The scale of the human stakes is enormous. India is the world’s second-largest fish producer, with a record 175.45 lakh tonnes of fish production in 2023, and its fisheries sector has grown by 10.87 percent since 2014–15. Odisha alone produces roughly 8.73 lakh metric tonnes annually, drawing on a 480 kilometre coastline and nearly 11 lakh hectares of inland and brackish waters. Globally, small-scale fisheries account for more than 90 percent of active fishers and support nearly two-thirds of the global fish catch, yet they remain chronically underreported in statistics and overlooked in policy. Chilika exemplifies this blind spot: more than 400,000 fishers live in nearly 150 settlements around the lagoon, many operating under a unique governance system that grants exclusive fishing rights administered through cooperatives and supported by the Chilika Development Authority.

Salinity in Chilika is governed by a delicate tug-of-war between seawater pushing in through tidal inlets from the Bay of Bengal and freshwater discharging from inland rivers. The lagoon spans nearly 1,100 square kilometres during the monsoon and contracts to about 906 square kilometres in the dry months, with an average depth of just 1.8 metres. This shallow, hydrologically dynamic system is divided into four ecological sectors: the freshwater-dominated Northern Sector, the Central and Southern Sectors, and the saline-rich Outer Channel. Seasonal salinity ranges from nearly zero during the rains to around 17 parts per thousand in winter and roughly 35 parts per thousand in summer, creating one of the steepest estuarine gradients in Asia and a natural laboratory for studying how salt shapes biodiversity.

The historical record reveals dramatic swings. Average salinity fell from 22.3 parts per thousand in 1957–1958 to between 9.4 and 11.8 parts per thousand by the early 1960s, and dropped to a critical low of 8.3 parts per thousand by 1999. The culprit was partly geomorphological: the commissioning of the Hirakud Dam on the Mahanadi River in 1957 unexpectedly increased the silt load entering the lagoon, driving progressive sedimentation, choking of the Arakhakuda mouth, reduced tidal exchange, salinity decline, and rampant weed overgrowth. In response, an artificial sea mouth was opened near Sipakuda village on 23 September 2000, restoring seawater ingress. Natural inlets subsequently formed at Gabakunda in 2008, Dhalabali in 2012, and during Cyclone Phailin in October 2013, and research by Panda and Mohanty showed that the shift from a single to a multiple inlet system between 2006 and 2009 produced pronounced changes in annual mean salinity, with cascading effects on sedimentation, marine species intrusion, and ecological balance.

Extreme weather adds another layer of volatility. The Super Cyclone of 1999 devastated fisheries resources and infrastructure. Cyclone Phailin in 2013 triggered a dramatic post-monsoon salinity decline and altered nutrient concentrations, lowering phosphate and nitrate while raising silicate and ammonia. Cyclone Fani in 2019, striking in May during the lagoon’s peak salinity period, instead elevated salinity relative to other storms, while Hudhud in 2014 had minimal impact. Data from 1999 to 2021 show average salinity of 10.69 parts per thousand, ranging from 0.1 to 36.9, with the Northern Sector experiencing sharp fluctuations and the Southern Sector remaining more stable. Most recently, a deep depression over the northwestern Bay of Bengal on 13 July 2022 opened a new inlet, driving Outer Channel salinity from 21 to 34 parts per thousand in June down to zero to 2 parts per thousand by August. Broader climate phenomena, including the El Niño–Southern Oscillation, modulate these patterns by influencing precipitation, river discharge, and lagoon–sea exchange.

The biological consequences are striking. Fish diversity in Chilika is structured along the salinity gradient: freshwater species dominate the north, brackish species the centre and south, and the tidal Outer Channel supports both brackish and marine fishes. Species counts have climbed from 138 aquatic species recorded in 1918 to 336 by 2008, including 261 finfish, 28 prawns, and 34 crabs, before slipping slightly to 317 in 2023 across 207 genera, 88 families, and 23 orders. The lagoon also shelters around 700 plant and 800 animal species, including the endangered Irrawaddy dolphin, and serves as a critical stopover on the Central Asian Flyway for migratory birds. Salinity shifts impose oxidative stress on aquatic organisms, altering survival, reproduction, and distribution, and declining salinity has stressed brackish biota such as prawns, which form the backbone of the local fishery.

The 2000 hydrological intervention, however, demonstrates that salinity management can also drive recovery. Enhanced seawater exchange improved recruitment of juvenile marine fish, lifting fish landings from 11,989 metric tonnes in 2001–02 to 14,228 metric tonnes in 2011–12, documenting 56 new species, and coinciding with the reappearance of the Irrawaddy dolphin. Phytoplankton communities responded too: diatoms replaced cyanobacteria and came to dominate up to 72 percent of phytoplankton biomass, benefiting fish production. After the new inlet opened in July 2022, landings rose to 223.62 metric tonnes, with mullets and other marine species featuring prominently. Yet fishers also reported disturbances, including sand infestation, fluctuating water depths, and the arrival of unfamiliar marine organisms such as stingrays, octopuses, and jellyfish, which reshaped fishing seasons and species composition.

Habitat degradation compounds the problem. Declining salinity converts brackish habitats into freshwater-dominated systems, eliminating niches for estuarine species such as mullets and anchovies, narrowing tidal channels, and degrading seagrass meadows that serve as critical spawning and feeding grounds for prawns and crabs. Long-term desalination has fuelled invasive weed growth, particularly in the northern sector, while excessive sedimentation and intensive prawn aquaculture, locally known as gheri or bund fishing, have altered hydrology and sediment transport, impeding fish migration and nutrient flow. Embankments and dams further disrupt natural flow, fragmenting habitats and reducing species resilience. The socioeconomic fallout is cascading: declining catches and unstable incomes exacerbate poverty, malnutrition, and occupational migration, and in some cases entire villages have shifted away from fishing altogether, while shrimp aquaculture introduced in the 1980s disrupted traditional access rights and intensified competition.

The review’s authors frame salinity not merely as a physical parameter but as a socio-ecological determinant linking ecological balance with human well-being, and they chart a path forward. Key strategies include restoring ecological buffers such as mangroves, seagrass beds, and wetlands that stabilize salinity and provide fish nurseries; promoting livelihood diversification through eco-tourism, aquaculture, and small enterprises; enforcing fisheries laws such as the Marine Fishing Regulation Acts in collaboration with local communities; and building fisher capacity in adaptive practices like seasonal restrictions, spatial management, and catch diversification. Regular monitoring of salinity and hydrological parameters is deemed indispensable for guiding adaptive management, and economic valuation shows fishery resources account for over 71 percent of the lagoon’s total economic value, underscoring what is at stake.

Ultimately, the study lays the groundwork for future econometric analyses quantifying how salinity variation cascades through biodiversity and artisanal livelihoods. As climate change accelerates sea-level rise, saltwater intrusion, and cyclone intensity across low-lying Asian coasts, Chilika’s experience offers a cautionary tale and a template: salinity management, if pursued inclusively and grounded in fishers’ rights, can allow Asia’s largest brackish water lagoon to thrive both as an ecological jewel and as a lifeline for the communities whose fortunes rise and fall with its salt.

Subject of Research: Salinity dynamics and their ecological and socioeconomic impacts on artisanal fisheries in Chilika Lagoon, India

Article Title: Salinity changes and their environmental impacts on artisanal fisheries in Chilika Lagoon

Article References: Salinity changes and their environmental impacts on artisanal fisheries in Chilika Lagoon. (n.d.). https://doi.org/10.1007/s44289-026-00137-1

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00137-1

Keywords: Chilika Lagoon, salinity, artisanal fisheries, brackish water, climate change, biodiversity, tidal inlets, cyclones, Odisha, small-scale fisheries, habitat degradation, hydrology

The research was led by Dr. Meng Li of the Institute for Advanced Study at Shenzhen University, working with colleagues across six national nature reserves that protect seven representative mangrove wetlands along the Chinese coast. In total, the team collected 300 sediment samples, a sampling intensity that allowed them to compare fungal assemblages both among distant wetlands and within individual sites. Mangrove wetlands are among the most demanding habitats on Earth for microbial life. They sit at the tropical and subtropical land-sea interface, where sediments experience high salinity, low oxygen availability, and an abundance of organic matter, conditions that together create a powerful environmental filter for any organism attempting to persist there.

Fungi matter enormously in these systems. They are among the few organisms capable of efficiently decomposing lignocellulose, the tough structural material of plant tissues, and their activity drives much of the nutrient cycling that sustains mangrove food webs. Despite this ecological importance, the diversity, biogeographic distribution, and assembly mechanisms of sediment fungal communities in mangroves had remained poorly characterized, a gap the new study set out to close with a combination of high-throughput sequencing and ecological modeling.

