Permutational analysis of variance showed that each aquatic–lung pair shared a highly significant, pair-specific diatom signal, with the pairing factor explaining 86 per cent of the variation in the data (R2 = 0.86, p = 0.001). Differences between the water samples and the corresponding lung samples were statistically insignificant, indicating that lung diatom assemblages reflected the communities present at the drowning site. This established lung samples as highly representative of the site-specific aquatic community in the analysed cases.

The strength of the matching depended on geography. Beta regression analysis identified the spatial tightness of the sampling locations as the sole significant factor affecting pairing accuracy, with a pseudo-R2 of 0.50. The authors describe this as confirming the strong site-specific character of the aquatic–lung pairs.

To simulate real casework, in which one lung sample may be compared against several possible water bodies, the team applied a mutual nearest neighbour criterion. When one lung sample was compared to two candidate aquatic samples, the correct site was identified in 95 per cent of cases. Accuracy declined as the candidate pool grew, but even with eleven competing water bodies the method still reached the correct match in 79 per cent of cases.

To control false positives, the researchers introduced the nearest neighbour distance ratio as a decision parameter and calibrated empirical thresholds at the 95 per cent level, limiting the false-positive rate to 5 per cent within the resampling framework. Corresponding true-positive sensitivity was reported for the three best-performing quantitative distance metrics: Bray–Curtis dissimilarity, quantitative Jaccard distance and Hellinger distance. From these results the authors built a practical decision guide for selecting the most probable drowning site and assessing how distinctive the match is relative to the candidate pool.

The authors are explicit about the method's boundary. The framework performs well when the true drowning site is present among the candidates, but the analysis cannot confirm that the actual site was sampled at all. If the genuine water body is missing from the pool, a false candidate may still emerge as the nearest neighbour, and the current criteria cannot reliably flag such a case.

The study's results indicate that quantitative analysis based on sample distance metrics provides a statistically quantifiable framework for drowning-site determination in cases where the true site is included in the candidate pool, while rejecting false pairings when the true site is absent remains beyond the sensitivity of the method.

Subject of Research: Quantitative diatom analysis for determining the site of drowning in forensic medicine

Article Title: Quantitative diatom analysis for drowning-site determination: Evaluation of accuracy and a practical decision guide

Article References: Bešta, T., Dohnalová, P., Zubíčková, K., Tomášek, P., Markvartová, J., Tomášková, E., Hauer, T., Zagatová, I., Lefnar, R., Hamrová, H., & Kaštovský, J. (2026). Quantitative diatom analysis for drowning-site determination: Evaluation of accuracy and a practical decision guide. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04047-x

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04047-x

Keywords: diatoms, drowning, forensic science, legal medicine, lung tissue, PERMANOVA, Bray-Curtis, site determination, microalgae, quantitative analysis, decision threshold, aquatic ecology

The review, which combines decades of published studies with the author’s own doctoral research, focuses on four pillars of charophyte biology: the formation of the sexual organs and fertilisation, the dormancy of oospores, the induction of germination, and the cultivation of these algae under artificial conditions. The stakes are considerable. Characeae are sensitive indicators of clean water, and their decline under eutrophication has been documented across Europe and beyond. At the same time, their evolutionary position as part of the sister group to land plants makes every insight into their reproduction a potential window into how plants first conquered the terrestrial world. Understanding why these algae appear, disappear and return in aquatic systems, the review argues, requires a multidimensional approach that fuses morphology, anatomy, physiology, genetics, geobotany and ecology.

Sexual reproduction in charophytes is a spectacle in miniature. Male and female organs, the antheridia and oogonia, arise from short shoots formed at the nodes of branchlets. The male antheridium matures through a striking colour transformation, from green through pale yellowish-green to vivid orange, before releasing thousands of flagellated spermatozoids into the water. As long ago as 1967, researchers linked that orange hue to the accumulation of carotenoid-rich plastoglobuli. The female oogonium is an ovoid structure encircled by spiral cells, and its fertilisation was described in exquisite detail as far back as 1871 by Anton de Bary, who observed spermatozoids massing at five tube-like channels and threading through a narrowed funnel at the apex of the oocyte. What follows is the formation of a thickened cellulose layer around the zygote, a layer whose absence is thought to signal infertility.

