Antimicrobial resistance, or AMR, is widely described by scientists and policymakers as one of the most pressing global challenges of the coming decades, and it is formally categorised as a ‘One Health’ problem because the forces driving it cut across human, animal and environmental health. Aquatic environments occupy a particularly awkward position in this picture. Water is an exceptional medium for the movement of bacteria and the genetic elements that carry resistance between them, and aquaculture systems both depend on and continuously interact with the rivers, canals and groundwater around them. When antimicrobial compounds enter pond water, whether through deliberate treatment or residual shedding, selective pressure favours bacteria that survive, and resistance genes can circulate through sediment, water columns and microbial communities in ways that are difficult to monitor and even harder to reverse. Professor Crumlish’s team argues that understanding these dynamics in a real production environment is essential to designing interventions that actually work.

Vietnam’s pangasius sector offers what the researchers describe as an ideal natural laboratory. Pangasius catfish farming is one of the world’s most important freshwater aquaculture industries by volume and export value, and its intensification over recent decades has been accompanied by growing recognition of AMR issues in the freshwater environments that host production. Intensive systems concentrate fish at high densities, which raises disease pressure, and when bacterial outbreaks strike, farmers frequently turn to antimicrobials as a first line of defence. The Stirling-led project will examine the causes and complexity behind resistance in these systems, but it will go a step further by also investigating the social and economic barriers that prevent alternative disease-management approaches from being adopted in the first place. That dual focus, on both the biology and the behaviour surrounding antibiotic use, is what the team describes as the study’s defining transdisciplinary character.

Professor Crumlish has been candid about the practical realities that drive antibiotic reliance on farms. When antibiotics stop working effectively in aquaculture, particularly in freshwater systems in Southeast Asia, farmers often have few alternatives available to them, yet they continue to trust antibiotic products even when those products are no longer effective. The result, she explains, is rapid development of resistance that can spill over into human, environmental and animal health, a pattern she identifies as a major concern. Rather than simply documenting the problem, the project has been designed to produce a novel research roadmap and a practical framework that can be adapted and applied in other countries facing similar challenges, an ambition that reflects the global nature of aquaculture and the shared biology of the resistance mechanisms involved.

The methodology at the heart of the project is co-creation. Over the next four years, researchers will work directly with farmers, policymakers, industry leaders and other stakeholders to ensure that any interventions they develop are both scientifically robust and realistically implementable. Alongside colleagues Dr Darren Green and Dr Noel Juvigny-Khenafou from Stirling’s Institute of Aquaculture, Professor Crumlish will collaborate with Dr Andrew Hoyle from the School of Computing, Data and Mathematical Sciences, Dr Saihong Li from the School of Communication, and Dr Till Stowasser from Stirling Business School. The inclusion of social scientists, data scientists and business researchers from the outset, rather than as an afterthought, is intended to surface the economic incentives, communication gaps and decision-making habits that determine whether a technically sound alternative to antibiotics ever reaches the pond.

The new grant builds directly on a body of previous research at Stirling investigating novel fish vaccines, including a recent trial conducted at the university’s National Aquaculture Technology and Innovation Hub, known as NATIH. Vaccination is widely regarded as one of the most promising tools for reducing antimicrobial dependence in finfish aquaculture, because preventing bacterial disease in the first place removes the need for therapeutic treatment. The transdisciplinary project will draw on data generated by these vaccine studies and share the findings with stakeholders as raw material for co-developing viable solutions and promoting better antibiotic stewardship across freshwater aquaculture. In effect, the team hopes to convert laboratory and trial-scale advances into a system-level change in how disease is managed on working farms.

The work will be carried out in partnership with the University of Glasgow, the University of Sydney, Can Tho University and Vietnam National University, a consortium that pairs UK and Australian research strength in microbiology, epidemiology and aquatic disease with Vietnamese institutions embedded in the regions where pangasius is actually farmed. This geographic and institutional spread matters for a problem of this kind. Resistance genes do not respect farm boundaries or national borders, and the conditions that shape antibiotic use, from extension services to market pressures, are locally specific. By grounding the research in Vietnamese production systems while connecting it to international expertise, the consortium aims to produce findings that are both locally actionable and globally transferable.

The funding envelope surrounding the project signals how seriously UK funders now treat the intersection of infection biology and food production. The £54 million programme, coordinated through UK Research and Innovation, is designed to prepare for future epidemics, tackle antimicrobial resistance and accelerate the development of next-generation animal vaccines. Professor Anne Ferguson-Smith, UKRI’s Executive Champion for Tackling Infections and Executive Chair of the Biotechnology and Biological Sciences Research Council, said the investment reflects UKRI’s central role in delivering government priorities and its long-standing commitment to convening partners across government to fund vital One Health research into human, animal and plant health. By pooling expertise from across the UK and global research and innovation ecosystem, she argued, related infectious disease challenges can be tackled in a more coordinated way, getting ahead of emerging biological threats and helping to protect people, animals, plants and the environment both domestically and internationally, advancing knowledge, improving lives and driving growth.

Professor Lucy Chappell, Chief Scientific Adviser at the Department of Health and Social Care and Chief Executive Officer of the National Institute for Health and Care Research, framed the investment in similarly interconnected terms. In a world where human, animal and environmental health are inherently linked and interdependent, she noted, diseases do not respect borders, and countries must work together to address their greatest health threats. Taking a One Health approach and bringing together experts from the UK and around the world, she said, allows threats to be identified earlier, strengthens resilience and delivers better health outcomes for the public. For the pangasius project specifically, that framing translates into a concrete ambition: within 48 months, to understand how resistance emerges in one of the world’s largest freshwater aquaculture industries, to map its impacts on production, and to chart a credible, farmer-endorsed path toward more sustainable disease management.

The stakes extend well beyond Vietnam. Aquaculture is among the fastest-growing food production sectors on the planet, and freshwater systems in Asia supply a substantial share of global fish consumption. If resistance renders existing antibiotics ineffective in these systems while alternatives remain out of economic or practical reach, the consequences will ripple through food security, rural livelihoods and public health simultaneously. What the Stirling-led consortium is proposing is essentially a test case for whether the aquaculture industry can decouple intensification from antimicrobial dependence, not through top-down regulation alone but through solutions built with the people who will have to use them. If the roadmap that emerges proves adaptable to other countries and other species, as the team intends, the humble catfish ponds of the Mekong Delta may end up shaping how the world manages infection far beyond their own waters.

Subject of Research: Antimicrobial resistance in Vietnamese pangasius catfish aquaculture

Article Title: University of Stirling secures £2.4M grant for major aquaculture project

Article References: University of Stirling secures £2.4M grant for major aquaculture project. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: antimicrobial resistance, aquaculture, pangasius catfish, Vietnam, One Health, University of Stirling, UKRI, fish vaccines, antibiotic stewardship, freshwater farming, Institute of Aquaculture, transdisciplinary research

The review, conducted by Emmanuel Kaboja Magna of the University of Environment and Sustainable Development in Somanya, Ghana, followed the PRISMA framework for systematic reviews. The initial search identified 1,246 records from databases including Scopus, Web of Science, PubMed and Google Scholar, supplemented by reports from the World Health Organisation, the United Nations Environment Programme, the Ghana Environmental Protection Agency and the Food and Agriculture Organisation. After rigorous screening, 46 studies met the inclusion criteria, of which 21 were judged high quality, 18 moderate and 7 low. Where methodologies were comparable, 32 studies were pooled into a quantitative synthesis. Concentration values reported in different units were standardised to allow comparison across water, sediment, soil and waste matrices.

The headline numbers are striking. Hospital effluents in Sunyani contained amoxicillin at concentrations reaching 8,760 micrograms per litre, alongside ciprofloxacin at 4,740 micrograms per litre and doxycycline at 2,930 micrograms per litre, figures the review describes as among the highest environmental antibiotic concentrations reported globally. In Kumasi, leachate from the Dompoase landfill recorded penicillin concentrations as high as 67,420 micrograms per litre, a level approaching therapeutic doses. For context, published predicted no-effect concentrations for resistance selection in aquatic environments are around 0.25 micrograms per litre for amoxicillin and 0.064 micrograms per litre for ciprofloxacin. The Ghanaian effluent values therefore exceed these thresholds by tens of thousands of times, indicating that untreated pharmaceutical waste is being discharged directly into the environment.