Methodologically, the team employed dual-amplicon high-throughput sequencing, simultaneously targeting the fungal internal transcribed spacer 2 region and the prokaryotic 16S rRNA gene. This design allowed fungal and prokaryotic communities to be characterized from the same samples, opening the door to direct analysis of cross-kingdom relationships. The sequencing effort recovered 14,771 fungal operational taxonomic units, distributed across 15 phyla, 51 classes, and 594 genera. Perhaps the most humbling number in the dataset is this: roughly one-third of the observed fungal diversity could not be assigned to any known phylum. Mangrove sediments, it turns out, harbor a substantial reservoir of fungi that are effectively unknown to science, lineages whose ecological roles remain entirely unexplored.

The survey also highlighted the prominence of early-diverging fungal lineages. Rozellomycota and Chytridiomycota, groups that branch near the base of the fungal tree of life, proved to be relatively diverse and widely distributed across the sampled wetlands. Their prevalence in these sediments suggests that mangrove ecosystems may serve as important refugia for ancient fungal lineages, and it underscores how much of fungal evolutionary history remains concentrated in environments that have historically been undersampled by mycologists, who have traditionally focused on soils, forests, and freshwater systems.

When the researchers examined biogeographic patterns, a clear hierarchy of influences emerged. Geographic location exerted a stronger effect on fungal community composition than the identity of the mangrove plants themselves. Fungal communities clustered primarily by sampling site rather than by vegetation type, and two factors were associated with these patterns: mean annual temperature and dispersal limitation. The explanation likely lies in the fragmented geography of mangrove forests themselves. Because mangroves occur in patchy stands separated by stretches of unsuitable coastline, long-distance dispersal of fungal propagules between wetlands is restricted. Each forest effectively functions as a partially isolated microbial island, allowing communities to diverge over time through the combined action of environmental sorting and limited gene flow.

Zooming in to the local scale, the picture changes. Within individual wetlands, salinity and the carbon-to-nitrogen ratio emerged as the main environmental factors associated with variation in fungal community structure. Salinity acts as a physiological gatekeeper: high salt concentrations limit fungal growth to taxa capable of tolerating osmotic stress, filtering out sensitive lineages and favoring halotolerant specialists. The carbon-to-nitrogen ratio reflects the balance between carbon availability and nitrogen supply in the sediment. When this ratio is elevated, it signals an imbalance that may constrain which taxa can persist, because decomposer fungi require nitrogen to build the enzymes that break down carbon-rich plant litter. Intriguingly, total phosphorus showed an indirect positive association with fungal diversity, likely operating through its influence on nutrient availability and on the connectivity of the microbial co-occurrence network, rather than through any direct effect on fungal physiology.

To probe these biotic interactions, the team constructed a co-occurrence network from the most abundant fungal and prokaryotic taxa. The resulting network contained 777 nodes and 3,680 edges, and a remarkable 99 percent of those edges represented positive correlations, suggesting that coexistence and cooperation, rather than exclusion, dominate the visible structure of the mangrove sediment microbiome. Bacteria and archaea exhibited higher average connectivity than fungi and formed the structural backbone of the network. Yet certain fungal nodes occupied central positions, acting as potential bridges that link fungal and prokaryotic components of the community. These hub fungi may represent keystone taxa whose activities, perhaps through the decomposition of complex organic matter, create resources and conditions that shape the surrounding microbial neighborhood.

The analytical centerpiece of the study is a piecewise structural equation model, a statistical framework that allows researchers to test networks of hypothesized causal pathways rather than isolated correlations. Using this approach, the authors integrated their results into a three-tier model of fungal community assembly. At the regional scale, temperature and dispersal limitation filter which lineages can reach and survive in a given wetland. At the local scale, salinity and nutrient conditions, including the carbon-to-nitrogen ratio and phosphorus availability, further sort the regional species pool. At the micro scale, cross-kingdom interactions with bacteria and archaea fine-tune community structure. No single factor explains who lives in the mud; instead, nested layers of environmental and biological filtering operate simultaneously across spatial scales.

The implications extend beyond basic mycology. Mangrove wetlands are under sustained pressure from coastal development, sea-level rise, and changing salinity regimes, and the microbial communities that power their nutrient cycles will respond to these changes in ways that are only beginning to be understood. By establishing that salinity and nutrient chemistry govern local fungal assemblages while temperature and dispersal shape regional patterns, the study provides a predictive framework for anticipating how sediment fungal communities might shift as coastal environments warm and saltwater intrusion intensifies. Just as importantly, the large fraction of unclassified fungal diversity signals that a vast amount of functional novelty remains hidden in these sediments, potentially including enzymes relevant to lignocellulose degradation and other biotechnological applications. For now, the muddy forests of the Chinese coast have offered a rare, scale-resolved glimpse of the hidden fungal architecture beneath one of the planet’s most productive ecosystems, and that architecture turns out to be built layer by layer, from the regional climate down to the microscopic handshakes between species.

Subject of Research: Scale-dependent assembly and biogeography of fungal communities in Chinese mangrove sediments

Article Title: Chinese mangrove sediments reveal scale-dependent assembly of fungal communities

Article References: Chinese mangrove sediments reveal scale-dependent assembly of fungal communities. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: mangrove, fungal communities, sediment microbiology, biogeography, dispersal limitation, salinity, carbon-to-nitrogen ratio, co-occurrence network, structural equation modeling, Rozellomycota, Chytridiomycota, high-throughput sequencing

The technique at the heart of the study, electrical resistivity surveying, exploits a simple physical principle: different materials conduct electricity differently. Using an ABEM Tetrameter SAS 4000 in a Schlumberger configuration, the team drove current into the ground through two outer electrodes and measured the resulting voltage between two inner ones. By progressively widening the electrode spacing, they probed ever deeper layers, and computer-aided inversion converted the apparent resistivity readings into true subsurface resistivities with errors below five percent. Because salty water conducts electricity far better than fresh water or dry sand, the resistivity signatures allowed the researchers to distinguish aquifers from dry rock and, crucially, to estimate how saline the water would be before anyone drilled a well.

Converting resistivity into water quality required a calibration step. The team applied a regression model originally developed for the Lower Indus Plain, which relates earth resistivity to groundwater electrical conductivity with a coefficient of determination of 0.78. Groundwater was then classified into four categories: fresh water below 1500 microsiemens per meter, slightly saline water between 1600 and 2500, saline water between 2600 and 4000, and highly saline water above 4000. To validate the geophysical picture, the researchers also analyzed 168 water samples from dug wells and 672 soil samples collected on a ten-kilometer grid, measuring electrical conductivity, arsenic, and fluoride in an ISO-17025 accredited laboratory.

The results paint a starkly fragmented hydrological landscape. Water tables lie between 2 and 15 meters across 26 percent of the district, between 16 and 30 meters across 23 percent, and plunge below 31 meters, in places deeper than 90 meters, across the remaining 51 percent. Shallow groundwater clusters in the southern Talukas of Diplo, Islamkot, Nagarparkar, and parts of Dahli, where low-lying topography, seepage from 36 small dams, irrigation return flows, and the seasonal flooding of the Rann of Kutch create localized recharge. In contrast, central Chachro and northern Mithi show water tables exceeding 60 meters, reflecting upland terrain, the absence of dams or perennial streams, and thick unsaturated zones that swallow the sparse monsoon rain before it can reach an aquifer.

Perhaps the most sobering finding is how quickly water quality collapses with depth. At depths of 25 meters or less, the unsaturated vadose zone dominates 59 percent of the area, saline to highly saline water occupies 31 percent, and only about 10 percent of the district holds water fit for drinking, roughly 3 percent fresh and 7 percent slightly saline, concentrated in the southern parts of Diplo, Islamkot, and Nagarparkar. By 26 to 50 meters, fresh water shrinks to a single percent of the territory while highly saline water expands to 51 percent. Between 51 and 75 meters, highly saline conditions blanket 76 percent of the district; at 76 to 100 meters, 82 percent. Below 100 meters, essentially the entire aquifer system, about 19,615 square kilometers or 99 percent of the area, is highly saline, with electrical conductivity across much of the region ranging from 4100 to 35,900 microsiemens per meter.

The geology explains much of this vertical salinity gradient. The Thar Desert sits atop the Thar Basin, a granitic basement shaped by pre-Jurassic rifting and buried beneath roughly 80-meter-high Quaternary sand dunes. The stratigraphy comprises a loose dune zone, a largely non-water-bearing oxidized zone of clays and silts, coal-bearing formations hosting confined aquifers, and the crystalline basement itself. Researchers attribute the region’s inherent salinity partly to ancient marine transgressions from the Arabian Sea, which left salt deposits embedded in the sedimentary record as the sea retreated. With annual rainfall of less than 200 millimeters, nearly all of it falling in a erratic monsoon between June and September, and no irrigation network to spread recharge as in the rest of the Indus Plain, there is simply too little fresh water entering the system to flush these salts out. High evapotranspiration and long residence times concentrate dissolved minerals further.

