Estuaries are among the most productive and most crowded environments on Earth. Semi-enclosed water bodies where rivers meet the sea, they nurture diverse habitats and support roughly 60 percent of the global population, including 22 of the world’s 32 largest cities. The total economic value of estuarine ecosystems has been estimated at more than six trillion US dollars. Yet they are also among the most threatened landscapes on the planet, battered by climate change, rapid development and disaster risk. Half of the world’s salt marshes, 35 percent of its mangroves and 29 percent of its seagrass beds have already been lost or degraded, and the decline has cut nature’s capacity for self-recovery by a third.

The research team, working across the estuaries of Quang Ninh and Quang Nam Provinces, chose the Thu Bon Estuary near Hoi An for detailed modelling. The area is a study in contradictions. In 2019 it welcomed more than 7.8 million visitors and earned over 14,570 billion Vietnamese dong from tourism, while its mangrove coconut forests shelter aquatic species and anchor a UNESCO World Cultural Heritage Site and a biosphere reserve. At the same time, more than 112 hectares of wetland ecosystems vanished from the biosphere reserve between 2004 and 2016, including mangroves, seagrass beds and coral reefs, as land was converted for infrastructure and tourism.

The methodological core of the study is the Bayesian Belief Network, or BBN, a modelling framework built on Bayes’ theorem that represents cause-and-effect relationships through two components: directed acyclic graphs, which map the independence between variables, and conditional probability tables, which quantify the strength of each link. In this application, the network’s root nodes represent landscape type and land use or land cover, while seventeen intermediate nodes correspond to individual ecosystem services drawn from the Common International Classification of Ecosystem Services, spanning provisioning, regulating and cultural categories. Three child nodes aggregate the final values for each service group.

Building such a network in a data-scarce environment demanded creative synthesis. The researchers first classified terrestrial and wetland ecosystems using thirty years of satellite imagery, including ALOS and Worldview-2 data processed with a random forest algorithm at an accuracy of 78 to 85 percent. They then distilled expert judgement through a Delphi process, in which twenty-one specialists from universities and research institutes iteratively scored the capacity of sixteen land-use types to deliver each of the seventeen services on a scale from 0 to 100, refining their answers across rounds until consensus emerged. Scores were averaged when disagreements fell between 20 and 40 points, and further consultation was triggered when gaps exceeded 40.

A key innovation lies in how the team wired the network together. Rather than guessing the relationships between services, they ran the expert matrix through generalised linear and structural equation models in the R programming environment. The structural equation model proved decisive: where many BBN applications leave the connections between variables ambiguous, the SEM analysis identified which correlations were strong enough to keep, converting them into one-way links between parent and child nodes. The finished network was implemented in Netica software, and total service values were calculated by multiplying each land-use type’s provision potential by its mapped area, then summing across the landscape.

The statistical analysis exposed a fundamental tension in how estuarine ecosystems function. Cultural and regulating services clustered into groups with strong positive interdependence, with correlation coefficients between 0.7 and 0.9, meaning they tend to rise and fall together. Provisioning services behaved differently, showing negative correlations with nearly everything else. Fish and seafood provision correlated at minus 0.8 to minus 0.9 with timber and even more negatively with cultural services, a quantitative confirmation of the classic trade-off: intensify extraction and the other benefits of nature decline. Mineral extraction stood out as particularly damaging, correlating at minus 0.7 with air quality regulation, as riverbed sand mining triggers landslides, air pollution and the salinisation of coastal groundwater.

Running the model across the period from 1991 to 2020 produced a nuanced picture. Total ecosystem service value drifted upward from 627 to 670 points, but the composition shifted in worrying ways. Cultural services, the highest-scoring group, grew by 4.4 percent, led by regional identity and tourism values that surged after Hoi An’s heritage designation in 1999, when the town drew fewer than 100,000 visitors; by 2019 it hosted more than 7.6 million. Regulating services moved in the opposite direction, falling 4.36 percent from 234 to 222 points, with groundwater recharge the strongest performer and air quality regulation the weakest. Among the six landscape types identified, the alluvial and river-swamp landscapes delivered the highest values, but both trended downward as mangrove coconut forests gave way to aquaculture ponds that supply seafood yet offer almost no regulating or cultural benefits.

The model’s real power emerged in scenario testing. Drawing on Hoi An’s 2030 planning targets, which envision a 40 percent urbanisation rate, the researchers modelled two futures. Under continued urbanisation and tourism expansion, with roughly 400 hectares of new housing carved from farmland and forest and more than 250 hectares of forest lost, cultural services climbed while regulating services fell faster, raising the risk of flooding in low-lying districts where storm-driven water levels can reach 150 to 200 centimetres. Under a preservation scenario that expands protective forests by 20 percent and stabilises urban land, regulating services recovered visibly, a gradual environmental restoration that contrasts with the rapid degradation of the development pathway. Both scenarios showed declining provisioning services, but the decline was milder where nature was conserved.

The stakes are far from abstract. Coastal erosion at Cua Dai has been advancing at 3 to 10 metres per year, sometimes exceeding 10 metres, while floods in the rainy season can strip 40 to 50 metres of land in a single year. Storm Nari destroyed more than 80,000 hectares of fruit and forestry trees in 2013, and more than 3,000 houses in Tam Ky endured deep flooding at the end of 2021. The authors argue that policy-makers should prioritise expanding protective forest ecosystems along the Thu Bon coastline to buffer inundation, improve air quality and control erosion. More broadly, they contend that the BBN approach, which combines expert knowledge, geographic information systems and statistical modelling, offers a transparent and transferable tool for managers anywhere who must weigh the immediate rewards of development against the slow, silent depreciation of the natural systems that keep coastal communities safe.

Subject of Research: Bayesian Belief Network assessment of ecosystem services and socio-economic development in Vietnam's threatened estuarine regions

Article Title: A Bayesian Belief Network for assessing ecosystem services and socio-economic development in threatened estuarine regions

Article References: Nguyen, T. D. L., Tran, T., Dang, K. B., Do, T. T. T., Dong, H., Pham Thi Phuong, N., Hoang Thi, T., & Giang, T. L. (2024). A Bayesian Belief Network for assessing ecosystem services and socio-economic development in threatened estuarine regions. One Ecosystem, 9, Article e124989. https://doi.org/10.3897/oneeco.9.e124989

Image Credits: AI Generated

DOI: 10.3897/oneeco.9.e124989

Keywords: Bayesian Belief Network, ecosystem services, estuaries, Vietnam, Hoi An, urbanisation, tourism, mangroves, coastal erosion, land use change, structural equation modelling, sustainability

The significance of the work lies in what mangroves represent for public health. Although mangrove forests cover only about 700 square kilometres of French Guiana, less than one percent of the territory, they occupy more than 80 percent of its coastline. That same coastal strip is home to 90 percent of the human population of this French overseas department, including the capital city of Cayenne. Wherever people and mosquitoes overlap, questions about nuisance biting and disease transmission follow, and until now, data on the mosquitoes of these intertidal forests were remarkably sparse.

French Guiana is, in many ways, the right place to look. The territory is recognised as having one of the highest mosquito species richness in the world relative to its surface area, with 250 recorded species. Earlier georeferenced databases, compiled by entomologists in the 1960s and 1970s and updated in 2015, catalogue valuable biodiversity records, but their structure does not allow researchers to analyse how species assemblages and relative abundances vary across space and time. The new dataset was designed precisely to fill that gap, using standardised sampling events so that future comparisons among habitats and seasons become possible.

The fieldwork stretched from October 2023 to July 2025 and covered 14 locations. Most sat on the Island of Cayenne and its surroundings, a stretch of roughly 50 kilometres of coast and 25 kilometres inland that includes six municipalities. A second cluster of sites lay about 100 kilometres southeast, along the lower Oyapock River on the border with Brazil, in a 30-kilometre upstream and downstream transect between the villages of Trois-Palétuviers and Ouanary. The sites spanned young pioneer mangroves barely a year old, mature homogeneous stands dominated by a single tree species, and structurally complex mixed forests, some within sight of Cayenne’s urban centre and others more than 10 kilometres from any human infrastructure.

Sampling relied primarily on two complementary trap types. BG-Pro traps baited with BG-Sweetscent lures, sometimes paired with ultraviolet light, are known to be effective at capturing mosquito species that prefer to feed on humans. CDC light traps, suspended about 1.5 metres above the ground along transects of 30 to 60 metres, sample a broad diversity of nocturnal species. Traps typically ran for 8 to 9 hours during daytime deployments or around 16 hours overnight, with occasional continuous 24-hour sessions when logistics prevented immediate retrieval. Two larval dipping events added 64 immature specimens to the tally, a tiny fraction of the total but a deliberate inclusion, since locating larvae is one of the few ways to identify which parts of the mangrove actually serve as breeding habitat.

