference trees are manually delineated and partitioned into 1 m × 1 m grid cells; to augment the training dataset and reduce sensitivity to grid placement, each crown is sampled using 10 shifted grid configurations generated by systematically offsetting the grid origin. Tree-level AGB is then distributed across the cells using the canopy height model as a structural weighting function, generating a physically consistent, cell-level AGB reference while conserving total tree biomass. Spectral, structural, and index-based features extracted at the cell-level are used to train a Random Forest regression model. Model performance is evaluated using leave-one-tree-out cross-validation by aggregating predicted cell-level AGB back to the tree-scale and comparing it against field-derived AGB reference values. Once trained, the model is applied to a continuous 1 m × 1 m grid across the entire UAV-covered area, enabling spatially explicit AGB mapping without requiring individual-tree delineation. In addition to the methodological contributions, our results provide quantitative insights into AGB distribution in arid mangrove ecosystems. Mean site-level AGB densities ranged from ~25 to 31 Mg ha⁻¹, with localized hotspots associated with denser or taller vegetation. By resolving sub-canopy variability and integrating structural and spectral information, the framework improves our ability to characterize vegetation patterns that influence ecosystem function, productivity, and resilience, which are key components of blue-carbon dynamics in extreme environments. Finally, the approach establishes a pathway for upscaling UAV-derived AGB estimates to broader coastal regions, offering a critical bridge between field observations, high-resolution remote sensing, and satellite-based AGB products. Such scalable, non-destructive methods are essential for developing robust blue-carbon inventories, improving carbon accounting in regions where destructive sampling is limited, and supporting management and restoration strategies under accelerating climate and anthropogenic pressures.
How to cite: Elías-Lara, M., Lopez Camargo, O., Rodríguez, J. L., Al-Mashharawi, S. K., Angulo-Morales, V., Scilla, D., Johansen, K., and McCabe, M. F.: UAV-Mapping of Aboveground Biomass in Arid Mangrove Forests: A Crown-to-Grid Machine Learning Approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19001, https://doi.org/10.5194/egusphere-egu26-19001, 2026.
Rainfall deficits are reshaping plant communities worldwide, yet their impacts on non-tidal coastal wetlands remain unclear. In non-tidal systems, rainfall is essential for flushing soil salts and sustaining biodiversity. Here, we tested the hypothesis that rainfall deficit undermines ecosystem stability by eroding biodiversity in such systems. We conducted a seven-year experiment in the Yellow River Delta, simulating summer-autumn rainfall loss under both ambient and elevated winter-spring temperatures. Rainfall loss increased soil salinity (+43.3% under ambient; +25.2% under warming), promoted stress-tolerant species dominance (+36.9%; +8.76%), and reduced species richness (-26.6%; -14.7%). These shifts led to a consistent decline in community stability. Analytical partitioning demonstrated that this destabilization was primarily driven by biodiversity loss rather than by dominance or compensatory effects. Structural equation modeling further confirmed the rainfall-biodiversity-stability pathway. Our findings show that rainfall deficit destabilizes non-tidal coastal wetlands by weakening biodiversity-based buffering, revealing an overlooked vulnerability to intensifying climate extremes.
How to cite: Wang, X., Yan, L., Jiang, M., Wang, Z., Sun, B., Li, H., Shi, J., Liu, W., Han, G., and Xia, J.: Rainfall deficit reduces biodiversity and destabilizes a non-tidal coastal wetland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1734, https://doi.org/10.5194/egusphere-egu26-1734, 2026.
Posters virtual: Wed, 6 May, 14:00–18:00 | vPoster spot 2
EGU26-4468 | Posters virtual | VPS6
South-West England seagrasses: ecology, evolution and contribution to biodiversity and carbon sequestrationThu, 07 May, 14:12–14:15 (CEST) vPoster spot 2
The EU Nature Restoration Regulation is the first continent-wide, comprehensive law of its kind and is a key component of the EU Biodiversity Strategy. This sets binding targets to restore degraded ecosystems, particularly those with the most potential to capture and store carbon and to prevent, and reduce, the impact of natural disasters. The EU Nature Restoration Regulation contains seven specific targets, including:
‘marine ecosystems – restoring marine habitats such as seagrass beds or sediment bottoms that deliver significant benefits, including for climate change mitigation…….’