Salinity is not the only hazard. Laboratory analysis revealed that arsenic concentrations exceed the World Health Organization guideline of 10 micrograms per liter in 10 percent of the sampled wells, particularly around Chachro and parts of Mithi and Diplo. The arsenic is predominantly geogenic, released when reducing conditions dissolve iron oxyhydroxides in sedimentary aquifer materials, a process well documented across the Indus Basin. Fluoride poses an even broader problem: 28 percent of wells exceeded the WHO limit of 1.5 milligrams per liter, likely because alkaline groundwater with pH between 7.1 and 8.6, low calcium activity, and prolonged water-rock interaction, possibly including weathering of the fluoride-bearing granitic rocks near Nagarparkar, favor dissolution of fluoride minerals. Chronic exposure to these contaminants has been linked to cardiovascular disease, diabetes, cancer, and dental and skeletal fluorosis, making water quality monitoring a public health imperative, not merely an engineering question.

So what can be done in a landscape where 90 percent of the water is undrinkable and the deeper you drill, the worse it gets? The study’s authors argue for precision rather than brute force. The 10 percent of resources that are potable should be targeted for careful, sustainable abstraction at shallow depths, while deeper saline aquifers could be repurposed entirely. Salt-tolerant crops, grasses, shrubs, and trees could turn brackish water into productive saline agriculture, and related research in Mithi has already demonstrated that salt-resistant fish species thrive in water of 9000 microsiemens per meter, opening a path to saline aquaculture as an alternative livelihood. Meanwhile, Pakistan’s experience with managed aquifer recharge in Punjab and Balochistan shows that rainwater harvesting through injection wells can meaningfully replenish aquifers; during the 2021 monsoon, roughly 55 percent of captured precipitation reached groundwater through recharge wells, and filter pits cut turbidity from 80 to 6 nephelometric turbidity units.

The study is not without limitations, which the authors acknowledge candidly. The resistivity-to-conductivity conversion relies on a regression model calibrated for the Lower Indus Plain rather than the desert itself, so site-specific calibration could sharpen future maps. Soil sampling focused on texture rather than full chemistry, precluding a quantitative assessment of soil-groundwater salinity interactions, and the survey represents a temporal snapshot that cannot capture seasonal or long-term variability in recharge and quality. Future work should pair resistivity surveys with complementary geophysical methods, numerical groundwater modeling, and sustained monitoring to build a full hydrogeochemical conceptual model of the basin.

Even with those caveats, the significance of the work extends well beyond Tharparkar. As global water shortages are projected to affect 40 percent of the world’s population by 2030, and as groundwater already sustains some 2.5 billion people, the integration of high-resolution geophysics, hydrochemistry, and GIS mapping offers a replicable, cost-effective template for other data-scarce arid regions, from the Sahara to the Kalahari to the Sonoran Desert. For the communities of the Thar, the message is more immediate: the desert’s water is finite, fragmented, and increasingly salty with depth, but it is now, at last, mapped. Knowing precisely where the thin lenses of drinkable water lie, and where drilling deeper would only deliver brine laced with arsenic and fluoride, may be the most valuable resource this water-starved district has gained in decades.

Subject of Research: Groundwater occurrence and quality mapping using high-resolution electrical resistivity surveys in the hyper-arid Thar Desert, Pakistan

Article Title: Groundwater occurrence and quality in a hyper-arid desert: Insights from high-resolution electrical resistivity surveys in Tharparkar, Pakistan

Article References: Abdul Salam, H., Gul, N., Ashraf, M., Iqbal, N., Memon, S., & Taie Semiromi, M. (2026). Groundwater occurrence and quality in a hyper-arid desert: Insights from high-resolution electrical resistivity surveys in Tharparkar, Pakistan. Hydrogeology Journal. https://doi.org/10.1007/s10040-026-03168-2

Image Credits: AI Generated

DOI: 10.1007/s10040-026-03168-2

Keywords: groundwater, Thar Desert, electrical resistivity survey, hydrogeology, salinity, arsenic, fluoride, water scarcity, Pakistan, aquifer mapping, managed aquifer recharge, hyper-arid climate

The team measured the full suite of physicochemical parameters, major ionic species, and selected trace metals using standard field and laboratory methods. What they found was a groundwater system under pressure from both natural geogenic processes and human activity. In the pre-monsoon period, salinity exceeded acceptable limits in 54.16 percent of samples, while sodium and chloride concentrations breached thresholds in 58.33 percent. Heavy metals told an even starker story: iron surpassed the standards set by Bangladesh’s Department of Environment in 75 percent of samples, manganese in 91.67 percent, potassium in 71.17 percent, and arsenic in 66.67 percent. These are not marginal exceedances confined to a few unlucky wells; they describe a broad regional pattern of contamination affecting the majority of the water sources tested.

After the monsoon, the pattern shifted but did not improve. Salinity exceedance dropped to 43.48 percent of samples, suggesting that monsoon recharge dilutes some of the salt burden, yet sodium concentrations exceeded limits in 65.22 percent of samples and chloride in 47.83 percent. More alarmingly, arsenic exceedance jumped to 95.65 percent of post-monsoon samples, while iron and manganese remained problematic in 86.96 percent and 73.91 percent respectively, and potassium in 60.87 percent. The monsoon, rather than flushing the aquifer clean, appears to mobilize or concentrate certain contaminants, particularly arsenic, in ways that make post-monsoon water in many wells less safe than the same wells produced months earlier.

To understand why, the researchers turned to the classical tools of hydrogeochemistry. Integrated analysis of the water’s ionic composition indicated that groundwater evolution in the district is strongly controlled by mineral dissolution and water-rock interaction, the slow chemical conversation between infiltrating rainwater and the sediments it percolates through. Ratios of sodium to chloride below one pointed to chloride enrichment driven by evaporation and localized saline-water influence, a signature consistent with coastal intrusion and concentration effects. Positive values of the chloro-alkaline indices revealed the occurrence of reverse ion exchange, a process in which calcium and magnesium in the water swap places with sodium held on clay mineral surfaces, further reshaping the water’s chemistry as it moves through the aquifer matrix.

The study’s methodological novelty lies in how it translates all this chemistry into a single, defensible measure of drinkability. Rather than relying on a conventional water quality index, which weights every parameter equally regardless of how much it actually varies, the team employed an entropy-based water quality index, or EWQI. Rooted in Shannon’s information theory, entropy weighting assigns greater influence to parameters that show the most variability and uncertainty across samples, letting the data itself decide which contaminants matter most. In the pre-monsoon season, 20 percent of samples rated as excellent and 35 percent as good, but a striking 30 percent fell into the extremely poor category. After the monsoon, excellent samples rose to 30 percent, yet extremely poor samples climbed to 43 percent, meaning that while some wells improved, the worst wells got worse, widening the gap between safe and unsafe water sources across the district.

Because water quality classification is inherently fuzzy, a sample is rarely purely good or purely bad, the researchers also deployed a fuzzy inference system coupled with three-dimensional response surface analysis. This modeling approach, borrowed from control engineering, allows partial memberships in multiple quality categories simultaneously and can probe how pairs of contaminants jointly influence the overall index. The analysis revealed that interactions between iron and potassium, and between manganese and arsenic, were strongly associated with variations in the EWQI. In other words, the degradation of water quality in Lakshmipur is not simply the sum of individual contaminants but emerges from combinations of metals acting together, a finding that has direct implications for which wells should be prioritized for treatment or abandonment.

Independent pollution indices corroborated the EWQI results. The heavy metal pollution index, the heavy metal evaluation index, the degree of contamination, and the nitrate pollution index all confirmed widespread heavy metal contamination across the sampled wells. The convergence of four separate indices, each constructed differently, on the same conclusion strengthens the case that metal contamination in the district’s aquifers is systemic rather than incidental. Given that arsenic enrichment in the alluvial aquifers of the Bengal delta has been documented for decades, the new study adds Lakshmipur to the map of districts where the problem persists and, in the post-monsoon window, intensifies.

The most consequential part of the analysis concerns human health. Using standard exposure models, the team calculated hazard quotients for non-carcinogenic effects of the detected contaminants and aggregated them into a hazard index. The results showed that children face greater non-carcinogenic risks than adults, with hazard index values exceeding the safe threshold of one. A hazard index above one indicates that the combined exposure to contaminants through drinking water surpasses the level considered acceptable over a lifetime, and the fact that children exceed this threshold more readily reflects their higher water intake relative to body weight and their developing physiology. In practical terms, the water from a substantial fraction of wells in the district poses measurable health risks to the most vulnerable members of the community.