Identifying tropical mosquitoes is notoriously difficult, and the researchers went to unusual lengths to get the names right. No single identification key covers all the mosquito species recorded in French Guiana, so the team combined multiple taxonomic keys, one for each genus, following nomenclature updated through the Mosquito Taxonomic Inventory. Most species of the genus Culex simply cannot be identified reliably from external adult features, so the team examined the internal structures of male genitalia for 1,762 male Culex specimens, 98 percent of all Culex males in the dataset. The abdominal segments were cleared in potassium hydroxide, stained with acid fuchsin, and in 100 difficult cases fully dissected and mounted on slides for microscopic examination at up to 1000-times magnification.

Molecular tools provided a further layer of confidence. For uncertain identifications, the researchers removed three legs from selected specimens and stored them for DNA barcoding of the standard 658-base-pair region of the mitochondrial cytochrome c oxidase subunit I gene, the COI barcode widely used in animal taxonomy. A total of 400 female mosquitoes and 50 male Culex were confirmed this way, with sequences compared against an existing DNA reference library dedicated to the mosquitoes of French Guiana. All barcode sequences will be deposited in the Barcode of Life Data System under the ongoing Mosquitoes of French Guiana project, and voucher specimens are preserved in ethanol or mounted in the entomological collection of the Institut Pasteur de la Guyane.

The results reveal a mosquito fauna strongly dominated by a handful of taxa. Unidentified Culex of the subgenus Melanoconion topped the list with 8,580 specimens, or 39.4 percent of the total, followed by Coquillettidia venezuelensis with 4,471 specimens at 20.5 percent, the crab-hole mosquito Deinocerites magnus with 3,354 specimens at 15.4 percent, and Culex portesi with 1,496 specimens at 6.9 percent. Together, these four taxa accounted for 82.2 percent of everything collected and occurred at most of the sampling sites. That a few species so thoroughly dominate the catch, while dozens of others appear only rarely, is itself ecologically informative, hinting at how tightly many tropical mosquito species are adapted to particular microhabitats within the mangrove mosaic.

The authors are candid about the dataset’s limits. Because it combines a standardised repeated survey, a structured but less replicated river transect, and a set of exploratory and opportunistic collections, sampling effort was not homogeneous across all sites. Roughly two-thirds of all collection events came from the standardised design, providing a robust core for comparison, but the team advises that any comparative analysis be restricted to subsets collected under comparable protocols. Trap biases are also acknowledged: light traps and scent-baited traps each miss part of the fauna, and some taxa will inevitably remain underrepresented no matter how diverse the toolkit. Environmental conditions, from tidal flooding and freshwater flushing to stand age and salinity, vary across mangrove habitats and shape which salt-tolerant species thrive where.

Why should the wider public care about an insect inventory in South American swamps? Mangroves worldwide are recognised both as nurseries for pest and arbovirus-carrying mosquitoes and, paradoxically, as sometimes poor larval habitats, since frequent tidal flushing can wash out eggs and larvae before they complete development. Understanding which side of that balance a given mangrove occupies, and which species dominate it, directly informs assessments of public health risk and the design of management strategies for coastal zones under pressure from urbanisation and climate change. By releasing the dataset as fully documented sampling events, complete with georeferenced coordinates, trap metadata, specimen identifiers, DNA barcodes and dissected voucher material, the researchers have transformed a regional entomological campaign into an open, reusable scientific resource. For a territory where 250 mosquito species share a coastline with nearly the entire human population, that kind of traceable baseline is not a luxury. It is the foundation on which every future question about mosquitoes, mangroves and disease in the Guianas will be built.

Subject of Research: Ecology and diversity of Neotropical mosquito assemblages in mangrove habitats of French Guiana

Article Title: A mangrove-based dataset to study the ecology of Neotropical mosquitoes ( Diptera , Culicidae ) in French Guiana

Article References: Collet, M., Proisy, C., Talaga, S., Guidez, A., Vlandis, I., Keovongsack, A., Carinci, R., Gaborit, P., Davy, D., & Duchemin, J.-B. (2026). A mangrove-based dataset to study the ecology of Neotropical mosquitoes (Diptera, Culicidae) in French Guiana. ZooKeys, 1290, 227-239. https://doi.org/10.3897/zookeys.1290.189084

Image Credits: AI Generated

DOI: 10.3897/zookeys.1290.189084

Keywords: mosquitoes, Culicidae, mangroves, French Guiana, biodiversity dataset, DNA barcoding, Culex, vector ecology, Neotropical, entomology, sampling-event data, arboviruses

The study tested Marine Basic Spatial Units, or MBSUs, the grid-based statistical cells that underpin ocean accounting aligned with the United Nations System of Environmental-Economic Accounting for Ecosystem Accounting (SEEA EA). Ocean accounting aims to bring economic, social and environmental information together in a coherent, standardised frame, treating nature as stocks that generate flows of ecosystem services. But while the SEEA EA standard works reasonably well on land, the ocean presents a messier picture: complex biophysical flows, patchy data and ecosystems whose boundaries rarely align with administrative maps.

Using empirical data from Saleh Bay, the research team compared two grid cell sizes, 10 by 10 metres and 25 by 25 metres, and two methods for assigning each cell to an ecosystem type. The dominance method assigns a cell to the ecosystem with the largest coverage within it, while the hierarchy method follows a criteria-based order of management priority, in this case ranking mangroves first, then coral reefs, then seagrasses. That produced four schemes to compare: 10H, 10D, 25H and 25D.

The baseline data, called the Source, came from Sentinel-2 satellite imagery, field ground-truthing and official Indonesian government maps, including the Indonesian Mangrove Map 2021. Analysis showed Saleh Bay holds 4,809.01 hectares of coral reef, 1,625.00 hectares of seagrass and 2,172.95 hectares of mangrove, within a total ecosystem extent account covering 357,539.96 hectares. The researchers generated more than 36 million grid cells at the finer resolution and nearly 5.8 million at the coarser one, then joined the Source layers to each scheme using GIS tools in ArcMap 10.8.

The results were striking. Larger grid cells produced higher errors in estimating both total area per ecosystem and the spatial configuration of assets across the bay. The worst performer was the 25-hectare-scale hierarchy scheme, 25H, with percentage errors ranging from 16.54 to 44.06 percent relative to the Source, an overall accuracy of just 73.56 percent and a KHAT score of 0.59, rated only moderate. The coarse hierarchy approach systematically inflated the extent of ecosystems it prioritised, particularly mangroves, whose fine, intricate features were absorbed into neighbouring cells regardless of actual coverage.

The dominance method fared far better. Both dominance schemes, 10D and 25D, stayed above the roughly 85 percent overall accuracy benchmark commonly used in remote sensing, with 10D rated almost perfect alongside the Source itself and 25D rated very good. The researchers attribute this to a compensating effect: when a non-dominant ecosystem type is squeezed out of one cell, it tends to dominate an adjacent cell, so area lost in one grid is offset in its neighbour. Errors in total extent remained minor, even though local-scale spatial distributions still shifted at ecosystem boundaries.

But accuracy comes at a price. Computation times varied enormously: the 10 by 10 metre hierarchy scheme took 941 minutes, the 10 by 10 dominance scheme 1,604 minutes, the 25 metre hierarchy scheme just 286 minutes and the 25 metre dominance scheme 459 minutes. The finer grids required roughly 400 percent longer for grid generation alone, and the dominance method needed 120 to 250 percent more processing time than its hierarchy counterpart at the same cell size, largely due to additional data pivoting in RStudio. For countries with limited computing capacity, those trade-offs matter.

The stakes extend well beyond cartography. Ecosystem extent accounts form the foundation for condition accounts, ecosystem services accounts and asset accounts, so errors introduced at the gridding stage can propagate through the entire accounting chain. Monetary valuations are typically expressed per hectare, meaning extent errors directly distort economic estimates. Carbon stock accounting for blue carbon ecosystems such as mangroves and seagrasses depends on accurate extent, and misclassification can lead to misplaced conservation budgets or ineffective protection measures, either through overestimation that wastes costs or omission errors that leave ecosystems unprotected.

In Indonesia, the implications are concrete. The archipelagic nation, with roughly 17,508 islands and more than 91,300 kilometres of coastline, began testing ocean accounting in 2020 and has committed to national-scale accounts as a member of the High-Level Panel for a Sustainable Ocean Economy. Ocean accounts feed directly into marine spatial planning, permit granting, the Suitability of Marine Space Use evaluation (PKKPRL) and marine protected area management, including the Liang Ngali MPA and the developing Lipan Rakit MPA within Saleh Bay itself. Errors in the spatial frame would ripple into all of these frameworks.