Yet even this well-trodden path conceals one of the great mysteries of the field: nobody knows exactly when meiosis occurs in charophytes. Over more than a century, researchers have proposed at least four conflicting hypotheses, placing meiosis just before oospore germination, in the early stages of gametangia, during protonema development, or immediately after fertilisation. The problem is technical as much as conceptual. Oogonia and oospores are loaded with starch, which makes ultrathin sectioning for microscopy notoriously difficult. The review identifies establishing reliable sectioning methods for every developmental stage as one of the most important prerequisites for finally solving this puzzle, a reminder that even foundational cell biology can stall on the limitations of laboratory technique.

Genetics is beginning to fill gaps that morphology alone cannot. Studies of Chara globularis have revealed the presence of MIKC-type MADS box genes in both oogonia and antheridia, suggesting these key regulators of sex-specific cell differentiation existed before the major diversification of plant lineages. Immunofluorescence work has shown PIN2-like auxin transporters in antheridial filaments, along with polar auxin transport in internodal cells, features long thought to be hallmarks of land plants that evidently evolved far earlier. Cell wall chemistry tells a similar story: charophytes contain the same cellulose, pectin, hemicellulose, lignin and proteins as land plants, differing mainly in proportions, although recent work has found that some species lack hydroxyproline and arabinogalactan proteins that are ubiquitous in terrestrial flora.

Asexual reproduction adds a second, quieter strategy. Many charophytes propagate vegetatively through modified rhizoid or nodal cells, forming starch-filled bulbils that act as overwintering reserves, star-shaped in Nitellopsis obtusa, strawberry-shaped in Chara baltica, cardioid-shaped in Chara fragifera. These structures can regenerate new shoots after drought, fragmentation or the death of apical cells, ensuring population persistence when conditions are unfavourable for oospores. One species stands apart: Chara canescens has never been observed reproducing vegetatively and depends entirely on oospores, reproducing either sexually in dioecious populations or parthenogenetically, with genetically and chromosomally distinct female lines. Notably, the review reports that severing the rhizoid filaments connecting bulbils prevents new shoot development, hinting at unknown signalling pathways that modern molecular tools have yet to touch.

The oospore is the charophyte’s long-term insurance policy, a resting stage embedded in aquatic sediments that resists drought and mechanical stress far better than any vegetative fragment. Whether it germinates depends on a cascade of cues. The review maps these onto the biogeographic concept of zonobiomes, showing that the climate zone from which material originates predicts which dormancy-breaking treatment works: species of the warm-temperate zonobiome V generally respond to pre-treatment at 15 degrees Celsius, whereas species of zonobiome VI require cold storage. Cold treatment followed by irradiation with long-wave light emerges as the most broadly effective method, though species-specific exceptions abound, such as a New Zealand Nitella that prefers room-temperature storage. Freshly extracted oospores, it turns out, are more deeply dormant than those recovered from sediments, likely because abscisic acid is gradually degraded during storage.

Light, nutrients and chemistry complicate the picture further. Some studies find that light intensity and quality trigger germination; others find no effect at all, contradictions the review attributes to differences in geography, species and sample type. Purely inorganic culture media actually inhibit germination, while the addition of organic material, though critical for success, invites contamination by microbes and epiphytes. Desiccation matters too: drying oospores increased germination in some species but not others, and dried oospores of several Chara species germinated after freezing, chilling or warming across storage periods of up to four years. Sediment depth plays a role as well, with heavier Chara oospores germinating from deeper layers than lighter Nitella ones, a finding that underpins the emerging restoration science of so-called ghost ponds, where long-buried viable oospores can resurrect lost aquatic floras.

Perhaps the most practically significant contribution of the review is a new cultivation approach the author calls Eco-in-vitro-cultivation. Traditional laboratory media have long failed to induce the formation and maturation of gametangia in monoecious, diplostichous Chara species such as Chara hispida, with cultures instead succumbing to biofilm overgrowth and reproductive senescence. By combining environmental logger data from outdoor mesocosms at Rostock University, records of temperature, light intensity and light-dark cycles under which germination and gametangia development naturally occurred, with refined in-vitro techniques and a nutrient medium, the researchers achieved successful gametangia initiation and oospore maturation under fully artificial conditions. Because such cultures carry a drastically reduced microbiome, they should also make it easier to distinguish contaminant-specific and bacterial-specific gene sequences in future molecular work.