What emerges from the study is a call to action grounded in seasonal reality. The authors emphasize the need for regular seasonal groundwater monitoring, safe-well mapping so that households can identify which wells are safe at which times of year, treatment of metal-contaminated wells, and sustainable management of the coastal aquifer as a whole. Because water quality in Lakshmipur is not static, a well that tests clean in March may deliver arsenic-laden water in November, monitoring programs that sample only once a year risk systematically missing the worst conditions. The integration of entropy weighting, fuzzy logic, pollution indices, hydrogeochemical interpretation, and health risk assessment in a single framework offers a template that could be applied to other coastal districts of Bangladesh and to deltaic aquifers worldwide facing similar combinations of salinity, geogenic metals, and human pressures.

The researchers also chart a path forward. Future work, they note, should include long-term seasonal observations, denser sampling networks, and formal uncertainty and sensitivity analyses to sharpen groundwater quality assessments under changing climatic and anthropogenic conditions. As sea levels rise and extraction intensifies across the Ganges-Brahmaputra-Meghna delta, the pressures on aquifers like Lakshmipur’s will only grow. This study demonstrates that with the right analytical toolkit, it is possible to see not just whether groundwater is contaminated, but when, where, and why, knowledge that coastal communities will need in increasing measure as the seasons continue to reshape the water beneath their feet.

Subject of Research: Seasonal hydrogeochemistry, water quality, and health risks of coastal groundwater in Lakshmipur District, Bangladesh

Article Title: Hydrogeochemical evaluation and entropy-driven water quality assessment of Lakshmipur District’s groundwater, Southeastern Bangladesh

Article References: Hasan, M. M., Haque, K. E., Ahmed, S., Hasan, M. N. I., & Hasan, M. M. (2026). Hydrogeochemical evaluation and entropy-driven water quality assessment of Lakshmipur District’s groundwater, Southeastern Bangladesh. Environmental Geochemistry and Health, 48(15), Article 616. https://doi.org/10.1007/s10653-026-03501-4

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03501-4

Keywords: groundwater, Bangladesh, coastal aquifer, arsenic, heavy metals, salinity, entropy water quality index, fuzzy inference, health risk assessment, hydrogeochemistry, water pollution, seasonal monitoring

Researchers led by Aine O’Nuanain of Louisiana State University set out to measure how the decomposition of smooth cordgrass, Spartina alterniflora, varies across brackish marshes at different distances from the West Pointe à la Hache freshwater siphon in Plaquemines Parish. The siphon, built in 1991, consists of eight tubes each 183 centimeters in diameter and can push up to 76.5 cubic meters of Mississippi River water per second into wetlands that were historically disconnected from the river. Its stated goals are to raise the ratio of marsh to open water, reduce salinity, and improve growing conditions for saltmeadow cordgrass. Yet the freshwater and nutrients it delivers could also accelerate or slow the breakdown of plant litter—a process that recycles nutrients, builds soil, and ultimately determines whether a marsh can keep pace with rising seas.

Decomposition sits at the heart of marsh survival. In organic-rich marsh soils, the balance between plant production and plant decay controls whether the land surface gains or loses elevation. Fast decay can release carbon to the atmosphere and water, while slow decay allows organic matter to accumulate and support the soil. Prior research has linked decomposition rates to inundation, temperature, salinity, and precipitation, but the picture is messy: some studies find that more flooding speeds decay, others find it slows it, and salinity has been reported to have positive, negative, or negligible effects depending on the marsh. Disentangling these collinear drivers is notoriously difficult, and the effects of river diversions on litter decomposition in brackish and saltwater wetlands had never been well quantified.

The team deployed a classic litter bag experiment at three Spartina alterniflora-dominated sites—WPH1, WPH2, and PS7—located 1.2, 6.2, and 11.5 kilometers from the siphon. Live cordgrass collected near Cocodrie, Louisiana was dried at 60 degrees Celsius, and exactly 25.0 grams of leaves and stems were sealed into each mesh bag. Five bags were strung along a line and staked to the marsh surface at plots 1, 10, 25, 50, and 100 meters from the marsh edge along a transect at each site. The bags sat through two-month deployments in the summers of 2018 and 2019, when the siphon was closed, and 2021, when it was open, for durations of 63 to 65 days. Recovered bags were rinsed over a 125-micron sieve, dried to constant mass, and weighed to the nearest 0.1 milligram to calculate the percentage of litter lost per day and an exponential decay coefficient.

The results defied the researchers’ expectations. Decomposition was fastest in 2021—the year the siphon was running—when rates averaged 1.27 percent of mass lost per day, compared with 1.20 percent in 2018 and 1.15 percent in 2019. But 2021 was also the year with the lowest water temperature, the lowest air temperature, and the lowest salinity, contradicting the common finding that warmer, saltier conditions accelerate decay. Salinity in 2021 averaged just 3.42 practical salinity units, versus 10.93 in 2018 and 8.17 in 2019, a dramatic freshening driven by the combination of siphon discharge and heavy rainfall. When the team ran a formal model selection analysis using the Akaike Information Criterion corrected for small sample size, a single variable emerged as the best predictor of decomposition: precipitation, with a positive relationship and an AIC weight of 0.56.

The explanation lies in the dual role of rain. Precipitation directly wets plant litter on the marsh surface, and wetting is known to enhance microbial breakdown of the labile, easily decomposed fraction of organic matter. Indirectly, rainfall and river discharge both push salinity down, and lower salinity may favor different microbial communities and improve litter quality for decomposers. Because water temperature, salinity, and precipitation were cross-correlated across years, the authors caution that their relative contributions cannot be fully separated. Still, the coincidence of high rainfall, low salinity, and peak decomposition in 2021—when the siphon was open—suggests that freshwater inputs from both sky and river acted together to speed the decay of cordgrass litter.

Among sites, the pattern was equally surprising. The marsh farthest from the siphon, PS7, had the highest decomposition rate at 1.29 percent per day, while the two sites closer to the siphon, WPH1 and WPH2, averaged 1.16 and 1.17 percent per day and did not differ from each other. Elevation and inundation explained this gradient: PS7 sat highest above the water at 0.248 meters NAVD88 and was flooded only 8.90 hours per day on average, whereas WPH1, the lowest site at 0.109 meters, was inundated 15.83 hours per day. Contrary to the prediction that more flooding means faster decay, the driest site decayed fastest. The likely mechanism is oxygen: prolonged flooding starves the marsh surface of air, slowing the metabolism of detritivores and aerobic microbes. Previous work by White and Trapani likewise found that increased tidal inundation reduced Spartina litter decomposition, and the authors note that detritivore activity, which they did not measure directly, may underlie the pattern.

The study has honest limitations. The team could not measure nutrient conditions across sites or years, even though Mississippi River water carries elevated nitrate and ammonia that prior research suggests can accelerate microbial breakdown of organic matter. If nutrient enrichment mattered, its effect should have been strongest at WPH1, closest to the siphon—yet that site did not have the highest decomposition rates, even in 2021. Soil chemistry may also cap how much added nutrients can stimulate decay. Site-specific precipitation and air temperature data were unavailable, and a sonde failure at WPH1 in 2019 forced the researchers to interpolate water temperature and salinity from a nearby station using regression models with r-squared values of 0.98 and 0.51 respectively. These compromises are common in litter bag studies, but they add uncertainty to an already tangled web of correlated drivers.

The broader implications reach into the heart of Louisiana’s fifty-billion-dollar coastal master plan. River diversions and siphons hold genuine promise for rebuilding land, but this study shows they can also alter the ecological machinery that determines whether rebuilt land persists. Wet years will bring more freshwater runoff into brackish marshes, higher river stages, and more frequent opening of diversions—compounding freshwater conditions and, apparently, accelerating litter decay. Faster decay could undermine the carbon sequestration and soil-building services that make marshes resilient to sea-level rise, a concern other researchers have raised about nutrient influx from rivers. The authors recommend that future restoration monitoring quantify litter decomposition, soil and water nutrients, and—critically—the decay of belowground biomass, which contributes most of the organic matter in marsh soils. As the delta’s engineers reopen the pipes to the Mississippi, the invisible world of decomposers may prove just as important as the sediment they deliver.

Subject of Research: Effects of a Mississippi River freshwater siphon and environmental drivers on Spartina alterniflora litter decomposition in Louisiana brackish marshes

Article Title: Decomposition of Spartina alterniflora (smooth cordgrass) in coastal Louisiana brackish marshes influenced by a freshwater siphon

Article References: O’Nuanain, A., Benelli, A., Winston, J., Swenson, E. M., López-Duarte, P. C., Roberts, B. J., & Polito, M. J. (2025). Decomposition of Spartina alterniflora (smooth cordgrass) in coastal Louisiana brackish marshes influenced by a freshwater siphon. Discover Ecology, 1(1), Article 16. https://doi.org/10.1007/s44396-025-00019-4

Image Credits: AI Generated

DOI: 10.1007/s44396-025-00019-4

Keywords: Spartina alterniflora, litter decomposition, coastal Louisiana, Mississippi River, freshwater siphon, brackish marsh, wetland restoration, salinity, precipitation, inundation, carbon sequestration, land loss

Coastal lagoons are among the most dynamic ecosystems on Earth. Stranded between rivers and the sea, often connected to the ocean only by a narrow, intermittently open inlet, they experience swings in salinity, water level, and temperature that would kill most marine or freshwater communities outright. The animals that thrive there, collectively known as macrozoobenthos, the worms, snails, insect larvae, and crustaceans large enough to see with the naked eye, are therefore extreme specialists in tolerating instability. For decades, ecologists have used these bottom-dwelling assemblages as biological barometers: because they live in the sediment and cannot easily flee deteriorating conditions, their species composition integrates environmental stress over weeks, months, and years. In Garzón, that barometer registered a dramatic change of weather, metaphorically and literally.