The authors recommend that practitioners carefully select grid size and assignment method according to their country’s management goals, the ecosystems present and available computational capacity. Where hierarchy methods and larger grids must be used, they urge that error and accuracy values be clearly reported and disclaimers added to linked accounts. Future research, they note, should explore weighted scoring approaches that consider multiple environmental and management factors, along with the influence of geomorphology and natural patterns, while cloud-based GIS computing may help dissolve the hardware constraints that currently force such trade-offs. For a field trying to put a credible price on the ocean, the humble grid cell, it turns out, is anything but a trivial choice.

Subject of Research: Optimising Marine Basic Spatial Units for ocean accounting using empirical data from Saleh Bay, Indonesia

Article Title: Optimising Marine Basic Spatial Units (MBSU) for Ocean Accounting using empirical data from Saleh Bay, Indonesia

Article References: Rahayu, A. K., Arhatin, R. E., Gacutan, J., Agung, F., Pingkan, J., Rosdiana, A., & Yulianto, I. (2024). Optimising Marine Basic Spatial Units (MBSU) for Ocean Accounting using empirical data from Saleh Bay, Indonesia. One Ecosystem, 9, Article e125578. https://doi.org/10.3897/oneeco.9.e125578

Image Credits: AI Generated

DOI: 10.3897/oneeco.9.e125578

Keywords: ocean accounting, marine basic spatial units, SEEA EA, ecosystem extent, mangroves, coral reefs, seagrass, Indonesia, Saleh Bay, remote sensing, natural capital accounting, marine spatial planning

The effort, led by Indonesia’s Ministry of Marine Affairs and Fisheries in collaboration with the Geospatial Information Agency, the National Research and Innovation Agency and Rekam Nusantara, was anything but a routine mapping exercise. It required coaxing data out of five separate ministries and agencies, each the custodian of a different slice of the marine picture, and reconciling them under a single task force established by ministerial decree in 2023. Data were pooled in a cloud-based database with formal sharing procedures, and quality control was anchored to a new Indonesian national standard, SNI 9257:2024, which specifies metadata and quality requirements for geospatial information on shallow coastal and benthic habitats.

The technical core of the project relied on satellite imagery at a resolution fine enough for accounting purposes. Coral reefs and seagrass beds were mapped from SPOT 6 and 7 imagery, which resolves features at roughly five to six metres, far sharper than the 30-metre Landsat data that has historically constrained large-scale mapping. Before classification, the imagery underwent geometric correction, sun glint removal and water column correction using the Lyzenga algorithm, which exploits the different rates at which red, green and blue light attenuate through seawater to strip out the darkening effect of depth. Without this correction, an identical patch of reef looks darker in deeper water, confusing automated classifiers; with it, the reflectance signal reflects the substrate itself rather than the water above it.

Once corrected, the shallow benthic zone from the shoreline to the reef crest was clipped from each scene, enhanced through density slicing into as many as ten segments, and converted into binary ecosystem maps using thresholds trained on field data from Biak Numfoor in Papua. Mangroves followed a different route: analysts digitised them on screen in ArcGIS under the national standard SNI 7717:2020, using false-colour composites to make the forests stand out, and falling back on Sentinel-2 imagery where cloud cover compromised the SPOT scenes. Ground-truthing teams then snorkeled survey transects in Central Java, Central Papua and the Maluku islands, along with five marine protected areas including Raja Ampat and the Anambas Islands, recording habitat classes and cover percentages at fixed intervals to validate the maps.

The headline numbers are striking. Indonesia’s mangroves, already the most extensive in the world, expanded from 3,329,459.72 hectares in 2018 to 3,364,769.05 hectares in 2021, a gain of more than 35,000 hectares. Coral reefs grew from 1,212,207.46 to 1,216,249.74 hectares, and seagrass meadows from 273,122.60 to 273,950.87 hectares. But the national totals conceal a more troubling story told by the study’s Sankey analysis of ecosystem transitions: in several fisheries management areas, mangroves were converted to non-mangrove land uses, while reef and seagrass areas slipped into macroalgae and bare substrate. Degradation hotspots clustered in Fisheries Management Areas 571, 573, 711, 713, 714, 715 and 716, with the heaviest mangrove loss in FMA 716, seagrass decline concentrated in FMA 711 and coral reef loss in FMA 714.

The drivers behind those localised declines are overwhelmingly human. In FMA 711, mangroves have been converted for aquaculture and other uses, while seagrass beds suffer from pollution, port development and boat traffic. In FMA 714, destructive fishing practices and unsustainable tourism have battered the reefs. By contrast, the mangroves of FMA 718, the largest and healthiest in the country and a critical nursery ground underpinning Indonesia’s fish production, expanded over the study period, largely because their remoteness shields them from development pressure. The pattern is a familiar one in conservation: where people and infrastructure press hardest, ecosystems retreat, even as national averages look healthy.

Why does precision mapping matter so much? Because ecosystem extent is the denominator in nearly every calculation of what nature delivers. Coral reefs blunt wave energy and shelter coastlines from erosion; seagrass meadows bury an estimated 10 to 18 percent of the organic carbon locked into the global ocean; mangroves stabilise shorelines and buffer floods. A nationwide literature review cited in the study values these services at roughly 12,145 US dollars per hectare per year for coral reefs, 14,953 for seagrass and 18,544 for mangroves. Multiply those figures by an uncertain map and the error propagates straight into policy. Ocean accounts, aligned with the UN System of Environmental-Economic Accounting, are designed to close that gap by linking ecosystem extent and condition to the location of economic activity and human beneficiaries.

The study also exposes how wildly previous estimates diverged. Independent global datasets, built on coarser imagery, produced mangrove and seagrass figures that differed substantially from Indonesian government maps, while coral reef estimates varied by more than a million hectares depending on the source, partly because some classifications mistook sand, rubble and seagrass for reef. The new maps, derived from consistently higher-resolution imagery and validated against field data, are intended to end that ambiguity and serve as the official baseline. They are the first national seagrass maps produced at high resolution under government leadership, a notable milestone given that the only prior Indonesian-led effort relied on moderate-resolution Landsat 8 data in 2018.

The practical payoff extends across marine spatial planning, protected area management and fisheries. Ocean accounts give planners a systematic way to track whether marine protected areas are actually meeting conservation goals, to quantify the economic case for expanding them, and to inform decisions on marine use permits and catch limits. Because the accounts are spatially explicit and maintained over time, they can flag early warnings of overfishing or habitat degradation and trigger timely intervention. The authors acknowledge the hurdles that remain: training datasets drawn from 30-metre Landsat imagery did not always match the spectral and radiometric characteristics of the 5-metre SPOT scenes, ground-truthing was limited to priority sites by budget constraints, and data remain scattered across institutions.

The way forward, the team argues, demands regular satellite image acquisition, whether through government purchase or international partnership, alongside site-specific classification algorithms for reefs and seagrass and a commitment to update the maps at least every three years. Funded in part by the UK’s Blue Planet Fund through the Global Ocean Accounts Partnership, the project stands as a test case for other maritime nations wrestling with the same question: how to make the invisible value of coastal ecosystems visible in the ledgers that drive decisions. For Indonesia, the maps are more than pictures of green forests and blue reefs. They are the first entries in an account book meant to ensure that the country’s marine wealth is counted, and therefore protected, before it is spent.

Subject of Research: National-scale satellite mapping of Indonesia's coral reef, seagrass and mangrove ecosystems to support ocean accounting and marine management

Article Title: National-scale mapping of ecosystems to improve ocean accounting for marine and coastal management in Indonesia

Article References: Gunawan, T. S., Hamidah, M., Rahayu, A. K., Septiani, N. N., Pingkan, J., Hermansyah, A., Farhan, M., Sholihah, R., Arundina, A. B., Minarni, D. R., Susanti, R., Gustiar, G. G., Kusumastuti, D. N., Maharani, G. R., Nurhakim, M. D., Khalishah, P. V., Rahman, I. F., Nugianto, N., Hakim, A., … Yulianto, I. (2025). National-scale mapping of ecosystems to improve ocean accounting for marine and coastal management in Indonesia. One Ecosystem, 10, Article e155166. https://doi.org/10.3897/oneeco.10.e155166

Image Credits: AI Generated

DOI: 10.3897/oneeco.10.e155166

Keywords: Indonesia, ocean accounting, coral reefs, mangroves, seagrass, remote sensing, Sentinel-2, SPOT satellite imagery, marine spatial planning, ecosystem services, marine protected areas, fisheries management

The study, conducted in the coastal zone of Tien Hai district in Thai Binh province, targeted mangrove forests inside the Red River Delta Biosphere Reserve and the Tien Hai Nature Reserve. The Red River is the largest river system in northern Vietnam, and its delta hosts dense aquaculture, rice cultivation, and domestic wastewater discharge. Earlier water-quality research had flagged a potential risk of nutrient excess in the delta’s coastal waters, but the long-term storage of nutrients in mangrove sediments — where they can persist for decades — had remained poorly quantified.

