Diatoms, single-celled algae encased in ornate silica shells called frustules, are among the most trusted bioindicators in aquatic science. Under the European Water Framework Directive, benthic diatoms are one of five biological elements used to assess the ecological status of surface waters, with diatom indices built on the relative abundance of species and their known sensitivities to pollution and salinity. That system works only if species are identified accurately and consistently, which is precisely where the trouble begins. Traditional identification relies on subtle features of valve shape and stria density, demanding deep taxonomic expertise and often yielding subjective results.

DNA metabarcoding has been proposed as a more objective alternative. The technique amplifies short barcode regions of DNA from an environmental sample, sequences them in bulk on next-generation platforms, and matches the resulting sequences against reference databases to identify the taxa present. Yet studies comparing the two approaches have repeatedly found significant deviations, and the research team behind the new work points to one dominant cause: reference libraries are incomplete, particularly for species from unusual habitats. Soda pans, with their high sodium and hydrogen carbonate content, host rare and halophilic organisms that are exactly the kinds of species missing from genetic databases.

The loss of sodic character is the principal threat facing these habitats, as water management practices can channel lower-salinity water into the pans and dilute them. Accurate identification of species and precise knowledge of their salinity tolerance are therefore essential for judging ecological status. Within the framework of a Hungarian national monitoring project, the researchers sampled 37 soda pans and soda lakes across spring and autumn campaigns in 2019 and 2020, producing 69 samples analysed by light microscopy, of which 26 were also subjected to DNA sequencing. Twenty-two of the water bodies were subsaline and 15 hyposaline, ranging from natural to disturbed conditions.

The team focused on Halamphora, the fourth most common and seventh most species-rich genus among the 72 genera found in their soda samples. Two species in particular, Halamphora dominici and Halamphora veneta, occurred in nearly half of all samples and were frequently dominant, sometimes reaching relative abundances of 40 to 60 percent. The Halamphora veneta group, which also includes H. kevei and H. paraveneta, is notoriously difficult to resolve morphologically, with species boundaries resting on fine differences in stria density and valve outline that can shift with environmental stress, including salinity.

The molecular results delivered a striking revelation. Of 23 short amplicon sequence variants that automated pipelines assigned to H. veneta, phylogenetic analysis and BLAST searches showed they actually belonged to H. dominici. The culprit was a misidentified sequence in the Diat.barcode reference database. Using long-read sequencing of a sample where both species co-occurred, the researchers obtained a full 1547-nucleotide rbcL sequence for H. dominici that showed roughly 2 percent divergence from H. veneta, confirming the two are genuinely distinct species. The newly deposited sequences now supplement the reference library, and the team emphasizes that sequences should only enter databases after precise morpho-taxonomic verification.

Overall, six Halamphora species were detected in the soda habitats. Five were recovered by both methods, while H. oligotraphenta was found only by microscopy because it appeared exclusively in samples that were not sequenced. The comparison between techniques revealed a significant positive correlation between microscopy- and metabarcoding-based relative abundances for H. dominici, with a Pearson correlation coefficient of 0.73. Discrepancies in the other direction were also informative: DNA detected species in some samples where microscopy missed them, likely because sequencing draws on far more cells than the minimum 500 valves counted per slide, while some microscopically observed valves may have belonged to dead cells.

The ecological payoff is clear. Classified as mesohalobous, H. dominici showed a positive correlation with salinity, with an average salinity of 3.1 parts per thousand in the waters where it occurred, compared with 1.6 parts per thousand for the more cosmopolitan H. veneta, which tolerates freshwater to slightly brackish conditions. Given that the ecological status of Hungarian soda pans depends fundamentally on salinity, the correct discrimination between these two species, one a reliable flag of sodic character and the other a generalist, is critical for conservation-relevant assessments.

The study also contributed taxonomic housekeeping. By comparing length-to-width ratios and ultrastructural features, the researchers questioned whether Halamphora elongata is truly distinct from the older H. subcapitata, noting overlapping morphometrics and absent areolar occlusions in their specimens, though formal synonymisation awaits type-material analysis. Meanwhile, H. paraveneta, which lacks any reference sequence in Diat.barcode or GenBank, may have been lurking as an outlier sequence variant assigned to H. veneta, a hypothesis flagged for future work.

As environmental DNA methods face growing pressure to replace traditional microscopy in routine monitoring across Europe, this study offers both a caution and a roadmap. Misidentified dominant species in reference databases can silently distort the results of ecological status assessments, potentially misclassifying protected habitats. But the combination of meticulous morphology and DNA sequencing, applied to extreme habitats that represent environmental endpoints of genetic diversification, can close the gaps. For Hungary’s soda pans, some of Europe’s most distinctive and threatened aquatic ecosystems, that means the microscopic sentinels of their salty character can finally be named with confidence.

Subject of Research: Diatom biodiversity and salinity indicators in Hungarian soda pans assessed by microscopy and rbcL metabarcoding

Article Title:  Halamphora taxa in Hungarian soda pans and shallow soda lakes detected via metabarcoding and microscopic analyses

Article References: Ács, É., Bíró, T., Boros, E., Dobosy, P., Duleba, M., Földi, A., Kiss, K. T., Levkov, Z., Orgoványi, P., Szén, O. P., Trábert, Z., Vadkerti, E., & Grigorszky, I. (2023). Halamphora taxa in Hungarian soda pans and shallow soda lakes detected via metabarcoding and microscopic analyses. Metabarcoding and Metagenomics, 7, Article e111679. https://doi.org/10.3897/mbmg.7.111679

Image Credits: AI Generated

DOI: 10.3897/mbmg.7.111679

Keywords: diatoms, metabarcoding, soda pans, Halamphora, salinity, rbcL, ecological status, Water Framework Directive, reference database, Hungary, bioindicators, phylogeny

Marine bivalves have long been favored as bioindicators of pollution, and for good reason. Because they feed by filtering large volumes of phytoplankton and suspended particulate matter, they rapidly accumulate lipophilic contaminants such as PAHs, polychlorinated biphenyls, pesticides and heavy metals in their soft tissues. The wedge clam is particularly well suited to this role along the Bulgarian coast, where it dominates fine sandy habitats of the upper infralittoral subzone, typically between 1.0 and 6.5 meters depth, exposed to intense wave action and constant fluctuation of abiotic conditions. Although local consumers do not traditionally eat wedge clams, the species is increasingly harvested with dredges for export, driven by high prices on foreign markets, which makes its contaminant burden a matter of direct human-health relevance.

The research team gathered two to three kilograms of adult clams of similar shell length, averaging about 2.1 centimeters, from each location, spanning sites from Varna Bay in the north to Tsarevo and Elenite in the south. Soft tissues were removed, homogenized into 250-gram samples and stored at minus 20 degrees Celsius until analysis. Ten grams of homogenized tissue from each sample were spiked with internal standards, extracted with a hexane and dichloromethane mixture in a Soxhlet extractor for sixteen hours, and cleaned up on a multilayer silica column before being concentrated and reconstituted in hexane for instrumental analysis.

Quantification was performed by gas chromatography coupled with an ion-trap mass spectrometer, using a TG-5 ms capillary column and helium as carrier gas. The thirteen target compounds included acenaphthylene, fluorene, phenanthrene, anthracene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene. Each sample was analyzed in triplicate, procedural blanks were run between every five samples to monitor laboratory contamination, and limits of detection for individual compounds ranged from 0.075 to 0.294 nanograms per gram wet weight, based on three times the standard deviation of low-concentration measurements.

The results revealed a coast that is measurably, though not alarmingly, contaminated. Total PAH content, summed across the thirteen compounds, ranged from 5.59 to 50.50 nanograms per gram wet weight, a level the authors describe as comparable with other European studies. Phenanthrene was the dominant compound everywhere, ranging from 3.24 to 48.22 nanograms per gram, followed by fluorene. Four of the thirteen target PAHs appeared in almost all samples, while acenaphthylene, anthracene, benzo[a]anthracene, indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene fell below detection limits throughout. The most carcinogenic of the group, benzo[a]pyrene, was detected in only 20 percent of the analyzed samples, with a mean of 1.30 nanograms per gram.

