The numbers behind the review are striking. Mangroves can hold up to 1,023 megagrams of carbon per hectare below ground, supported by anoxic, sulfate-reducing sediments and vertical accretion rates of 3 to 10 millimetres per year. Salt marshes sequester between 150 and 250 grams of carbon per square metre annually, while seagrass meadows bury 30 to 218 grams per square metre each year. Per unit area, these figures rival or exceed the sequestration rates of tropical rainforests, and salt marshes have been reported to store up to ten times more carbon per hectare than many terrestrial ecosystems. Because roughly half of all photosynthesis on Earth occurs in the ocean, the marine carbon cycle exerts a profound influence on atmospheric chemistry, and vegetated coastal habitats sit at the sharp end of that cycle.

The secret to mangrove carbon storage lies largely underground. Between 50 and 70 percent of the carbon in a mangrove forest resides in roots and soils, where prop roots, pneumatophores and fine root networks continuously deliver organic matter to the sediment. Waterlogged, oxygen-poor conditions suppress aerobic decomposition, forcing microbes down slower metabolic pathways such as fermentation and sulfate reduction. As a result, organic matter in mangrove soils breaks down three to ten times more slowly than in upland soils. The leaves and woody tissue of mangroves add another layer of defence, containing high concentrations of lignin, tannins and other polyphenolic compounds that resist microbial attack, extending the residence time of carbon in the sediment for centuries or even millennia.

Physical processes reinforce the biological ones. Dense canopies and root mats slow water flow, trapping fine mineral and organic particles delivered by rivers, tides and waves. This promotes vertical accretion, allowing mangroves in sediment-rich regions to accumulate surface elevation at rates exceeding 10 millimetres per year, which helps them keep pace with moderate sea-level rise while continuously burying carbon. Salt marshes operate on similar principles, trapping suspended sediments and building elevation under favourable tidal conditions. Seagrass meadows, descended from land plants that returned to the sea roughly 100 million years ago, stabilise sediments with dense root and rhizome mats, and global syntheses indicate they can store roughly twice as much carbon per hectare as terrestrial forests. Nutrient supply through their roots allows seagrasses to keep accumulating carbon even in otherwise nutrient-poor waters.

Microbes and algae add further dimensions to the story. The review highlights the microbial carbon pump, a process by which marine bacteria convert labile organic matter into refractory dissolved organic carbon that resists degradation and persists in the ocean for long periods. Alongside the biological pump, which transports roughly 10 to 15 percent of ocean primary production into the deep sea, and microbially induced carbonate precipitation, these mechanisms extend carbon storage far beyond the coastal zone. Macroalgae contribute as well, with an estimated 90 percent of algal carbon sequestration exported to the deep sea and the remainder buried in coastal sediments. Microalgae, which fix carbon dioxide at rates up to ten times more efficient per unit of solar energy than terrestrial plants, are attracting attention as candidates for engineered carbon removal.

Yet the review is equally clear about the fragility of these systems. Disturbance can flip a blue carbon sink into a carbon source with alarming speed. Converting mangrove forests to aquaculture ponds can release carbon at rates up to 50 times higher than the sequestration achieved by intact forests, while deforestation and hydrological alteration raise emissions to levels 10 to 40 times above normal sequestration. Drainage and aeration of organic-rich soils accelerate decomposition, and sediment erosion exposes long-buried carbon to oxidation. Methane generation under shifting hydrological regimes adds another greenhouse gas pathway. The authors also flag bioturbation as a double-edged factor: crabs remove an average of 87 percent of daily mangrove litter fall in some Thai forests, and burrowing animals in marshes and seagrass beds alter sediment mixing, burial depth and porewater exchange in ways that can either aid or undermine carbon retention.

Environmental drivers complicate the picture further. Moderate sea-level rise can actually enhance carbon burial by encouraging sediment trapping and peat formation, but rapid rise can drown marshes and mangroves, releasing stored carbon and, in some conditions, promoting methane and nitrous oxide emissions. Elevated temperatures accelerate decomposition of tropical wetland soils, stronger storms erode seagrass meadows and their carbon reserves, and Mediterranean droughts have reduced primary production in Posidonia oceanica meadows. Hydrology matters enormously: tidal connection in mangroves raises sediment deposition from less than 2 millimetres per year in restricted systems to more than 10 millimetres per year in open tidal habitats, and carbon accumulation in salt marshes correlates strongly with tidal amplitude. Nutrients cut both ways, since moderate nitrogen and phosphorus inputs stimulate productivity while excessive loading from agriculture and wastewater drives algal blooms, reduces water clarity and accelerates greenhouse gas emissions.