To test whether aquaculture leaves a measurable imprint on the sediment record, the team collected six sediment cores from mangrove stands along two transects running from shrimp ponds to the river estuary. Sampling took place at low tide in September 2020, during the rainy season, using a Russian Peat Corer. Each core extended 100 centimeters deep and was sliced at 5-centimeter intervals from the surface to 50 centimeters, then at 10-centimeter intervals from 50 to 100 centimeters. At every site, the researchers also recorded mangrove species composition and counted dead trees within 5-meter circular plots, repeated three times alongside the core sampling.

Laboratory analysis combined classical geochemistry with automated colorimetry. Sediment samples were dried at 60 degrees Celsius, ground to powder, and assessed for organic matter using the loss-on-ignition method at 550 degrees Celsius for at least three hours. Grain size was measured by laser diffraction. Available phosphate was extracted with the Bray II method, while ammonium and nitrate were drawn out with a 2N potassium chloride solution. The extracts then ran through a Skalar SAN++ continuous flow analyzer, which quantified ammonium via the Berthelot reaction at 630 nanometers, nitrate through cadmium reduction and diazotization at 540 nanometers, and phosphate as a blue molybdate complex at 880 nanometers. Detection limits were 10 micrograms per liter for ammonium and nitrate and 2 micrograms per liter for phosphate, with standard samples repeated after every ten analyses to keep analytical drift below 5 percent.

The results revealed a sediment profile dominated by silt — 81.66 to 97.47 percent on average — with clay ranging from 2.31 to 15.27 percent and sand making up the remainder. Median grain size averaged 9.8 ± 1.8 micrometers, confirming the quiet, muddy depositional environment typical of mangrove forests. Organic matter content ranged from 4.88 to 9.79 percent, averaging 7.10 ± 0.94 percent, and declined significantly from the top to the bottom of the cores. The transect closer to the aquaculture ponds showed slightly higher organic matter than the transect nearer the estuary, hinting at a gradient of organic enrichment flowing outward from the ponds.

Nutrient concentrations told a more nuanced story. Ammonium ranged from 0.925 to 32.278 milligrams per kilogram, averaging 9.879 ± 4.485 milligrams per kilogram, and varied significantly by location, depth, and their interaction. Nitrate, ranging from 0.236 to 7.240 milligrams per kilogram, averaged just 0.823 ± 0.745 milligrams per kilogram and showed no statistically significant variation by location or depth. Phosphate, ranging from 0.047 to 9.124 milligrams per kilogram, averaged 1.134 ± 1.294 milligrams per kilogram and varied significantly by the location-by-depth interaction. Across all cores, nutrient levels were highest in the surface layer from 0 to 20 centimeters, declined between 20 and 50 centimeters, and changed minimally from 50 to 100 centimeters.

The spatial gradient was the study’s most striking finding. Ammonium averaged 11.281 ± 6.362 milligrams per kilogram near the aquaculture ponds, dropping to 9.206 ± 2.784 in the transition zone and 9.148 ± 3.231 near the main estuary. Phosphate followed a similar pattern, with the highest values near the ponds in one transect and in the transition area of the other. The researchers attribute this to tidal dynamics: nutrient-rich effluent from extensive shrimp ponds, which typically lack water-monitoring equipment, deposits organic matter into adjacent mangrove sediments, where microbial ammonification converts organic nitrogen into ammonium. The consistency of this pattern with earlier seawater-quality studies in the Red River estuary strengthens the case that aquaculture is the dominant nutrient source.

Depth profiles add a second layer of interpretation. The anaerobic conditions and abundant litterfall and root material in mangrove forests favor ammonification, concentrating ammonium in the upper sediment. Mangrove roots of the dominant species Kandelia obovata and Sonneratia caseolaris are most developed in the 0-to-50-centimeter layer, where they actively absorb nutrients and drive exchange between sediment and trees. Organic matter correlated positively with ammonium and phosphate at a medium level, consistent with mineralization and microbial activity releasing nitrogen and phosphorus from organic pools. Nitrate, by contrast, showed no such correlation, suggesting it is more tightly controlled by nitrification and denitrification processes than by organic matter availability.

The ecological consequences may already be visible. In sampling plots near the aquaculture ponds, the researchers counted more dead mangrove trees than in plots farther away, echoing fertilization experiments in the Indo-Pacific that showed nutrient enrichment increases tree mortality during droughts. Excess nutrients can alter detritus-based food webs, reduce the carbon-to-nitrogen ratio in sediments, and favor methanogenic bacteria — potentially accelerating greenhouse gas emissions such as carbon dioxide, methane, and nitrous oxide from mangrove soils. High nutrient loading also risks eutrophication in adjacent coastal waters, supporting algal blooms and degrading coral reefs and ecosystem resilience.

The study’s authors emphasize that ongoing monitoring is essential to determine the long-term impacts of aquaculture on mangrove forests and adjacent coastal ecosystems. Because mangroves act as natural filters and net sinks of nutrients, their capacity to absorb excess inputs is finite; when discharge exceeds uptake, the surplus spills into coastal waters and destabilizes the forest itself. Future research, the team suggests, should quantify methane emissions under different nutrient conditions and link nutrient dynamics with mangrove biomass and carbon storage, providing the evidence base for sustainable management strategies in tropical developing regions where aquaculture and mangrove conservation increasingly collide.

Subject of Research: Nutrient accumulation in mangrove sediments near aquaculture ponds in the Red River Delta, Vietnam

Article Title: Nitrate, ammonium, and phosphate patterns from mangrove sediment cores near extensive aquaculture areas in the Red River Delta, Vietnam

Article References: Toan, N., Ngoc, P., Dung, L., Tue, N., Quy, T., & Nhuan, M. (2025). Nitrate, ammonium, and phosphate patterns from mangrove sediment cores near extensive aquaculture areas in the Red River Delta, Vietnam. One Ecosystem, 10, Article e150217. https://doi.org/10.3897/oneeco.10.e150217

Image Credits: AI Generated

DOI: 10.3897/oneeco.10.e150217

Keywords: mangroves, aquaculture, Red River Delta, Vietnam, sediment cores, nutrients, ammonium, nitrate, phosphate, eutrophication, coastal ecosystems, tree mortality

Litterfall, the process by which plants shed leaves, flowers, fruits and twigs due to ageing, environmental stress, wind and weathering, is far more than botanical housekeeping. It is the primary conduit through which organic matter returns from plants to soil, feeding decomposers, enriching sediments and driving nutrient cycling. In mangrove ecosystems, litterfall is widely used as an essential measure of productivity and plays a critical role in assessing carbon accumulation rates, organic matter export and nutrient availability. Mangrove detritus is recognised as a significant carbon source for coastal food webs in tropical regions, nourishing the detrital food web and sustaining fish assemblages that in turn attract higher predators such as elasmobranchs. Understanding the quality and quantity of this litter is therefore central to grasping how mangrove forests function, how much blue carbon they sequester and how they will respond to shifting climatic conditions.

The research team selected three mangrove habitats along the coastlines of Ras Al Khaimah, dominated by the resilient grey mangrove Avicennia marina within lagoon systems at Khor, Saraya and Rams, covering a total of 474.85 hectares. The UAE’s climate is classified as hyper-arid, characterised by extremely high summer temperatures and low mean precipitation, with daily maximum temperatures in July and August reaching up to 44 degrees Celsius. From April 2021 to May 2022, the study monitored litter mass through 12 monthly collection events, deploying 34 litterfall traps designed according to the ICP Forests Level II network, a pan-European forest monitoring programme. Each trap consisted of a nylon mesh bag with a pore size of 0.5 millimetres stitched to a square iron frame, placed one metre above the ground beneath mangrove trees to avoid tidal flushing. Three control traps were positioned in areas with no canopy cover. Collected litter was oven-dried at 70 degrees Celsius for 48 hours until constant weight, weighed on a precision balance and ground for carbon estimation through loss-on-ignition at 550 degrees Celsius.