Three urban hotspots emerge consistently from the evidence: Kumasi, Sunyani and Sefwi Wiawso. These cities combine intensive healthcare activity, high population density, widespread pharmaceutical consumption and inadequate wastewater treatment infrastructure. In Sefwi Wiawso, ciprofloxacin concentrations in dumpsite soils ranged from 2,140 to 4,060 micrograms per kilogram, while antibiotic-related compounds reached 670 micrograms per litre in water samples. The review attributes these patterns to a combination of continuous source loading, leachate infiltration into organic-rich soils, and episodic runoff into receiving waters. Poorly engineered landfills that lack containment systems allow contaminants to migrate into groundwater and surface water, turning municipal waste sites into continuous secondary sources of pollution.

Yet contamination is not confined to these hotspots. A comprehensive 118-kilometre transect study of the Lower Volta River, one of Ghana’s most critical freshwater resources, detected antibiotics at every sampled location, generally in the low nanogram-per-litre range, together with antibiotic resistance genes. The authors of that study also found per- and polyfluoroalkyl substances, or PFAS, in the same system, highlighting the co-occurrence of multiple classes of emerging contaminants. In fish farms on the Lower Volta Lake, antibiotics including ciprofloxacin, sulfamethoxazole, sulfadiazine, chlortetracycline and tetracycline were measured at concentrations up to 9.14 micrograms per litre in farm waters, with residues also detected in fish tissues. Even the Owabi and Barekese reservoirs, which supply drinking water, contained antibiotics at levels between 0.06 and 36.51 micrograms per litre, suggesting incomplete removal during water treatment.

The review also exposes a technical weakness in Ghana’s monitoring capacity. Among the principal residue-monitoring studies with identifiable analytical platforms, 62.5 per cent relied on high-performance liquid chromatography with ultraviolet or diode-array detection, methods that are accessible but less sensitive than mass spectrometry. Only 25 per cent used tandem mass spectrometry, which offers superior sensitivity and the ability to quantify many compounds simultaneously. The review cautions that differences in reported concentrations, and even some non-detections, may partly reflect analytical performance rather than genuine differences in contamination. Greater adoption of validated multi-residue LC-MS/MS methods, harmonised sampling protocols and consistent reporting of detection limits and recoveries would substantially strengthen the reliability of environmental monitoring.

The public health consequences flow through several pathways. Humans are exposed through contaminated drinking water, the consumption of fish and vegetables grown with polluted irrigation water, occupational contact and recreational use of polluted water bodies. More alarmingly, the review documents antibiotic-resistant bacteria and resistance genes across rivers, reservoirs, drinking water systems and sediments. Urban rivers such as the Odaw and Okurudu carry especially high resistance burdens, including extended-spectrum beta-lactamase-producing Escherichia coli. Warm temperatures, high organic loading and dense microbial populations in tropical aquatic systems favour horizontal gene transfer through conjugation, transformation and transduction, mechanisms that allow resistance genes to spread rapidly between bacterial species. Mobile genetic elements associated with carbapenem and aminoglycoside resistance have been detected in Ghanaian hospital and urban wastewater systems, underscoring the potential for environmental resistance to reach clinical settings.

Ecologically, the picture is equally concerning. Antibiotic contamination alters microbial community structure, disrupts nutrient cycling and organic matter decomposition, and may reduce microbial diversity in heavily impacted receiving environments. Aquatic ecosystems face risks to phytoplankton productivity, food-web dynamics and fish health, while sediments and soils act as long-term reservoirs that can prolong impacts even after direct discharges decline. In terrestrial systems, disruption of beneficial soil organisms such as nitrogen-fixing bacteria and mycorrhizal fungi could undermine soil fertility and agricultural productivity. Compound chemistry shapes where these effects concentrate: strongly sorbing fluoroquinolones like ciprofloxacin accumulate in soils and sediments, whereas more hydrophilic sulfonamides remain mobile in water.

The sources of this pollution are diverse. Hospitals discharge wastewater containing unmetabolised antibiotics and resistant bacteria, often without specialised treatment. Households discard expired medicines with domestic refuse, and over-the-counter access to antibiotics compounds the problem. In agriculture and aquaculture, antibiotics are used not only to treat disease but also to promote growth, with residues excreted in partially metabolised form and entering soils and waterways through manure and medicated feed. Pharmaceutical manufacturing may add localised industrial discharges, though empirical evidence in Ghana remains limited. The review notes that these patterns mirror those seen elsewhere in sub-Saharan Africa, with river sediments in Kenya reaching 4,125 micrograms per kilogram and Lake Victoria sediments in Uganda up to 130 micrograms per kilogram, suggesting a regional crisis driven by rapid urbanisation and weak regulatory enforcement.

Addressing the problem, the review concludes, will require coordinated national action spanning environmental monitoring, pharmaceutical waste management, wastewater treatment upgrades, antimicrobial stewardship and regulatory reform. Ghana’s current framework is fragmented, with overlapping responsibilities among the Environmental Protection Agency, the Food and Drug Administration and the ministries of health and agriculture, and no specific permissible limits for most pharmaceuticals in wastewater or surface waters. The review recommends specialised pharmaceutical waste treatment in hospitals, take-back programmes for unused medicines, engineered landfills, veterinary oversight and antibiotic stewardship in farming. Advanced treatment technologies such as activated carbon adsorption, membrane bioreactors and advanced oxidation processes show promise but are costly, so nature-based alternatives like constructed wetlands and algae-based treatment may offer more sustainable options. Above all, long-term surveillance programmes that integrate chemical monitoring with antimicrobial resistance tracking are essential to identify emerging hotspots and guide evidence-based policy before environmental reservoirs of resistance further erode the effectiveness of life-saving antibiotics.

Subject of Research: Antibiotic residue contamination and antimicrobial resistance in Ghanaian environmental systems

Article Title: Antibiotic residues in Ghanaian environmental systems: sources, distribution patterns, and public health implications

Article References: Magna, E. K. (2026). Antibiotic residues in Ghanaian environmental systems: sources, distribution patterns, and public health implications. Discover Chemistry, 3(1), Article 498. https://doi.org/10.1007/s44371-026-00955-4

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00955-4

Keywords: antibiotic residues, Ghana, antimicrobial resistance, hospital effluents, landfill leachate, water pollution, pharmaceutical pollution, systematic review, aquaculture, resistance genes, wastewater treatment, environmental monitoring

The researchers call their model HA-DETR, short for Hierarchical Adaptive Feature Enhancement Detection Transformer. It builds on the detection transformer family of architectures, which replaced the hand-engineered region proposal pipelines of earlier detectors with an end-to-end attention mechanism that reasons about an entire image at once. Since the original DETR appeared in 2020, the family has evolved rapidly through variants such as Deformable DETR, DAB-DETR, and DINO, and recent work has shown that detection transformers can now rival or exceed the one-stage YOLO detectors that long dominated real-time applications. Liu and Jiao’s contribution is not a new backbone or a new loss function, but a set of three modules that intervene at specific points in the feature hierarchy, each tailored to the particular kind of degradation that dominates at that level.

The key observation motivating the architecture is that underwater degradations affect low-level details and high-level semantic representations differently. At the bottom of a convolutional or transformer feature pyramid, the network encodes fine-grained structure: edges, textures, and the delicate outlines of fins, tentacles, and shells. These are precisely the cues that scattering and blur destroy first. Higher up the pyramid, features become more abstract and semantic, encoding what an object is rather than where its boundaries lie, but they become vulnerable to a different problem: attention drifts toward the water column, sediment, and background clutter instead of locking onto the sparse object regions that matter. A single, uniform enhancement strategy applied to all levels therefore tends to help one level at the expense of another, which is why previous enhancement-plus-detection pipelines have delivered mixed results.

HA-DETR’s first component, the Frequency-Domain Feature Enhancement module, addresses the low-level problem by moving the computation into the frequency domain. The idea draws on a growing body of work showing that frequency analysis can separate image content in ways that spatial processing cannot: blur and haze tend to suppress high-frequency components, while object contours and textures concentrate there. By transforming features with operations related to the fast Fourier transform and adaptively reweighting frequency bands, the module restores the perception of blurred objects before the information is lost to deeper layers. This follows a broader trend in vision research, from frequency-aware transformers for image restoration to discrete cosine transform hybrids, that treats spectral information as a first-class citizen rather than a curiosity.

The second component, the Polarity-Aware Feature Interaction module, works at the opposite end of the hierarchy. Its job is to refine high-level semantic features so that the model’s attention concentrates on object regions rather than on the visually dominant but uninformative background. The term polarity refers to the module’s ability to distinguish and separately handle the opposing contributions of foreground and background signals during feature interaction, strengthening the positive evidence for objects while suppressing the negative pull of the surrounding water. In an underwater scene where a fish may occupy only a few percent of the pixels, this foreground-background asymmetry is the difference between a confident detection and a network that dutifully describes the emptiness around the fish.