The research team assembled an unusually comprehensive dataset, combining regular benthic sampling with measurements of salinity, water depth, temperature, nutrient concentrations, and the biomass of submerged macrophytes, the rooted aquatic plants that grow entirely underwater. They also examined regional climatic trends to place the lagoon’s behavior in a broader context. The statistical analysis, which included methods for detecting shifts in multivariate community structure and partitioning the contributions of individual environmental drivers, revealed two clearly demarcated phases. The first, spanning 2018 to 2022, was a period of high environmental variability in which the lagoon had no submerged vegetation at all and the entire benthic community was dominated by a single estuarine gastropod, a small snail identified as Heleobia aff. australis.

That first phase tells a story of ecological simplification under stress. When salinity and temperature fluctuate widely, as they did in Garzón during those years, most bottom-dwelling species are pushed beyond their physiological limits. What survives is often a handful of generalists, and in this case one snail genus proved supremely well adapted to the lagoon’s erratic conditions. Heleobia snails are classic inhabitants of South American brackish waters, tolerant of both marine influence and freshwater pulses, and capable of reaching enormous densities on soft sediments. A community reduced essentially to one dominant species is not necessarily a dead community, but it is a fragile one, with simplified food webs and diminished functional redundancy, the insurance policy that biodiversity provides when conditions change.

The second phase, from 2023 to 2024, could hardly have been more different. Salinity dropped to stable low levels, and into that newly freshened water came an exuberant growth of Myriophyllum quitense, a submerged macrophyte also known as Andean water milfoil. The plant spread through the lagoon with such vigor that the researchers describe it as excessive growth, blanketing sediments that had been bare sand and mud for years. Where plants go, animals follow. The benthic assemblage reorganized around a new cast of characters: Heleobia parchappii, a freshwater-tolerant relative of the earlier dominant snail, and chironomids, the larval stage of non-biting midges, which are classic opportunists in nutrient-rich, vegetated freshwaters. Both are considered opportunistic taxa, species that capitalize rapidly on newly available habitat and resources.

The mechanistic chain the researchers traced is a textbook example of how climate variability can cascade through an ecosystem. Regional climatic anomalies during the study period altered the hydrological balance of the lagoon, changing the mix of freshwater inflow and marine exchange that determines its salinity regime. Between 2018 and 2022, the statistical models showed that species responses were governed primarily by salinity and temperature, the abiotic master variables of any estuarine system. Once those variables stabilized at low salinity in 2023 and 2024, the picture changed. Salinity relief opened the door for macrophyte colonization, and once the plants established, the dominant factors structuring the benthic community became a broader set that included macrophyte biomass itself. In other words, the ecosystem shifted from being controlled purely by physical stress to being co-organized by its own living structure.

This transition from physical to biological control has deep roots in ecological theory. Submerged macrophytes are ecosystem engineers: they slow water movement, trap fine sediments, release oxygen through their tissues into the sediment, and provide a three-dimensional habitat that shelters small invertebrates from predators. Their presence can lock a shallow lagoon into a clear-water, vegetated state, while their absence leaves the system vulnerable to wind-resuspended sediments and phytoplankton dominance. Theorists have long described such systems as having alternative stable states, with abrupt transitions between them. Garzón’s seven-year record provides a real-time illustration of one side of that switch: a bare, salinity-stressed, single-species benthos giving way to a vegetated, freshened, multi-taxon community within roughly two years.

The findings carry practical weight for environmental management well beyond Uruguay. Coastal lagoons worldwide face a pincer movement from climate change and eutrophication, with warming, altered rainfall, sea-level rise, and nutrient runoff all pushing on the same sensitive levers of salinity and nutrient balance. Monitoring programs, which many countries maintain at considerable expense, are sometimes criticized as slow to reveal anything actionable. This study demonstrates the opposite: a well-designed monitoring series, combining physicochemical measurements with benthic sampling, can detect structural reorganization in an ecosystem as it happens, and can attribute that reorganization to identifiable drivers. The physicochemical data underlying the work are publicly available through Uruguay’s National Environmental Observatory, and the monitoring itself was conducted under a formal collaboration between Uruguay’s Ministry of Environment and the Universidad de la República, a model of how government science agencies and universities can pool resources.

There is also a cautionary note embedded in the data. The arrival of lush submerged vegetation and a more diverse benthic community might look like recovery, and in some respects it is: more species, more habitat structure, more pathways for energy flow. But the new assemblage is dominated by freshwater-tolerant opportunists, and the underlying driver was climatic anomaly, not pollution control or restoration. If regional rainfall and hydrology swing back, the lagoon could flip again, and each flip resets the benthic community to whichever species can colonize fastest. Ecologists have increasingly recognized that biodiversity change in dynamic ecosystems is often about turnover rather than simple loss, with species replacing one another as conditions cycle. Garzón’s record captures that turnover in unusually sharp relief, showing that the identity of a lagoon’s inhabitants can be rewritten almost entirely within the span of a monitoring career.

For the researchers, the broader lesson is about speed. Rapid submerged plant growth, triggered by a window of stable low salinity, restructured an entire benthic assemblage faster than most ecological studies are designed to detect. As climate variability intensifies, the windows are opening and closing more abruptly in transitional ecosystems everywhere, from Mediterranean lagoons to Baltic coastal bays. The Garzón study suggests that the communities living in these systems are not slowly adjusting to a changing world but are instead being periodically dismantled and reassembled, with each reassembly contingent on the particular sequence of salinity, temperature, and vegetation that precedes it. Seven years of patient sampling on a windswept Uruguayan lagoon has made that hidden choreography visible, and it is a choreography that coastal managers, and the ecosystems they steward, will need to learn to anticipate.

Subject of Research: Temporal changes in macrobenthic diversity during rapid submerged macrophyte growth in a subtropical coastal lagoon

Article Title: Temporal changes of macrobenthic diversity during rapid submerged plant growth in a subtropical coastal lagoon

Article References: Temporal changes of macrobenthic diversity during rapid submerged plant growth in a subtropical coastal lagoon. (n.d.). https://doi.org/10.1007/s10661-026-15968-w

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15968-w

Keywords: coastal lagoon, macrobenthos, biodiversity, submerged macrophytes, Myriophyllum quitense, salinity, climate variability, Uruguay, environmental monitoring, benthic communities, ecosystem regime shift, Heleobia

The team, led by Charrel A. Williams with Murty S. Kambhampati and Rayan Demery, set out to test a deceptively simple question: does salinity change how toxic copper is to aquatic life? The hypothesis going in was that a moderate salinity of 10 parts per thousand, combined with a copper concentration of 1.0 parts per million, would offer shrimp the best protection. The data told a different story. Optimal survival occurred at the highest salinity tested, 20 parts per thousand, paired with the lowest copper dose of 0.25 parts per million. In other words, the protective effect of salt was stronger than the researchers anticipated, and it scaled upward rather than peaking at an intermediate level.

The experimental design was methodical. Saltwater solutions were prepared at 1, 5, 10, and 20 parts per thousand and aerated in glass aquaria for up to ten days to stabilize the media. Copper treatments were made from copper sulfate pentahydrate at concentrations of 0.25, 0.50, 1.0, and 2.0 parts per million, alongside copper-free controls. Shrimp measuring roughly two to two and a half centimeters were acclimated overnight to their assigned salinity before being placed four to a bowl, with each treatment run in triplicate for a total of twelve animals per salinity-copper combination. The animals were then monitored at intervals spanning three to ninety-six hours for mortality, behavioral changes, and visible deformities.

Water quality was held steady throughout the trials, with dissolved oxygen averaging 8.675 parts per million, pH at 6.88, and temperature at 28.75 degrees Celsius—conditions within the known tolerance range for Palaemon species. That stability matters, because it means the differences in survival the team recorded can be attributed to the variables under test rather than to drifting environmental conditions. The shrimp themselves are well suited to this kind of work. Native to North American estuaries, they are euryhaline, meaning they tolerate salinities from near-freshwater to hypersaline, and previous research has established them as sensitive bioindicators of metal contamination.