The results revealed a striking seasonal signature. Annual litterfall ranged from 0.107 to 0.768 megagrams per hectare, with the lowest values observed in February and the highest in August. The average monthly litterfall rate was 0.2607 megagrams per hectare, and significant differences amongst monthly rates were confirmed through the Kruskal-Wallis test. Seasonal analysis showed that litterfall production was highest in summer, averaging 0.405 megagrams per hectare, followed by spring at 0.320 and lowest in winter at 0.175. Summer contributed 47.8 percent of the total annual litterfall, spring 32.2 percent and winter just 20.0 percent, with all seasons differing significantly. Across the entire 474.85-hectare study area, annual litterfall was estimated at 139.605 megagrams, with carbon input from litterfall estimated at 44.41 megagrams. The median carbon content per gram of dry litter was 0.319 grams, and average monthly litterfall carbon input was 0.083 megagrams per hectare, significantly higher in summer months at 0.129 compared to 0.056 in winter.

Two scenarios could explain the pronounced summer peak. First, summer is the UAE’s flowering and fruiting season for Avicennia marina, a pattern consistent with studies from Qatar and Kuwait, where flowering typically starts in May and June and reproductive peaks coincide with the hottest months. Second, the plant may respond to water stress during high-temperature periods. Increased evaporation and low rainfall raise salinity levels along the Arabian Gulf coast, impacting conditions in semi-closed lagoons. Under such stress, transpiration becomes metabolically costly, potentially necessitating canopy thinning as an adaptive response. The Gulf’s arid and hypersaline coastal region represents a habitat where most marine species have already reached their tolerance limits, making these mangroves an exceptional case study in plant resilience at the edge of survival.

To link these ground observations to satellite data, the researchers acquired all available Sentinel-2A and Sentinel-2B imagery from March 2021 to February 2022 through Google Earth Engine, filtering scenes with less than five percent cloud cover and computing monthly averages of spectral bands. From these, they derived ten distinct vegetation indices, each targeting a specific aspect of vegetation dynamics: greenness through NDVI, EVI, SAVI and TVI; structure through RVI, LAI and RFDI; water status through MSI and NDMI; and senescence through PSRI. The Normalised Difference Vegetation Index quantifies vegetation greenness and vigour, while the Normalised Difference Moisture Index tracks vegetation water content using near-infrared and shortwave-infrared reflectance. The Plant Senescence Reflectance Index indicates vegetation stress and senescence through the pigment balance between chlorophyll and carotenoids. All index rasters were standardised to a uniform 10-metre resolution, litterfall data were interpolated to match the satellite pixel size, and 315 point values were extracted, correlated pixel-by-pixel with the index rasters over 12 months, yielding 37,800 observations.

Spearman rank correlation analysis revealed generally weak linear relationships between litterfall and the vegetation indices. RVI showed a very weak positive correlation of 0.13, while LAI and EVI were negatively correlated at -0.46 each, and SAVI at -0.35. Moderate positive correlations were observed for TVI at 0.44 and NDMI at 0.39, while PSRI exhibited a weak positive correlation of 0.17. The pairwise correlation matrix amongst the indices themselves revealed several strongly intercorrelated pairs, including LAI-EVI at 0.999 and RVI-RFDI at 0.998, indicating high redundancy due to shared spectral sensitivity to canopy greenness, a natural consequence of indices derived from similar multispectral bands. Predictors with correlations of 0.8 or above were filtered to minimise multicollinearity, retaining the index with the stronger correlation to monthly litterfall.

Because simple correlation could not capture the complex, non-linear interdependencies at play, the team turned to random forest regression, an ensemble learning method that generates large quantities of relatively uncorrelated regression trees using randomly assigned subsets of features. The dataset was split into 75 percent training and 25 percent testing sets, and hyperparameters were optimised using the Out Of Bag root mean square error from the training data. The full model demonstrated strong predictive performance, with an initial R² of 0.78 and an RMSE of 6.71, improving to R² = 0.81 following tuning with RandomizedSearchCV. The optimal configuration used 1000 trees with three features considered per split. A reduced six-index model achieved nearly identical performance, with a test R² of 0.78 improving to 0.79 after tuning. In the full model, NDMI accounted for the highest variable importance at 0.264, followed by PSRI at 0.203 and TVI at 0.156, though the reduced model produced a different ranking, indicating that importance estimates are sensitive to the composition of the predictor set.

The dominance of NDMI, PSRI and TVI carries ecological meaning. NDMI has recorded strong correlations with field measures of vegetation parameters, including plant area index and canopy gap fraction, underscoring its effectiveness in monitoring vegetation health and moisture content. PSRI has proven to outperform NDVI in tracking canopy senescence dynamics, providing clear advantages for detecting early senescence by assessing the chlorophyll-to-carotenoid ratio in leaves and fruits. That moisture and senescence indices, rather than classic greenness measures, proved most informative suggests that litterfall in these hyper-arid mangroves is governed more by water stress and pigment breakdown than by canopy vigour alone. Random forest algorithms are less vulnerable to the multicollinearity plaguing these datasets, as bootstrap aggregation and randomised feature selection at each split reduce inter-tree correlation, allowing the inclusion of multiple partially redundant indices to enhance the model’s ability to capture subtle spectral variations.

The study is not without limitations. Random forest regression cannot predict outcomes outside the range of training data, meaning pest outbreaks or extreme weather producing litterfall beyond historical records would elude the model. The approach is region-specific, as both the remote-sensing indices and ground-truth litterfall data were derived from local conditions, and previous studies of random forest spatial transfer indicate that accuracy losses can be substantial when moving to unseen regions or resolutions. Reliable replication elsewhere would require compatible vegetation-index layers, local ground-truth data for calibration, retraining under region-specific canopy, tidal and edaphic conditions, and thorough documentation of preprocessing steps. Without appropriate spatial or temporal validation, performance metrics may be overly optimistic. Nevertheless, the findings provide a basis for developing a future framework for large-scale litterfall assessment, one that could facilitate broader analyses of carbon and nutrient fluxes and ecosystem health by integrating field measurements, spatial analysis and remotely sensed vegetation indices. As the IPCC projects with high confidence that heatwaves will intensify in the Arabian Gulf, such satellite-based monitoring of the region’s mangroves may soon become indispensable for conservation amid shifting climatic conditions.

Subject of Research: Litterfall dynamics and remote sensing-based carbon modelling in hyper-arid Arabian Gulf mangrove forests

Article Title: Seasonal dynamics of litterfall production and carbon input in arid mangroves: Modelling aboveground litterfall in Arabian Gulf mangroves using remotely sensed and ground data

Article References: Gopi, K., Ksiksi, T., & Henderson, A. C. (2026). Seasonal dynamics of litterfall production and carbon input in arid mangroves: Modelling aboveground litterfall in Arabian Gulf mangroves using remotely sensed and ground data. One Ecosystem, 11, Article e146607. https://doi.org/10.3897/oneeco.11.e146607

Image Credits: AI Generated

DOI: 10.3897/oneeco.11.e146607

Keywords: mangroves, litterfall, blue carbon, remote sensing, Sentinel-2, random forest, Avicennia marina, Arabian Gulf, vegetation indices, carbon input, United Arab Emirates, machine learning

The numbers underpinning the review are striking. African rivers discharge an estimated 3,271.4 cubic kilometres of freshwater into the surrounding seas every year, roughly 8.7 percent of the global river flow into the oceans. The continent counts more than 150 rivers, but seven dominate: the Nile, Congo, Niger, Zambezi, Orange, Limpopo, and the Ubangi, a major Congo tributary. The Congo alone ranks as the world’s second-largest river after the Amazon, with an average annual discharge of approximately 1,293 cubic kilometres, contributing about 3.4 percent of all freshwater reaching the global ocean. Notably, about 71 percent of Africa’s total estuarine discharge originates from West African rivers, a fact that concentrates both ecological productivity and human pressure along that coastline.

People cluster where the water is. In 2017, an estimated 62 million people lived on African deltas and estuaries, representing about 19 percent of the total global population residing in delta environments. The Nile and Niger deltas host the overwhelming majority of these residents, with the Nile delta alone home to roughly 58 million people. Megacities including Lagos, Alexandria, Durban, Dakar, Abidjan, Mombasa, and Maputo sit on or near estuarine systems, and the review estimates that harbour operations in these seven ports alone generate between 22 and 37 billion US dollars annually, spanning cargo handling, storage, pilotage, and the broader logistics economies that depend on navigable estuarine waterways.