The third component, the Hierarchical Attention Feature Pyramid Network, tackles the fusion problem that sits between the two extremes. Feature pyramid networks and their many descendants are the standard machinery for combining multi-scale features so that small objects benefit from high-resolution detail and large objects benefit from semantic depth. HA-DETR’s variant uses attention to optimize how information flows across scales and reinforces semantic-guided representation, ensuring that the enhanced low-level detail from the frequency module and the sharpened semantics from the polarity module are combined coherently rather than averaged into mush. The three modules together perform what the authors describe as differentiated processing and adaptive enhancement across semantic levels, allowing the network to preserve fine-grained structures and maintain robust semantic discrimination simultaneously.

The experimental evidence comes from two widely used underwater benchmarks. On DUO, a dataset of underwater object detections assembled from marine imagery with annotations for creatures such as fish, jellyfish, and sea urchins, HA-DETR achieves an average precision of 70.7 percent. On UTDAC2020, a dataset collected in a real aquaculture environment where turbidity and crowding are severe, it reaches 53.2 percent. Both figures represent the model’s superiority over competing approaches reported in the study, and the gap is particularly meaningful on the aquaculture data, where low contrast and heavy occlusion have historically dragged detection scores down. The authors report no competing interests, and the work was accepted by Cluster Computing after revisions in June 2026 and published on 18 September 2026.

What makes the approach notable beyond its benchmark numbers is the way it reframes the relationship between image enhancement and object detection. Much prior work treats underwater enhancement as a preprocessing step, using generative or physics-based models to produce a cleaner image before detection begins. That strategy can help, but it adds computational cost, can introduce artifacts that mislead the detector, and optimizes for visual quality rather than detection performance. HA-DETR instead embeds enhancement directly inside the detection architecture, applying it selectively where the feature hierarchy needs it. This echoes a recent line of research, including edge-aware DETR variants and CNN-transformer hybrids for underwater scenes, that argues detection-aware feature processing beats generic image restoration for this task.

The practical stakes are considerable. Automated monitoring of fish populations, coral reef health, and invasive species depends on reliable detection in conditions no human photographer would choose. Aquaculture operations use cameras to track feeding behavior, growth, and disease outbreaks in pens where visibility is often measured in meters. Autonomous underwater vehicles conducting infrastructure inspection or deep-sea surveying need to identify objects in real time with limited bandwidth back to shore. A detector that maintains accuracy under blur, low contrast, and occlusion extends the operational envelope of all of these systems, potentially reducing the need for human divers in hazardous or remote environments.

There are, of course, caveats. The reported results come from two datasets, and performance on other water bodies, lighting conditions, and sensor types remains to be demonstrated. Transformer-based detectors also carry computational costs that matter for the power-constrained embedded platforms on which many underwater vehicles run, although the field is moving quickly toward efficient attention designs. Still, the hierarchical adaptive principle at the heart of HA-DETR, matching the enhancement strategy to the semantic level being processed, is a general one, and the authors’ results suggest that respecting the structure of the feature hierarchy is one of the most effective ways to make machine vision work where the water refuses to cooperate.

Subject of Research: Transformer-based hierarchical adaptive feature enhancement for underwater object detection

Article Title: HA-DETR: Hierarchical adaptive feature enhancement for underwater object detection

Article References: Liu, T., & Jiao, G. (2026). HA-DETR: Hierarchical adaptive feature enhancement for underwater object detection. Cluster Computing, 29(13), Article 768. https://doi.org/10.1007/s10586-026-06577-w

Image Credits: AI Generated

DOI: 10.1007/s10586-026-06577-w

Keywords: underwater object detection, detection transformer, HA-DETR, frequency-domain enhancement, feature pyramid network, attention mechanism, computer vision, marine monitoring, aquaculture, deep learning, multi-scale feature fusion, image degradation

The research, published in BMC Genomics by a team at Guangdong Ocean University led by Mei-Zhen Zhang and corresponding author Dong-Neng Jiang, set out to answer a question that had lingered after the group’s earlier work on liver transcriptomes: what governs the expression of the many liver genes tied to ovarian development? Their prime suspect was DNA methylation, an epigenetic mark in which methyl groups are attached to DNA bases, most commonly cytosines in CpG dinucleotides. Methylation in promoter regions is classically associated with gene silencing, while methylation within the body of a gene can have more varied and sometimes stimulatory effects on transcription.

To map this chemical landscape, the researchers turned to whole-genome bisulfite sequencing (WGBS), the gold-standard technique for charting methylation at single-base resolution. Bisulfite treatment converts unmethylated cytosines into uracils while leaving methylated cytosines untouched, so sequencing the treated DNA reveals exactly which cytosines carry the mark. The team applied this method to livers sampled at three stages of ovarian development, designated II, III, and IV, spanning the progression from early maturation toward full vitellogenesis and approaching final oocyte maturation.

The resulting methylome maps delivered a striking pattern: overall CpG methylation in the liver was highest at ovary stage II, at 74.57 percent, and then declined to 70.20 percent at stage III before ticking back up to 71.68 percent at stage IV. In other words, as the ovary advanced from early to mid-development, the liver underwent a substantial global demethylation, a shift consistent with the idea that the organ opens up its transcriptional machinery to ramp up production of egg-supporting molecules.

But global methylation is only half the story. The real power of the study came from integrating the methylome data with RNA sequencing data from the same livers, allowing the team to ask which genes showed both a change in methylation and a corresponding change in expression across developmental transitions. Spearman correlation analysis revealed modest but meaningful associations between expression levels and CpG methylation in both promoter and gene body regions, hinting that methylation contributes to, without wholly dictating, the transcriptional program of the developing liver.

When the researchers overlapped differentially expressed genes with differentially methylated genes, they identified 28 overlapping genes in the stage II versus III comparison, 256 in the II versus IV comparison, and 99 in the III versus IV comparison. The largest set, spanning the full transition from early maturation to late development, contained some of the most compelling candidates, including genes central to the two defining products of the reproductive liver: yolk precursors and egg envelopes.

Among these were the estrogen receptor gene erα, the yolk protein genes vtgb and vtgc, and the egg envelope, or zona pellucida, genes zp4a and zp4b. In the II versus IV and III versus IV comparisons, these vitellogenesis and egg envelope genes showed decreased methylation in their promoter or gene body regions, accompanied by increased expression. The logic is elegant: as estrogen signaling ramps up during ovarian maturation, the liver appears to lift an epigenetic brake on the very genes needed to manufacture yolk proteins and the protective envelopes that surround the egg. The team validated one key finding, methylation of the erα promoter, using bisulfite sequencing PCR (BSP), an independent targeted method, and the results matched the WGBS data, strengthening confidence in the genome-wide map.

The study also traced methylation changes in genes governing the lipid raw materials of the egg. In the II versus IV comparison, hsd17b7, which participates in cholesterol formation, showed decreased promoter methylation together with increased expression, while cyp51, another cholesterol biosynthesis gene, showed decreased gene body methylation alongside increased expression. Cholesterol is the biochemical backbone from which steroid hormones and membrane components are built, so its upregulation fits the demands of a liver preparing to provision thousands of oocytes. In a more nuanced twist, dgat2, a gene involved in triglyceride formation, showed decreased gene body methylation together with decreased expression, illustrating that gene body methylation does not follow a simple one-directional rule and that its relationship with transcription can vary by gene and context.

Why does this matter beyond the spotted scat? Epigenetic regulation of reproduction has been studied extensively in mammals, but fish present a distinctive system: the liver, not the ovary, is the primary factory for yolk precursors, and environmental cues such as temperature and nutrition can leave lasting epigenetic imprints on farmed stocks. Demonstrating that methylation changes in the liver track the ovarian developmental cycle provides a mechanistic bridge between an animal’s environment, its epigenome, and its reproductive output. For aquaculture, that bridge could eventually point to epigenetic markers that predict which broodstock females are primed for spawning, or to interventions that synchronize egg production across a farmed population.

The authors are careful about the limits of the correlation-based analysis. Methylation and expression were measured at matched developmental stages rather than manipulated experimentally, so the study establishes association rather than causation, and the modest strength of the Spearman correlations suggests methylation is one contributor among many, alongside transcription factors, hormones, and chromatin modifications not measured here. Still, the convergence of genome-wide mapping, transcriptome integration, and targeted validation marks this as one of the most complete pictures yet of how a fish liver’s epigenome shifts to support egg development. As sequencing costs fall, similar methylome-transcriptome pairings are likely to follow in other aquaculture species, turning a once-obscure chemical mark into a practical handle on one of farming’s oldest challenges: getting fish to reproduce reliably on schedule.

