The significance of the work lies in what foraminifera can reveal. Because the standing crop, diversity and species composition of benthic foraminiferal communities respond rapidly to shifts in salinity, pH, dissolved oxygen, organic matter input and anthropogenic stress, they serve as powerful bioproxies for ecological monitoring. Indices such as the FORAM Index, originally developed for coral reefs and later extended to estuaries, and Foram-AMBI, which assigns observed taxa to sensitivity eco-groups, depend entirely on accurate species-level taxonomy and region-specific reference data. Without a reliable local inventory, misidentification or missing baseline information can compromise the ecological interpretations drawn from these tools. The new study directly addresses that gap for a globally significant but understudied region.

The research focused on two contrasting mangrove systems. The first is the Indian portion of the Sundarbans, which covers 9630 square kilometres, of which 4267 square kilometres is forested, and hosts 24 species of true mangroves. Seven major rivers flow through the delta; the Hooghly and Mooriganga still receive freshwater from the Ganges-Brahmaputra-Meghna system, delivering the world’s second-largest freshwater input of roughly 42,000 cubic metres per second, surging to 138,700 cubic metres per second during the monsoon. The remaining five rivers have lost their freshwater connection to the Ganga and are tidally fed, producing a steady salinity gradient that rises towards the east. The second study area, the Budhabalanga estuary near Chandipur, is a smaller system dominated by Avicennia officinalis, Ceriops decandra, Rhizophora mucronata and Phoenix paludosa, and home to the mangrove horseshoe crab Carcinoscorpius rotundicauda.

Both systems face mounting pressure. Previous research has estimated that air temperature over the Sundarbans is increasing at 0.19 degrees Celsius per year, while relative sea level rises at close to 3.14 millimetres per year. The IPCC Sixth Assessment Report projects a further 0.5 degree Celsius increase in mean temperature and a 10 to 45 centimetre rise in sea level across the Sundarbans. A coastal vulnerability assessment of a 269 kilometre stretch of coastline found that approximately 42 percent falls within moderate to very high vulnerability categories. Against this backdrop, establishing which foraminiferal species persist, where they occur, and how assemblages differ between ecosystems provides an essential reference point for detecting future shifts.

Methodologically, the team compiled published studies that reported benthic foraminiferal assemblages from mangrove-associated environments with sufficient species-level taxonomic detail, excluding work that lacked such information or focused on non-mangrove settings. They then collected 112 sediment core samples across the region: 30 from Ajmalmari, Dulibasani and Chulkathi in the Sundarbans Biosphere Reserve between June 2019 and November 2020, four from Dhanchi in January 2024, 72 from Sagar Island between November 2021 and October 2022, and six from the Budhabalanga estuary between 2021 and 2022. Sampling took place at low tide from intertidal mangrove-associated mudflats using a hand-held vertical corer, 10 centimetres long and 3.5 centimetres in diameter, ensuring consistent sampling volume across sites.

In the laboratory, the uppermost 0 to 2 centimetres of each core were homogenised and subsampled, with roughly 10 cubic centimetres of sediment analysed in full. Specimens were stained with Rose Bengal at 1 gram per litre to distinguish living individuals, whose cytoplasm takes up the stain, from dead tests, and preserved in 70 percent molecular-grade ethanol. The sediment was wet-sieved through stacked 500 and 63 micrometre meshes, and the fraction larger than 63 micrometres was examined under an Olympus BX 53i bright-field microscope at 400 times magnification. Taxonomic identifications were verified against the World Register of Marine Species, the Foraminifera.eu database and established taxonomic references, with surface water temperature and salinity measured in triplicate at each site using calibrated instruments equipped with automatic temperature compensation.

The contemporary samples yielded a rich if modest picture. In the Sundarbans Biosphere Reserve, the team recorded 13 taxa, eight calcareous and five agglutinated, belonging to nine families, while Sagar Island yielded 14 taxa, ten calcareous and four agglutinated. Assemblages were dominated by small specimens under 500 micrometres, a feature typical of mangrove environments worldwide. The intertidal communities included the calcareous taxa Ammonia sp.1, Ammonia sp.2, Bolivina sp.1, Elphidium and Nonionella stella, the porcelaneous Quinqueloculina seminulum, and the agglutinated Entzia macrescens, Trochammina inflata and Textularia agglutinans. Notably, the standing crop of live tests was extremely low, below 3 percent in the Sundarbans and below 1 percent at Chandipur, meaning dead shells overwhelmingly dominate the assemblages, a pattern consistent with earlier regional studies and one that makes time-averaged death assemblages an effective basis for documenting regional species inventories.

