Environmental DNA Research Articles

Phylogeny and ultrastructure of a non-toxigenic dinoflagellate Amphidoma fulgens sp. nov. (Amphidomataceae, Dinophyceae), with a wide distribution across Asian Pacific

Amphidoma languida, a marine thecate dinoflagellate that produces the lipophilic toxin azaspiracids (AZAs), is primarily found in the Atlantic. Although this species has not been recorded in the Asian Pacific, environmental DNAs related to Am. languida have been widely detected in the region by metabarcoding analysis. Their morphology and AZA production remain unclear. In this study, the morphology, ultrastructure, phylogeny, and AZA production of nine Amphidoma strains isolated from Japan, Malaysia, and Philippines were investigated. Phylogenetic trees inferred from rDNAs (SSU, ITS, and LSU rDNA) showed monophyly of the nine Pacific strains and were sister to the Am. languida clade, including the toxigenic strains from the Atlantic. Cells were ellipsoid, 8.7–16.7 µm in length and 7.4–14.0 µm in width, with a conspicuous apical pore complex. A large nucleus in the hyposome, parietal chloroplast with a spherical pyrenoid in the episome, and refractile bodies were observed. Thecal tabulation was typical of Amphidoma, Po, cp, X, 6ʹ, 6ʹʹ, 6C, 5S, 6ʹʹʹ, 2ʹʹʹʹ. A ventral pore was located on the anterior of 1ʹ plate, beside the suture to 6ʹ plate. The presence of a ventral depression, on the anterior of anterior sulcal plate, was different from Am. languida. A large antapical pore, containing approximately 10 small pores, was observed. Cells were apparently smaller than Am. trioculata, a species possessing three pores (ventral pore, ventral depression, and antapical pore). TEM showed the presence of crystalline structures, resembling guanine crystals, and cytoplasmic invaginations into the pyrenoid matrix. Flagellar apparatus lacking the striated root connective is similar to peridinioids and related dinoflagellates. AZAs were not detected from the Pacific strains by LC-MS/MS. This non-toxigenic Amphidoma species, here we propose as Amphidoma fulgens sp. nov., is widely distributed in the Asian Pacific. Moreover, molecular comparison also suggested that most of the environmental DNA sequences previously reported as Am. languida or related sequences from the Asian Pacific were attributable to Am. fulgens.

A sedimentary DNA record of the Atacama Trench reveals biodiversity changes in the most productive marine ecosystem.

The hadopelagic environment remains highly understudied due to the inherent difficulties in sampling at these depths. The use of sediment environmental DNA (eDNA) can overcome some of these restrictions as settled and preserved DNA represent an archive of the biological communities. We use sediment eDNA to assess changes in the community within one of the world's most productive open-ocean ecosystems: the Atacama Trench. The ecosystems around the Atacama Trench have been intensively fished and are affected by climate oscillations, but the understanding of potential impacts on the marine community is limited. We sampled five sites using sediment cores at water depths from 2400 to ~8000 m. The chronologies of the sedimentary record were determined using 210Pbex. Environmental DNA was extracted from core slices and metabarcoding was used to identify the eukaryote community using two separate primer pairs for different sections of the 18S rRNA gene (V9 and V7) effectively targeting pelagic taxa. The reconstructed communities were similar among markers and mainly composed of chordates and members of the Chromista kingdom. Alpha diversity was estimated for all sites in intervals of 15 years (from 1842 to 2018), showing a severe drop in biodiversity from 1970 to 1985 that aligns with one of the strongest known El Niño events and extensive fishing efforts during the time. We find a direct impact of sea surface temperature on the community composition over time. Fish and cnidarian read abundance was examined separately to determine whether fishing had a direct impact, but no direct relation was found. These results demonstrate that sediment eDNA can be a valuable emerging tool providing insight in historical perspectives on ecosystem developments. This study constitutes an important step toward an improved understanding of the importance of environmental and anthropogenic drivers in affecting open and deep ocean communities.