Perhaps the most diagnostic finding concerns the composition of the PAH mixture. Low molecular weight compounds with two and three aromatic rings accounted for 91 percent of the total, while high molecular weight compounds with four, five and six rings made up only about 8.9 percent on average. Because low molecular weight PAHs are characteristic of petrogenic sources, such as diesel and fuel oil spills, whereas high molecular weight compounds arise mainly from incomplete combustion of organic matter, the ratio between the two classes points to the origin of pollution. In this study the low-to-high molecular weight ratio was far above one, with a mean of 17.61, strongly indicating that petroleum, not combustion, is the principal source of PAH contamination along the Bulgarian Black Sea coast.

Geography told its own story. The highest total PAH burden appeared in clams from Tsarevo, at 87.29 nanograms per gram wet weight, followed by Arkutino and Nessebar, while the cleanest samples came from Elenite, at just 5.59 nanograms per gram. Elevated levels at Arkutino and Duni were most plausibly linked to the 2018 oil spill from the sunken ship SS Mopang near Sozopol, an interpretation reinforced by the strongly petrogenic molecular ratios measured in clams from those locations. Elevated benzo[a]pyrene in Varna Bay clams, meanwhile, reflected the ecological pressure of intensive maritime traffic and industrial activity around the harbor. The authors also suggest that discharges from the Danube River, carrying degraded petroleum and fresh oil, may explain why phenanthrene levels were significantly higher in clams from the northern coastal section than in the south.

Seasonal patterns added further nuance. The sum of the four regulated PAHs was significantly higher in autumn, with the difference significant for autumn 2019, while total PAHs peaked significantly in summer compared with spring 2020 and the autumn sampling periods. Low molecular weight PAH accumulation was lower in autumn, whereas high molecular weight compounds were higher, again significantly for autumn 2019. These shifts likely reflect the interplay of tourist-season traffic, weather-driven resuspension of contaminated sediments and the clams’ own seasonal physiology and lipid dynamics, which are known to modulate how lipophilic pollutants are retained in bivalve tissue.

From a regulatory standpoint, the news is reassuring. European Commission Regulation n.835/2011 sets an admissible limit of 35 nanograms per gram wet weight for the sum of benzo[a]pyrene, chrysene, benzo[a]anthracene and benzo[b]fluoranthene, known as Sum PAH4, in bivalve species. In the Bulgarian wedge clams, Sum PAH4 ranged only from 0.72 to 5.93 nanograms per gram, well below the legal threshold, with the highest value recorded in industrial Varna Bay and the lowest at Shkorpilovtsi, Primorsko and Elenite, sites far from urbanized and industrial areas. Benzo[a]pyrene, classified by the International Agency for Research on Cancer as a Group 1 carcinogen, never exceeded its admissible limit of 6 nanograms per gram, despite being detected in a fifth of samples.

The study also places the Bulgarian coast in a broader European context. Comprehensive PAH data for wedge clams are scarce; most published work concerns the Mediterranean mussel, Mytilus galloprovincialis, and the only substantial comparable wedge clam study comes from the Mediterranean Sea, where PAH levels of 247.4 nanograms per gram wet weight were reported, roughly fifty times higher than the 4.75 nanograms per gram mean found off Bulgaria. Earlier Black Sea work on bivalves from the Crimean Peninsula, Sevastopol Bay and the Turkish coast had already signaled regional contamination, and the new data confirm that pattern while showing that the Bulgarian stretch remains comparatively moderate. The authors conclude that the wedge clam can serve as a practical bioindicator for tracking PAH pollution levels and assessing the risk of human exposure along the coast, providing a baseline against which future changes, whether from shipping, tourism or accidental spills, can be measured.

Subject of Research: Bioaccumulation of polycyclic aromatic hydrocarbons in wedge clams as bioindicators of Black Sea coastal pollution

Article Title: Assessment of PAHs accumulation in Donax trunculus (Linnaeus, 1758) ( Bivalvia , Donacidae ) from the Bulgarian Black Sea Coast

Article References: Georgieva, S. K., Stancheva, M. D., Peteva, Z. V., Ivanova, T. I., & Alexandrova, A. V. (2022). Assessment of PAHs accumulation in Donax trunculus (Linnaeus, 1758) (Bivalvia, Donacidae) from the Bulgarian Black Sea Coast. BioRisk, 17, 95-104. https://doi.org/10.3897/biorisk.17.77343

Image Credits: AI Generated

DOI: 10.3897/biorisk.17.77343

Keywords: polycyclic aromatic hydrocarbons, wedge clam, Donax trunculus, Black Sea, bioindicators, petrogenic pollution, bivalves, benzo[a]pyrene, marine pollution, food safety, gas chromatography mass spectrometry, Bulgaria

The survey formed part of a biodiversity initiative marking the twentieth anniversary of the foundation behind Alp Flix, an alpine farm perched on a high plateau at about 1,950 metres within Parc Ela, Switzerland’s largest nature park. While previous studies had documented the fauna on and below the plateau, the subalpine and alpine slopes above it remained largely unexplored territory. Ground beetles of the family Carabidae were chosen as the focal group for good reason: they are well-established bioindicators, easy to capture with pitfall traps, and their taxonomy and ecological requirements are among the best understood of any insect family in Central Europe.

Between 20 June and 11 November 2020, seven sampling stations operated continuously, each equipped with three white plastic cups sunk flush into the ground, covered by wire mesh and a transparent Plexiglas roof and filled with a four percent formalin solution. The traps were emptied at two-week intervals, with one collection skipped in October because of persistent snowfall. In the laboratory, specimens were softened using cherry laurel leaves, and genital preparations were made for selected species to confirm identifications. Reference specimens are now housed at the Natural History Museum Basel.

The haul was modest in numbers but rich in information. A total of 393 individual ground beetles were captured, representing 21 species across nine genera. The most abundant species, Pterostichus multipunctatus, accounted for 108 individuals, while five species, including Amara equestris, Harpalus solitaris and the delicately built Leistus montanus rhaeticus, were each recorded only once. Remarkably, seven of the 21 species had never before been documented at Alp Flix, among them two species considered very rare in Switzerland: Amara nigricornis and Leistus montanus rhaeticus.

To interpret these finds, the researchers went beyond a simple species list. They compared the beetle communities of all seven stations using a battery of quantitative similarity measures: Sørensen’s and Jaccard’s indices of species identity, Renkonen’s index of dominance identity, and the Wainstein index, which multiplies two percentage values and therefore yields markedly lower figures. High similarity between two sites suggests comparable ecological conditions, allowing sites to be grouped into shared habitats even when their vegetation types differ.

The analysis revealed a clear three-part structure along the mountainside. The lowest station, at 2,067 metres, sits in half-shaded green alder scrub with moderate moisture and dense shrub and herb layers, forming a distinctly subalpine habitat. Between roughly 2,146 and 2,375 metres lies a second, alpine zone of sun-exposed sites with strong herbaceous cover and moderately fresh to dry conditions, favoured by species such as Notiophilus aquaticus and Calathus micropterus. Above about 2,432 metres, a third, high-alpine habitat emerges: short-turfed or sparsely vegetated ground under full sun exposure and markedly dry-warm conditions, where the cold-adapted Amara erratica dominates.

Perhaps the most thought-provoking result is what the beetles did not do. The transect encompassed six distinct plant-sociological habitat types, yet the similarity indices could not separate the beetle communities along these same lines. Instead, the beetles carved the landscape into their own three zones, hinting that elevation itself may be overprinted by the ecology of each habitat type, as earlier work on spiders at Alp Flix had suggested. Some station pairs, such as sites 6 and 7 near the top, showed strikingly similar faunas, while others, notably the alder scrub site and the high summit scree, shared almost nothing at all.

The findings also underscore how incomplete our knowledge of alpine insect life remains. A third of the species recorded in 2020 were new to Alp Flix, even though the area had hosted a well-publicised biodiversity blitz in 2000 that documented 33 ground beetle species. The lower tally this time likely reflects the method: passive pitfall traps sample ground-dwelling beetles selectively, whereas the earlier event relied on expert hand-collecting, sweeping and sieving. Comparisons with comparable transect studies at the Albula Pass in 2008 and the Furkapass in 2012, which yielded similar species counts, suggest the 2020 results are indeed representative for these elevations.