Ecologically, the review frames African estuaries as multifunctional systems performing at least six critical services: biodiversity support, nursery provision, water quality regulation, carbon sequestration, coastal protection, and nutrient cycling. The mixing of fresh and saltwater creates conditions that sustain mangrove forests, salt marshes, seagrass beds, and dense communities of invertebrates and fish. African estuaries and deltas contain approximately 3.36 million hectares of mangrove forest, about 19 to 20 percent of the global mangrove cover, with West Africa holding the largest share and the Niger Delta standing out as one of the most extensive mangrove ecosystems on Earth. East African mangroves are particularly species-rich, hosting a significant proportion of the world’s mangrove diversity.

The carbon mathematics of these systems deserves particular attention. Coastal wetlands are among the most effective carbon sinks on the planet, and the review cites estimates that West African mangroves store around 854 million metric tons of carbon across roughly 1.97 million hectares, with an average ecosystem carbon density of approximately 799 megagrams of carbon per hectare in the West-Central Africa region. Because mangroves bury carbon in waterlogged sediments where decomposition is slow, protecting them offers a rare double dividend: emissions avoided through conservation and carbon locked away in soils that can persist for centuries.

The economic ledger extends well beyond ports. South African estuaries alone are estimated to generate 4.2 billion rand, roughly 250 to 300 million US dollars, in economic value each year. In Tanzania’s Rufiji Delta, the provisioning services of the mangrove sanctuary were valued at nearly 16,000 US dollars per household per year in 2025. Perhaps most remarkable is the West African shellfish economy: estuarine and mangrove-based shellfisheries yield more than 300,000 metric tons annually, worth an estimated 336 million US dollars, and women constitute 79 percent of the harvesters, supporting roughly 571,935 households across 11 countries. Estuaries also function as nurseries for commercially important fish and shellfish, meaning their health directly determines the productivity of the coastal fisheries that feed millions.

Yet the review is unflinching about the threats. Pollution data from South Africa’s Knysna Estuary reveal chromium concentrations in sediments reaching nearly 1,590 milligrams per kilogram, while historical analysis of persistent organic pollutants in the Buffalo River recorded polychlorinated biphenyl levels of up to 2,329 nanograms per litre, far exceeding health advisory thresholds. In Ghana’s Pra and Ankobra estuaries, microplastic fragments and fibres permeate the sediments. Habitat degradation compounds the chemical assault: dredging, land reclamation, and dam construction disrupt the sediment and freshwater flows on which estuarine function depends, and oil exploration has severely damaged the Niger Delta’s mangroves. Globally, mangroves lost 5,245 square kilometres between 1996 and 2020, and African deforestation rates range from 0.2 to 0.5 percent annually on average, with Ghana’s historical losses reaching as high as 2 percent per year.

Overfishing is hollowing out estuarine food webs from within. Studies in Ghanaian and Nigerian estuaries report declines of 30 to over 70 percent in catches of certain commercially important species over recent decades, and fish landings in parts of the Niger Delta have fallen by as much as half since the 1980s. The pattern, familiar to ecologists worldwide, is one of fishing down the food web: large, valuable predators disappear and are replaced by smaller, faster-reproducing species of lower market value. Climate change stacks a further layer of stress, with sea-level rise threatening to inundate low-lying habitats, saltwater intrusion contaminating freshwater supplies, and shifting rainfall regimes destabilising the salinity balance that estuarine life depends on. West African coastlines are identified as especially vulnerable to rising seas.

The review’s authors argue that piecemeal responses will not suffice and call instead for integrated coastal zone management that treats catchments, estuaries, and the nearshore ocean as a single connected system. Their recommendations include strict regulation of industrial and agricultural discharges, large-scale restoration of mangroves and salt marshes, sustainable fishing regimes built on community co-management, and climate adaptation planning that explicitly accounts for sea-level rise and storm intensification. They also stress the need for sustained research and monitoring, noting that many African estuaries remain poorly instrumented compared with systems elsewhere, and for capacity building that empowers local communities as stewards rather than bystanders.

What emerges from the synthesis is a stark equation. Estuaries that shelter 62 million people, filter the continent’s runoff, nurse its fisheries, and anchor tens of billions of dollars in trade are being degraded at precisely the moment their buffering services are most needed. The review’s central message is that African estuaries are not peripheral conservation concerns but strategic infrastructure, as vital to regional and global sustainability as any engineered system, and that the window for protecting them affordably is narrowing with every polluted discharge and every hectare of mangrove cleared.

Subject of Research: The ecological, economic, and climatic importance of African estuaries and the threats facing them

Article Title: Why African estuaries matter? An expert perspective on regional and global sustainability

Article References: Hoguane, A. M., & Hoguane, C. A. M. (2026). Why African estuaries matter? An expert perspective on regional and global sustainability. Estuarine Management and Technologies, 3, 23-40. https://doi.org/10.3897/emt.3.183511

Image Credits: AI Generated

DOI: 10.3897/emt.3.183511

Keywords: African estuaries, mangroves, blue carbon, river discharge, Niger Delta, coastal fisheries, sea-level rise, pollution, integrated coastal zone management, biodiversity, ecosystem services, climate change

The research, published in Frontiers in Marine Science, was led by Zhouxiang Zheng of Huizhou University with colleagues at Sun Yat-Sen University and partner institutions. The team ran two field experiments in the Hailing Island Mangrove National Wetland Park in Guangdong Province, a subtropical monsoon site where roughly 1,816 millimeters of rain falls each year and where natural and planted mangrove stands share the intertidal flats. One experiment examined how added nitrogen changed decomposition; the other, the study’s centerpiece, tested what happens when leaves from three mangrove species are mixed in the same litterbag.

The three species were ecologically telling choices. Sonneratia apetala is an introduced fast-growing species, while Kandelia obovata and Avicennia marina are natives of southern China. Freshly fallen yellow leaves and small branches were collected from all three, along with fine and coarse roots, sealed into mesh litterbags, and staked out on the sediment or buried twenty centimeters below the surface. The researchers then retrieved the bags at intervals ranging from seven days to a year and measured how much dry mass remained, along with concentrations of total organic carbon, total nitrogen, and total phosphorus.

Species identity mattered enormously. Avicennia marina leaves decomposed fastest, with a fitted decay constant of 0.0227 per day and an estimated half-life of just 18 days. Sonneratia apetala followed closely at 20 days, but Kandelia obovata lingered, holding half its mass for 55 days. That sluggish pace tracked the leaf chemistry: Kandelia litter started with only 6.72 grams of nitrogen per kilogram and high carbon-to-nitrogen and carbon-to-phosphorus ratios of 66.36 and 625.30, whereas the two faster species carried roughly double the nitrogen and far lower ratios. Below ground, the hierarchy largely repeated itself, though fine roots everywhere decomposed glacially slowly, with half-lives stretching past a thousand days for Sonneratia.

The nitrogen-enrichment experiment, conducted earlier on the same island, applied urea to four adjacent plots at rates of zero, 22.85, 114.24, and 228.48 grams of nitrogen per square meter per year, spanning the range of nutrient pollution that aquaculture and wastewater can deliver to mangrove wetlands. Because each treatment occupied a single plot, the authors are careful to frame these results as descriptive rather than statistically conclusive. What emerged was not a tidy dose-response curve. Mass loss varied among plots in species-specific, non-monotonic ways, and the most striking signal was chemical rather than physical: in the highest-nitrogen plot, aboveground litter carried 14.02 percent more phosphorus and an 11.53 percent lower nitrogen-to-phosphorus ratio than litter from the untreated control.

That decoupling between nutrient balance and bulk decay set the stage for the mixing experiment, which asked a deceptively simple question: when two or three species’ leaves rot together, does the mixture behave as the weighted average of its parts? For each mixture and each sampling date, the team calculated an expected value from separately deployed single-species bags, weighted by the initial mass proportions, and compared it with what the mixed bag actually contained. Across four mixture compositions and five sampling dates, that yielded twenty comparisons for each response variable.

The results were lopsided in a way that should make ecologists rethink their instruments. Only four of twenty mass-remaining comparisons, or 20 percent, deviated significantly from expectation, and those departures split evenly between faster and slower than predicted. But for total organic carbon, 65 percent of comparisons were non-additive; for total nitrogen, 70 percent; for total phosphorus, 55 percent. The carbon-to-phosphorus and nitrogen-to-phosphorus ratios each departed from expectation in 60 percent of cases. In other words, mixing rewrote the elemental ledger of the decaying litter several times more often than it changed how much material remained.

Timing and direction added further texture. Most elemental departures occurred during the early and intermediate stages of decomposition, between days 15 and 60, when soluble compounds and readily available nutrients are most mobile. The deviations also leaned downward: concentrations of nitrogen and phosphorus fell below the weighted expectation far more often than they rose above it, suggesting that mixed litters tend to shed or immobilize nutrients in ways single-species bags do not capture. Notably, the three-species mixture did not consistently out-decompose the two-species combinations, reinforcing that species identity and chemical contrast, not species count, drive the dynamics.