The results were unambiguous. Copper toxicity increased as salinity decreased, with the fastest and most severe mortality occurring at 1 part per thousand, the lowest salinity tested. At that salinity, every shrimp exposed to 1.0 parts per million copper was dead within twelve hours, and the 5 parts per thousand replicates reached complete mortality by twenty-four hours. By contrast, at 10 and 20 parts per thousand, death came more gradually, with the lethal threshold for half the population not exceeded until around forty-eight hours. The lethal concentration, or LC50, values rose steadily with salinity, confirming a clear protective gradient.

Dose mattered as much as salt. Mortality followed a strict dose-response relationship across every salinity level: 0.25 parts per million copper produced the lowest death rates, while 2.0 parts per million was the most lethal concentration tested, pushing all replicates past the LC50 threshold by forty-eight hours regardless of salinity. Intermediate doses of 0.50 and 1.0 parts per million fell in between, with mortality accelerating more rapidly at the higher of the two. Notably, even in copper-free control bowls, shrimp held at 1 and 5 parts per thousand reached the LC50 threshold within twenty-four hours—a baseline observation suggesting that low salinity alone stresses these animals enough to influence survival, independent of any metal exposure.

The chemistry behind this pattern is well understood. In saltier water, abundant sodium and chloride ions compete with copper ions for binding sites on cell membranes, effectively crowding the metal out of biological uptake pathways. Chloride ions also bind copper into dissolved complexes that are far less bioavailable than the free copper ions that wreak havoc inside cells. The net effect is that the same nominal copper concentration delivers a much smaller toxic payload to an animal’s tissues in seawater than it does in nearly fresh water. This mechanism aligns with earlier findings in fish and crabs showing that copper toxicity tracks closely with the osmoregulatory demands of the organism.

The visible toll on the shrimp told the same story. Animals in the highest salinity treatments were noticeably more active and showed fewer deformities—discoloration, reduced mobility, and failure to respond when their bowls were gently agitated—than those in dilute media, a trend consistent across all copper concentrations. Shrimp dying at higher copper doses, 1.0 and 2.0 parts per million, took on a redder hue at death than those exposed to lower concentrations, echoing prior reports that copper exposure alters shrimp pigmentation. Copper is known to generate free radicals through its redox cycling between oxidation states, driving oxidative stress that damages lipids, proteins, and DNA, and to disrupt ion regulation through the chloride cells that aquatic animals rely on to maintain their internal salt balance.

Statistical analysis sharpened the temporal picture. A two-way analysis of variance found significant interactions between salinity and copper on survival at exposure times of 3, 6, 9, 12, and 24 hours, with p-values below the 0.05 threshold, indicating that during the critical first day of exposure both variables—and their combination—strongly shaped whether shrimp lived or died. At longer exposure times of 48, 72, and 96 hours, the effect lost statistical significance, suggesting that by then the fate of the animals had largely been sealed by the early hours of intoxication. The practical lesson is that the first day of a pollution event may be the decisive window for estuarine organisms.

The authors caution that species-level identification of the shrimp was not performed, and different Palaemon species may vary in salinity tolerance and copper sensitivity, a limitation worth bearing in mind. Still, the broader message is clear and consequential: salinity is not a background variable in metal toxicity but an active modulator of it. The team calls for follow-up work using techniques such as inductively coupled plasma spectrometry to quantify how much copper actually accumulates in shrimp tissue at different salinities, and for long-term studies of how chronic exposure affects reproduction, growth, and population dynamics. For the roughly 190 million pounds of metallic ions released into United States waters each year, the findings suggest that where a pollutant lands—up a freshened river delta or out in the saline bay—may matter as much as how much of it there is.

Subject of Research: The modulating effect of water salinity on acute copper toxicity in estuarine grass shrimp (Palaemon spp.)

Article Title: The impact of salinity on copper-induced toxicity in Palaemon spp.: effects on survival, morphological deformities, and toxicity indicators

Article References: Williams, C. A., Kambhampati, M. S., & Demery, R. (2026). The impact of salinity on copper-induced toxicity in Palaemon spp.: effects on survival, morphological deformities, and toxicity indicators. Discover Toxicology, 3(1), Article 3. https://doi.org/10.1007/s44339-025-00027-9

Image Credits: AI Generated

DOI: 10.1007/s44339-025-00027-9

Keywords: copper toxicity, salinity, Palaemon, grass shrimp, estuarine ecotoxicology, LC50, heavy metal pollution, osmoregulation, bioavailability, water quality, dose-response, Discover Toxicology

The Muriganga estuary, part of the Indian Sundarbans delta, is a macro-tidal system fed by freshwater from the Ganges, known locally as the Hooghly River. Under stable conditions it remains mesohaline, meaning its salinity sits in a moderate range, and slightly alkaline with a pH above 8. The estuary had already endured a punishing sequence of storms: Cyclone Fani in 2019, then Bulbul and Amphan in 2020 and 2021. Paul and colleagues had anticipated this vulnerability. In 2019 they established a dedicated ‘Cyclone Ecology’ research program with three permanent sampling stations arranged along a north-south axis of the estuary, specifically so that when the next storm arrived, they would have baseline data in hand rather than scrambling to reconstruct it afterward.

That foresight proved decisive. Yass made landfall near Dhamra Port in Odisha with maximum sustained winds of 130 to 140 kilometers per hour, gusting to 155, before sweeping across the West Bengal coast and passing directly over the program’s sampling stations. The timing was brutal in more ways than one. The storm coincided with an astronomical high tide of 5.71 meters at nearby Sagar Island, and Yass drove a storm surge of 3.5 to 5 meters, with tidal waves rising 1 to 2 meters above the astronomical tide. Nearly 1,195 millimeters of rain fell in a short period, triggering massive inundation on both banks of the estuary. In the Bay of Bengal itself, sea surface temperature dropped by about 3 degrees Celsius, while salinity and water density rose by roughly 1 practical salinity unit and 2 kilograms per cubic meter respectively.

The team’s sampling design was deliberately asymmetric, reflecting the realities of fieldwork in a disaster zone. Pre-cyclone samples were collected on three occasions between November 2020 and April 2021, providing a solid baseline of the estuary’s copepod community. After Yass, the flooding destroyed roads to Namkhana, the town adjacent to the estuary, and the COVID-19 pandemic complicated the mobilization of scientific resources. Despite these obstacles, the researchers managed four post-cyclone sampling trips at six-day intervals between 4 and 22 June 2021. On each visit they towed a 200-micrometer plankton net fitted with a mechanical flowmeter from a dinghy boat after sunset on the high tide, sampling sub-surface water at depths of 0.3 to 0.5 meters. Water temperature, salinity and pH were recorded simultaneously with a multi-parameter probe, and copepods were preserved in 4 percent formalin for species-level identification under the microscope.

The physical fingerprint of the storm was unmistakable. Before Yass, salinity in the estuary ranged from 7.50 to 17.90; afterward it climbed to a sustained range of 15.90 to 20.80, transforming the system from mesohaline to polyhaline for weeks. This saltwater intrusion from the adjacent Bay of Bengal echoed the aftermath of Cyclone Aila in 2009, but stood in contrast to Fani, Bulbul and Amphan, none of which had shifted the estuary’s salinity regime in this way. Water temperature, by comparison, showed no drastic change, remaining between 29.10 and 31.20 degrees Celsius in the post-cyclone period, consistent with the typical seasonal behavior of a tropical estuary. The pH stayed slightly alkaline, likely a consequence of the persistent high salinity, a pattern previously observed after Cyclone Phailin pushed salt water toward the estuary mouth.

What happened to the copepods was more surprising. Previous cyclones hitting the Muriganga had consistently knocked down both species richness and total abundance, and similar declines have been reported after storms in estuaries across India, South Africa and Taiwan. After Yass, the opposite occurred. Species richness rose from a pre-cyclone range of 17 to 20 species to a post-cyclone range of 20 to 24. Shannon diversity climbed from 2.37 to 2.61 up to 2.79 to 3.00, while Simpson’s index and Pielou’s evenness both increased as well. Most strikingly, total copepod abundance more than doubled, from 307,044 individuals per cubic meter before the storm to 650,635 individuals per cubic meter afterward. The authors caution that the asymmetry in temporal replicates before and after the storm means these figures should be interpreted carefully, but the direction of change contradicts nearly every previous cyclone study in the region.