The broader significance is hard to overstate. Long-term, controlled cultures that complete the full life cycle would open the door to identifying the gene networks governing different modes of reproduction, resolving the timing of meiosis, and testing whether land-plant-like hormone responses in charophytes depend on uniport transporters capable of shuttling both nutrients and phytohormone conjugates. The review also highlights striking gaps, from the complete absence of studies on soil microbes in Chara meadows to the unknown function of mucilage on rhizoids and oospores. What emerges is a portrait of a scientifically glamorous group, central to one of evolution’s greatest transitions, whose everyday biology has been quietly understudied. With standardised, species-specific protocols now within reach, the humble stoneworts may finally give up their secrets, from the sleeping spores in the mud to the genes that first taught green cells to live on land.

Subject of Research: Reproduction, oospore dormancy, germination and cultivation of charophyte algae (Characeae)

Article Title: What we really know about the dormancy, reproduction, germination and cultivation of charophytes ( Characeae )

Article References: Holzhausen, A. (2024). What we really know about the dormancy, reproduction, germination and cultivation of charophytes (Characeae). One Ecosystem, 9, Article e117655. https://doi.org/10.3897/oneeco.9.e117655

Image Credits: AI Generated

DOI: 10.3897/oneeco.9.e117655

Keywords: charophytes, Characeae, stoneworts, oospore dormancy, germination, sexual reproduction, asexual reproduction, gametangia, phytohormones, in-vitro cultivation, aquatic ecology, land plant evolution

The findings carry implications far beyond the rivers where the work was conducted. As rainfall patterns grow more erratic across the globe, the study suggests that the productivity, stability, and very architecture of river ecosystems may be undergoing a quiet but profound transformation. Lead author Bradley Strickland, a former postdoctoral research associate at VIMS and the Batten School, described the shifting food webs as a potential early warning sign of deeper ecological change. If rain can reshape the foundations of a river’s energy economy this dramatically, he noted, then any rainfall-dependent system — from grasslands to coastal seas — may be vulnerable to similar restructuring as the climate continues to change.

The research team found its ideal testing ground in an unlikely place: the Gulf Coast prairie ecoregion of South Texas. There, dry air spilling out of the Chihuahuan Desert collides with moisture-laden winds from the Gulf of Mexico, producing a steep and remarkably clean rainfall gradient. Annual precipitation drops sharply over a short geographic distance, and crucially, rainfall is the only major variable that changes along that gradient. Co-author Chris Patrick, an associate professor at VIMS and the Batten School, explained why this matters. In most of the United States, a comparable rainfall gradient would be driven by geological features such as mountain ranges, which confound the picture by altering soils, geology, and hydrology simultaneously. In South Texas, rainfall stands alone as the explanatory factor, making the region what Patrick called a natural laboratory — one he described as unique within the continental United States, with few parallels anywhere in the world.

Over four years, Patrick’s team sampled fish, snails, algae, and other organisms across nine rivers, while also measuring water quality, temperature, and a suite of physical and chemical variables. The result is a dataset of unusual scope, tracking both vertebrate and invertebrate communities across multiple sites and multiple years. But the researchers were not simply cataloging species. Their central goal was to quantify a metric that ecologists consider one of the most informative — and most labor-intensive — measures of ecosystem function: secondary production.

Secondary production, as Patrick defined it, is essentially the growth of new animal tissue over time. It captures how much living biomass a community generates, which in turn reflects the flow of energy from the base of the food web upward through consumers. Compared with simpler metrics like species abundance or diversity, secondary production integrates efficiency, ecological structure, population dynamics, and community organization into a single number. Strickland called it truly one of the best measures available for understanding how an ecosystem actually functions. And the scale of the measurement effort was extraordinary. Patrick noted that empirical, directly measured secondary production is rare even for a single species; doing it for an entire invertebrate community and an entire fish community, across multiple years and multiple sites, is essentially unheard of in the field.