Subject of Research: Epigenetic regulation of liver gene expression during ovarian development in spotted scat

Article Title: Integration of liver methylome and transcriptome provides new insights into the regulation of ovarian development genes in spotted scat (Scatophagus argus)

Article References: Zhang, M.-Z., Li, Y., Jiao, K.-Z., Huang, Y.-Q., Jiang, M.-Y., Shi, H.-J., Tian, C.-X., Deng, S.-P., Chen, H.-P., & Jiang, D.-N. (2026). Integration of liver methylome and transcriptome provides new insights into the regulation of ovarian development genes in spotted scat (Scatophagus argus). BMC Genomics. https://doi.org/10.1186/s12864-026-13425-z

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13425-z

Keywords: DNA methylation, epigenetics, spotted scat, Scatophagus argus, ovarian development, vitellogenesis, liver transcriptome, whole-genome bisulfite sequencing, aquaculture, gene expression, egg envelope formation, fish reproduction

The scale of the problem is enormous. The 2016 bloom of the flagellate Pseudochattonella verruculosa in southern Chile generated losses exceeding 800 million US dollars. Three years later, blooms of Chrysochromulina leadbeateri in Norwegian fjords produced the largest harmful-algal-bloom impact ever recorded on northern European aquaculture. The culprit taxa span a phylogenetically distant assemblage of raphidophytes, kareniacean dinoflagellates, prymnesiophytes and dictyochophytes that share no common toxin class, yet their damage converges on a single organ: the fish gill, whose epithelium maintains a continuous, unbuffered interface with the surrounding water.

The surveillance architecture in use today was built for a different problem. In shellfish monitoring, filter-feeding bivalves integrate exposure to intracellular phycotoxins, certified analytical standards allow direct quantification of toxin burden in tissue, and that tissue burden, not cell abundance in seawater, triggers regulatory action. Transferred to fish-killing blooms, this logic carries a hidden premise: that cell abundance translates roughly into proportional mortality risk. Field evidence says otherwise. During the 2016 Chilean event, routine cell counts showed no statistically significant correlation with mortality across affected farms, partly because thin layers concentrated the bloom vertically and fragile cells lost integrity under standard fixation. Nearly a decade later, a Prymnesium parvum bloom in the Oder River reached densities comparable to the catastrophic 2022 fish kill yet caused no documented mortality, with temperature, river flow and salinity acting as conditional drivers of toxin production independent of cell numbers.

Laboratory work reinforces the decoupling between abundance and hazard. Screening of Chilean fish-killing flagellates with the RTgill-W1 rainbow trout gill cell line revealed that species differed by more than an order of magnitude in cytotoxic potency under standardised conditions, and that mechanically disrupted cells consistently produced stronger responses than intact suspensions. The likely explanation combines active secretion of defensive metabolites across the plasma membrane with experimental release of polyunsaturated fatty acids and reactive oxygen species during cell rupture. In other words, what fish gills actually encounter at cage depth depends on bloom physiology and cell integrity, not on how many cells are floating in a sample.

The Perspective dissects why the shellfish triad of intracellular toxin, bivalve sentinel and certified standard cannot simply be completed for fish. The relevant bioactive agents in most ichthyotoxic blooms reach the water through active export, stress-induced production or cell lysis; no sentinel organism integrates ichthyotoxin exposure on behalf of fish before injury occurs; and for most fish-killing taxa the chemical identities of the harmful compounds remain unknown, leaving the field without certified analytical standards. Even the genus Alexandrium exposes the divergence: the same species can produce paralytic shellfish toxins that fit neatly into certified workflows while simultaneously releasing structurally unrelated extracellular compounds that remain largely uncharacterised. In Chilean Alexandrium catenella, paralytic toxin quotas failed to explain gill-cell cytotoxicity, which was instead driven by polyunsaturated fatty acids acting synergistically with cell-derived superoxide.

Where the chemistry has been resolved, a common functional theme emerges. Karlotoxin 2 from Karlodinium veneficum is a large amphipathic polyketide that non-selectively increases plasma-membrane permeability, producing ionic imbalance and osmotic lysis. Prymnesins from P. parvum disrupt chloride and calcium regulation and kill gill cells at nanomolar concentrations. Chilean A. catenella lysates induce net potassium efflux from gill cells while purified paralytic toxins from the same strain produce no measurable ionic disturbance. For Chattonella marina, superoxide alone is insufficient to kill fish and fatty acid alone acts only at high concentrations, but together they triple the mortality rate. These findings argue against treating any fish-killing bloom as a single-target toxin problem.

The proposed alternative is a tiered, effect-based framework. Tier 1 retains taxonomic surveillance but redesigns sampling around fish exposure, with depth-resolved sampling at cage depth paired with hydrographic measurements, because vertically structured blooms can expose fish to concentrations that surface samples systematically miss. The extreme Heterosigma akashiwo bloom that killed more than 6,000 tonnes of farmed salmon in Chile’s Comau fjord in 2021 reached 70,000 cells per millilitre concentrated in the upper three metres under strong stratification. Tier 2 activates when a known fish-killing taxon is detected, measuring gill-toxic potency in paired water fractions: whole water, cell-free filtrate, resuspended cell-associated material and standardised lysate. The RTgill-W1 assay, which reads metabolic activity, membrane integrity and lysosomal integrity on the same cell population, showed EC50 values within a factor of five of whole-fish acute toxicity for 73 percent of 35 benchmark chemicals, with interlaboratory variation around 31 percent.

Tier 3 pursues chemical discovery through effect-directed analysis coupled with non-target high-resolution mass spectrometry, fractionating active samples, retesting each fraction and prioritising only those retaining activity. Two recent demonstrations prove the workflow works for fish-killing taxa. Bioassay-guided fractionation of the 2019 Norwegian C. leadbeateri blooms concentrated gill-toxic activity into a single fraction and yielded a candidate compound, proposed as leadbeaterin-1, detected in situ in bloom water. During the 2022 Oder River P. parvum disaster, in which several hundred tonnes of fish died, effect-based analysis detected B-type prymnesins alongside more than 120 organic micropollutants, with mixture modelling showing the neurotoxicity was predominantly explained by the prymnesins. The institutional urgency is documented: the IOC-UNESCO biotoxin database held only one formally catalogued ichthyotoxin as of March 2025, against more than 120 fish-killing microalgal taxa reported worldwide.

Mardones is explicit that the framework is a proposal requiring validation, not a system ready for regulation. No study has yet compared gill-cell potency in bloom water with mortality outcomes in caged fish at the same site and time, and the assay has documented blind spots, including compounds requiring metabolic activation and the mismatch between a freshwater-derived trout cell line and marine salmonid aquaculture. Marine matrix effects pose practical problems too: karlotoxins adsorb quantitatively onto standard filter membranes, meaning routine sample handling can erase the very signal being measured. Universal toxicity thresholds are premature, and the first generation of action levels should be calibrated locally against paired observations of blooms, fish behaviour, gill pathology and mortality. Even mitigation carries risk, since hydrogen peroxide treatment of dinoflagellate blooms has been shown to increase gill-cell cytotoxicity by generating persistent toxic aldehydes.

The deeper message is a convergence of fields. Fish-killing HAB science, the Perspective argues, should formally adopt the methodological infrastructure that the ecotoxicology of emerging contaminants built over two decades to assess hazard from chemically unresolved mixtures: effect-directed analysis, high-resolution mass spectrometry, adverse outcome pathways and effect-based monitoring. Cell counts remain indispensable for tracking blooms and forecasting exposure potential, but they answer only whether a hazard may be present. Waterborne gill-toxic potency, once validated, would answer the question that matters to a salmon farmer watching the water: whether that hazard is being expressed right now, at the depth where the fish are breathing.

Subject of Research: Effect-based monitoring of fish-killing harmful algal blooms using waterborne gill-toxic potency as an endpoint

Article Title: Waterborne gill-toxic potency as an effect-based endpoint for monitoring fish-killing harmful algal blooms

Article References: Mardones, J. I. (2026). Waterborne gill-toxic potency as an effect-based endpoint for monitoring fish-killing harmful algal blooms. Discover Ecology, 2(1), Article 28. https://doi.org/10.1007/s44396-026-00045-w

Image Credits: AI Generated

DOI: 10.1007/s44396-026-00045-w

Keywords: harmful algal blooms, ichthyotoxicity, aquaculture, gill-toxic potency, RTgill-W1, effect-directed analysis, high-resolution mass spectrometry, Pseudochattonella verruculosa, Prymnesium parvum, ecotoxicology, fish kills, monitoring

Salmon lice are ectoparasites that feed on the skin, mucus, and blood of fish. Their feeding activity creates open wounds that can become infected, reducing the market value of farmed fish and increasing the likelihood of secondary infections. Beyond the direct damage to individual animals, infestations impose enormous costs on the aquaculture sector. Sea lice infestations in Atlantic salmon farming cost the industry more than one billion dollars a year through mortality, lost production, and the implementation of control measures. Understanding the biology of the parasite at a molecular level is therefore considered a critical step in developing new, safe, and effective strategies for its control.