The identity of the dominant species changed too. Before Yass, the tiny calanoid copepod Bestiolina similis was the most abundant member of the community, contributing up to 20.52 percent of total abundance, with Paracalanus parvus and Acartiella tortaniformis as co-dominants. After the storm, Acartiella tortaniformis took over as the most abundant species, followed by the cyclopoid Oithona brevicornis and Paracalanus parvus. Relative abundances of Canthocalanus pauper, Temora turbinata, Corycaeus crassiusculus and various Oithona species all rose. At the family level, the Paracalanidae, which had made up 49 to 59 percent of the community before the storm, fell to 28 to 35 percent, while the Oithonidae surged from 3 to 8 percent up to 13 to 19 percent. Two species, Labidocera euchaeta and Oithona nana, appeared in post-cyclone samples despite being entirely absent before. Labidocera euchaeta is not a resident of the Muriganga at all; it is a marine intruder, and the polyhaline conditions created by the storm surge likely allowed it to thrive temporarily, much as marine migrant species had flooded into South Africa’s St. Lucia estuary after Cyclone Imboa.

The rise of the Oithonidae carries a plausible ecological explanation. Oithona species are omnivores that feed heavily on organic debris, dinoflagellates, diatoms and proto-zooplankton, and cyclones typically flush large quantities of organic matter into estuarine waters. The same pattern emerged after Cyclone Aila, when the relative abundance of Oithona brevicornis jumped from zero to 10.5 percent, and after Cyclone Hudhud struck Chilika Lagoon, where cyclopoid copepods also increased. In other words, Yass may not have simply scattered the community; it may have restructured the food web’s resource base in a way that favored debris-feeding cyclopoids over the calanoids that had dominated under stable conditions.

Perhaps the most conceptually important finding concerns spatial homogenization. Before the cyclone, multivariate analyses using non-metric multidimensional scaling, Bray-Curtis dissimilarity and PERMANOVA revealed significant station-to-station differences in copepod assemblages, with a Pseudo-F of 17.66 and a p-value of 0.005, indicating that each sampling site hosted a distinct community. After Yass, that spatial structure vanished entirely: the PERMANOVA returned a Pseudo-F of just 0.41 with a p-value of 0.95, and SIMPER analysis showed average within-period similarity jumping from 37.04 percent to 77.09 percent. The storm, through its massive flooding and mechanical forcing, appears to have blended the copepod community into a single homogeneous assemblage across the estuary, a short-term homogenization of the spatial niche also observed after Cyclone Amphan.

Beyond its findings about one estuary, the study delivers a pointed methodological message. The rapid recolonization and restructuring observed within days to weeks suggests that bi-weekly, monthly or seasonal sampling frequencies are too coarse to capture the short-term ecological dynamics that follow a cyclone. The authors recommend that sampling begin within the first week after landfall and continue at daily or weekly intervals for weeks or months, with the timeline calibrated to the estuary’s water residence time, the distance from the landfall site and the complexity of the copepod community. They even suggest deploying Lagrangian floats to record real-time changes as a cyclone passes. Because India has no institutional mechanism for regular estuarine monitoring, the researchers argue that the United Nations Ocean Decade, running from 2021 to 2030, should serve as the baseline for establishing such programs. With cyclone intensity increasing in the Bay of Bengal, the copepods of the Muriganga may be among the most sensitive early-warning indicators of how tropical estuaries will weather a stormier future.

Subject of Research: Short-term effects of tropical cyclone Yass on copepod community structure in the Muriganga estuary, India

Article Title: Short-term impact of cyclone Yass on the copepod community of Muriganga estuary of India

Article References: Paul, S., Karan, S., & Bhattacharya, B. D. (2026). Short-term impact of cyclone Yass on the copepod community of Muriganga estuary of India. Discover Ecology, 2(1), Article 7. https://doi.org/10.1007/s44396-026-00024-1

Image Credits: AI Generated

DOI: 10.1007/s44396-026-00024-1

Keywords: Cyclone Yass, copepods, Muriganga estuary, Indian Sundarbans, zooplankton, estuarine ecology, Bay of Bengal, tropical cyclones, Oithona brevicornis, salinity, biodiversity, cyclone ecology

The method, called Salinity Zones Distribution (SZD) mapping, was created by T. S. Franklin of the Federal University of Bahia, together with P. C. C. Rosman of the Federal University of Rio de Janeiro and R. C. Carvalho of James Cook University. Rather than simply averaging salinity values across space and time, the technique counts how often each salinity class occurs at every point in the estuary over a full calendar year. The class that dominates most frequently is assigned to that location, producing a map of the most permanent ecological salinity conditions rather than a smoothed statistical blur.

To generate the underlying salinity fields, the team used TELEMAC-2D, a depth-averaged hydrodynamic model that solves the vertically averaged Navier-Stokes equations for free-surface flow and salinity transport. The model domain was discretized with a finite-element mesh of 34,699 triangular elements ranging from 16 to 700 meters, built from bathymetric data supplied by the Brazilian Navy and earlier field campaigns. Tidal forcing came from harmonic constituents measured at the Madre de Deus terminal, while salinity at the ocean boundary was set from moored sensor data collected between 2012 and 2014 near the estuary mouth in Todos os Santos Bay.

Validation was extensive and multi-metric. Water levels at stations near the estuary head and mouth achieved Model Prediction Skill values above 0.9, with root-mean-square errors of 0.12 and 0.29 meters respectively, well below the local tidal range. Depth-averaged currents at three mid-channel sections reached Skill values between 0.85 and 0.95. Salinity validation across five stations produced Skill values from 0.53 to 0.91, and the researchers were careful to explain that low Skill at the euhaline mouth station reflects the extremely narrow observed salinity range there rather than poor physical performance. Crucially, all salinity biases remained smaller than the width of any salinity class in the Venice System, the classification scheme adopted for the ecological zoning.

That classification, first consolidated at the 1958 Venice symposium, divides aquatic environments into five zones from limnetic fresh water below 0.5 practical salinity units to marine waters above 30 psu. It remains the most widely used framework for salinity-based ecological zones, and the SZD method can accommodate it or any alternative scheme, including multivariate classifications derived from local biological data. For each month of the simulated year, the researchers computed the dominant salinity class at every mesh node, resolving ties in favor of the class with the narrower salinity range to minimize classification uncertainty.

The team ran two contrasting scenarios for 2010, a year chosen because its wet and dry seasons were typical and because fish survey data were available. In the Natural scenario, freshwater inflow to the estuary equaled the river inflow entering the dam reservoir. In the Regulated scenario, inflow reflected the actual operation of Pedra do Cavalo, which releases water in daily pulses of roughly 45 cubic meters per second for four to eight hours, driven by electricity generation norms and a minimum sanitary discharge of about 10 cubic meters per second. The contrast between these two worlds proved dramatic.

Under regulated flows, polyhaline conditions between 18 and 30 psu dominated Iguape Bay for most of the year, whereas natural flows would have produced euhaline conditions above 30 psu much of the time. During the dry month of February 2010, the limnetic zone extended only 3 kilometers downstream of the dam under natural conditions but stretched 10 kilometers under regulation. Conversely, during the April 2010 flood, when natural discharges exceeded 1,000 cubic meters per second, the upper estuary shifted abruptly to limnetic conditions and the mesohaline zone expanded deep into Iguape Bay. The regulated regime, in short, holds the estuary in a persistently saltier state in the bay while pushing fresher, more variable conditions into the upstream channel.

The ecological consequences follow directly from the maps. Previous fish surveys in the Paraguaçu estuary identified three guilds: estuarine residents that complete their entire life cycle within the estuary, estuarine migrants with larval stages outside it, and marine stragglers that venture in from the sea. Estuarine residents concentrate in salinities of 18 to 26 psu, squarely within the polyhaline class that regulation now sustains in Iguape Bay, suggesting these fish may benefit. But the simulations also show that regulated discharges impose limnetic conditions along the channel upstream of the bay, implying significant stress for the oligohaline and mesohaline biota that historically inhabited those reaches, including larval and juvenile fishes that depend on low-salinity nursery habitats.

Benthic communities tell a parallel story. Local studies of the Paraguaçu system show a clear longitudinal replacement of taxa along the salinity gradient, with bivalves of the families Tellinidae and Veneridae, cirolanid isopods, cyclopoid copepods and nereidid polychaetes dominating low-salinity sectors, while nuculid bivalves, cirratulid polychaetes and amphiurid brittle stars characterize high-salinity, finer-sediment areas. The SZD maps can therefore be read as habitat-suitability predictors: expansion of polyhaline and euhaline zones under regulation should favor the marine-affiliated assemblages, while shrinking the spatial footprint available to freshwater-tolerant taxa. The framework also connects to broader phenomena, since the position of the low-salinity front relates to the estuarine turbidity maximum, where nutrients and phytoplankton concentrate and where algal blooms, including the red tide recorded in the bay in 2007, can originate.

Beyond its immediate findings, the study positions SZD mapping as a versatile management tool. The authors argue it can support environmental flow planning, help resolve conflicts between dam operators and artisanal fishing communities such as those in the Iguape Bay Extractive Reserve, guide aquaculture siting for species like the mangrove oyster whose larvae favor 25 to 30 psu, and even serve as a climate-change indicator by mapping how sea-level rise and altered rainfall shift salinity zones. Because the method works with any salinity classification and any estuary with hydrodynamic model output, the researchers believe it offers a practical, visually intuitive foundation for sustainable catchment management worldwide, from the lagoon of Venice to dam-removal sites on the Elwha River.