The authors are candid about the limits of their null model. Because the component species could not be separated after co-decomposition, expected values relied on initial mass fractions, which become increasingly inaccurate as faster-decaying species shrink in contribution over time. Some apparent non-additivity in elemental concentrations may therefore reflect shifting mixture composition rather than true interspecific transfer of nutrients. The 90-day window also captures only early and intermediate decay, leaving long-term stabilization unexplored, and the measurements stopped at bulk carbon, nitrogen, and phosphorus without lignin, tannins, microbial biomass, enzymes, or sediment redox chemistry.

Even with those caveats, the implications ripple outward. Mangroves are among the planet’s most carbon-rich ecosystems, and restoration programs increasingly rely on species choices to rebuild blue-carbon stocks. If particular species combinations alter the timing and stoichiometry of nutrient return without visibly changing mass loss, then planting decisions could shift whether litter-derived nitrogen and phosphorus feed microbes, flush into coastal waters, or lock into sediments, all beneath the radar of conventional decay measurements. For a field that has long equated decomposition with disappearing mass, the message from Hailing Island is that the most consequential chemistry may be happening invisibly, in the ratios rather than the remainder.

Subject of Research: Elemental stoichiometry and decomposition of mixed mangrove litter under nitrogen enrichment

Article Title: Mangrove litter mixing alters elemental composition more frequently than mass loss, with species-specific patterns across nitrogen-enrichment plots

Article References: Zheng, Z., Cao, Q., Chen, Y., Zheng, M., Liu, Z., & Peng, Y. (2026). Mangrove litter mixing alters elemental composition more frequently than mass loss, with species-specific patterns across nitrogen-enrichment plots. Frontiers in Marine Science, 13, Article 1976668. https://doi.org/10.3389/fmars.2026.1976668

Image Credits: AI Generated

DOI: 10.3389/fmars.2026.1976668

Keywords: mangroves, litter decomposition, ecological stoichiometry, nitrogen enrichment, blue carbon, litter mixing, carbon cycling, nutrient cycling, coastal wetlands, Frontiers in Marine Science, Mangrove, litter

The Mediterranean, the authors contend, encapsulates this global crisis in a single concentrated basin. The sea is warming faster than the global average, its coasts are densely populated, its waters carry some of the world’s heaviest shipping traffic, and it is under sustained assault from invasive species arriving through the Suez Canal and other pathways. That combination makes the region an ideal laboratory for testing a new model of governance, and it is no accident that the University of Malta Maritime Platform, whose international conference on marine and maritime sustainable development seeded this research collection, sits at its heart. The editorial proposes a unified blueprint built on three pillars: Precision Science, Ecosystem-Specific Law, and Adaptive Governance. Together, these pillars aim to move ocean management away from passive observation and toward what the editors call high-resolution, evidence-based precision policy, in which every regulatory decision is anchored to quantifiable, reproducible ecological data.

The first pillar rests on a technical transformation in how scientists measure harm. In the Calabrian Ionian Sea, a team led by Menniti and colleagues has moved beyond broad-brush pollution reporting by spatially overlapping the sighting tracks of three emblematic cetacean species, the bottlenose dolphin Tursiops truncatus, the Risso’s dolphin Grampus griseus, and the striped dolphin Stenella coeruleoalba, with detailed maps of floating macro-litter. The result is a set of identified critical zones where the risk of interaction between marine mammals and debris is highest. That granularity matters, the editorial argues, because it converts vague regional pollution statistics into targeted, source-based prevention measures that can be written directly into the management programs of adjacent Special Areas of Conservation. Instead of reacting to stranded animals and entangled whales, regulators can act upstream, at the point where debris enters the water.

Complementary work in Albania’s Vlora Bay shows how computational modeling can elevate even sunken wreckage into a governed conservation asset. Modugno and colleagues combined underwater visual census, photogrammetry, and side-scan sonar to characterize wrecks on the seabed as ecological hubs operating on decadal timescales. Using graph-based spatial representations, they demonstrated that these structures function as physical barriers to sediment transport and as critical refuges for endangered species, including the Mediterranean monk seal, Monachus monachus, one of the rarest marine mammals on Earth. By translating localized ecological interactions into reproducible quantitative structures, the study gives policymakers an objective basis for validating artificial reefs within Marine Protected Area management, replacing intuition with metrics that can be audited, compared, and adaptively revised as conditions change.

At the molecular end of the precision spectrum, Vella and Vella tackle one of the most consequential blind spots in marine biosecurity: the failure of traditional taxonomy to detect cryptic species and early life stages of invasive organisms. Their analysis of alien species in the central Mediterranean deploys environmental DNA, DNA barcoding, and population-level genomics to reveal something alarming. Multiple introduction events create complex genetic admixture within invasive populations, effectively restoring genetic diversity and boosting the adaptive potential of invaders precisely as warming waters make Mediterranean habitats more hospitable to them. The technical lesson is that rapid, accurate species identification must be the first step of any invasive species response, and the policy lesson is that molecular tools belong inside regional biosecurity frameworks, where they can predict invasion pathways and shift defenses from reaction to anticipation.

The second pillar, Ecosystem-Specific Law, addresses a structural flaw in environmental regulation: broad protective mandates that ignore the particular physiological and geographic vulnerabilities of individual habitats. Badawi and Almohammadi illustrate the stakes with their study of mangrove ecosystems in the Red Sea and Arabian Gulf. These blue carbon sinks are among the planet’s most valuable climate mitigation assets, and the researchers show that high-resolution remote sensing is essential for evaluating whether restoration projects actually succeed. But their central finding is legal rather than technical. Without strict, location-specific conservation laws restricting nearby industrial impacts and unregulated exploitation, restored mangroves remain fragile. Ecological permanence, they conclude, requires mature regulation that firmly balances habitat protection with sustainable local livelihoods, calibrated to the ecotone settings where land and sea meet.

Perhaps the most striking example of sub-lethal harm escaping regulatory notice comes from the loggerhead sea turtles nesting along Maltese beaches. Koroma and Vella synthesized a six-year dataset spanning 2020 to 2025, covering the expanding nesting range of Caretta caretta in the central Mediterranean, and found that conventional conservation metrics such as simple hatching success percentages are deeply inadequate. Their innovation is embryonic morphometrics, a technique the authors describe as a biological ledger that records the physiological toll of human disruption. The ledger identified late-stage developmental arrests associated with forced nest relocations and chronic coastal noise pollution, harms invisible to standard counting methods. The implication is that reproductive rookeries demand legislation capable of countering subtle, chronic stressors such as artificial light and noise, which accumulate quietly across a six-week incubation period even when nest temperatures and hatchling numbers appear normal.

The third pillar confronts the machinery of governance itself. Enet’s analysis of the European Union’s Maritime Spatial Planning Directive calls for holistic, whole-system planning that can mediate the increasingly fierce competition for finite marine space among offshore renewable energy installations, commercial shipping lanes, and protected areas. The argument is that instruments such as the United Nations Convention on the Law of the Sea and the Global Biodiversity Framework must operate in deliberate synergy rather than parallel isolation, with spatial allocations that are dynamic and responsive to shifting ecological and economic conditions. Meanwhile, in areas beyond national jurisdiction, Sundararajan and Simon expose a legal vacuum that grows more dangerous by the year. Their assessment of the Indian Ocean Region reveals a patchwork relationship between UNCLOS, the new BBNJ Agreement on biodiversity beyond national jurisdiction, and the international climate treaty regime, within which ocean observation technologies and potential resource extraction now operate without clear accountability for damages. Their remedy is a framework of transboundary liability, capacity development, and equitable benefit sharing.

What binds these seven studies together is a conviction that the era of documenting decline must end. The editorial distills its conclusions into three recommendations for regulators and legislators. First, environmental impact assessments should be required to incorporate advanced molecular tools and high-resolution spatial interaction modeling, so that every major coastal or offshore project is evaluated against the same precision standards the science now achieves. Second, lawmakers should draft obligatory, ecosystem-specific legislation tailored to the physiological and geographical requirements of threatened habitats, from mangrove ecotones to turtle rookeries. Third, international frameworks must define institutional liability for impacts in the high seas and embed climate-smart, dynamic marine spatial planning, while institutions actively empower early-career marine conservation professionals to lead the transition. That final human dimension, the editors suggest, may prove decisive, shifting the maritime community from mere resource users into invested stewards.