The pollution control function of blue carbon ecosystems is one of the review’s most intriguing threads. Mangrove and salt marsh root systems slow water flow and promote deposition of suspended particles, immobilising heavy metals such as lead, cadmium and zinc, along with hydrocarbons and persistent organic pollutants, in anoxic soils. Seagrass canopies trap fine particles and microplastics, reducing their transport into coastal waters, while plant uptake and microbial denitrification remove excess nitrogen and improve water quality. Mangrove sediments have even been identified as major sinks for plastic burial. However, the authors caution that accumulating plastics impose physical stress on organisms, risk ingestion by invertebrates and fish, and may alter sediment structure and microbial activity in ways that could affect organic carbon burial and greenhouse gas fluxes, making the interaction between pollution and carbon storage a priority research area.

Restoration offers genuine grounds for optimism. Meta-analyses and long-term field studies indicate that restored mangroves, salt marshes and seagrass beds can recover 50 to 90 percent of depleted carbon stocks over several decades, with some planted mangroves regaining significant portions of ecosystem carbon in under 20 years. Restored seagrass meadows have achieved carbon accumulation rates of roughly 20 to 40 grams per square metre per year within a decade, and managed realignment of salt marshes has produced rapid carbon accumulation in its early years. Measurement techniques are advancing in parallel, with lidar remote sensing enabling precise biomass estimates in inaccessible terrain, sediment coring paired with radiometric dating revealing long-term storage, and GIS-based carbon budgeting scaling local measurements to regional estimates.

The policy implications are substantial. Mangroves alone are estimated to capture up to 42 million tons of carbon annually worldwide, and blue carbon offsetting is emerging as a mechanism for channelling finance into coastal conservation, with co-benefits spanning storm protection, fisheries support and biodiversity. The authors argue that realising this potential requires marine protected areas, hydrological restoration, catchment-level management of nutrient inputs, standardised monitoring protocols and integration of blue carbon into national climate strategies and carbon markets. The IPCC’s Sixth Assessment Report recognises ecosystem restoration as a significant natural option for boosting carbon burial and coastal resilience. As the review concludes, protecting intact mangroves, marshes and meadows is not merely a carbon accounting exercise; it is an investment in living infrastructure that filters pollutants, buffers storms and quietly performs one of the most valuable services on the planet, one gram of buried carbon at a time.

Subject of Research: Blue carbon sequestration mechanisms and pollution control in coastal ecosystems for climate change mitigation

Article Title: Mechanisms, processes, and implications of blue carbon sequestration and pollution control for climate change mitigation

Article References: Dinakarkumar, Y., Selvam, M. M., Inayathullah, N., Pavithra, K. S., Mallikarjuna, H. N., Indhusuvitha, S., Jebacani, M. J., Romauld, S. I., & Muthezhilan, R. (2026). Mechanisms, processes, and implications of blue carbon sequestration and pollution control for climate change mitigation. Discover Oceans, 3(1), Article 5. https://doi.org/10.1007/s44289-026-00118-4

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00118-4

Keywords: blue carbon, mangroves, salt marshes, seagrass meadows, carbon sequestration, climate change mitigation, coastal ecosystems, sediment carbon burial, pollution control, sea-level rise, ecosystem restoration, microbial carbon pump

The research, published in the journal Microbial Ecology, was carried out by a team from the University of Padova and the National Biodiversity Future Centre in Italy. Led by Irene Gregori and corresponding author Alessandro Vezzi, the researchers sampled sediments from two salt marshes in the Venice Lagoon, a productive microtidal coastal ecosystem in the northern Adriatic. Rather than tracking the marshes across weeks or seasons, the team focused on a much finer timescale: a single summer diel cycle, with sampling at four carefully chosen moments: sunset, night, dawn and solar noon. This design allowed them to capture the most extreme short-term physicochemical oscillations that intertidal ecosystems experience, driven by the interplay of sunlight, tides and biological activity.