The analysis confirmed one of the team’s expectations while delivering a genuine surprise. Along the gradient, streams receiving less rainfall showed higher secondary production — a pattern rooted in the physics of light and the biology of algae. Less precipitation means less tree canopy, and less canopy means more sunlight reaching the streambed. That light fuels abundant algal growth, which feeds fast-reproducing invertebrates such as non-biting midges. In the drier streams, this resource pulse also favored herbivorous fish like sailfin mollies, females of which reach sexual maturity within roughly 32 days. Together, these rapid-turnover consumers supported a comparatively small population of predators, including fish like spotted gar.

What startled the researchers was the shape of the biomass distribution that emerged. The drier streams displayed a classic bottom-heavy biomass pyramid — a structure ecologists associate with terrestrial ecosystems, not aquatic ones. Marine and many freshwater systems typically show inverted, top-heavy pyramids because algae and phytoplankton at the base cycle so quickly, being consumed nearly as fast as they reproduce. A bottom-heavy pyramid in a stream signals that the entire energy pathway has been rerouted. Strickland put it plainly: rainfall changes the amount and type of resources at the base of the food web, and consumers respond dramatically. In the wetter streams, by contrast, the team observed inverted pyramids supported not only by algae but also by detritivorous invertebrates — organisms feeding on leaves, animal carcasses, and other litter falling into the water. Strickland characterized that wetter-end existence as a slower, steadier way of living, compared with the stressful, fast-paced life of the drier streams.

The quantitative contrast between the two ends of the gradient was stark. Streams receiving less annual rainfall exhibited twice the secondary production and twice the biomass turnover rates of their wetter counterparts, despite being otherwise similar. On the strength of that result, the study characterizes rainfall as a master variable — a single environmental factor with the power to reshape the foundations of an ecosystem, from the resources fueling primary producers to the trophic structure of the animal communities above them. In the drier systems, energy flows fast and shallow, channeled through a few rapidly reproducing species. In the wetter systems, it moves slowly and diffusely through more diverse webs built on decaying organic matter. Neither configuration is inherently better, but the transition between them represents a wholesale reorganization of how a river works.

The study’s authors argue that this conclusion resonates well beyond South Texas. Precipitation’s capacity to control energy flow through animal communities, they note, has parallels in ecosystems ranging from grasslands and savannas to coastal and marine environments. As rainfall becomes more variable under climate change, Strickland said, we should expect big changes in the productivity, energy flow, and stability of river ecosystems — and possibly in any rainfall-dependent system. The research therefore calls for improved models and continued field data collection to understand how precipitation regimes shape biodiversity and productivity across ecosystem types, improving our ability to predict ecological responses to a changing climate. Patrick framed the takeaway in similarly broad terms: some regions will see deserts expand while others grow wetter on average year-round, and rainfall stands as another important mechanism through which climate change will alter ecosystems.

For river managers and conservation scientists, the message is that monitoring rainfall-driven shifts in food web structure may provide an earlier and more sensitive indicator of climate stress than temperature records alone. A stream can look superficially intact — the same channels, the same general cast of species — while its internal energy economy has been quietly rebuilt around a different resource base. Detecting that reorganization requires exactly the kind of exhaustive, multi-year, multi-trophic measurement this study pioneered. As drying trends advance across many of the world’s river basins, the bottom-heavy pyramids of South Texas may offer a preview of what happens when the rain that rivers depend on begins to fade.

Subject of Research: Effects of rainfall gradients on stream secondary production, trophic structure, and energy flow in riverine food webs

Article Title: Rainfall reshapes river ecosystems and food webs, study finds

Article References: Rainfall reshapes river ecosystems and food webs, study finds. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: rainfall, stream ecosystems, food webs, secondary production, climate change, biomass pyramid, energy flow, South Texas, trophy structure, aquatic ecology, precipitation gradient, Virginia Institute of Marine Science

The research, published in Scientific Reports and funded by the Great Lakes Fishery Commission, was conducted by scientists from SUNY Brockport, the University of Vermont, and Oregon State University. It is the first study to examine whether fish embryos can acquire thiamine naturally in their wild incubation environment. Led by Matthew Futia of the University of Vermont’s Rubenstein Ecosystem Science Laboratory, in collaboration with the Rinchard Lab at SUNY Brockport, the team chose Lake Champlain as its experimental arena because thiamine deficiency has already been documented in stocked populations of lake trout and Atlantic salmon there, and the lake’s spawning sites are well studied.