Optimization and application of bacterial environmental DNA and RNA isolation for qualitative and quantitative studies

AbstractMolecular detection of environmental DNA (eDNA) and RNA (eRNA) allows highly sensitive qualitative (i.e., presence or absence) and quantitative (i.e., abundance) monitoring of aquatic bacteria. However, bacterial molecular diagnostics are limited by low positive predictive values. Protocols for bacterial eDNA and eRNA molecular monitoring have primarily focused on optimizing specimen collection, and the optimal method to purify bacterial nucleic material from postcollection aquatic specimens to maximize the analytical sensitivity of molecular diagnostics remains poorly defined. Accordingly, strategies to isolate bacterial eDNA and eRNA from fresh and saltwater were investigated. We evaluated two filtration and four nucleic acid purification systems as representative of current generation bacterial eDNA and eRNA isolation strategies for capacity to isolate bacterial eDNA and eRNA from prelysed (i.e., free‐nucleic acids) and viable (i.e., colony forming units, CFU) bacterial cells. We also compared the sensitivities of reverse transcription quantitative PCR (RT‐qPCR) and metagenomic shotgun microbiome sequencing. The optimal protocol used 0.7 μm borosilicate glass filters (Whatman plc) followed by extraction with the RNeasy PowerWater kit (Qiagen). The protocol had a very high analytical sensitivity (10−3–100 ng and 102–101 CFU detected in 500 mL) across multiple species of bacteria, when tested with either RTqPCR or metagenomic sequencing. Importantly, this study highlighted several limitations which are restrictive to both qualitative and quantitative bacterial eDNA and eRNA studies. First, a 12‐h time course between sampling and extraction revealed significant species‐specific changes in cell number and free‐nucleic acid concentrations can occur postspecimen collection. Second, we found Gram‐positive bacteria yielded less nucleic material compared to Gram‐negative bacteria suggesting bacterial eDNA and eRNA studies could be biased by microorganism genome stability and extraction efficiency. This study highlights the need to define the species‐specific diagnostic sensitivity of a protocol when monitoring aquatic bacterial eDNA and eRNA with molecular diagnostics.

Environmental DNA reveals fine‐scale spatial and temporal variation of marine mammals and their prey species in a Scottish marine protected area

AbstractMarine mammal foraging grounds are popular focal points for marine protected area (MPA) implementation, despite being temporally dynamic, requiring continuous monitoring to infer prey availability and abundance. Marine mammal distributions are assumed to be driven by their prey in foraging areas, but limited understanding of prey distributions often prevents us from exploring how shifting prey availability impacts both seasonal and long‐term marine mammal distributions. Environmental DNA (eDNA) metabarcoding could enhance the understanding of marine mammal habitat use in relation to their prey through simultaneous monitoring of both. However, eDNA applications focused on marine mammals or predator–prey dynamics have been limited to date. In this study, we assess spatiotemporal changes in the distribution and abundance of cetaceans, minke whales (Balaenoptera acutorostrata), bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) in relation to key prey species in a newly established MPA, employing eDNA metabarcoding. We recovered 105 molecular operational taxonomic units (OTUs) from marine vertebrates using two primer sets targeting 12S and 16S genes, along with 112 OTUs from a broader eukaryotic primer set targeting 18S rRNA. Overall, key forage fish prey species, sandeels and clupeids, were the most abundant teleost fishes detected, although their availability varied temporally and with distance from shore. We also found clear spatial partitioning between coastal bottlenose dolphins and the more pelagic minke whales and harbor porpoises, paralleling availability of their main prey species. Other species of conservation interest were also detected including the critically endangered European eel (Anguilla anguilla), Atlantic bluefin tuna (Thunnus thynnus), and the invasive pink salmon (Oncorhynchus gorbuscha). This study demonstrates the application of eDNA to detect spatiotemporal trends in the occurrence and abundance of cetacean predators and their prey, furthering our understanding of fine‐scale habitat use within MPAs. Future long‐term monitoring of predator–prey dynamics with eDNA could improve our ability to predict climate‐induced shifts in foraging grounds and enhance rapid responses with appropriate management actions.