The physicochemical measurements confirmed just how dynamic these environments are. Temperature and dissolved oxygen concentrations showed pronounced oscillations over the sampled cycle, with oxygen levels in particular responding to the balance between photosynthetic production during daylight hours and continuous respiratory consumption around the clock. Such fluctuations are typical of productive intertidal systems, where mats of microalgae and aquatic plants flood the water with oxygen by day and leave it depleted by night. For organisms living in the sediment, these swings represent a genuine physiological challenge, because oxygen availability dictates which metabolic pathways are energetically feasible at any given moment.

To characterise the biological players, the team employed two complementary DNA-based approaches. Prokaryotic communities, encompassing bacteria and archaea, were profiled using metabarcoding of the 16S ribosomal RNA gene, a standard molecular fingerprinting technique that reveals which microbial taxa are present and in what relative abundances. Eukaryotic organisms, ranging from microscopic algae to fungi and protists, were similarly catalogued using the 18S rRNA gene. But the researchers went a step further than simple taxonomic inventories: they also applied metagenomics, sequencing the collective genomes of the prokaryotic communities to assess their functional potential, in other words, which genes and metabolic pathways the communities carried and could, in principle, deploy.

The results were striking for what they did not show. Despite the pronounced swings in temperature and dissolved oxygen, both the prokaryotic and eukaryotic communities displayed only minor shifts in taxonomic composition across the four sampling points of the diel cycle. The same microbial lineages dominated the sediments at sunset as at dawn, and the relative abundances of most taxa remained essentially unchanged from night to solar noon. In many aquatic ecosystems, particularly the open ocean, researchers have documented clear diel rhythms in microbial communities, with different taxa rising and falling in abundance as light and nutrient conditions change. The Venice Lagoon salt marsh sediments, by contrast, appear to host assemblages that simply do not need to restructure themselves on this timescale.

The metagenomic data help explain why. The prokaryotic communities proved to be functionally redundant and metabolically versatile, meaning that multiple different taxa carried out the same key processes and that individual organisms possessed a broad repertoire of metabolic capabilities. The communities were dominated by taxa involved in organic-matter degradation, the cycling of sulphur compounds, denitrification, which converts bioavailable nitrogen into gaseous forms, and sulphur-oxidising chemolithoautotrophic carbon fixation, a process in which microbes use chemical energy from oxidising sulphur compounds, rather than sunlight, to fix carbon dioxide into biomass. This functional breadth means that whatever the prevailing oxygen and temperature conditions at a given hour, some members of the community are equipped to keep the essential biogeochemical machinery running.

The authors conclude that modulating their activities, rather than undergoing compositional restructuring, is likely how these communities sustain key ecological processes relevant to carbon and nutrient cycling over the diel timescale. In practical terms, a sulphate-reducing bacterium that dominates the community at midnight, when oxygen has been exhausted, does not need to be replaced by a different species at noon; it can simply slow down or speed up its metabolic output as conditions permit. Similarly, chemolithoautotrophs that fix carbon using sulphur-derived energy can ramp up their activity when their substrates become available, without any change in who is present. Activity-level regulation is a faster and energetically cheaper strategy than community turnover, and the study suggests it is the dominant mode of short-term response in these sediments.

The findings carry broader significance for the conservation and restoration of salt marshes, which are globally threatened by anthropogenic pressures including land reclamation, pollution, nutrient loading and sea-level rise. Because restoration efforts are increasingly needed to recover the carbon sequestration capacity, water quality regulation and coastal protection that these habitats provide, understanding the stability and resilience of their microbial engines is essential. If sediment microbial communities are functionally robust in the face of strong short-term physicochemical fluctuations, this suggests a degree of intrinsic resilience that could help restored marshes establish functioning biogeochemical cycles relatively quickly. At the same time, the central role of sulphur cycling, denitrification and organic-matter degradation in these communities underscores how tightly salt marsh ecosystem services are coupled to microbial metabolism, and how disturbances that alter sediment chemistry could ripple through the entire system.