The disorder at the center of the work is Thiamine Deficiency Complex, or TDC, a syndrome caused by insufficient vitamin B1. Thiamine is an essential cofactor in carbohydrate metabolism and neural function, and fish cannot synthesize it in useful amounts; it must be obtained from diet or the surrounding environment. In salmonines, TDC is typically observed in hatcheries that rear eggs collected from wild adults, where it produces severe behavioral and neurological abnormalities and extremely high mortality in newly hatched fish. Hatchery staff can mitigate the effects with thiamine baths or injections, but until now, essentially everything scientists knew about TDC-related mortality came from those controlled settings.

That hatchery-centric knowledge base left a glaring gap. Eggs of lake trout incubate in the wild for more than five months before haking, resting in the interstices of rocky spawning reefs where water flows continuously around them. Because thiamine is potentially highly available dissolved in water, the researchers reasoned that embryos might be absorbing the vitamin from their environment throughout that long incubation period, something no laboratory rearing protocol had ever replicated or measured.

To test the idea, the team fertilized lake trout eggs from Lake Champlain and split them between two very different fates. One portion was deployed in the lake itself, placed in egg incubation bags on natural spawning substrate, while the paired portion was reared under controlled laboratory conditions. The researchers then measured thiamine concentrations at four developmental stages in both groups, and separately analyzed the lake water to determine how much thiamine was actually available in the embryos’ surroundings.

The results were striking. Lake-reared embryos accumulated substantial amounts of thiamine as development proceeded, showing significant increases in thiamine concentrations at the time of hatching and in the weeks that followed. Their lab-reared siblings, incubated in the same water source but under controlled conditions, showed no increase at all. The contrast between the two groups demonstrates that something about the natural environment, likely the continuous exchange of lake water across the egg membranes, allows embryos to take up the vitamin in quantities that artificial rearing does not provide.

The team also detected thiamine precursors and byproducts in Lake Champlain, adding a biochemical dimension to the findings. Together, the measurements indicate that developing embryos may be able to take up sufficient concentrations of thiamine during their months in the substrate to offset problems that would otherwise arise from thiamine deficiency. In other words, the wild may be quietly doing for lake trout embryos what hatcheries must accomplish with vitamin treatments.

Futia emphasized how much this changes the interpretive frame. Prior to this study, practically everything known about the effects of TDC on newly hatched fish was based on laboratory and hatchery work, he noted, and the findings suggest that what occurs in natural environments may actually be quite different, and thankfully in a good way for the fish. That distinction matters enormously for conservation planning, because assessments of TDC risk have so far been extrapolated from hatchery observations that may not reflect what wild embryos actually experience on a spawning reef.

The implications extend well beyond Lake Champlain. Thiamine Deficiency Complex is considered a major threat to conservation and restoration efforts for salmonines across a wide geographic range, and it has complicated recovery programs for Atlantic salmon, steelhead, and other species wherever thiamine-poor forage fish dominate adult diets. By revealing a previously unknown pathway for thiamine acquisition in the wild, the study opens the door to improved restoration strategies, more accurate field assessment of TDC, and better-informed management decisions for lake trout and related species across the Great Lakes and beyond.

For a species whose wild reproduction has frustrated managers for decades, the message is one of cautious optimism. The barriers to lake trout recovery remain real, from lamprey predation to habitat loss, but the new evidence suggests that one suspected obstacle, embryonic thiamine starvation in nature, may be less severe than hatchery data implied. Future work building on this experimental design could help managers distinguish which populations genuinely face thiamine-limited recruitment in the wild and which have been quietly rescuing themselves from the lake water all along.

Subject of Research: Thiamine uptake by lake trout embryos in natural versus laboratory incubation environments

Article Title: UVM study reveals how lake trout embryos acquire thiamine in the wild

Article References: UVM study reveals how lake trout embryos acquire thiamine in the wild. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: lake trout, thiamine, Thiamine Deficiency Complex, vitamin B1, Lake Champlain, Great Lakes, fish embryos, fisheries restoration, salmonines, aquatic ecology, Scientific Reports, conservation