Integration of citizen science and eDNA reveals novel ecological insights for marine fish conservation

AbstractIn the face of climate change, the accelerating nature crisis, and other anthropogenic impacts, conserving biodiversity demands effective monitoring. While innovative approaches have emerged to enhance biodiversity assessment, significant data gaps persist, particularly within marine ecosystems. In this study, we assess the utility of combining citizen (community) science with environmental DNA (eDNA) metabarcoding for characterizing and quantifying marine fish biodiversity. Over the summer of 2022, 32 volunteers conducted extensive water sampling in a large Norwegian fjord, yielding 96 samples. Contrasting eDNA findings with conventional observational surveys (such as a national species registration database and beach seine surveys) unveiled a substantial overlap in recorded species inventories. The eDNA citizen science initiative identified previously undocumented species and rediscovered others emphasizing an increase in warm‐water species within the study area. Additionally, eDNA data unveiled reduced diversity within the inner fjord relative to the outer fjord. To conclude, our study demonstrates the successful integration of eDNA within a citizen science framework, facilitating comprehensive biodiversity tracking across coastal marine regions. These findings hold promise for advancing marine conservation efforts by providing valuable data to inform critical decision‐making processes.

Enhancing metabarcoding of freshwater biotic communities: A new online tool for primer selection and exploring data from 14 primer pairs

AbstractFreshwater ecosystems are complex, diverse, and face multiple imminent threats that have led to changes in both structure and function. It is urgent that we develop and standardize monitoring tools that allow for rapid and comprehensive assessment of freshwater communities to understand their changing dynamics and inform conservation. Environmental DNA surveys offer a means to inventory and monitor aquatic diversity, yet most studies focus on one or a few taxonomic groups because of technical challenges. In this study, we (1) create an eDNA metabarcoding dataset (natural water bodies) with 14 validated primer pairs; (2) create a free online, user‐friendly tool for primer selection that can be used for any metabarcoding data (SNIPe); and (3) using SNIPe, explore our dataset to derive subsets of informative, cost‐effective primer pairs that maximize detection of freshwater diversity. We first evaluated the completeness of public reference sequence databases and the efficiency of 14 primer pairs in silico, in vitro on five mock communities (mix of DNA from tissues of select taxa), in vivo on water samples from aquarium samples with known taxonomic composition, and finally in vivo on water samples from freshwater systems in Eastern Canada. Results from analyses using SNIPe revealed that 13 or 14 primer pairs are necessary to recover 100% of the species in water samples (natural systems), but that four primer pairs are sufficient to recover almost 75% of taxa with little overlap. Our work highlights the power of eDNA metabarcoding for reconstructing freshwater communities, including prey, parasite, pathogen, invasive, and declining species. It also emphasizes the importance of marker choice on species resolution, and primer characteristics and filtering parameters on detection success and accuracy of biodiversity estimates. Together, these results highlight the usefulness of eDNA for freshwater monitoring and should prompt more studies of tools to survey all communities.

The use of environmental DNA for biodiversity monitoring in lentic and lotic ecosystems

Abstract Global biodiversity is facing an extinction crisis leading to increasing pressure on industries to monitor their potential environmental impact. Relatedly, there is demand for more efficient biodiversity monitoring methods, resulting in growing interest in the use of environmental DNA (eDNA). Many questions, however, regarding the reliability of this relatively novel method remain, particularly for non‐specialist end‐users of the technology. Here, the use of commercially available (in the UK) eDNA assays for monitoring freshwater fish and invertebrate biodiversity was compared to conventional surveillance techniques. Samples were collected from different habitats, on varying spatial scales and using multiple sampling regimes to assess how eDNA results were affected. For aquatic macroinvertebrates and fish, more taxa were detected by eDNA than conventional surveys conducted in parallel, and for fish, all taxa detected by conventional monitoring were confirmed by eDNA. For aquatic macroinvertebrates, several species were only detected through conventional methods, and the number of families detected by eDNA was lower than for conventional monitoring at all sites. eDNA results varied significantly between sampling locations within lentic sites and, for lotic sites, with the number of subsamples collected. Practical implication. This study demonstrates the need for bespoke sampling protocols when collecting eDNA samples. It also improves understanding of using eDNA for detecting aquatic taxa that could inform species surveillance protocols. These are essential if eDNA is to be used by practitioners as a regulatory monitoring tool.