For conservationists, the message is twofold. Rarity is easy to overlook when only a handful of individuals turn up in a season, and species such as Amara nigricornis and Leistus montanus rhaeticus may persist in small, specialised pockets that standard surveys can miss. Establishing a robust baseline, as this study has done, is the essential first step toward tracking how these sensitive mountain communities respond to a warming climate, in which alpine species face the twin pressures of shifting habitat zones and nowhere left to climb.

The researchers argue that biodiversity monitoring at Alp Flix should continue and expand, closing knowledge gaps about one of Europe’s most fragile ecosystems. Ground beetles, with their precisely mapped distributions and exacting habitat requirements, will remain indispensable guides in that effort, quietly mapping the changing architecture of life on the mountainside one specimen at a time.

Subject of Research: Ground beetle diversity and habitat preferences along a 2,100 to 2,500 metre elevational transect in the Swiss Alps

Article Title: Laufkäfer und ihre Habitatpräferenzen entlang eines Höhentransekts von 2100 bis 2500 m ü. M. oberhalb der Alp Flix in den Schweizer Alpen ( Coleoptera , Carabidae )

Article References: Lüdeke, M., Germann, C., & Jentzsch, M. (2023). Laufkäfer und ihre Habitatpräferenzen entlang eines Höhentransekts von 2100 bis 2500 m ü. M. oberhalb der Alp Flix in den Schweizer Alpen (Coleoptera, Carabidae). Alpine Entomology, 7, 57-62. https://doi.org/10.3897/alpento.7.102534

Image Credits: AI Generated

DOI: 10.3897/alpento.7.102534

Keywords: ground beetles, Carabidae, Swiss Alps, Alp Flix, elevational transect, biodiversity, bioindicators, alpine ecology, pitfall traps, habitat similarity, Parc Ela, entomology

The Euphrates-Tigris catchment is one of the major drainage basins of the Middle East, but decades of overexploitation have pushed the water system to its ecological limits. Iraqi waterbodies suffer from salinization driven by water losses caused by upstream dam construction, water policies during the Iraq wars and the intensifying impact of climate change on a region that already experiences minimal rainfall. Against this backdrop, diatoms, a diverse group of microalgae with silicified cell walls, serve as the world’s most widely used bioindicators of water quality, reflecting ecosystem conditions with unique sensitivity. Epiphytic diatoms, which live attached to submerged macrophytes, are particularly interesting because they interact with their living hosts in ways that can shape their own community structure.

Accurate taxonomic identification of diatoms is essential for sound biodiversity evaluation, yet classical identification by light microscopy requires highly specialized taxonomic skills and can produce discrepancies between researchers. Cryptic diversity, species that look identical under the microscope but are genetically distinct, further hinders accurate identification. In regions where literature on the local diatom flora is scarce, researchers often rely on European floras, which may force identifications into existing taxonomic concepts and overlook local variation or unique species. DNA metabarcoding, which enables the concurrent identification of numerous species from environmental samples, has become an increasingly popular alternative, but until now there has been a notable absence of such studies in Iraq.

The research team collected 47 samples during the summer of 2019, the dry season, and the winter of 2020, the rainy season, at six sites across two water bodies: the River Tigris in the city of Al-Qurnah and the River Euphrates in the city of Al-Midaina. Because no stones were available as habitats at the sampling stations, samples were taken separately from 11 different taxa of macrophytes and macroalgae, including common reed, cattail, hornwort, watermilfoil, several pondweed species, green algae of the genus Cladophora, naiad and sea aster. At least five stems and branches of each plant were shaken vigorously with distilled water to dislodge the attached diatoms, and the resulting suspensions were preserved with 70 percent alcohol for transport to the Botanic Garden and Botanical Museum at Freie Universität Berlin, where each sample was split for morphological and molecular analysis.

For the morphological analysis, samples were treated with 35 percent hydrogen peroxide to oxidize organic materials, and the cleaned diatom frustules were mounted in the high refractive index medium Naphrax. Using a Zeiss Axioplan microscope with differential interference contrast and a 100x Plan Apochromat objective, the researchers counted a minimum of 400 valves per sample to document the presence and relative abundance of each taxon, and turned to a Hitachi FE 8010 scanning electron microscope when finer details were needed. This meticulous dual-microscope approach identified 284 infrageneric taxa belonging to 59 genera, a species richness notably higher than in previous Iraqi studies. Remarkably, 46 species were recorded for the first time in the region, and 62 others could not be identified to species level and are possibly new to science, including Prestauroneis furatensis, which was newly described from the epiphytic community of the River Euphrates.

The metabarcoding analysis targeted the V4 region of the 18S rRNA gene, amplified with the DIV4 primer pair and sequenced on an Illumina MiSeq platform with 300-bp paired-end reads. After bioinformatic processing with the DADA2 pipeline, which denoises reads and infers amplicon sequence variants, and quality control with the metabaR package to remove contaminants and tag-jumps, 5,461,214 reads remained from 43 successfully amplified samples. These reads belonged to 2,953 ASVs, of which 1,454, or 49.2 percent, were classified as Bacillariophyta, the diatoms. The molecular approach recovered 54 genera and 108 species, with many ASVs assigned to the same taxa, and in most cases metabarcoding detected more taxa per sample than microscopy.

The comparison between the two methods exposed striking technical discrepancies. At the genus level, 38 genera were retrieved in both datasets, while 21 genera were identified only by morphology, including Amphipleura, Aulacoseira, Caloneis, Prestauroneis and Synedropsis, and 16 only by metabarcoding, including Campylodiscus, Chaetoceros, Eunotia, Fistulifera and Skeletonema. The incomplete taxonomic reference database for the studied sites turned out to be the major limitation of the molecular approach, as many morphologically identified species in genera such as Mastogloia and Achnanthidium are absent from any reference library. Intraspecific genetic variation, multiple rRNA operons within diatom genomes evolving at different rates, and sequencing artifacts can also generate multiple ASVs from a single species, artificially inflating molecular richness. Conversely, some abundant species identified microscopically, such as Navicula recens, Navicula rostellata and Nitzschia clausii, had no corresponding match in the metabarcoding inventories, possibly because of insufficient DNA concentrations in those samples.

Community-level statistics revealed further contrasts. Shannon diversity indices and average taxa richness were mostly higher in the metabarcoding analyses than in the morphological ones, with the highest molecular species count of 345 recorded at one winter Euphrates station and the lowest of 5 at another. Both approaches agreed that taxon richness was lowest at station E3 on the Euphrates and highest at station E1 on the same river. The non-metric multidimensional scaling plots for morphology showed a clear seasonal effect in diatom community composition, separating the dry summer from the rainy winter, and PERMANOVA confirmed statistically significant differences between the two seasons and the two rivers. In contrast, the NMDS plots for the 18SV4 analyses did not show a seasonal effect for the same samples, a discrepancy the authors attribute to gaps in the DNA barcode reference databases, particularly at the species level, which hinder accurate taxonomic assignment.

The ecological picture emerging from the morphological data is consistent with the environmental stress documented in the region. Pennate diatoms dominated the epiphytic assemblages, constituting 93.7 percent of identified species, while centric diatoms accounted for only 6.3 percent. The distribution of diatom assemblages showed a prevalence of freshwater species at 65.5 percent, followed by brackish species at 13.5 percent and marine species at 10 percent, with the remaining 11 percent being euryvalent species tolerant of a broad range of conditions. Several taxa of marine origin, including Tabularia fasciculata, Seminavis strigosa and Surirella striatula, were recorded, likely because the Qurna marsh connects directly with the Shatt Al-Arab River and receives water from the Arabian Gulf during high tides, creating a conduit for marine diatom migration to a region situated around 200 kilometers from the Gulf. Brackish diatoms such as Bacillaria paxillifera and Nitzschia filiformis reflect salinity fluctuations that intensify as less freshwater flows from the rivers and more seawater ingress from the Gulf.