To assess spatial structure, the researchers built a species-site occurrence matrix in which each taxon was coded as recorded in the literature, in the present study, or in both, then applied Bray-Curtis similarity analysis with UPGMA hierarchical clustering in the R statistical environment. The results were striking: the contemporary Sundarbans sites of Chulkathi, Ajmalmari, Dhulibhasani, Sagar Island and Dhanchi clustered tightly together, indicating broadly comparable assemblages despite differences in location and sampling period. The Chandipur site in the Budhabalanga estuary, by contrast, formed a separate cluster, reflecting differences in community composition even though several dominant taxa are shared. One species, the calcareous Asterorotalia pulchella, was recorded only at Chandipur and was absent from the Sundarbans assemblages, contributing to that separation.

The study’s interpretation of these patterns draws on global comparisons. Mangrove foraminiferal communities worldwide tend to be low-diversity and often dominated by agglutinated forms, as documented in Puerto Rican mangrove-lagoon systems, French Guiana’s Kaw estuary, Australian intertidal flats and Brazilian mangrove estuaries. Tidal elevation strongly influences the balance: agglutinated taxa such as Entzia macrescens and Trochammina inflata favour higher intertidal positions, while calcareous forms like Ammonia are common in mudflat zones. The co-occurrence of both groups in the Bay of Bengal samples is consistent with ecological zonation across mangrove microhabitats. The dominance of Ammonia species, described in the literature as opportunistic generalists with rapid reproduction and broad physiological flexibility, alongside the ecologically tolerant Quinqueloculina seminulum and the widespread agglutinant Entzia macrescens, underscores the resilience of a core regional species pool adapted to salinity fluctuations, organic enrichment and hypoxic conditions.

The authors are careful to acknowledge limitations. The compiled dataset integrates studies spanning different periods, locations and methodologies, which may introduce sampling bias and underrepresent rare, cryptic or seasonally restricted taxa, and shifting taxonomic nomenclature complicates species-level comparisons despite standardisation against contemporary databases. The study was not designed to quantify environmental drivers or seasonal variation, so interpretations remain qualitative. Even so, the strong agreement between historical records and new observations confirms the persistence of key taxa across years and sampling campaigns, and the discovery elsewhere of the endemic agglutinant Srinivasania sundarbanensis hints at undocumented diversity still awaiting description. What emerges is a robust, region-specific framework: a verified checklist of benthic foraminifera for the mangroves of the northeast Bay of Bengal that can anchor foraminifera-based ecological monitoring, sharpen biotic indices, and help conservationists track how these climate-stressed coastal ecosystems respond in the decades ahead.

Subject of Research: Benthic foraminiferal assemblages and their use as ecological indicators in Bay of Bengal mangrove ecosystems

Article Title: Inventorization of spatial patterns and reassessment of benthic foraminiferal assemblages from mangrove ecosystems of Bay of Bengal

Article References: Mandal, A., Ghosh, A., & Bhadury, P. (2026). Inventorization of spatial patterns and reassessment of benthic foraminiferal assemblages from mangrove ecosystems of Bay of Bengal. Discover Oceans, 3(1), Article 63. https://doi.org/10.1007/s44289-026-00169-7

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00169-7

Keywords: benthic foraminifera, mangroves, Sundarbans, Bay of Bengal, Budhabalanga estuary, ecological monitoring, bioproxy, Bray-Curtis clustering, Ammonia, Entzia macrescens, sea-level rise, species inventory

The researchers sampled herbaceous vegetation monthly from May to November, spanning the pre-monsoon, rainy, and post-monsoon periods that structure the growing season in the region. Sampling relied on replicated one-by-one-meter quadrats, a standard but labor-intensive approach that demands repeated visits across rugged terrain. By returning month after month to the same forest types, the team could separate the effects of season from the effects of forest identity, a distinction that single-snapshot surveys routinely miss. Their statistical framework combined one-way and two-way analyses of variance to test for differences among forest types and seasons, with community structure characterized through species diversity indices, Importance Value Index scores, Bray–Curtis similarity, and hierarchical clustering.

The headline result is that both forest type and season leave strong, statistically significant fingerprints on herbaceous biomass. Biomass differed markedly among the three forest types, with maple forest supporting the highest mean standing crop at 185.3 grams per square meter, followed by birch–rhododendron forest at 162.7 grams per square meter and rhododendron forest at 128.4 grams per square meter. Seasonal variation was even more pronounced, with biomass peaking during the rainy season, when monsoon moisture transforms the forest floor into a brief but intense flush of growth. Crucially, the analysis revealed a significant interaction between forest type and season, meaning the seasonal trajectory of biomass was not simply shifted up or down in different forests but followed genuinely different patterns depending on canopy composition.

That interaction matters because it points to the canopy as an active filter rather than a passive backdrop. Maple, birch, and rhododendron canopies differ in density, leaf phenology, and the quality and quantity of light they transmit to the ground, and these differences cascade downward to shape which herbs can persist and how vigorously they grow. Earlier work by the same research group and others has shown that tree canopy composition influences soil properties, microbial biomass, and light attenuation in Himalayan forests, and the new findings extend that logic to the seasonal dynamics of the herb layer itself. In effect, each forest transition along the elevational gradient resets the understory clock, changing not only how much biomass accumulates but when it accumulates.