Environmental DNA metabarcoding on aquatic insects: Comparing the primer sets of MtInsects‐16S based on the mtDNA 16S and general marker based on the mtDNA COI region

AbstractLong‐term biodiversity monitoring is necessary for conservation and management. In such circumstances, environmental DNA (eDNA) surveys can enable easy and effective biomonitoring of aquatic insects. However, previous studies of aquatic insects based on the mtDNA COI region have revealed incomplete taxonomic coverage, and frequent amplification of nontarget taxa (e.g., algae and diatoms). Additionally, it has been indicated that there are few reference sequences registered in databases for metabarcoding analysis of insects. Therefore, we developed a new primer set, MtInsects‐16S, for eDNA analyses of insects based on the mtDNA 16S rRNA region in a previous study. To address the insufficient database records of insect DNA sequences, we also constructed a comprehensive reference database of aquatic insects that occur in Kanagawa Prefecture, Japan. We conducted eDNA analyses at six sites in the two river systems (the Sagami‐gawa River and Sakawa‐gawa River systems), with three replicates per site, based on both the mtDNA COI and the 16S rRNA regions. These results were compared physical capture surveys at the same sites to examine the detection capability of eDNA for Insecta with using a well‐established database. Among the list of species which were collected by physical capture surveys, 74.9% were detected by MtInsects‐16S, whereas 40.1% were detected by the primer set of the mtDNA COI region, and also 80.0% were detected by the both primer sets. This study demonstrated that the application of eDNA analyses using the MtInsects‐16S primer set can be conducted with accuracy and reliability, provided that the reference DNA database is improved. The MtInsects‐16S region can be considered indispensable in eDNA analysis for aquatic insects.

A quantitative analysis of vertebrate environmental DNA degradation in soil in response to time, UV light, and temperature

AbstractEnvironmental DNA (eDNA) degradation influences the effectiveness of eDNA‐based biodiversity monitoring, but the factors that determine the rate of decay of eDNA in terrestrial environments are poorly understood. We assessed the persistence of vertebrate eDNA from a mock vertebrate community created with soil from zoo enclosures holding 10 target species from different taxonomic classes (reptiles, birds, and mammals) and of different biomass (little penguin and giraffe). We examined species detection rates resulting from eDNA metabarcoding, as well as relative eDNA concentrations via qPCR, from soil samples over eight time points (0–12 weeks), during exposure to three ambient temperatures (10, 25, and 40°C) and three levels of ultraviolet B (UV‐B) radiation (0%, 50%, and 100% intensity). We recorded considerable variation in detectability between species, independent of temperature, and UV‐B effects. Quantitative polymerase chain reaction (PCR) indicated degradation of eDNA over time for all temperature and UV treatments, although it was still possible to detect eDNA from some species after 12 weeks. Degradation rates were lowest for high UV‐B treatments, presumably due to UV‐B reducing bacterial metabolism. The temperatures investigated did not influence eDNA decay. Our results indicate that eDNA in soil can persist under a range of temperatures and high UV radiation for longer than expected. Sheltered sites with minimal UV‐B radiation, which have previously been considered ideal sites for terrestrial eDNA collection, may not be optimal for eDNA persistence in some cases due to microbial decay. A better understanding of eDNA degradation in terrestrial environments is needed to enhance the accuracy of eDNA metabarcoding for surveying terrestrial vertebrate communities.

Detection differences between eDNA and mid‐water trawls are driven by fish biomass and habitat preferences

AbstractMarine scientific trawl surveys are commonly used to assess the distribution and population size of fisheries‐related species, yet the method is effort‐intensive and can be environmentally destructive. Sequencing environmental DNA (eDNA) from water samples can reveal the presence of organisms in a community without capturing them; however, we expect the detectability of taxa to differ between eDNA and trawl surveys, and understanding how species traits and population variables contribute to detection differences can help calibrate our expectations from each form of sampling. Here, we coupled eDNA metabarcoding and capture trawl surveys in British Columbia, Canada, to examine species traits that explain recurrent differences in detectability between the two methods, including habitat, body size, and biomass. At the regional scale, 17 of 23 fish species (74%) captured by the trawl were detected by eDNA metabarcoding, and 39 additional species were detected by eDNA sampling only. We found that eDNA metabarcoding disproportionately detected trawl‐caught species with greater local biomass (i.e., greater biomass in the adjacent trawl). Fish detected only in eDNA had a greater range of body lengths and a broader range of habitat preferences outside the trawls' target size and sampling areas. Our results suggest that with our level of sampling, eDNA metabarcoding can adequately recapitulate detection of fish communities detected by trawl surveys, but with a bias toward fish of high population biomass and greater inclusion of fish from outside the trawled area.