The central innovation of the new study lies in its sampling approach. Previous methods for extracting SEPs from salmon lice involved pooling together large numbers of individuals before analysis. While such pooled samples could yield enough material for detection, they averaged out the natural differences between individual lice. Those differences, the researchers argue, can provide vital insight for developing targeted treatments or vaccines, because they reveal how variable the parasite’s secretory arsenal is across a population. By contrast, the new method allows the collection of high-quality samples from a single louse per test, with substantial yields of secretory proteins per individual, while also reducing the potential for contamination of the samples with louse faecal material.

The collection procedure itself is elegantly simple in concept. Researchers place a small drop of solution over the mouthparts of an individual louse and allow the animal to release its secretory proteins into that droplet. The protein-laden solution is then examined using liquid chromatography tandem mass spectrometry, a state-of-the-art analytical technique that separates the components of a sample, breaks them into fragments, and analyses those fragments to reveal the exact protein composition of each sample. Applied to single-louse samples, this approach produces a detailed proteomic fingerprint of what each individual parasite is secreting at the moment of collection.

Using this assay, the team identified 148 secretory proteins in total, 64 of which were detected across each of the tested conditions. The consistency of that core set of proteins across individuals and conditions makes it particularly interesting from an applied perspective, because proteins that are reliably present in the parasite’s secretions could represent potential targets for vaccine development. A vaccine that prompts fish to mount an immune response against molecules the louse depends on for feeding or immune evasion could, in principle, reduce the parasite’s ability to establish itself on its host.

One of the most striking findings of the study was the degree of variation observed between individual lice. The secretory protein profiles of single animals showed wide variation in both the number and the diversity of proteins detected, a pattern the researchers note is consistent with what has been seen in other ectoparasites such as ticks and mosquitoes. This individual-level variability would have been invisible in pooled samples, and it underscores why the ability to study lice one at a time matters. If different lice deploy different combinations of secreted molecules, control strategies may need to account for that diversity in order to be effective across a whole parasite population.

The researchers emphasise that the methodology has value well beyond cataloguing proteins. Because the protocol allows reproducible, reliable, and efficient extraction of high concentrations of salmon louse secretions while minimising faecal contamination, it can serve as a platform for future experiments. Mr Dindial noted that the protocol could be used to investigate how drug or therapeutic treatments might alter louse secretory activity, which would allow scientists to test whether candidate interventions disrupt the parasite’s ability to feed or evade immunity. In this way, the assay functions both as a discovery tool and as a screening tool for evaluating new control measures.

The study also builds directly on a first-of-its-kind investigation led by Mr Dindial and published the previous year, which uncovered major differences in the secretions the parasite uses to feed and evade the immune system at different stages of its life cycle. Taken together, the two studies sketch a picture of a parasite whose chemical toolkit changes as it develops, and whose secretions vary from one individual to the next. That level of biological detail is exactly the kind of information needed to design interventions that are precise enough to work against the parasite while avoiding some of the drawbacks of existing treatments.

The need for better tools is pressing. Various treatments have been developed to tackle sea lice infestations in Atlantic salmon aquaculture, but some of these can be expensive, unreliable, environmentally damaging, or harmful to animal welfare. Chemical treatments can lose effectiveness as the parasite develops resistance, and mechanical or biological control approaches each carry their own limitations and costs. A strategy grounded in the parasite’s own secretory biology, whether through vaccination, targeted therapeutics, or the breeding of more resistant fish, offers the prospect of control measures that are both more effective and more sustainable than those currently available.

The research was funded by EastBio as part of Mr Dindial’s PhD studentship, with a funding contribution from the Moredun Research Institute. It was conducted in collaboration with the project Towards lice-resistant salmon: functional genetics and genome editing to enhance disease resistance in aquaculture, funded by the UK Biotechnology and Biological Sciences Research Council, the Sustainable Aquaculture Innovation Centre, and Benchmark Genetics Limited, and involving partners from the Roslin Institute at the University of Edinburgh, the Centre for Environment Fisheries and Aquaculture Science, the Atlantic Veterinary College at the University of Prince Edward Island, and Kames Fish Farming Ltd. The study, titled Investigation of a novel assay for the proteomic screening of the secretory and excretory products of individual salmon lice Lepeophtheirus salmonis, was published in Veterinary Parasitology on 1 May 2026. As the aquaculture industry continues to search for durable solutions to its costliest parasite problem, the ability to read the chemical language of individual lice may prove to be a decisive step forward.

Subject of Research: Proteomic analysis of secretory and excretory products of individual salmon lice for parasite control in aquaculture

Article Title: A University of Stirling study could pave the way for the more efficient study of the secretions that salmon lice use to avoid fish defences, potentially enabling the development of new strategies to protect salmon from infestations. Research led by PhD

Article References: A University of Stirling study could pave the way for the more efficient study of the secretions that salmon lice use to avoid fish defences, potentially enabling the development of new strategies to protect salmon from infestations. Research led by PhD. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: salmon lice, aquaculture, proteomics, mass spectrometry, secretory proteins, Lepeophtheirus salmonis, vaccine development, parasite control, Atlantic salmon, University of Stirling, Veterinary Parasitology, immune evasion

The research team, led by Shenji Wu and corresponding author Delin Qi of Qinghai University’s State Key Laboratory of Plateau Ecology and Agriculture, together with Fei Tian of the Northwest Institute of Plateau Biology at the Chinese Academy of Sciences, combined liver and blood biochemistry with transcriptome-wide gene expression profiling. They also tracked the expression of key immune-related genes in the gills and spleen, the two organs that sit at the front line of a fish’s interaction with its watery environment. By integrating biochemical measurements with mRNA expression data, the researchers were able to connect physiological damage with the genetic machinery that responds to it, painting a dynamic picture of immune regulation under oxygen stress.

The clearest signal emerged from the comparison between the two hypoxia regimes. Severe short-term hypoxia, the twelve-hour acute challenge, exacerbated oxidative damage in the fish and significantly altered the expression of genes governing apoptosis, the controlled program of cell death, and autophagy, the cellular recycling process that degrades damaged components. This makes intuitive biological sense: when oxygen supply collapses suddenly, mitochondria leak reactive oxygen species, membranes are peroxidized, and cells must decide whether to repair themselves or self-destruct. Malondialdehyde, a standard marker of lipid peroxidation, served as one of the biochemical readouts of this damage, alongside antioxidant enzymes such as total superoxide dismutase and catalase, which mop up reactive oxygen species before they can wreak havoc.

At the pathway level, the transcriptomic response to severe short-term hypoxia was strikingly specific. Gene sets involved in phagosome function, lysosomal activity, Toll-like receptor signaling and NOD-like receptor signaling were all significantly enriched under the acute challenge. These pathways form the backbone of the innate immune system: phagosomes and lysosomes engulf and digest cellular debris and invading microbes, while TLRs and NLRs are pattern-recognition receptors that detect molecular signatures of pathogens and tissue damage. Notably, none of these pathways showed comparable enrichment under moderate prolonged hypoxia, suggesting that the fish’s immune system interprets a sudden oxygen crash as an emergency requiring full innate immune mobilization, whereas a gradual, sustained oxygen decline is managed through quieter, more homeostatic mechanisms.

To move beyond simple lists of differentially expressed genes, the researchers applied two complementary computational approaches. Short Time-series Expression Miner, or STEM, was used to identify genes that follow coherent temporal expression profiles across the moderate hypoxia time course of 24, 96 and 168 hours. Weighted Gene Co-expression Network Analysis, or WGCNA, was then used to detect modules of genes that behave in a coordinated fashion and to link those modules to the measured biochemical traits. Together, these methods pinpointed a set of key immune-related genes whose expression patterns define the fish’s hypoxic immune response, including nod1, irf3, ifnα, pi3k, akt, p38, il-12, jak1, stat1, nlrp3, bax, bcl2, bcl-xl, atg5 and lc3.