The study demonstrates that combining metabarcoding with classical microscopy increases the detection and identification of diatom species and lays the foundation for understanding diatom biodiversity in this region. Even amid major advances in molecular tools for biodiversity assessment, the role of morphology in species discovery remains central. The authors recommend repeating the analysis with the rbcL marker, which has shown promise in providing higher resolution for diatom identification, and producing unialgal diatom strains from the studied sites to close the gaps in reference libraries. Such investigations are essential for illustrating the importance of sustainable ecosystem management and the conservation of water as a vital resource, both regionally and globally, in a catchment that climate change, overuse of waters and subsequent salinization have brought to the brink of ecological devastation.

Subject of Research: Diatom biodiversity in the Euphrates-Tigris rivers revealed by combined microscopy and DNA metabarcoding

Article Title: Comparison of the biodiversity of epiphytic diatoms in the Euphrates-Tigris rivers using morphological and metabarcoding analyses

Article References: Mohamad, H., Schimani, K., Al-Shaheen, M., Abarca, N., Jahn, R., Al-Handal, A., Kusber, W.-H., & Zimmermann, J. (2024). Comparison of the biodiversity of epiphytic diatoms in the Euphrates-Tigris rivers using morphological and metabarcoding analyses. Metabarcoding and Metagenomics, 8, Article e135082. https://doi.org/10.3897/mbmg.8.135082

Image Credits: AI Generated

DOI: 10.3897/mbmg.8.135082

Keywords: diatoms, DNA metabarcoding, Euphrates, Tigris, biodiversity, bioindicators, water quality, Iraq, 18S rRNA, epiphytic algae, Comparison, epiphytic

Microplastics, defined as plastic particles smaller than five millimeters, have become one of the most pervasive environmental contaminants on the planet. Generated by the fragmentation of larger plastic waste, they now contaminate soil, water, and air, and they have been detected inside living organisms, including humans, in blood and everyday consumer products. Bees are particularly effective bioindicators of this contamination because their foraging behavior forces them into constant contact with environmental surfaces. As they visit flowers, collect nectar and pollen, and return to the hive, electrostatic charges on their hairy bodies attract and retain airborne and surface-deposited particles, effectively turning each bee into a mobile pollution monitor.

The threat that microplastics pose to pollinators is not merely theoretical. Previous research has documented a spectrum of acute, chronic, and sublethal effects. Ingested particles can obstruct the digestive tract, reduce nutrient absorption, and in severe cases cause death. Fibers and sharp fragments can lodge in respiratory passages or physically damage wings and legs, hindering movement and foraging efficiency. Over the longer term, exposure has been linked to reduced egg laying, lower offspring viability, weakened immune systems, and altered behaviors such as difficulty navigating back to the hive. Because bees pollinate crops and wild plants alike, these effects ripple through agriculture and ecosystem health, and microplastics can bioaccumulate in food chains that include humans.

Earlier studies had already detected microplastics in bees and honey around the world, including in Denmark, where bees from urban, suburban, and rural sites all tested positive, and investigations had suggested that polystyrene ingestion could increase bees’ susceptibility to viral infections by disrupting their gut microbiota. Work in Ecuador itself had found synthetic fragments and fibers in at least 12 percent of commonly consumed beverages, including milk, honey, and beer, and had documented heavy microplastic contamination in the coastal waters of Esmeraldas province. What remained missing was a systematic test, in the southern Ecuadorian highlands, of whether proximity to human settlements actually predicts the plastic load carried by bees.

The research team, working with laboratories at the Salesian Polytechnic University in Cuenca, focused on nine peri-urban apiaries distributed around the city of Gualaceo, an urban core of roughly 13,981 inhabitants located in the Santa Bárbara river valley. The participating apiaries spanned sites to the north, south, east, and west of the city, all within the transitional zone where agricultural and residential land uses blend. With the voluntary collaboration of local beekeepers, the researchers collected approximately 50 dead worker bees from around three hives at each apiary over the course of about a month, repeating the sampling after 15 days. Samples were sealed in glass jars, refrigerated, frozen, and transported to the laboratory for analysis in the penultimate quarter of 2022.

The laboratory protocol was deliberately meticulous to prevent contamination and false positives. In a laminar flow hood, bee bodies were gently agitated for 15 minutes in a solution of ethanol and ultrapure Milli-Q water to dislodge adhered particles. The resulting suspension was vacuum-filtered through 11-micrometer paper, then digested with 33 percent hydrogen peroxide at 60 degrees Celsius for 24 hours to strip away organic matter. Microplastics were then captured on 0.45-micrometer cellulose nitrate membranes and stained with Nile red, a fluorescent dye whose solvatochromic properties make it bind preferentially to hydrophobic plastic particles, allowing rapid visual discrimination of plastics from other debris. A Nikon Eclipse Ti2 inverted fluorescence microscope, operating with green-filter excitation at 430 to 490 nanometers, was used to count and measure fibers and fragments on filters divided into four quadrants.

Chemical confirmation came from Fourier Transform Infrared (FTIR) spectroscopy using attenuated total reflectance with a diamond crystal, scanning wavelengths from 400 to 4000 inverse centimeters and comparing each particle’s spectrum against polymer reference libraries such as the Hummel Polymer and Additives databases. Only matches exceeding 70 percent similarity were accepted. The results were sobering: out of 1269 polymeric particles initially observed across all samples, 583 were fragments and 686 were fibers, yielding an overall average of 24 microplastics per 50 bees. The most contaminated hive averaged 57 particles per 50 bees, while the least contaminated registered 10. Fragment diameters ranged from 5.63 to 1834.69 micrometers, and fiber lengths from 6.65 to 4980.57 micrometers, with fibers making up 54.06 percent of the total load.

FTIR analysis of 341 identified particles revealed a diverse polymer cocktail spanning 23 synthetic types. Poly(4-methylcaprolactam) dominated at 25.29 percent of identified particles, followed by Nylon 12 and polyethylene at 11.73 percent each, ethylene propylene diene monomer at 9.9 percent, polytetrafluoroethylene at 6.45 percent, and polyamide 8 and polycarbonate at 4.4 percent each, with polyethylene terephthalate, better known as PET, appearing at 3.23 percent. These seven polymer types alone accounted for nearly 74 percent of all identified particles. Notably, PET was detected at almost every site, underscoring how thoroughly plastic waste from packaging and textiles has penetrated the peri-urban environment. The authors caution that fluorescence microscopy is more sensitive to very small particles than FTIR, whose lower spatial resolution limits detection, which is why the two techniques were used in complementary fashion to filter out false positives and build a robust picture of contamination.

The statistical core of the study addressed the central hypothesis directly. Because initial data violated the normality assumptions of analysis of variance, the researchers applied a Box-Cox procedure, settling on a logarithmic transformation that normalized residuals and validated the model. A Welch ANOVA then confirmed significant differences in microplastic loads among the nine apiaries, and Games-Howell post hoc tests pinpointed significant contrasts between the most contaminated site and six others. Finally, linear regression against distance from the Gualaceo urban center revealed a statistically significant negative relationship: the fitted equation was logarithm of microplastic concentration equal to 4.34 minus 0.52 times distance. The slope of minus 0.5256 was significantly different from zero, and the model explained approximately 47.6 percent of the variability in contamination levels, a moderate correlation the authors attribute partly to the modest sample size of nine apiaries.

The implications extend well beyond Ecuador. The study confirms that no area, even a small highland city far from industrial mega-centers, is immune to microplastic contamination, and it quantifies how urban centers function as pollution sources whose influence decays with distance. It also raises urgent questions about whether microplastics are being incorporated into honey and other bee products, and what that means for consumers, a question the researchers flag as a priority for future work. The team frames its findings as a call for action at individual and institutional levels alike, arguing that effective environmental policies and engineering solutions for waste management must keep pace with the sheer volume of plastic now fragmenting into the environment. If bees, the sentinels flying at the interface between human landscapes and natural ecosystems, are this heavily contaminated on the outskirts of a mid-sized Andean town, the global scale of the problem becomes difficult to ignore.