Comparison of soil eDNA to camera traps for assessing mammal and bird community composition and site use.

Species detections often vary depending on the survey methods employed. Some species may go undetected when using only one approach in community-level inventory and monitoring programs, which has management and conservation implications. We conducted a comparative study of terrestrial mammal and bird detections in the spring and summer of 2021 by placing camera traps at 30 locations across a large military installation in northern Michigan, USA and testing replicate soil samples from these sites for environmental DNA (eDNA) using an established vertebrate metabarcoding assay. We detected a total of 48 taxa from both survey methods: 26 mammalian taxa (excluding humans, 24 to species and two to genus) and 22 avian taxa (21 to species and one to genus). We detected a relatively even distribution of mammalian taxa on cameras (17) and via eDNA analysis (15), with seven taxa detected from both methods. Most medium-to-large carnivores were detected only on cameras, whereas semi-fossorial small mammals were detected only via eDNA analysis. We detected higher bird diversity with camera traps (18 taxa) compared to eDNA analysis (eight taxa; four taxa were detected with both methods), but cameras alone were most effective at detecting smaller birds that frequently occupy arboreal environments. We also used Bayesian spatial occupancy models for two widely distributed game species (white-tailed deer, Odocoileus virginianus, and ruffed grouse, Bonasa umbellus) that were moderately detected with both survey methods and found species-specific site use (occupancy) estimates were similar between cameras and eDNA analysis. Concordant with similar studies, our findings suggest that a combination of camera trap and eDNA surveys could be most useful for assessing the composition of terrestrial mammal communities. Camera traps may be most efficient for assessing bird diversity but can be complemented with eDNA analysis, particularly for species that spend considerable time on the ground.

Assessing the performance of short 18S rDNA markers for environmental DNA metabarcoding of marine protists

AbstractMarine protists are globally distributed and sensitive to environmental conditions, which makes them a focal group when studying the effects of climate change on biodiversity and ocean health. However, they are a highly diverse group with varying evolutionary histories and morphologies and widely variable preservation potential in the fossil record. Thus, their past diversity and composition are poorly known. Paleogenetics, which relies, among other approaches, on DNA metabarcoding of sedimentary ancient DNA (sedaDNA), provides a promising avenue to explore the past history and responses of marine protists to global change. Choosing the right marker for sedaDNA studies is critical, striking a balance between marker length and taxonomic resolution. While marker guides exist for modern environmental DNA surveys, a thorough assessment of existing short markers for sedaDNA studies targeting protists is lacking. In this study, we report on a comparison of in silico PCR for eight short 18S rDNA markers, including one from the Tara Oceans initiative and a longer marker commonly used in modern marine eDNA studies. We analyze their taxonomic coverage and resolution, taxonomic overlap and uniqueness between markers, co‐amplification of non‐protist taxa, and amplicon size differences across taxonomic groups. Additionally, we provide a detailed analysis of diatoms, dinoflagellates, haptophytes, and chlorophytes. Our study is aimed at supporting project‐specific marker choices for characterizing protist composition and diversity. While we focus on marine protists, our results are applicable to other aquatic and terrestrial environments.