Each of these genes tells part of the story. NOD1 is an intracellular pattern-recognition receptor that senses bacterial peptidoglycan and triggers inflammatory signaling. IRF3 and interferon alpha sit at the heart of the antiviral response, while the IL-12, JAK1 and STAT1 axis connects innate detection to the activation of adaptive immune cells. PI3K and AKT are central survival kinases that also feed into autophagy regulation, and the BAX, BCL2 and BCL-XL proteins are the arbiters of the mitochondrial apoptosis pathway, deciding whether stressed cells live or die. ATG5 and LC3 are core components of the autophagy machinery itself, and NLRP3 is the inflammasome sensor that can ignite potent inflammatory responses. The fact that most of these genes showed similar expression trends in the hypoxia-challenged gills indicates that the respiratory epithelium, in constant contact with the oxygen-poor water, orchestrates a coordinated immune program.

The spleen told its own story. In this immune organ, the expression of nod1, irf3, akt, pi3k, jnk and cyld was remarkably induced by severe short-term hypoxia. CYLD, a deubiquitinating enzyme, acts as a brake on inflammatory signaling pathways including NF-κB, so its induction alongside NOD1 and IRF3 suggests a carefully balanced response: the fish activates antiviral and antibacterial defenses while simultaneously engaging negative regulators to prevent runaway inflammation. This kind of calibrated response is critical, because uncontrolled inflammation in a hypoxic animal can compound tissue damage rather than repair it. The spleen’s sensitivity to the acute challenge underscores that hypoxia is not merely a respiratory problem but a systemic immune event.

Why does this matter beyond the biology of one Tibetan fish? Aquatic hypoxia is an increasingly common stressor in natural waters and aquaculture systems alike, driven by eutrophication, warming temperatures and high stocking densities. Hypoxic episodes suppress growth, impair immune competence and increase susceptibility to disease in farmed fish, imposing substantial economic losses. Understanding how a naturally hypoxia-tolerant species regulates its immune system under different oxygen regimes provides a template for what robust fish look like at the molecular level. The authors explicitly frame their results as valuable information for breeding hypoxia-tolerant fish, and the gene set they identified, from pattern-recognition receptors to apoptosis regulators, offers candidate markers for selective breeding or genome editing programs aimed at hardier aquaculture stocks.

The study also carries a broader conceptual message about how stress biology should be measured. Had the researchers tested only a single hypoxia condition or a single time point, they might have concluded that hypoxia uniformly activates innate immune pathways. Instead, the contrast between severe short-term and moderate prolonged exposure reveals that the nature of the stressor, not just its presence, determines the immune strategy. Acute severe hypoxia triggers oxidative damage, cell-death decisions and full innate immune mobilization, while chronic moderate hypoxia appears to be absorbed without triggering the same pathway-level enrichment, implying that the fish either adapts metabolically or relies on regulatory mechanisms that do not register as classical immune activation in the transcriptome.

For Gymnocypris eckloni itself, the work adds a new dimension to its reputation as a survivor of the roof of the world. Plateau fishes face a double challenge: cold temperatures slow their metabolism while low oxygen constrains their aerobic capacity, and immune defenses are energetically expensive to maintain. The dynamic regulation documented in this study, with its interplay of phagocytosis, inflammasome signaling, interferon responses, apoptosis and autophagy, shows that tolerance to hypoxia is not a passive tolerance of damage but an actively managed physiological state. As climate change alters oxygen dynamics in lakes and rivers worldwide, the molecular playbook of this high-altitude fish may prove to be one of the most valuable resources aquaculture and conservation biology have yet uncovered, and the Qinghai-Tibetan Plateau continues to yield insights found nowhere else on Earth.

Subject of Research: Immune gene regulation in the Tibetan plateau fish Gymnocypris eckloni under severe short-term and moderate prolonged hypoxia

Article Title: Dynamic immune regulation of Gymnocypris eckloni in response to severe short-term hypoxia and moderate prolonged hypoxia

Article References: Wu, S., Wang, Z., Xia, M., Liu, D., Wang, W., Zhang, C., Jia, J., Tian, F., & Qi, D. (2026). Dynamic immune regulation of Gymnocypris eckloni in response to severe short-term hypoxia and moderate prolonged hypoxia. BMC Genomics. https://doi.org/10.1186/s12864-026-13296-4

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13296-4

Keywords: hypoxia, Gymnocypris eckloni, immune regulation, transcriptome, Qinghai-Tibetan Plateau, innate immunity, apoptosis, autophagy, TLR signaling, NLR signaling, WGCNA, aquaculture

Marine heatwaves are defined as extended periods during which ocean temperatures remain far above the seasonal norm. As the climate warms, these events are becoming more frequent, longer-lasting and more intense, a trend that climate models project will accelerate through the middle of the century. The ecological consequences are well documented: mass coral bleaching, seagrass die-offs, shifts in species distributions and collapses of locally important fisheries have all been recorded after major marine heatwave events. What has been missing, the authors argue, is a systematic accounting of what these environmental disruptions mean for people, particularly the coastal communities whose food, income and cultural identity are bound to the sea.

The study lays out several pathways through which ocean warming translates into human harm. The first is extreme weather. Higher ocean temperatures pump additional energy and moisture into the atmosphere, contributing to more intense storms and flooding. The health consequences of such events are immediate and severe, ranging from injury and death during the events themselves to displacement, loss of shelter and the long-term disruption of health services in affected regions. By intensifying these hazards, marine heatwaves extend the reach of ocean warming well beyond the coastline and into the domain of disaster preparedness and emergency medicine.

A second pathway runs through the food supply. Marine heatwaves can trigger blooms of harmful algae, some of which produce toxins that accumulate in shellfish and finfish. When contaminated seafood reaches markets, it can cause outbreaks of poisoning that public health authorities may struggle to trace back to an oceanic origin. At the same time, heat-driven damage to fisheries and aquaculture operations can sharply reduce seafood availability. This is not merely an economic problem. For communities that depend heavily on marine resources for protein and micronutrients, a decline in seafood supply translates directly into risks for food security and nutrition, with children and other vulnerable groups most exposed.

The third pathway is psychological. Professor Bayden Russell, Associate Professor of Ecology and Biodiversity at HKU and senior author of the paper, emphasised that for many people the ocean is far more than a place for recreation. It provides food, income, cultural identity and a sense of place. When marine heatwaves damage coral reefs, fisheries and other marine resources, the communities that depend on them can experience grief, anxiety and uncertainty about the future. Russell noted that these mental health impacts are likely to be substantial, yet they remain largely unrecognised and understudied in both the climate science literature and public health practice.

The geographic distribution of this risk is deeply uneven, and Asia sits at its centre. Hundreds of millions of people across the region depend on the ocean for food, livelihoods and cultural practices, from small-scale fishing households in Southeast Asia to coastal megacities that draw a substantial share of their animal protein from the sea. The same region is also projected to experience some of the fastest increases in marine heatwave days over the coming decades. The combination of high exposure, high dependence and rapid warming makes ocean-dependent Asian communities a priority case for the kind of integrated planning the researchers are calling for.

The core policy argument of the paper is that marine heatwaves deserve the same institutional treatment as heatwaves on land. Over the past two decades, many governments have developed heat-health action plans that link meteorological forecasts to hospital preparedness, public warnings and outreach to vulnerable populations. No comparable framework exists for the ocean. The researchers propose incorporating marine heatwave forecasts into public health planning, considering health impacts explicitly in marine and coastal management decisions, and building stronger collaboration between ocean scientists, health authorities and natural resource managers. In their view, the technical ingredients for such a system already exist; what is lacking is the institutional connection between them.

Dr Laura Falkenberg of Adelaide University framed the challenge in blunt terms, saying that recognising these health impacts is the first step towards better protecting communities. She added that as marine heatwaves become increasingly common, the scientific and policy community needs to move from simply documenting impacts after they occur to preparing communities in advance, and that better planning today can reduce future health risks. This shift from retrospective damage assessment to anticipatory risk management mirrors the transformation that land-based heatwave science underwent after the deadly European heatwave of 2003, which forced public health systems to treat extreme heat as a forecastable, preventable hazard rather than an unavoidable natural event.

The technical foundations for anticipatory management are advancing rapidly. Oceanographers can now detect the atmospheric and oceanic conditions that precede marine heatwaves, and seasonal forecast systems are improving in their ability to flag regions at risk weeks to months in advance. Fisheries managers can use such outlooks to adjust catch limits, aquaculture operators can time harvesting and relocate stock, and health agencies can pre-position monitoring for harmful algal blooms and seafood contamination. Russell observed that the devastating effects of marine heatwaves on marine ecosystems have been recognised for some time, but that what has been missing from the conversation is what these events mean for people, adding that scientists are only just beginning to understand how these environmental impacts can produce large negative effects on human health.