The 800 hectares of seagrass meadows in South-West England are rightly regarded as important biodiversity ‘hot spots’, providing habitats for many species of juvenile fish, cuttlefish and sea horses. Many of the meadows in the region have been impacted by a ‘Seagrass Wasting Disease’ in the 1930s and the more recent damage caused by the anchoring of small boats (usually pleasure craft). This damage is being rectified by re-planting of seagrass, but many of those engaged in this work do not appreciate the full story behind the present distribution and development of the meadows.
The oldest seagrasses are known from the Maastrichtian of The Netherlands and are found in the Maastricht Chalk Formation (70 million years’ old). Between that time and the present day there are very few direct records of seagrass fossils, and this is because:
- Seagrass meadows from the tidal/inter-tidal boundary are not in an environment that is commonly preserved in the geological record; and
- In modern seagrass meadows, the plants are rarely – if ever – preserved and are rarely found in cores drilled into the meadows below ~30 cm.
In marine cores taken in Plymouth Sound and elsewhere in Southern England there are only low levels of carbon (spores, pollen, dinoflagellates, seeds, and organic debris) and not the high levels that would be required to suggest that sea grasses sequester high levels of ‘blue carbon’ for extended periods of time. The accumulation of low carbon levels can be explained by the enhanced sedimentation created by the seagrass, the so-called allochthonous carbon. The one element of carbon sequestration that is often ignored is that of foraminifera, ostracods and bryozoans, all of which are extremely abundant in meadow sediments. In many cases, the biodiversity of the foraminifera (>100 species) dwarfs the usual biodiversity counts of larger organisms. Such fixed calcium carbonate does have a long-term storage potential.
The other issue that can be ignored by those studying seagrasses is that the marine environment has undergone significant change throughout the 1 million years of the Pleistocene/Holocene and many of the seagrass meadows have only just re-established themselves following the Last Glacial Maximum, when sea levels were 120‒130 m below present-day levels. How seagrass migrated back into the present-day coastal areas is not yet fully understood, including the separation of the inter-tidal and sub-tidal taxa.
How to cite: Hart, M. and Fisher, J.: South-West England seagrasses: ecology, evolution and contribution to biodiversity and carbon sequestration , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4468, https://doi.org/10.5194/egusphere-egu26-4468, 2026.
EGU26-6116 | ECS | Posters virtual | VPS6
Spatial Variation in Sediment Bacterial Communities Along a Salinity Gradient in a Northern Gulf of Mexico Coastal EcosystemThu, 07 May, 14:15–14:18 (CEST) vPoster spot 2
Microorganisms in estuarine and coastal ecosystems are subject to changes in salinity and nutrient loads as well as threats from emerging contaminants, sea level rise, extreme weather patterns, and human encroachment. These ecosystems are of economic and ecological importance due to their biological diversity as well as their role in carbon sequestration, flood protection, and erosion prevention. However, the microbial community structure in the sediment of estuarine systems remains under researched despite the abundant ecosystem services they provide. In this study, we surveyed 25 sites within Econfina River State Park located in the eastern portion of the Northern Gulf of Mexico along a salinity gradient from freshwater upstream to coastal seagrass beds downstream. DNA extracted from the top 10 cm of sediment were 16S rRNA amplicon sequenced to determine microbial community structure. Results contribute to the understanding of microbial ecology of coastal ecosystems in the Northern Gulf of Mexico.
How to cite: Parker, S. G., Tryzbiak, B., Patel, A., Pereira, G., Chambers, L., and Beazley, M.: Spatial Variation in Sediment Bacterial Communities Along a Salinity Gradient in a Northern Gulf of Mexico Coastal Ecosystem, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6116, https://doi.org/10.5194/egusphere-egu26-6116, 2026.
EGU26-15259 | ECS | Posters virtual | VPS6
Landward Migration of Coastal Wetlands under Land-Use Constraints in AustraliaThu, 07 May, 14:18–14:21 (CEST) vPoster spot 2
Sea level rise (SLR) is a key driver in altering spatial boundaries, species distribution, and functioning of coastal wetlands in the 21st century. Wetland adaptation to SLR depends on vertical accretion and landward migration; however, the magnitude and rate of these processes remain uncertain and are constrained by factors such as sediment supply and the availability of inland accommodation space. To enhance adaptive capacity, spatially explicit assessments are critical for identifying areas suitable for wetland migration. Nevertheless, much of the existing literature emphasises global-scale analyses with coarse spatial resolution and limited use of local SLR projections, which reduces their applicability for regional and local decision-making.