Gestational exposure to environmental chemicals and epigenetic alterations in the placenta and cord blood mononuclear cells

BackgroundExposure to environmental chemicals such as phthalates, phenols, and polycyclic aromatic hydrocarbons (PAHs) during pregnancy can increase the risk of adverse newborn outcomes. We explored the associations between maternal exposure to select environmental chemicals and DNA methylation in cord blood mononuclear cells (CBMC) and placental tissue (maternal and fetal sides) to identify potential mechanisms underlying these associations.MethodThis study included 75 pregnant individuals who planned to give birth at the University of Cincinnati Hospital between 2014 and 2017. Maternal urine samples during the delivery visit were collected and analyzed for 37 biomarkers of phenols (12), phthalates (13), phthalate replacements (4), and PAHs (8). Cord blood and placenta tissue (maternal and fetal sides) were also collected to measure the DNA methylation intensities using the Infinium HumanMethylation450K BeadChip. We used linear regression, adjusting for potential confounders, to assess CpG-specific methylation changes in CBMC (n = 54) and placenta [fetal (n = 67) and maternal (n = 68) sides] associated with gestational chemical exposures (29 of 37 biomarkers measured in this study). To account for multiple testing, we used a false discovery rate q-values < 0.05 and presented results by limiting results with a genomic inflation factor of 1±0.5. Additionally, gene set enrichment analysis was conducted using the Kyoto Encyclopedia of Genes and Genomics pathways.ResultsAmong the 29 chemical biomarkers assessed for differential methylation, maternal concentrations of PAH metabolites (1-hydroxynaphthalene, 2-hydroxyfluorene, 4-hydroxyphenanthrene, 1-hydroxypyrene), monocarboxyisononyl phthalate, mono-3-carboxypropyl phthalate, and bisphenol A were associated with altered methylation in placenta (maternal or fetal side). Among exposure biomarkers associated with epigenetic changes, 1-hydroxynaphthalene, and mono-3-carboxypropyl phthalate were consistently associated with differential CpG methylation in the placenta. Gene enrichment analysis indicated that maternal 1-hydroxynaphthalene was associated with lipid metabolism and cellular processes of the placenta. Additionally, mono-3-carboxypropyl phthalate was associated with organismal systems and genetic information processing of the placenta.ConclusionAmong the 29 chemical biomarkers assessed during delivery, 1-hydroxynaphthalene and mono-3-carboxypropyl phthalate were associated with DNA methylation in the placenta.

Streamlining large-scale oceanic biomonitoring using passive eDNA samplers integrated into vessel's continuous pump underway seawater systems

Passive samplers are enabling the scaling of environmental DNA (eDNA) biomonitoring in our oceans, by circumventing the time-consuming process of water filtration. Designing a novel passive sampler that does not require extensive sample handling time and can be connected to ocean-going vessels without impeding normal underway activities has potential to rapidly upscale global biomonitoring efforts onboard the world's oceanic fleet. Here, we demonstrate the utility of an artificial sponge sampler connected to the continuous pump underway seawater system as a means to enable oceanic biomonitoring. We compared the performance of this passive sampling protocol with standard water filtration at six locations during a research voyage from New Zealand to Antarctica in early 2023. Eukaryote metabarcoding of the mitochondrial COI gene revealed no significant difference in phylogenetic α-diversity between sampling methods and both methods delineated a progressive reduction in number of Zero-Radius Operational Taxonomic Units (ZOTUs) with increased latitudes. While both sampling methods revealed comparable trends in geographical community compositions, distinct clusters were identified for passive samplers and water filtration at each location. Additionally, greater variability between replicates was observed for passive samplers, resulting in an increased estimated level of replication needed to recover 90 % of the biodiversity. Furthermore, traditional water filtration failed to detect three phyla observed by passive samplers and extrapolation analysis estimated passive samplers recover a larger number of ZOTUs compared to water filtration for all six locations. Our results demonstrate the potential of this passive eDNA sampler protocol and highlight areas where this emerging technology could be improved, thereby enabling large-scale offshore marine eDNA biomonitoring by leveraging the world's oceanic fleet without interfering with onboard activities.