The study’s publication in Nature Sustainability signals a deliberate attempt to move the issue out of marine ecology and into the interdisciplinary mainstream of sustainability and health research. Its authors hope that framing marine heatwaves as a public health threat will unlock new sources of funding, new institutional partners and new policy levers, from health ministry early-warning systems to coastal development rules that account for the psychological value of intact marine ecosystems. As ocean temperatures continue to climb and heatwave days accumulate through mid-century, the researchers argue that the cost of inaction will be measured not only in bleached corals and collapsed fisheries, but in injuries, poisoned seafood, lost livelihoods and the quiet burden of anxiety and grief carried by communities watching the sea they depend on change faster than they can adapt.

Subject of Research: Human health impacts of marine heatwaves

Article Title: HKU ecologists warn that marine heatwaves pose an underestimated threat to public health

Article References: HKU ecologists warn that marine heatwaves pose an underestimated threat to public health. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: marine heatwaves, public health, ocean warming, food security, harmful algal blooms, mental health, fisheries, aquaculture, coastal communities, climate change, Nature Sustainability, early warning systems

The stakes are considerable. Shrimp aquaculture has become one of the fastest-growing food production sectors on the planet, and India sits at its center. The country ranks third in global aquaculture output after China and Indonesia, accounting for 7.70 percent of world production, and its sector has posted double-digit annual growth exceeding 10 percent over the past decade. Yet the industry’s Achilles heel lies at the very start of the production line: hatcheries that supply healthy seed stock. Poor quality larvae during the initial stages constrain survival, growth, and ultimately the productivity of entire farming operations downstream.

Conventional shrimp hatcheries solve their water quality problems the old-fashioned way—by flushing. Large volumes of water are exchanged continuously to keep toxic nitrogenous wastes in check, a strategy that carries heavy costs in pumping, collection, filtration, and disinfection, while also creating pathways for disease and discharging nutrient-rich effluent into the environment. Biofloc technology, or BFT, offers a fundamentally different approach. Instead of removing nitrogenous waste, the system recruits communities of heterotrophic bacteria to convert it into microbial biomass. By manipulating the carbon-to-nitrogen ratio in the water, farmers encourage these bacteria to proliferate, forming dense suspended aggregates—the flocs—that shrimp can graze on as a natural, continuously available food source.

The catch is that bacteria need carbon to do this work, and not all carbon sources are created equal. Simple sugars such as molasses, glucose, and fructose are rapidly degraded, while complex materials like rice bran and cellulose break down slowly. The choice of carbohydrate shapes how quickly flocs form, how efficiently nutrients are assimilated, and how stable the microbial community remains. Despite the technology’s successful adoption across broodstock, nursery, and grow-out phases of shrimp production, information on its effectiveness during the delicate larval and postlarval stages of Penaeus vannamei has remained scarce—precisely the gap the Indian team set out to fill.

The experiment took place at the BKMN shrimp hatchery in Undavalli, in the Guntur district of Andhra Pradesh. The researchers used eight circular high-density polyethylene tanks of 1000 liters capacity, each with a working volume of 800 liters, meticulously cleaned and treated with bleaching powder before use. Specific pathogen-free shrimp nauplii, confirmed disease-free by PCR testing, were stocked at an extraordinarily high density of 100 larvae per liter—80,000 animals per tank—at the mysis-1 stage. Three biofloc treatments were established at a fixed carbon-to-nitrogen ratio of 15:1, using fructose, lactose, or dextrose as the carbon source, alongside a control with no carbohydrate addition. The trial ran for 13 days, until the larvae reached postlarval stage 10, with zero water exchange throughout.

Building the flocs required careful staging. Following the protocol pioneered by aquaculture researcher Yoram Avnimelech, the team introduced nitrogen on the first day by adding 1.5 grams of ammonium chloride, then added carbon sources on days three and five at 5.62 grams, doubling the dose to 11.25 grams on day seven. The water’s transformation from clear and transparent to light brown signaled that floc formation was underway. Larvae were fed a commercial microencapsulated diet with a minimum protein content of 52 percent, distributed across six daily feedings, with quantities adjusted to floc volume at each developmental stage.

The water chemistry results told a clear story. Temperature remained in the optimal 27 to 29 degrees Celsius range, and dissolved oxygen stayed between 5.30 and 6.24 milligrams per liter, comfortably above the lethal threshold of 1.0 ppm reported for the species. More striking were the differences in nitrogen compounds. Total ammonia nitrogen in the biofloc tanks ranged from 0.69 to 0.78 milligrams per liter, significantly lower than the control’s 1.07. Un-ionized ammonia, which is highly toxic to shrimp, measured just 0.12 milligrams per liter in the biofloc treatments against 0.36 in the control. Nitrite, which damages the circulatory and immune systems of aquatic animals, was a mere 0.06 milligrams per liter in the biofloc systems compared with 1.53 in the control—well above the 1.0 milligram per liter considered optimal for successful culture. Nitrate and alkalinity also differed significantly among treatments, with biofloc alkalinity of roughly 127 to 128 milligrams per liter far exceeding the control’s 91.38.

Survival data sealed the case for dextrose. At postlarval stage 1, dextrose-fed tanks achieved 93 percent survival, followed by fructose at 88.67 percent, lactose at 86.33 percent, and the control at 79.33 percent. By postlarval stages 5 and 10, the gap widened: 90.67 percent for dextrose, 85.67 percent for fructose, 78.33 percent for lactose, and a sobering 66.67 percent for the control. The researchers attribute dextrose’s advantage to its chemistry. As a monosaccharide derived from simple starch, it is readily broken down by bacteria, driving robust floc formation—the dextrose treatment produced the greatest floc volume at 1.62 milliliters per liter, compared with 1.12 for fructose and just 0.84 for lactose, a disaccharide that microbes decompose more slowly.

The broader implications extend beyond a single hatchery in coastal India. Every biofloc treatment group surpassed the 70 percent survival benchmark considered appropriate for the species and for experimental hatcheries, and the overall biofloc survival range of 71 to 86 percent dwarfed the control’s 53 percent. Because the systems operated with zero water exchange, they promise reduced water costs, enhanced biosecurity against pathogens, and a smaller environmental footprint—attributes that matter enormously as the industry confronts disease outbreaks and tightening environmental regulations. The flocs themselves add nutritional value, offering shrimp a supplementary microbial food source alongside formulated feeds.

For an industry that contributes roughly 1.24 percent to India’s gross value added and more than 7.28 percent to agricultural GVA, with exports of 12.22 million tonnes valued at 1.42 billion US dollars in 2023, even incremental gains in hatchery survival compound into substantial economic returns. The study’s conclusion is pragmatic: fertilization with dextrose at a 15:1 carbon-to-nitrogen ratio can efficiently maintain a shrimp hatchery system without any water exchange. As biofloc technology continues its march from experimental tanks to commercial operations worldwide, this finding suggests that one of the most consequential decisions a hatchery manager makes may be as simple as choosing the right sugar.

Subject of Research: Biofloc technology with different carbon sources for Pacific white shrimp hatchery production

Article Title: Hatchery performance of Pacific white shrimp, Penaeus vannamei in Biofloc technology by using different carbon sources

Article References: Suneetha, K., Padmavathi, P., & Chatla, D. (2024). Hatchery performance of Pacific white shrimp, Penaeus vannamei in Biofloc technology by using different carbon sources. Blue Biotechnology, 1(1), Article 13. https://doi.org/10.1186/s44315-024-00016-4

Image Credits: AI Generated

DOI: 10.1186/s44315-024-00016-4

Keywords: biofloc technology, Pacific white shrimp, Penaeus vannamei, aquaculture, dextrose, carbon source, water quality, larval survival, hatchery, zero water exchange, carbon-nitrogen ratio, sustainable aquaculture

Unlike vertebrates, which deploy both adaptive and innate immune responses, mollusks rely exclusively on innate immunity. Their defense toolkit includes enhanced phagocytic activity, pattern recognition receptors, and effector molecules that identify and neutralize invading microorganisms. Among these molecular sentinels is the mannose receptor, a member of the C-type lectin superfamily and a type I transmembrane protein that functions as what researchers describe as a non-standard pattern recognition receptor. Rather than serving as a conventional first-line sensor, the mannose receptor contributes to host defense primarily by recognizing and binding endogenous ligands and pathogen-associated molecules, thereby modulating immune responses and maintaining immune homeostasis under external stress. Its importance has been demonstrated previously in aquatic animals such as the red swamp crayfish Procambarus clarkii and the orange-spotted grouper Epinephelus coioides, where MR-mediated responses showed antiviral and antibacterial activity against Vibrio species.