We conducted a scenario-based assessment of the potential extent of landward migration for mangroves and saltmarshes in Victoria, Australia, using high-resolution (10 m) regional spatial data under two socio-economic pathways (SSP2 and SSP5) for 2070 and 2090. The results indicate that, for both ecosystems, potential area gains from landward migration exceed losses from seaward inundation. For saltmarshes, ecosystem losses are driven more by mangrove encroachment (53%) than by inundation (47%). Land tenure emerges as a key factor shaping wetland migration capacity. Future accommodation space for mangroves is largely under public ownership (56%), primarily within protected areas and nature reserves (56.2%), providing a relatively secure buffer for inland migration. In contrast, most accommodation space for saltmarshes is privately owned (56.4%) and predominantly associated with primary production land use (45.4%). Without specific management actions, saltmarshes are likely to experience losses from both expanding mangroves and ongoing land-use pressures. Overall, these findings provide valuable insights to support stakeholders in scenario-based planning and the management of coastal and urban areas to enable wetland adaptation to rising sea levels.
How to cite: Perera, N., Wartman, M., Nuyt, S., Macreadie, P., and Duarte de Paula Costa, M.: Landward Migration of Coastal Wetlands under Land-Use Constraints in Australia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15259, https://doi.org/10.5194/egusphere-egu26-15259, 2026.
EGU26-984 | ECS | Posters virtual | VPS6
A systematic review of the diverse values of Seagrass Contributions to People (SCP) in Indonesia: A pilot studyThu, 07 May, 14:21–14:24 (CEST) vPoster spot 2
Seagrass ecosystems in Indonesia provide a diverse array of services and societal benefits that helps to mitigate the impacts of climate change, yet they face complex threats and ongoing declines. Assessing their diverse values through pluralistic lenses can provide important baseline information to guide future conservation and restoration policies. Utilising the Seagrass Ecosystem Contributions to People (SCP) framework, a systematic review was conducted in representative seagrass ecosystem regions—west (Bintan), central (Selayar), and east (Ternate)—to examine the current state of research on their diverse values. Specifically, we identified the presence, perceived worldviews, characteristics, specific values, and their overlaps of SCP categories.
Publications were retrieved from Scopus, Web of Science, and the first ten pages of Google Scholar between February and April 2025. Then, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 Guideline, a thorough literature analysis was conducted using six established inclusion criteria. Present SCPs, perceived worldviews, specific values, and their overlaps were assessed in accordance with core meanings derived from McKenzie and Colleagues, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) report on the diverse values of nature, and Himes and Colleagues’ publication, respectively.
Overall, 54 publications were included in this review, spanning the years 1989 to 2025 and identifying 25 SCPs across three regions, with a decreasing number of studies for each SCP from west to east. There were imbalances in the SCP perception, with bioindicator and scientific research being perceived in all regions and having twice the number of publications compared to other SCPs. These two prevalent SCPs generally studied the ecological status of seagrasses, their associated biota, and experimental results on their monitoring methods (e.g. remote sensing).
Biocentric and anthropocentric worldviews were researched more and dominated interchangeably between SCPs, focusing on seagrass conservation values and societal perceptions of its services. Meanwhile, the pluricentric worldview had singular studies limited to several Material and Nonmaterial SCPs. Excluding the east region, all three specific values (intrinsic, instrumental, and relational) were present, with instrumental as the most frequent overlapping value. These value overlaps demonstrated fuzzy boundaries between material and nonmaterial groups, but not with the regulating SCPs, which were all studied with a singular specific value.
Regional differences in seagrass ecosystem management, benefit utilizations, and research focus might reflect the variability of the perceived SCPs, worldviews, and value overlaps. Although these perceptions are still biased towards tangible benefits for human ends. However, most of the reviewed publications were short-term studies and distinct from each other, demonstrating the need for local experts’ knowledge elicitation to further weave the information. Our study further developed the SCP framework by incorporating the concept of nature’s diverse values, which is highly relevant and applicable to the seagrass socio-ecological setting and management initiatives in Indonesia.
How to cite: Widanto, D. S., Sasmito, S. D., and Waltham, N.: A systematic review of the diverse values of Seagrass Contributions to People (SCP) in Indonesia: A pilot study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-984, https://doi.org/10.5194/egusphere-egu26-984, 2026.