The study also highlights the value of combining fine-scale temporal sampling with functional genomics. Taxonomic metabarcoding alone might have led researchers to conclude that diel dynamics are unimportant in salt marsh sediments, but the metagenomic perspective reveals the hidden versatility that makes that stability possible. As sequencing costs continue to fall, similar integrated approaches are likely to be applied to other intertidal and coastal ecosystems, from mangrove sediments to seagrass meadows, where the same questions about short-term microbial dynamics and ecosystem function remain open. For now, the Venice Lagoon results provide a clear and somewhat reassuring message: beneath the mud, the microbial workforce keeps its composition steady through night and day, adjusting its activity to whatever the marsh throws at it, and in doing so quietly sustaining the processes on which these threatened coastal habitats depend.

Subject of Research: Diel stability of sediment microbial communities in Venice Lagoon salt marshes

Article Title: Night and day in the Salt Marshes: Sediment Microbial Communities Remain Stable Over a Summer Diel Cycle

Article References: Gregori, I., Mohamed, F., Barausse, A., Frizzo, R., Archetti, L., Martino, F., Zane, L., & Vezzi, A. (2026). Night and day in the Salt Marshes: Sediment Microbial Communities Remain Stable Over a Summer Diel Cycle. Microbial Ecology. https://doi.org/10.1007/s00248-026-02890-4

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02890-4

Keywords: salt marshes, microbial ecology, metabarcoding, metagenomics, diel cycle, Venice Lagoon, biogeochemistry, sulphur cycling, denitrification, carbon sequestration, coastal ecosystems, prokaryotes

The research, led by Yunshi Li and Gaosen Zhang of Shaanxi Xueqian Normal University and the Northwest Institute of Eco-Environment and Resources, together with colleagues in China and France, compared the rhizosphere microbial communities of the two Spartina species along gradients of environmental stress. Using 16S rRNA high-throughput sequencing and co-occurrence network analysis, the team mapped how bacterial and archaeal communities structured themselves around the roots of each plant at sites varying in distance from freshwater inputs. The findings point to a subtle but potentially decisive mechanism: topological reinforcement of microbial interaction networks, a process in which a plant actively reshapes the connectivity and complexity of its underground microbial society without changing who belongs to it.

Rhizosphere microbes are far more than passive hitchhikers on plant roots. They mediate nutrient cycling, buffer against salinity and heavy metals, suppress pathogens, and produce growth-promoting compounds. In salt marshes, where salinity, waterlogging and nutrient availability shift dramatically over short distances, the microbial community surrounding a plant’s roots can mean the difference between thriving and merely surviving. For decades, invasion biologists have debated whether invasive plants succeed by recruiting different microbes than natives do, by escaping their native soil enemies, or by cultivating a more favorable microbial entourage. The new study adds a crucial twist: perhaps the most important difference is not taxonomic at all, but structural.

The researchers sampled rhizosphere soils from S. anglica and the native S. maritima across locations spanning proximal sites near a freshwater stream to distal sites characterized by high abiotic stress, where salinity and other harsh conditions intensify. What they found was striking. At the level of species composition, the two plants told very different stories. S. anglica maintained remarkably stable rhizosphere microbial communities across all locations: no matter how stressful the environment, the taxonomic makeup of its root-associated microbes stayed largely consistent. S. maritima, by contrast, showed significant shifts in community composition in response to environmental variation, suggesting that its microbial partnerships were being reshuffled by the same pressures that S. anglica seemed to shrug off.

Yet the deeper surprise emerged when the team moved beyond simple taxonomic inventories and examined the topology of microbial co-occurrence networks, the mathematical webs that describe which groups of microbes tend to appear together, and how densely interconnected the resulting communities are. Despite keeping essentially the same cast of microbial characters, S. anglica adaptively rewired the relationships among them. At distal, highly stressed locations, the invasive plant’s rhizosphere networks exhibited significantly higher density, greater nodal connectivity and increased topological complexity compared with those at more benign sites. In plain terms, as conditions worsened, S. anglica did not replace its microbes; it knitted them more tightly together.