Structurally, the mannose receptor is an intricate machine. It comprises an extracellular cysteine-rich domain, a fibronectin type II domain, and eight tandem C-type lectin-like domains, along with a transmembrane segment and a short cytoplasmic tail. Functional studies have shown that the fibronectin type II domain and the second C-type lectin-like domain act synergistically to enhance the uptake of glycosylated collagen, while the fourth domain has been implicated in modulating T cell cytotoxicity. The receptor’s C-type lectin-like domains can specifically recognize and bind carbohydrate ligands such as mannan, trehalose, and N-acetylglucosamine on both endogenous and exogenous molecules, initiating immune responses upon binding. In the bream Megalobrama amblycephala, for example, the mannose receptor binds chitosan oligosaccharide and mediates its uptake by macrophages through lectin-dependent endocytosis, modulating the expression of tumor necrosis factor receptor-associated factors, interleukins, and nitric oxide synthase.

To understand how this receptor family operates in the Manila clam, the researchers mined the clam’s genome, which was previously sequenced and made available under NCBI BioProject PRJNA479743. Using Hidden Markov Model searches based on the C-type lectin-like domain model PF00059.23, they identified a remarkably large repertoire of 13 mannose receptor genes, designated RpMR1 through RpMR13. The predicted proteins displayed considerable diversity, with molecular weights ranging from 11.27 to 320.37 kilodaltons and theoretical isoelectric points between 4.42 and 6.82. Exon numbers varied from 2 to 60, and every RpMR protein contained at least one C-type lectin domain, with copy numbers ranging from 1 to 14 per protein, hinting at substantial functional redundancy or diversification within the family. Conserved motif analysis revealed ten distinct motifs across the proteins, and multiple sequence alignment highlighted conserved cysteine residues, calcium-binding sites, acidic amino acids, and aromatic residues such as phenylalanine and tryptophan, all characteristic features of C-type lectin family proteins.

Chromosomal localization added another layer of organization to the story. Ten of the 13 RpMR genes mapped to six annotated chromosomes, with chromosome 10 harboring three genes in what appears to be a gene cluster, while the remaining three genes sat on unplaced scaffolds. Phylogenetic analysis, built from 142 mannose receptor amino acid sequences across nine representative species, revealed that MR genes cluster into two major branches, with molluscan sequences from R. philippinarum, Crassostrea virginica, C. gigas, and Biomphalaria glabrata grouping predominantly within a single large clade. This pattern suggests that mannose receptor genes in mollusks have undergone evolutionary conservation, reflecting shared ancestry and potentially conserved functional roles across the phylum. Interestingly, when the researchers examined expression across developmental stages, all RpMR genes were expressed as the clams grew, with most showing significantly increased expression at the D-larva stage, indicating that this immune machinery is active from early life onward.

The infection challenge experiments brought the gene family’s defensive role into sharp focus. Wild clams collected from Jinshitan in Dalian were immersed in V. anguillarum at a concentration of 1 × 10⁷ CFU/mL, and hepatopancreas tissues were sampled at intervals from 0 to 96 hours post-challenge. The results showed that RpMR expression surged following infection, with RpMR1, RpMR2, RpMR3, RpMR4, and RpMR6 all peaking at 72 hours post-infection, reaching 3.2-, 6.8-, 8.3-, 1.68-, and 1.1-fold increases respectively relative to baseline. Tissue-specific analysis revealed that the genes were expressed throughout the clam body, including the adductor muscle, mantle, foot, gill, siphon, and digestive gland, but expression was most pronounced in the hepatopancreas, where RpMR2 reached twelvefold higher levels than in the adductor muscle. This organ, the researchers conclude, likely serves as a key site for mannose receptor-mediated immune responses.

The team then zeroed in on RpMR1 as a functional candidate. They cloned the gene’s coding region into a PET-28A(+) vector, expressed it in E. coli Rosetta (DE3) cells, and purified the recombinant protein, which appeared at its theoretical 123 kilodalton position on SDS-PAGE gels and was confirmed by Western blot. In vitro antibacterial assays tested the protein against eight bacterial strains, and the results were strikingly specific. RpMR1 significantly inhibited growth of three Gram-negative Vibrio pathogens: V. splendidus, with significant suppression observed at 4 hours, and V. anguillarum, with sustained inhibition at 6, 8, and 10 hours, along with V. alginolyticus. No inhibitory activity was detected against Bacillus subtilis, Staphylococcus aureus, Vibrio parahaemolyticus, V. harveyi, or Escherichia coli. The researchers attribute this bactericidal specificity to RpMR1’s affinity for lipopolysaccharides, the dominant outer membrane component of Gram-negative bacteria and a conserved pathogen-associated molecular pattern recognized by Toll-like receptor 4.

The most dramatic evidence came from in vivo experiments. Clams were divided into four groups receiving different injections: phosphate-buffered saline plus recombinant protein, V. anguillarum plus recombinant protein, V. anguillarum plus buffer, and buffer alone. By 96 hours, the cumulative mortality rate in the infected group that received only buffer reached 78.6 percent, while the infected group that also received RpMR1 protein saw mortality drop to 52.7 percent, a 26 percent reduction in deaths. Clams receiving protein without infection showed the same survival as untreated controls, confirming the protein’s safety. Complementary molecular measurements showed that injection of RpMR1 rapidly activated the Toll-like receptor signaling pathway, with the genes TLR, MyD88, TRAF, NF-κB, IKK, and AP-1 all peaking at 6 hours post-infection in the infected, protein-treated group, while most pathway genes in the infected, untreated group did not peak until 96 hours. Nitric oxide synthase activity was also significantly elevated at 12 and 72 hours in the protein-treated infected group, consistent with nitric oxide’s established role in promoting phagolysosome maturation and microbicidal activity.

To establish causality rather than mere correlation, the researchers turned to RNA interference. Injecting synthetic double-stranded RNA targeting RpMR1 successfully silenced the gene, reducing its expression significantly. The knockdown had cascading effects: TRAF6 expression dropped significantly, while TLR4 and AP-1 expression levels were also significantly reduced. This demonstrates that RpMR1 positively regulates components of the TLR signaling pathway during the immune response, confirming a functional interaction between the mannose receptor and TLR4. The finding fits with a broader literature on pattern recognition receptor crosstalk: mannose-binding lectin, another C-type lectin family member, has been shown to potentiate TLR4 signaling through direct interaction with its leucine-rich repeat domain, and cooperative interactions between mannose receptors and TLR4 have been documented in orchestrating pro-inflammatory mediator release, including interleukin-1β, tumor necrosis factor-alpha, and interleukin-6. Because the mannose receptor itself lacks intrinsic signaling capacity, such cooperative interactions with other receptors may be essential for transducing immune activation signals while maintaining immune homeostasis.

The implications for aquaculture are considerable. The authors suggest that the immunological functions of recombinant RpMR1 protein could eventually be applied in Manila clam farming, potentially incorporated into feed as an antimicrobial agent, though they caution that further research is needed to determine optimal dosage and whether sustained antibacterial activity can be maintained at scale. More broadly, the study marks the first functional demonstration of mannose receptor-mediated immunity in mollusks, bridging receptor-mediated pathogen recognition with downstream effector mechanisms such as nitric oxide production and TLR signaling in bivalve host defense. The researchers note that the precise molecular interplay by which RpMR1 confers anti-Vibrio immunity through nitric oxide synthase-dependent mechanisms remains to be fully delineated, and targeted investigations into the tripartite relationship between receptor activation, effector enzyme regulation, and pathogen clearance are still needed. Nevertheless, by identifying a concrete molecular target linked to survival during infection, the work opens a promising avenue for breeding or engineering disease-resistant clam strains, offering a potential lifeline for an aquaculture industry under relentless bacterial pressure.

Subject of Research: Mannose receptor-mediated innate immunity in the Manila clam against Vibrio anguillarum infection

Article Title: Mannose receptor RpMR1 of Manila clam (Ruditapes philippinarum) defense against Vibrio anguillarum infection

Article References: Yin, Z., & Nie, H. (2025). Mannose receptor RpMR1 of Manila clam (Ruditapes philippinarum) defense against Vibrio anguillarum infection. Advanced Biotechnology, 3(3), Article 23. https://doi.org/10.1007/s44307-025-00075-7

Image Credits: AI Generated

DOI: 10.1007/s44307-025-00075-7

Keywords: Manila clam, Ruditapes philippinarum, mannose receptor, RpMR1, Vibrio anguillarum, pattern recognition receptor, innate immunity, TLR4, nitric oxide synthase, RNA interference, aquaculture, bivalve defense