Subject of Research: Microplastic contamination of honeybees in relation to distance from urban centers in Ecuador

Article Title: Influence of Geographic Separation Between Urban Centers and Microplastic Burden on Bees ( Apis mellifera )

Article References: Arévalo, P. W., Orellana, V. P., Brito López, P. G., & Cajamarca, X. J. (2024). Influence of Geographic Separation Between Urban Centers and Microplastic Burden on Bees (Apis mellifera). One Ecosystem, 9, Article e127698. https://doi.org/10.3897/oneeco.9.e127698

Image Credits: AI Generated

DOI: 10.3897/oneeco.9.e127698

Keywords: microplastics, honeybees, Apis mellifera, pollinators, Ecuador, urban pollution, bioindicators, FTIR spectroscopy, fluorescence microscopy, plastic pollution, environmental monitoring, Influence

The selection of Gentiana asclepiadea for this comparative study was driven by two primary factors. First, the research team had previously collected detailed data on this specific plant and its pollinators in the 1990s, providing a robust baseline for comparison. Second, as a montane species growing at altitudes between 1500 and 1900 meters, it was hypothesized to be less exposed to the immediate threats of habitat destruction and agricultural chemicals that plague lowland pollinators. The plant is a perennial with thick, branched rhizomes and straight, non-branched stems that can reach up to 80 centimeters in height. Its funnel-shaped flowers, which are not capable of spontaneous self-pollination, rely heavily on specific insect vectors for reproduction, making them an ideal indicator species for assessing pollinator health.

The field investigations were conducted at three specific study sites in Mt. Vitosha, a mountain range located near Sofia. Sites one and two were situated in open woodlands within the coniferous forest belt, while site three was located in subalpine meadows just above the tree line. Observations took place during the flowering seasons of August and September in both the 1990-1994 period and the 2017-2020 period. The researchers spent a total of 66 hours over 48 days observing bumblebee activity under various meteorological conditions. To avoid altering the natural behavior of the insects, the team refrained from collecting specimens, relying instead on visual identification and recording of visitation rates and behavior.

Identifying bumblebee species in the field presented certain challenges, particularly for species with similar coloration. For instance, Bombus wurflenii and Bombus lapidarius, though belonging to different subgenera and possessing different ecological niches, are difficult to distinguish with certainty in the field. Similarly, Bombus hortorum and Bombus subterraneus, as well as Bombus lucorum and Bombus terrestris, were often recorded as undistinguished pairs. To maintain scientific rigor while acknowledging these limitations, the researchers used an approximate approach in their data analysis. A pollinator activity index was calculated by dividing the number of pollinators recorded by the minutes of observation, multiplied by 60, providing a standardized metric for comparison across years and sites.

The results indicated that the species composition of bumblebees visiting the Gentiana flowers remained largely consistent between the two study periods. The primary visitors included Bombus pascuorum, Bombus pratorum, and the aforementioned undistinguished pairs. However, a slight but notable decline in overall bumblebee activity was observed in the 2017-2020 period compared to the 1990-1994 baseline. Linear regression analyses, while limited by the significant time gap between the two observation periods, showed decreasing trends in total activity at all three study sites. This decline was not uniform; fluctuations were observed within years and between sites, likely influenced by local colony dynamics, foraging ranges, and the presence of competing floral resources.

The reproductive success of the Gentiana plants mirrored the trends in pollinator activity. The researchers tested free pollination fruit set by monitoring 100 flowers each year for the development of fruit capsules. They also assessed seed set by counting matured seeds and non-fertilized ovules in 10 fruit capsules annually. A slight decrease in both fruit set and seed set was recorded during the final four years of the study. This correlation suggests that the reduction in bumblebee visits directly impacted the plant’s ability to reproduce, highlighting the critical role these insects play in the life cycle of this medicinal species. The data underscores that even minor changes in pollinator abundance can have measurable effects on plant reproductive output.

Several ecological factors may contribute to the observed fluctuations and declines in bumblebee activity. The study notes that the foraging range of bumblebees can extend up to 10 kilometers, meaning that local populations may be influenced by conditions in surrounding areas. Colony failure rates are known to be high, with fewer than 30% of Bombus pascuorum colonies producing new queens, and success rates even lower for other species. At site three, the subalpine meadow, fewer bumblebees were recorded, possibly due to competition from large populations of Epilobium angustifolium and Solidago virgaurea, which are known to attract bumblebees. This competition for pollinators may have reduced the frequency of visits to the Gentiana flowers, further impacting seed set.

Behavioral observations also provided insights into the interactions between bumblebees and the plant. In 1991, high activity of male Bombus hortorum or Bombus subterraneus was recorded in early September, likely due to their phenology and the timing of colony life cycles. In 2017, high activity of Bombus wurflenii at site two was attributed to nectar robbing behavior, where workers extract nectar by making holes in the base of the corolla tube. While nectar robbing can have negative, neutral, or positive effects on plants, in this case, it was considered neutral to slightly positive, as the workers still pollinated the flowers while attempting to access the nectar through the normal route. These behavioral nuances highlight the complex nature of plant-pollinator interactions and the importance of detailed field observations.

The study concludes that the slight decline in bumblebee activity and subsequent reduction in fruit and seed set demonstrate that negative effects on pollinators are detectable even in mountain habitats with fewer direct hazards. This finding aligns with broader research, such as a study showing a 76% decline in insect biomass in German nature reserves between 1989 and 2016. While the specific causes of the decline in the Vitosha Mountains are not definitively established, the authors speculate that urbanization of the foothills and increased agricultural activity in the surrounding lowlands may play a role. Additionally, climate change is a known hazard for certain bumblebee species, potentially driving them to higher altitudes, though the study lacks sufficient data for definitive conclusions on this factor. The research emphasizes the need for continued long-term monitoring of pollinators in diverse habitats to fully understand the drivers of their decline and to develop effective conservation strategies.

Subject of Research: Long-term monitoring of bumblebee pollination and reproductive success in Gentiana asclepiadea in Mt. Vitosha, Bulgaria.

Article Title: Monitoring bumblebee pollinator visits to the medicinal plant Gentiana asclepiadea L. (Gentianacese) – a comparison between the periods 1990–1994 and 2017–2020

Article References: Kozuharova, E., & Simeonov, V. (2022). Monitoring bumblebee pollinator visits to the medicinal plant Gentiana asclepiadea L. (Gentianacese) – a comparison between the periods 1990–1994 and 2017–2020. BioRisk, 17, 317-327. https://doi.org/10.3897/biorisk.17.76577

Image Credits: AI Generated

DOI: 10.3897/biorisk.17.76577

Keywords: bumblebees, pollination, Gentiana asclepiadea, insect decline, montane habitats, Bulgaria, long-term monitoring, ecology, reproductive success, bioindicators, Monitoring, bumblebee

The family Characeae, commonly known as stoneworts, consists of green algae characterized by macroscopic thalli composed of a series of nodes and internodes. These structures are not merely botanical curiosities but play critical ecological roles in their respective environments. Stoneworts contribute to high water transparency, sequester significant amounts of carbon and nutrients, and serve as a foundational element of the aquatic food web. Furthermore, they provide essential habitat and refuge for various aquatic animals. Due to their sensitivity to environmental changes, including salinity, temperature, and water chemistry, Characeae species are widely recognized as effective bioindicators. Their presence or absence can offer valuable insights into the overall health and stability of freshwater and brackish ecosystems.

Despite their ecological importance, many Characeae species are currently facing severe threats to their survival. The combination of continuous human transformation of habitats and ongoing climate change has placed these algae at risk, particularly in arid and semiarid regions. Consequently, numerous species are protected under European directives, such as the Habitats Directive 92/43/EC and the Water Framework Directive 2000/60/EC. In several European countries, national legislation further safeguards these organisms, and they are included in national Red Lists to monitor their conservation status. However, Italy lacks a national Red List for Characeae, representing a significant gap in the country’s conservation framework. This absence hinders the implementation of targeted protection measures and the accurate assessment of population trends across the Italian peninsula and its islands.

The study conducted in spring and summer 2022 focused on sampling sites selected for their visual coverage of Characeae exceeding five percent. The locations included the Laghetto Monte Soro in Cesarò, the Lago Ancipa-Sartori in Troina, the Geloi Wetland in Gela, and the Curcuraggi area in Melilli. These sites varied significantly in altitude and water type, ranging from high-altitude natural lakes within the Nebrodi Regional Natural Park to low-lying brackish marshes fed by saline springs. The Geloi Wetland, for instance, is situated at approximately 30 meters above sea level and features artificial marshes with brackish water resulting from an underground saline spring. In contrast, the Monte Soro lake is located at about 1,575 meters above sea level, an environment where water often freezes during the winter months.