Diversity told a complementary story. The surveys recorded a total of 72 herbaceous species belonging to 34 families and 18 orders, a respectable tally for a temperate understory and a reminder of how much botanical richness is packed into the narrow band of elevation the study covered. Species richness differed significantly across both seasons and forest types, again peaking during the rainy season. The birch–rhododendron forest emerged as the diversity hotspot of the gradient, recording the greatest Shannon diversity index value of 3.58 alongside the lowest dominance, measured by a Simpson-type concentration index of just 0.07. Low dominance combined with high evenness indicates a community in which no single species monopolizes resources, a configuration often associated with greater resilience and more niches packed into the same space.

Each forest type also had its own ecological VIPs. The Importance Value Index, a composite measure that combines relative density, frequency, and dominance, identified Strobilanthes pentastemonoides var. dalhousieana as the most ecologically important herb in the maple forest, Aconitum heterophyllum in the birch–rhododendron forest, and Primula denticulata in the rhododendron forest. The identity of these dominants is more than a botanical footnote. Aconitum heterophyllum, for instance, is a highly valued and heavily harvested medicinal plant of the Himalaya, and understanding the forest contexts in which it achieves greatest ecological weight has direct implications for conservation planning. The fact that different species dominate in adjacent forest types underscores how quickly conservation priorities can shift across short elevational distances.

The multivariate analyses added a compositional dimension to the picture. Bray–Curtis similarity calculations followed by hierarchical clustering showed that the maple and birch–rhododendron forests share a greater degree of floristic affinity with each other, while the rhododendron forest formed a distinct assemblage of its own. This pattern suggests that the transition from maple to birch–rhododendron forest is relatively gradual in floristic terms, whereas the shift into pure rhododendron forest represents a sharper compositional break. Ecotones, the transitional zones where one community gives way to another, are increasingly recognized as biodiversity reservoirs and as sensitive early-warning systems for climate-driven range shifts, and the study’s findings reinforce the case for treating these Himalayan transition zones as conservation targets in their own right.

The seasonal dimension of the study carries particular weight in an era of climate change. Herbaceous plants, with their short generation times and limited ability to buffer environmental variation, are known from global syntheses to respond more strongly to climate anomalies than longer-lived woody species. In the Himalaya, where warming is proceeding faster than the global average and monsoon patterns are projected to become more erratic, the timing and magnitude of the understory’s rainy-season peak could shift in ways that ripple through the entire forest ecosystem. Changes in herb biomass affect soil erosion control, nutrient return through litterfall, and the food base for insects, birds, and mammals. A compressed or delayed growing season in the herb layer would be felt long before any visible change in the trees themselves.

The authors emphasize that their findings highlight the importance of maintaining forest continuity and transitional habitats for conserving understory biodiversity in temperate Himalayan ecosystems. That message has practical urgency. Himalayan temperate forests face pressure from livestock grazing, fuelwood extraction, medicinal plant harvesting, and land-use change, and fragmentation that severs the elevational continuum of forest types could eliminate precisely the transitional habitats where much of the understory’s diversity is concentrated. Because the study demonstrates that biomass and diversity patterns are jointly governed by forest identity and season, management interventions such as canopy thinning or plantation species selection will inevitably reshape the understory as well, whether or not that outcome is intended.

Methodologically, the study also illustrates the value of patience in mountain ecology. Monthly sampling across an elevational gradient for seven months is a demanding protocol, yet it is exactly this temporal resolution that allowed the researchers to detect the forest-by-season interactions that define the system. Single-season surveys, which remain common in the region’s literature, would have captured fragments of these patterns but missed their structure. As remote sensing and automated monitoring expand across the Himalaya, ground-truthed datasets of this kind become even more valuable, anchoring broad-scale models in ecological reality. For now, the study stands as a clear demonstration that the green carpet beneath the Himalayan canopy lives by its own calendar, one written jointly by the monsoon and by the trees standing above it, and that protecting it means protecting both the rhythm and the places where it plays out.

Subject of Research: Seasonal dynamics of herbaceous biomass and diversity across elevational forest transitions in the temperate Himalaya

Article Title: Influence of elevational forest transitions on seasonal patterns of herbaceous biomass and diversity in the temperate Himalaya

Article References: Influence of elevational forest transitions on seasonal patterns of herbaceous biomass and diversity in the temperate Himalaya. (n.d.). https://doi.org/10.1007/s44473-026-00270-x

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00270-x

Keywords: herbaceous diversity, Himalayan forests, understory vegetation, biomass, elevational gradient, seasonal dynamics, temperate forest, ecotones, species richness, Shannon diversity, Bray–Curtis clustering, plant ecology