Subject of Research: A novel salinity zone mapping method for assessing how dam-regulated freshwater inflow alters ecological salinity zones in estuaries

Article Title: Evaluating salinity alterations in estuaries through ecological mapping

Article References: Franklin, T. S., Rosman, P. C. C., & Carvalho, R. C. (2026). Evaluating salinity alterations in estuaries through ecological mapping. Discover Oceans, 3(1), Article 46. https://doi.org/10.1007/s44289-026-00159-9

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00159-9

Keywords: estuary, salinity, hydrodynamic modelling, Venice System, freshwater regulation, Paraguaçu River, Todos os Santos Bay, ecological zonation, environmental flows, benthic fauna, fish habitat, dam impacts

The review, led by Ya-Qiang Zheng of Guizhou University of Traditional Chinese Medicine together with Komivi Senyo Akutse, Song Mei, Artemio Mendoza-Mendoza and Bin Chen, is the first systematic synthesis to unite the drought, salt and heavy metal literature on endophytic entomopathogenic fungi within a single mechanistic framework. The timing could hardly be more pressing. Abiotic stresses are estimated to cause global yield losses exceeding fifty percent, and climate change is intensifying drought frequency while more than 800 million hectares of soil worldwide are already affected by salinity. Heavy metal pollution from mining, sewage irrigation and industrial emissions adds a third, largely irreversible threat to arable land.

The authors begin with an evolutionary observation that reframes how these fungi should be seen. Rather than being mere insect parasites that occasionally wander into plants, entomopathogenic fungi appear deeply entwined with the plant root mycobiome. Genomic analyses show that Metarhizium and Beauveria species are close relatives of established endophytes and plant-associated fungi such as Fusarium. The Metarhizium lineage may even have travelled the opposite evolutionary route: starting as saprophytes attracted to root exudates, becoming plant endophytes, and only later acquiring the machinery to kill insects. Many Metarhizium species retain the flexibility to switch between all three lifestyles, which is precisely what makes them so attractive as dual-purpose agricultural agents.

Under drought, the mechanisms these fungi deploy are remarkably layered. In red oak seedlings, B. bassiana colonisation maintained higher leaf relative water content and stomatal conductance while promoting root growth, giving trees better access to scarce water. In tomato, the same fungus pushed plants toward what researchers call a water spender strategy, growing larger and drawing more water through improved root function and stomatal regulation. In onion, colonisation enhanced uptake of phosphorus, calcium, magnesium and iron, nutrients central to energy transfer, membrane stability and chlorophyll synthesis. Wheat seeds primed with M. anisopliae MetA1 showed improved photosynthesis, growth and yield under drought, while maize plants colonised by M. robertsii grew taller under water stress, although the authors caution that results in maize have been inconsistent, likely because inoculation method strongly determines whether the fungus establishes at all.

Beneath these visible improvements lies a concerted molecular campaign against oxidative damage. Drought triggers the accumulation of reactive oxygen species, which shred membranes and proteins. The review documents how endophytic entomopathogenic fungi consistently boost the plant’s enzymatic arsenal, elevating superoxide dismutase, catalase, peroxidase and ascorbate peroxidase activity across species as diverse as tomato, onion, wheat and mallow. These enzymatic gains are mirrored by reductions in malondialdehyde, a chemical fingerprint of lipid peroxidation, indicating genuinely preserved membrane integrity. In parallel, the fungi stimulate non-enzymatic defences: polyphenols, flavonoids and ascorbic acid accumulate, most dramatically under severe drought, when fungal support matters most.

Osmotic adjustment, the accumulation of compatible solutes such as proline, soluble sugars and free amino acids, forms a third pillar of drought resilience, though the review is careful to note that this response is species-specific. Proline rose in colonised tomato, onion and wheat, helping cells retain turgor pressure, yet in red oak the fungus conferred drought tolerance without raising proline at all, suggesting alternative strategies such as enhanced root growth can substitute. Hormonal rewiring completes the picture: B. bassiana upregulated genes governing stomatal behaviour and abscisic acid signalling in tomato, elevated ABA in colonised maize, and in mallow increased gibberellins while suppressing ethylene, the senescence hormone that accelerates tissue damage under stress. The precise molecular dialogue between fungus and host under drought, the authors stress, remains largely unmapped and represents a major frontier.

Under salinity, the fungal playbook shifts toward ion management. The central challenge for salt-stressed plants is maintaining a favourable potassium-to-sodium ratio, and here the evidence is striking. Rice seeds primed with M. anisopliae MetA1 accumulated less sodium and more potassium in both roots and shoots, while B. bassiana strain BeauA1 improved the same ratio under both saline and non-saline conditions. The fungi also promoted proline and carbohydrate accumulation to maintain cell turgor, activated antioxidant enzymes including glutathione S-transferase, and in soybean reprogrammed hormone balance by lowering abscisic acid while raising jasmonic acid. Growth gains followed: improved shoot length, chlorophyll content, leaf area and even stolon production in potato, all under salt concentrations that would normally suppress them. One Metarhizium pinghaense strain even sustained indole-3-acetic acid production at up to 200 millimolar sodium chloride in vitro, sustaining root growth when it mattered most.

The heavy metal findings are arguably the most surprising, revealing the fungi as both detoxification engines and ecological regulators. On the fungal side, B. bassiana immobilises cadmium, lead, zinc and copper on its cell wall through carboxyl, phosphate, hydroxyl and amino groups, removing up to 84.5 percent of total metals from multi-metal wastewater. Inside fungal cells, cadmium entering through calcium channels is bound by glutathione and processed by upregulated cytochrome P450 enzymes, whose inhibition cuts cadmium removal by 45 percent. Some Metarhizium species acquired a bacterial gene, methylmercury demethylase, through horizontal gene transfer, allowing M. robertsii to convert highly toxic methylmercury into volatile elemental mercury that escapes the rhizosphere. Others, such as Beauveria caledonica, excrete oxalic acid that precipitates metals as insoluble oxalate crystals, locking them away from plant roots.

On the plant side, colonised hosts activate their own cadmium efflux pumps and metal-binding proteins while suppressing uptake transporters: in rice, M. robertsii silenced the cadmium importer OsNramp5, cutting cadmium in roots by up to 44.3 percent and in grains by 24.7 percent. In an especially timely result, M. anisopliae seed treatment disrupted what researchers describe as a Trojan Horse effect, in which nanoplastics act as carriers that smuggle lead into rice roots, reducing the soil-to-root transfer of lead by roughly a third while restoring antioxidant balance and rebuilding a beneficial rhizosphere microbiome rich in Sphingomonas and Burkholderia. The fungi even stabilise metals in soil itself, with B. bassiana FE14 cutting bioavailable cadmium from 26.23 to 5.41 milligrams per kilogram through organic acid secretion.

The review closes with a sober assessment of what stands between laboratory promise and field reality. Effectiveness depends on specific plant-fungus combinations and environmental contexts, so systematic strain screening across crops, climates and soils is paramount. Stable endophytic colonisation under fluctuating temperature, humidity, ultraviolet radiation and microbial competition remains difficult to achieve, demanding better formulations such as microencapsulation and optimised seed coating methods. The authors also urge rigorous ecological risk assessment: these fungi are potent insect pathogens, and their effects on pollinators and other beneficial insects must be evaluated before deployment, while growing concern frames all microbial inoculants as potential neomicrobiota that could disrupt native ecosystems. Yet if molecular tools such as CRISPR gene editing, multi-omics profiling and improved regulatory frameworks can unlock these fungi’s full potential, the authors argue, agriculture could gain a single microbial ally that fights pests, buffers climate extremes and cleans contaminated soils simultaneously, a combination no chemical input has ever offered.

Subject of Research: Mechanisms by which endophytic entomopathogenic fungi enhance plant tolerance to abiotic stresses including drought, salinity and heavy metal toxicity

Article Title: Entomopathogenic fungi: beyond biocontrol-unravelling mechanisms of enhanced plant abiotic stress tolerance

Article References: Zheng, Y.-Q., Akutse, K. S., Mei, S., Mendoza-Mendoza, A., & Chen, B. (2026). Entomopathogenic fungi: beyond biocontrol-unravelling mechanisms of enhanced plant abiotic stress tolerance. Crop Health, 4(1), Article 14. https://doi.org/10.1007/s44297-026-00077-4

Image Credits: AI Generated

DOI: 10.1007/s44297-026-00077-4

Keywords: entomopathogenic fungi, fungal endophytes, abiotic stress, drought tolerance, salinity, heavy metals, Beauveria bassiana, Metarhizium, plant-microbe interaction, bioremediation, sustainable agriculture, phytohormones