Among the species identified, Chara globularis was found in the Curcuraggi area, a site characterized by temporary pools used by grazing cattle. This species is cosmopolitan in distribution and has been reported from various regions in Italy, including Trentino Alto Adige, Piedmont, and Lombardy. Its presence in an area impacted by human activity is consistent with previous studies indicating that C. globularis is tolerant of eutrophication and anthropogenic disturbances. The morphology of the specimens collected showed thalli between 24 and 30 centimeters tall, with slender rays and rudimentary spine cells. The species is monoecious, bearing both oogonia and antheridia on the same thalli, which facilitates sexual reproduction in stable environments.

Chara vulgaris, another cosmopolitan species, was recorded in the Geloi Wetland and the Lago Ancipa-Sartori. This is the most widespread and frequently reported species of the genus Chara in Italy. The specimens observed had thalli ranging from 10 to 30 centimeters in height, with a main axis diameter of approximately 600 micrometers. The rays were slightly curved upwards, and the cortex was diplostichous and aulacanthous. The presence of C. vulgaris in these previously uninspected sites adds valuable data to its distribution map in Sicily. Conservation status assessments for this species vary across Europe, with classifications ranging from endangered in Norway to least concern in Wales, highlighting the need for localized monitoring and protection strategies.

Nitella capillaris, a less widespread species primarily found in Europe and Africa, was discovered in the Monte Soro Lake in Cesarò. This finding is significant because the species had not been previously reported in the province of Messina. The lake’s high altitude and cold climate pose unique challenges for algal survival. However, N. capillaris is known for its ability to withstand frost, producing oospores that are resistant to freezing stress and can germinate when conditions improve. The specimens collected were dioecious, with oogonia borne in the bifurcations of the rays. In several European countries, including Sweden and Great Britain, this species is considered extinct, while in others, it is classified as vulnerable or endangered, underscoring the importance of preserving its remaining habitats.

Tolypella glomerata was identified in the Geloi Wetland, specifically in the brackish marshes of Gela. This species is often found in slightly brackish waters and has a likely cosmopolitan distribution. The study noted that population density and fertility decreased as salinity increased, moving from the Acquitrino del Giunco Foglioso to the Pantano Pavoncelle. This observation aligns with previous research indicating that while T. glomerata adapts well to brackish environments, salinity remains a limiting factor for its reproductive success. The species has been reported in various parts of Italy, including Veneto, Emilia Romagna, and Tuscany, but its presence in the specific wetlands of eastern Sicily had not been documented until now. The findings suggest that brackish wetlands in Sicily may harbor unique algal communities that warrant further investigation.

The results of this study highlight the critical need for more comprehensive surveys of Characeae in Sicily. The distribution of these algae is not yet sufficiently known, and many areas remain unexamined. Filling these knowledge gaps is essential for developing effective conservation strategies and creating a national Red List for Characeae in Italy. Such a list would provide a standardized framework for assessing the conservation status of these species and guiding protection efforts. The study also emphasizes the ecological value of stoneworts in maintaining water quality and supporting aquatic biodiversity. By documenting new records and providing detailed morphological descriptions, the research contributes to the broader scientific understanding of freshwater algal ecology in the Mediterranean region.

Future research should focus on expanding surveys to other unexplored areas of Sicily and Italy, particularly in regions where data on Characeae distribution is scarce. Long-term monitoring of these populations will be crucial for detecting trends in abundance and health, especially in the context of climate change and human-induced environmental pressures. Collaboration between researchers, conservation organizations, and local authorities will be necessary to implement protective measures and ensure the survival of these ecologically important algae. The findings from eastern Sicily serve as a reminder of the hidden biodiversity that exists in seemingly ordinary wetlands and the urgent need to document and protect it before it is lost.

Subject of Research: Distribution and morphology of Characeae algae in eastern Sicily

Article Title: New Characeae ( Charophyceae , Charales ) report in eastern Sicily (Italy)

Article References: Pagana, I., Virzì, A., Zafarana, M. A., & Alongi, G. (2024). New Characeae (Charophyceae, Charales) report in eastern Sicily (Italy). Italian Botanist, 18, 109-122. https://doi.org/10.3897/italianbotanist.18.131661

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.18.131661

Keywords: Characeae, Stoneworts, Sicily, Freshwater Algae, Biodiversity, Conservation, Wetlands, Bioindicators, Italy, Ecology, Charophyceae, Charales

Nematodes are the fourth most speciose animal phylum, with roughly 25,000 described species, and by sheer numbers of individuals they are the most abundant animal group on the planet, accounting for around one percent of total animal biomass. They thrive in nearly every ecosystem on Earth, from polar sediments to agricultural soils, occupying niches that range from free-living grazers to parasites of plants and animals. In marine environments, free-living nematodes are generally the most speciose component of the meiofauna, the community of microscopic animals living between sediment grains. Their ubiquity and sensitivity to environmental conditions also make them valuable bioindicators, capable of signaling the health of estuarine and marine ecosystems long before changes become visible at larger scales.

To assess what is actually known about Costa Rica’s marine nematodes, the researchers systematically searched the scientific literature and four international biodiversity databases: the Ocean Biodiversity Information System (OBIS), the Global Biodiversity Information Facility (GBIF), Nemys, the world database of nematodes, and the World Register of Marine Species (WoRMS). From each publication they extracted the level of taxonomic identification, the sampling locality, and the year of collection. The search revealed just fourteen papers mentioning marine nematodes from Costa Rica, and of those, only three included any taxonomic detail at all. The remaining eleven treated nematodes simply as a group, reporting their abundance without identifying a single species.

The geographic pattern of this sparse record is equally telling. Thirteen of the fourteen publications concern the Pacific coast, while only one, a 1974 study of sandy beach infauna by Dexter, touches the Caribbean side. All ten identified species were found on the Pacific coast, and five of the free-living species were described in a single burst of taxonomy more than a century ago, by the nematologist Cobb in 1920, from samples collected at Puntarenas. No nematode data exist for Caribbean seagrass beds or coral reefs, and sampling on the Caribbean sandy beaches has been so limited that Dexter reported nematodes at only one of five Caribbean beaches surveyed, compared with one of eight Pacific beaches.

The five free-living species described by Cobb, Antomicron pellucidum, Hypodontolaimus punctulatus, Pseudochromadora quadripapillata, Pseudolella cephalata, and Zygonemella striata, have had complicated taxonomic histories. A. pellucidum, the type species of its genus, remains valid even though the illustrations in the original description are considered insufficient for comparison, and remarkably, a specimen later studied in the Gulf of Mexico off Florida was assigned to this species originally described from the Pacific coast of Costa Rica. P. quadripapillata has accumulated multiple synonyms and has been reported from locations as distant as Belize, Canada’s Bay of Fundy, the Maldives, Brazil, New Guinea, and Australia, with some databases even listing freshwater as a plausible habitat. Z. striata, the sole species of its genus, was recently matched by Operational Taxonomic Units in Antarctic sediments through DNA metabarcoding, with sequence identity above ninety percent, hinting at a distribution far broader than the historical record suggests.

The parasitic side of the record is equally thin but medically and ecologically significant. The most recent free-living-adjacent description is Echinocephalus janzeni, a parasite described in 1998 from the intestine of a Pacific sting ray, based on specimens collected in Costa Rica and Mexico. The remaining parasitic records come from stranded marine mammals: unidentified species of Anisakis, the genus responsible for human anisakiasis, have been recovered from the digestive tracts of striped, pantropical spotted, and spinner dolphins and Cuvier’s beaked whale. Crassicauda anthonyi, a kidney parasite that can be fatal, was found in a stranded Cuvier’s beaked whale, and nematodes of the genus Halocercus, including H. lagenorhynchi, were collected from the lungs and air passages of pantropical spotted dolphins. Four additional parasitic taxa were reported from stranded cetaceans in 2023, underscoring how much parasite diversity likely remains undocumented.