The urgency underlying these recommendations is difficult to overstate. The editorial opens by situating the ocean within the Triple Planetary Crisis, framing marine degradation not as a sectoral environmental problem but as a systemic failure at the intersection of climate, pollution, and biodiversity collapse. Its authors dedicated the collection to building a governance architecture worthy of the science now available, one in which eDNA samplers, side-scan sonar, and embryonic measurement datasets feed directly into binding legal instruments. Whether that integration happens quickly enough will determine whether the Mediterranean, and basins like it, remain functioning ecosystems or become managed declines managed only on paper. The blueprint is on the table; what remains is the political will to legislate at the resolution the ocean actually operates on.

Subject of Research: Precision science and adaptive governance for marine conservation and maritime sustainability

Article Title: Editorial: Innovations and research applications for marine conservation and maritime sustainability

Article References: Vella, A., Vella, N., & Bajada, T. (2026). Editorial: Innovations and research applications for marine conservation and maritime sustainability. Frontiers in Ocean Sustainability, 4, Article 1941722. https://doi.org/10.3389/focsu.2026.1941722

Image Credits: AI Generated

DOI: 10.3389/focsu.2026.1941722

Keywords: marine conservation, maritime sustainability, Mediterranean Sea, environmental DNA, invasive alien species, loggerhead sea turtles, mangroves, blue carbon, marine spatial planning, BBNJ Agreement, ocean governance, biodiversity loss

The study focused on seven coastal subdistricts—Panceng, Ujungpangkah, Bungah, Sidayu, Manyar, Gresik, and Kebomas—chosen because they harbor the region’s principal mangrove ecosystems while experiencing sharply different levels of urban pressure. Gresik Regency is a strategic and rapidly developing coastal zone where industrialization, urbanization, and transport continue to intensify, placing simultaneous pressure on the atmosphere and on the coastal wetlands that might otherwise buffer it. Indonesia holds the largest mangrove area on Earth, but between 1985 and 2019 the country lost roughly 430,000 hectares of mangroves to aquaculture, agriculture, plantations, and coastal development, a loss that directly erodes the national carbon sink.

The methodology combined ground truth with satellite eyes. In the field, survey teams laid 100-meter transects perpendicular to the shoreline and placed 10 by 10 meter observation plots along each line at 0, 50, and 100 meters. Within these plots they identified mangrove species and measured tree diameters at breast height, feeding those measurements into species-specific allometric equations for genera such as Rhizophora, Avicennia, Sonneratia, Ceriops, Lumnitzera, Xylocarpus, and Bruguiera. Biomass was converted to carbon content using the standard assumption that carbon constitutes half of dry biomass, and carbon stocks were then translated into absorbed carbon dioxide using the atomic mass ratio of CO2 to carbon, a conversion factor of 3.67 derived from the atomic weights of carbon and oxygen.

Space-based analysis relied on 2023 Landsat 8 imagery processed on the Google Earth Engine platform. Cloud-masking algorithms produced a clean annual composite, from which the Normalized Difference Vegetation Index was calculated as an input to machine-learning classification using Random Forest and CART algorithms. Training data came from the field plots, and classification accuracy was verified with a confusion matrix. Thirteen mangrove species were confirmed across the coast, with Avicennia and Rhizophora dominating. The mapping revealed dramatic contrasts: Ujungpangkah Subdistrict held 1,615.54 hectares of mangrove, while Kebomas, one of the most developed areas, retained just 0.75 hectares, with much of its former mangrove land repurposed for development.

On the emissions side, the researchers inventoried carbon dioxide equivalents from transport fuel, livestock and poultry, liquefied petroleum gas consumption, electricity use, and population-related activities, applying standard emission factors such as 2.31 kilograms of CO2 per liter of gasoline and 3 kilograms of CO2 per kilogram of LPG. The totals exposed a stark urban-rural gradient. Gresik Subdistrict, anchored by urban mobility and logistics, emitted the most at 6,795.91 tonnes of CO2-equivalent per year, with transportation alone contributing 5,712.52 tonnes—roughly 84 percent of its total. Registered vehicles in the regency number 801,969, a figure that underscores how rapid motorization drives coastal emissions. At the other extreme, Sidayu, with its traditional fisheries and agriculture, produced the least, at 2,375.30 tonnes per year.

Mangrove carbon performance proved equally uneven, and in an instructive way. Bungah recorded the highest carbon stock density at 189.35 tonnes of carbon per hectare and the highest sequestration rate at 694.91 tonnes of CO2 per hectare per year, yet Ujungpangkah’s sheer extent gave it the largest totals: 264,803.16 tonnes of stored carbon and 971,827.60 tonnes of annual CO2 sequestration. Ujungpangkah’s forests flourish at the estuary of the Bengawan Solo River, whose heavy sediment load—over 1,700 tonnes of suspended material annually—continuously builds new land through accretion. A telling comparison emerged between Manyar and Sidayu: despite having more mangrove area, Manyar stored less carbon overall, showing that stand structure, species composition, density, and productivity matter as much as raw acreage.

Balancing the ledger against local emissions, four subdistricts—Ujungpangkah, Bungah, Manyar, and Sidayu—emerged as net carbon sinks with absorption capacity exceeding their anthropogenic output. Ujungpangkah’s mangroves sequester nearly a million tonnes of CO2 annually against local emissions of just 2,750.34 tonnes, a net balance of minus 969,077.26 tonnes. But Kebomas, Panceng, and Gresik all ran deficits. Gresik Subdistrict’s mangroves, covering only 10.67 hectares, store a mere 346.03 tonnes of carbon and sequester 1,269.92 tonnes of CO2 per year, leaving more than 5,500 tonnes of CO2-equivalent unabsorbed each year. Kebomas, with three-quarters of a hectare of mangrove against 5,220.32 tonnes of annual emissions, is the most ecologically insolvent of all.

The spatial arithmetic of restoration follows directly. To neutralize current emissions, the analysis concluded that Kebomas needs an additional 52.07 hectares of mangrove for annual CO2 sequestration—or 191.08 hectares total to also restore ideal carbon storage. Panceng requires 50.21 additional hectares for sequestration, and Gresik 57.10 hectares, with Gresik needing the largest storage-based expansion at 198.89 hectares beyond its existing 10.67. The authors argue that in these urban-industrial zones, policy must move beyond passive conservation toward active landscape reconstruction, ideally prioritizing fast-growing, high-sequestration species, and that rehabilitation targets should be anchored to minimum area requirements rather than aspiration.

The broader significance of the study lies in its framework as much as its numbers. Few previous works have integrated field-based biomass inventories, satellite-derived mangrove mapping, and comprehensive emission accounting at the subdistrict scale, and fewer still have translated the resulting deficits into concrete hectare targets. Because mangroves sequester carbon in both woody biomass and organic coastal sediments—storing more carbon per unit area than most tropical terrestrial forests and holding it for decades to centuries—they represent one of the most efficient natural climate solutions available to coastal nations. They also deliver co-benefits that engineered offsets cannot: wave damping, shoreline protection against abrasion and sea-level rise, habitat for coastal biota, and filtration of pollutants through their root systems.

For Indonesia, the stakes extend to international commitments under the Paris Agreement and to the integrity of coastal communities facing tidal flooding and erosion. The Gresik results show that even where a regency enjoys an overall carbon surplus, thanks largely to one conserved estuarine forest, urban zones can accumulate unabsorbed emissions as habitat fragmentation and land conversion strip away sink capacity. The researchers frame their hectare-level estimates as a practical planning tool for blue carbon management: site-specific restoration quotas that can guide where to plant, how much to plant, and how to monitor whether restored mangroves are actually closing the emissions gap. In a warming century, the message from this stretch of the Java Sea is that every hectare of mangrove now carries a quantifiable climate price—and that the deficit, in some places, is only about fifty hectares wide.

Subject of Research: Estimating the mangrove area required to offset anthropogenic carbon emissions in coastal Gresik Regency, Indonesia

Article Title: Estimation of mangrove requirements for the absorption and storage of anthropogenic carbon emissions in the coastal area of Gresik Regency, East Java Province, Indonesia

Article References: Sodikin, Salsabiela, M., & Candra Maulana, Y. (2026). Estimation of mangrove requirements for the absorption and storage of anthropogenic carbon emissions in the coastal area of Gresik Regency, East Java Province, Indonesia. BioRisk, 24, 169-184. https://doi.org/10.3897/biorisk.24.189492

Image Credits: AI Generated

DOI: 10.3897/biorisk.24.189492

Keywords: mangroves, blue carbon, carbon sequestration, carbon emissions, Gresik Regency, Indonesia, remote sensing, Landsat, GIS, mangrove restoration, climate change mitigation, coastal management