The native S. maritima moved in the opposite direction. Under identical high-stress conditions, its microbial networks suffered a substantial reduction in organizational stability and complexity, with connections thinning and the interaction architecture fraying. This divergence matters because network structure is increasingly understood to govern how microbial communities function under disturbance. Densely connected, modular networks tend to be more robust: if one link or node is perturbed, alternative pathways of interaction can compensate, maintaining ecosystem processes such as nitrogen cycling and organic matter decomposition. Sparse, fragile networks, on the other hand, can cascade into dysfunction when stress pushes them past a threshold.

The implications of this pattern are considerable. If S. anglica engineers a cooperative, resilient microbial interaction environment through topological reinforcement, it effectively builds a biological insurance policy underground, allowing the plant to maintain nutrient acquisition and stress tolerance even where the native species’ microbial support systems begin to collapse. The study’s authors are careful to frame this as a proposed mechanism: the evidence links invasive success with network rewiring, but they note that further studies across seasonal and temporal scales are needed to confirm the causal relationship. Coastal salt marshes are dynamic systems, and microbial networks may fluctuate across tides, seasons and years in ways a single spatial survey cannot fully capture.

Still, the conceptual shift the study proposes is significant. Much of invasion ecology has focused on species lists: which taxa are present, which are absent, and how communities differ. This work argues that structural organization, the pattern of interactions rather than the roster of participants, may be the true determinant of competitive superiority in dynamic coastal ecosystems. It echoes a broader movement in microbial ecology toward network-level thinking, in which the same principle has been invoked to explain everything from gut microbiome stability to the collapse of soil communities under drought. Applying that lens to plant invasion provides a new diagnostic tool: managers assessing invasion risk might one day read not just which microbes live in a soil, but how tightly woven the microbial fabric is.

Spartina anglica itself is a fitting subject for such a study. The species originated as a hybrid between the North American S. alterniflora and the European native S. maritima, and its hybrid vigor, combined with vigorous clonal growth and high salinity tolerance, has made it one of the world’s most successful salt marsh invaders. In many regions it has transformed mudflats into dense meadows, altering sediment dynamics, displacing native vegetation and reshaping habitat for birds and invertebrates. Understanding why it dominates so thoroughly has practical stakes: restoration programs seeking to reestablish native marsh communities must contend with an invader whose advantage may be rooted, literally, in the microbial world it cultivates.

The study also raises intriguing evolutionary questions. How does a plant manipulate the topology of a microbial network it cannot directly see or control? Root exudates, the chemical cocktail of sugars, organic acids and secondary metabolites that plants release into the soil, are one plausible lever, shaping which microbes flourish and how they interact. The team’s finding that S. anglica’s taxonomic community remained stable even as its network architecture changed suggests a finely tuned feedback system, one in which the plant maintains a consistent microbial partner pool while flexibly adjusting the interaction structure to match prevailing stress levels. Disentangling the chemical and genetic mechanisms behind that flexibility will be a natural next step for the field.

For now, the study stands as a vivid demonstration that ecological competition plays out in dimensions invisible to the naked eye. On the surface, two cordgrasses may appear to be simply vying for space and light in the same marsh. Below ground, one is rewiring a vast microbial web into a denser, more resilient configuration while the other’s web slackens under stress. If future work confirms that this topological reinforcement drives invasion, it could reshape how scientists think about plant dominance, how conservationists approach restoration in invaded marshes, and how microbial ecology is integrated into invasion biology. The roots of an invasion, it turns out, may be best understood not as a list of species but as a map of connections.

Subject of Research: Rhizosphere microbial network topology underlying the invasive success of Spartina anglica in coastal salt marshes

Article Title: Topological Reinforcement of Rhizosphere Microbial Networks Facilitates the Invasive Superiority of Spartina anglica

Article References: Li, Y., Michalet, R., Chen, Y., Yue, M., Da, L., Xie, H., Jiang, J., & Zhang, G. (2026). Topological Reinforcement of Rhizosphere Microbial Networks Facilitates the Invasive Superiority of Spartina anglica. Microbial Ecology. https://doi.org/10.1007/s00248-026-02883-3

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02883-3

Keywords: Spartina anglica, plant invasion, rhizosphere microbiome, microbial networks, network topology, salt marshes, coastal ecosystems, microbial ecology, co-occurrence analysis, 16S rRNA sequencing, ecological resilience, invasive species