Where taxonomic identification is absent, abundance data still reveal how dominant nematodes can be. Studies of intertidal mud flats in the Gulf of Nicoya in the mid-1980s found nematodes comprising between 74.9 and 88.1 percent of total organisms, with vertical distribution analyses showing that over 82 percent of individuals concentrated in the top two centimeters of sediment. On coral reefs at Isla del Caño Biological Reserve, nematodes represented about 19 percent of sediment fauna. Around Isla del Coco, a remote oceanic island, nematodes were the second most abundant group at 24 of 27 sampling stations, totaling more than 3,300 individuals, yet every specimen was logged simply as unidentified Adenophorea, a broad subclass, with no species-level resolution.

Perhaps the most dramatic numbers come from deep water. A study of meiofauna along the central Pacific coast at depths of 400 and 1,800 meters found nematodes averaging nearly 80 percent of total abundance, peaking at 99.9 percent within the Oxygen Minimum Zone at 400 meters. The nematode density recorded there, roughly 3,688 individuals per ten square centimeters, is the highest reported for any oxygen minimum zone in the eastern Pacific, even though species richness in that zone was among the lowest. At a methane seep near Mound 12 at about 1,000 meters depth, nematodes made up nearly 10 percent of the meio-epifaunal organisms colonizing deployed woodblocks, and were more abundant on wood at inactive seep sites than at active ones.

The review’s authors emphasize that this scarcity of taxonomic data is not a reflection of the group’s true diversity. Comparable tropical ecosystems elsewhere tell a very different story: a single study of Cuban seagrass beds identified 215 nematode species across 138 genera, 35 families, seven orders, and two classes. Nematodes are also the most abundant taxon in methane seeps of the Gulf of Cádiz, and Costa Rica’s Pacific margin hosts numerous methane seeps of its own. On the parasitic front, Mediterranean studies have documented nematodes in edible scallops and in sea turtles such as the loggerhead, hosts that also occur in Costa Rican waters, suggesting similar or identical parasites await discovery there.

The message of the review is a call to action for tropical marine taxonomy. Because nematodes are simultaneously the most abundant meiofaunal group, sensitive indicators of environmental quality, and key players in sediment food webs, the near-total absence of species-level data from Costa Rica represents a significant gap in understanding the country’s marine biodiversity. The authors argue that dedicated taxonomic effort, combining classical morphology with modern molecular tools, is needed to explore the actual diversity of marine nematodes on both coasts, in habitats ranging from sandy beaches and mud flats to coral reefs, oxygen minimum zones, and deep-sea seeps. Until that work is done, the microscopic majority of Costa Rica’s marine fauna will remain, quite literally, unnamed.

Subject of Research: Diversity and taxonomy of marine nematodes in Costa Rica

Article Title: Marine nematodes of Costa Rica: state of the art

Article References: Sánchez-Monge, A., & Cortés, J. (2024). Marine nematodes of Costa Rica: state of the art. Neotropical Biology and Conservation, 19(2), 319-331. https://doi.org/10.3897/neotropical.19.e115345

Image Credits: AI Generated

DOI: 10.3897/neotropical.19.e115345

Keywords: marine nematodes, Costa Rica, meiofauna, taxonomy, biodiversity, bioindicators, oxygen minimum zone, parasitic nematodes, Pacific coast, Caribbean coast, deep sea, Neotropics

Coastal lagoons are saline or brackish shallow basins oriented parallel to the shoreline, cut off from the open ocean by sandy barriers, shoals, reefs or chains of islands, with only restricted or ephemeral connections to the sea through tidal channels. Because these channels may open and close naturally or through human intervention, lagoons can range from nearly fresh to hypersaline. They are true ecotones, transitional zones where terrestrial and marine systems intermingle, and their multiple boundaries — with the sea, the land, the atmosphere, sediments and freshwater inflows — generate steep physicochemical gradients that fuel extraordinary biological productivity. Annual primary production in these systems ranges from 50 to more than 500 grams of carbon per square meter per year, placing them on par with the ocean’s great upwelling regions. Because most lagoons are shallow enough for sunlight to reach the seabed, and because winds constantly resuspend nutrient-rich sediments, benthic algae and seagrasses can outproduce even the phytoplankton in the water column.

That productivity underwrites an impressive portfolio of ecosystem services. Lagoons serve as spawning grounds and nurseries for commercially valuable fish, sequester carbon, cycle nutrients, purify water, buffer local climates and support tourism, transport and food provision for densely populated coastal communities. But the same proximity to cities makes them vulnerable. Nearly half of the world’s coastal wetlands have been lost or degraded over the past century through the combined pressures of local human activity and climate change, and Brazilian lagoons face warming trends documented across every one of the country’s marine ecoregions, alongside projected sea-level rise of up to 0.98 meters by 2100. Within these systems, macroalgae occupy a pivotal position: they anchor food webs, drive nutrient cycling and respond rapidly to changes in depth, turbidity, light and nutrient levels, which is why they are widely used worldwide as bioindicators of pollution and ecological degradation.

To establish how much is actually known about Brazilian lagoon macroalgae, the research team first turned to satellite imagery. Using Google Earth at scales of 200 to 1,000 meters, they inspected the entire coastline, georeferencing every water body that met the classical definition of a coastal lagoon and applying a cutoff distance of 5.5 kilometers from the maritime shoreline to exclude inland lakes. The census identified 300 lagoons, distributed unevenly across all five of Brazil’s marine ecoregions. The Rio Grande ecoregion in the far south dominated the tally with 124 lagoons — 41.3 percent of the total — followed by the Northeast with 25.7 percent and the Southeast with 17 percent. Of Brazil’s 17 coastal states, only three — Amapá, Pará and Piauí — lacked typical lagoons, while Rio Grande do Sul alone accounted for 29 percent of them, with Santa Catarina, Rio de Janeiro and Bahia close behind.

The literature search was equally exhaustive. The team queried five databases — SciELO, Web of Science, Scopus, Google Scholar and the CAPES Periódicos portal — in English and Portuguese, using the keywords alga, seaweed, lagoon and Brazil in various combinations. More than 20,000 initial documents surfaced, but after rigorous screening under PRISMA guidelines only 13 peer-reviewed articles survived the filters. Snowballing through their bibliographies, searches of theses and dissertations, and a sweep of the publication records of all 62 authors involved eventually expanded the corpus to 48 studies. Even so, those 48 papers covered just 11 lagoons, and the effort was heavily skewed: 17 documents concerned the Patos Lagoon in Rio Grande do Sul, while 22 addressed seven different lagoons in Rio de Janeiro state. Only four states — Alagoas, Rio de Janeiro, Santa Catarina and Rio Grande do Sul — have any lagoon macroalgae research at all. Notably, the number of studies correlated strongly with lagoon size, with a Pearson correlation coefficient of 0.92, and with the proximity of research institutions, suggesting science follows convenience as much as ecological importance.

The catalogued flora comprised 213 macroalgal taxa, dominated by red algae (Rhodophyta, 56 percent of taxa), followed by green algae (Chlorophyta, 32.4 percent) and ochrophytes (11.7 percent). The richest site was the hypersaline Araruama Lagoon in Rio de Janeiro, with 119 taxa, followed by Itaipú with 72, Patos with 60 and Conceição with 56. The most frequently recorded genera were the green opportunists Ulva, Chaetomorpha and Cladophora, along with the red algae Bryocladia subtilissima and Gymnogongrus griffithsiae. Yet when the researchers compared assemblages across lagoons using Bray-Curtis similarity coefficients on presence-absence data, no two lagoons grouped above 50 percent similarity. Even at a lenient 20 percent cutoff, the Mundaú and Açú lagoons stood entirely alone. This striking dissimilarity presents the study’s central unresolved question: are Brazil’s lagoons genuinely unique, each harboring a distinct flora with high beta diversity, or are they simply understudied, their true floras unknown?

Several ecological patterns did emerge from the fragmented record. Algal richness and abundance generally decline from lagoon entrances toward their inner reaches, mirroring patterns described in bays and estuaries and likely driven by salinity — a key determinant of macroalgal distribution — along with substrate, light, nutrients and turbulence. Opportunistic green algae dominate the inner, low-salinity zones, while red algae and ochrophytes retreat toward the sea connections. Araruama Lagoon is a fascinating exception: despite salinity increasing toward its interior, reaching values of up to 80 in the world’s largest permanent hypersaline lagoon ecosystem, its stable extreme conditions support comparatively high richness. Even there, however, decades of shell extraction for soda ash production removed nearly half of the hard substrate algae need, and richness has fallen by roughly a third over 26 years as urbanization and tourism increased nutrient inputs and reduced water transparency.

The review also exposed how geography and history shape the science. The Patos Lagoon, the largest choked-type lagoon in the world and South America’s biggest at 10,227 square kilometers, hosts the longest-running research program thanks to the Brazilian Long-Term Ecological Research initiative (PELD), which has monitored its estuary continuously since 1998. It is the only Brazilian lagoon where isotope studies of macroalgae have been conducted, and the site of the country’s first macroalgal bioindicator study in 1982. By contrast, the Amazonian ecoregion contains a single lagoon — Jansen, in Maranhão, artificially maintained by a sluice gate against one of the world’s largest tidal ranges — with no macroalgae studies whatsoever. In the Northeast, strong sediment drift frequently seals lagoon entrances, leaving little hard substrate for algal attachment and murky waters that may explain both fewer algae and fewer phycologists.

The authors are candid about the limitations of their synthesis. Old identifications could not be re-examined, so taxonomically complex groups such as the morphologically plastic Ulva may inflate richness estimates; some historical references, including the only record of the Açú Lagoon flora — found in conference proceedings purchased from a used bookstore — could not be obtained at all, and inconsistent terminology for lagoons across languages and legal frameworks may have hidden relevant studies from the search. Still, the message is unambiguous. Macroalgae are cost-effective, sensitive and well-established ecological indicators, and Brazil’s management frameworks, including the ReBentos network and emerging Marine Spatial Planning, could integrate them immediately. The researchers call for targeted surveys, standardized comparative methods, digitization of historical collections and expansion of long-term monitoring to unstudied lagoons. Without baselines, they warn, conservation planning, pollution control and protected-area design for these 300 ecosystems will proceed blind — and whether each lagoon is a botanical treasure or a terra incognita may never be known before it changes forever.

Subject of Research: Distribution of coastal lagoons and the diversity and monitoring potential of their macroalgal flora in Brazil

Article Title: Macroalgae in coastal lagoons: a systematic review from Brazil

Article References: Amaral, H. B. F., Copertino, M., & Creed, J. C. (2026). Macroalgae in coastal lagoons: a systematic review from Brazil. Estuarine Management and Technologies, 3, 87-112. https://doi.org/10.3897/emt.3.186569

Image Credits: AI Generated

DOI: 10.3897/emt.3.186569

Keywords: coastal lagoons, macroalgae, Brazil, systematic review, bioindicators, biodiversity, eutrophication, Rhodophyta, Patos Lagoon, Araruama Lagoon, ecosystem services, marine ecoregions

The new book, whose German title translates as Heteroptera of Germany II: Identification Key to All Species, runs to 491 pages and builds directly on a predecessor published by the same team in 2020. That earlier volume provided a general introduction to the Heteroptera and their families, along with identification keys that stopped at the genus level. The sequel completes the project: it delivers dichotomous keys covering all of Germany’s true bug species, illustrated with mostly original drawings that depict the diagnostic characters needed to separate closely related taxa. For a group long hampered by the absence of up-to-date identification manuals, the arrival of a complete species-level treatment represents a genuine turning point.

One of the strongest features of the new volume is its visual documentation. The authors have assembled photographs of almost every German species of Heteroptera — living specimens wherever possible, and collection specimens in the case of rare species. Many nymphs are photographed as well, and these images are gathered into an appendix at the end of the volume. This photographic coverage is itself a major aid to identification, because it allows users to check whether the specimen in hand actually matches the species suggested by the key, rather than trusting a purely textual diagnosis. The combination of keys, drawings and photographs makes the book usable by a far broader audience than traditional taxonomic literature typically reaches.

Each species profile is rounded out with concise summaries of the insect’s ecology, distribution maps and phenological data — information on when during the year the species can be found in its various life stages. Taken together, these elements elevate the book beyond a simple identification manual into something closer to an encyclopaedia of German true bugs. For ecologists and environmental consultants, the ecological summaries and distribution maps are particularly valuable, since many Heteroptera serve as potential bioindicators whose presence or absence can signal the condition of a habitat. For naturalists, photographers and educators, the photographs and phenological data make the group accessible in a way that dense taxonomic prose never could.

The sheer physical size of the book could be seen as a hindrance for fieldwork — a 491-page volume is not something most researchers will casually slip into a pocket. But the authors turned that scale into an advantage. Because the book is large, the keys and pictures of several related species can be placed on the same page, which makes direct comparison between similar taxa far easier than flipping between distant sections. Anyone who has struggled to distinguish two lookalike species by shuffling between a key on one page and illustrations scattered elsewhere will appreciate how much friction this design choice removes.

The most obvious weakness of the work is that it is written in German only, which limits its immediate accessibility for the many readers outside Germany who might be interested in its content. The reviewer of the volume, Viktor Hartung, writing in the Deutsche Entomologische Zeitschrift, notes that in an era when machine translation tools are readily available on mobile phones, this may not be a very big hindrance in practice. A researcher in Poland or the Netherlands with a smartphone can now work through a German-language key with real-time translation assistance, something that would have been unthinkable when Wagner’s manual was the only option. Still, the language barrier remains a consideration for the international audience that a fauna of this scope inevitably deserves.

Hartung also points out that a manual of such scope will inevitably be worthy of minor improvements here and there — in diagnostic characters or in the keys themselves. This is a normal feature of any comprehensive taxonomic work: as more specimens are examined and more characters tested, small refinements accumulate. Such corrections do not diminish the achievement; they simply mark the starting point for the ongoing refinement that any living identification resource undergoes. The foundation laid by Niedringhaus, Stöckmann and Wachmann is solid enough that these future tweaks will be adjustments to a working system rather than repairs to a broken one.

The significance of the new volume extends well beyond Germany’s borders. By raising research on the true bugs of Germany to a new level, offering great help to experts and simultaneously lowering the entry barrier for beginners, the book gives hope that Heteroptera will become more popular objects of study in Germany and elsewhere in Europe in the future. A complete, well-illustrated, species-level fauna for one of Europe’s largest countries provides a reference point against which neighbouring countries can measure their own faunas, and a template for how a national true bug fauna should be documented. The ecological diversity of the group — with its bioindicators and economically important species — means that better identification tools translate directly into better environmental assessment.

The book also carries a poignant human dimension. Ekkehard Wachmann, one of its three authors, passed away in September 2023 while the new volume was still in preparation. Hartung’s review describes the completed work as a perfect memorial to Wachmann, whose lifelong commitment to the true bugs of Germany advanced the study of these insects like no other. The volume thus stands simultaneously as a technical milestone, a practical tool for a new generation of entomologists, and a tribute to a career devoted to making one of Europe’s most diverse insect orders knowable.

Subject of Research: Biodiversity and taxonomy

Article Title: Book review: Niedringhaus, R., Stöckmann, M. & Wachmann, E. (2025). Die Wanzen Deutschlands II: Bestimmungsschlüssel für alle Arten. [Heteroptera of Germany II: Identification key to all species.] (in German). WABV, Scheeßel, 491 S.

Article References: Hartung, V. (2026). Book review: Niedringhaus, R., Stöckmann, M. & Wachmann, E. (2025). Die Wanzen Deutschlands II: Bestimmungsschlüssel für alle Arten. [Heteroptera of Germany II: Identification key to all species.] (in German). WABV, Scheeßel, 491 S.. Deutsche Entomologische Zeitschrift, 73(1), 13-13. https://doi.org/10.3897/dez.73.180736

Image Credits: AI Generated

DOI: 10.3897/dez.73.180736

Keywords: Heteroptera, true bugs, identification key, German fauna, entomology, taxonomy, bioindicators, book review, Deutsche Entomologische Zeitschrift, species identification, ecology, Wachmann