Environmental DNA for monitoring the impact of offshore wind farms on fish and invertebrate community structures

AbstractTo reach the renewable energy targets set by the European Commission, a tenfold expansion of the installed offshore wind farms is needed. Since the construction of offshore wind farms may affect local soft‐sediment fauna, an efficient monitoring technique is needed to monitor the potential effects on the marine ecosystem. Here, we assess whether eDNA metabarcoding is a suitable alternative to monitor fish and epibenthos biodiversity in these difficult to access marine habitats. Water sampling and trawl surveys were conducted in parallel in 12 coastal and 18 offshore sites, the latter located inside and outside two offshore wind farms in the Belgian part of the North Sea. 12S eDNA metabarcoding retrieved 85.7% of the fish species caught in the beam trawls, whereas the COI eDNA metabarcoding only identified 31.4% of the epibenthic invertebrate species. Furthermore, the 12S marker resulted in an additional detection of 26 unique fish species, whereas the COI marker detected an additional 90 invertebrate species. Spatial patterns in alpha diversity recovered with eDNA metabarcoding were not significantly different from those observed with morphological determination. Significant differences were found in fish and invertebrate community structures between the coastal, transition and offshore zones as well as on the smaller wind farm scales, which agreed with the morphological beam trawl data. Indicator species found with morphological beam trawl monitoring for each of the three zones (coastal, transition, offshore) were also detected with 12S eDNA metabarcoding, and the latter method detected an additional 31 indicator species. Our findings show the need for adequate quality control of the obtained species lists and reveal that 12S eDNA metabarcoding analyses offers a useful survey tool for the monitoring of fish communities in offshore wind farms, but the used COI assay did not adequately capture the epibenthic communities as observed with beam trawl data.

When does a parasite become a disease? eDNA unravels complex host-pathogen dynamics across environmental stress gradients in wild salmonid populations

Infectious diseases stem from disrupted interactions among hosts, parasites, and the environment. Both abiotic and biotic factors can influence infection outcomes by shaping the abundance of a parasite's infective stages, as well as the host's ability to fight infection. However, disentangling these mechanisms within natural ecosystems remains challenging. Here, combining environmental DNA analysis and niche modelling at a regional scale, we uncovered the biotic and abiotic drivers of an infectious disease of salmonid fish, triggered by the parasite Tetracapsuloides bryosalmonae. We found that the occurrence and abundance of the parasite in the water—i.e., the propagule pressure— were mainly correlated to the abundances of its two primary hosts, the bryozoan Fredericella sultana and the fish Salmo trutta, but poorly to local abiotic environmental stressors. In contrast, the occurrence and abundance of parasites within fish hosts—i.e., proxies for disease emergence—were closely linked to environmental stressors (water temperature, agricultural activities, dams), and to a lesser extent to parasite propagule pressure. These results suggest that pathogen distribution alone cannot predict the risk of disease in wildlife, and that local anthropogenic stressors may play a pivotal role in disease emergence among wild host populations, likely by modulating the hosts' immune response. Our study sheds light on the intricate interplay between biotic and abiotic factors in shaping pathogen distribution and raises concerns about the effects of global change on pathogen emergence.

An updated LSU database and pipeline for environmental DNA identification of arbuscular mycorrhizal fungi

Recent work established a backbone reference tree and phylogenetic placement pipeline for identification of arbuscular mycorrhizal fungal (AMF) large subunit (LSU) rDNA environmental sequences. Our previously published pipeline allowed any environmental sequence to be identified as putative AMF or within one of the major families. Despite this contribution, difficulties in implementation of the pipeline remain. Here, we present an updated database and pipeline with (1) an expanded backbone tree to include four newly described genera and (2) several changes to improve ease and consistency of implementation. In particular, packages required for the pipeline are now installed as a single folder (conda environment) and the pipeline has been tested across three university computing clusters. This updated backbone tree and pipeline will enable broadened adoption by the community, advancing our understanding of these ubiquitous and ecologically important fungi.

Seasonal dynamics of Mediterranean fish communities revealed by eDNA: Contrasting compositions across depths and Marine Fully Protected Area boundaries

Marine fish communities suffer from anthropogenic pressures and climate change, which influence their spatio-temporal dynamics. Marine Protected Areas (MPAs) have been established worldwide to preserve these communities, while mesophotic ecosystems could provide natural refugia. Assessing the extent to which MPAs and deeper ecosystems can mitigate human and climate change impacts requires regular monitoring of temporal community dynamics. Environmental DNA (eDNA) surveys – being time- and cost-effective – can provide valuable insights on biodiversity change. Here, we initiated a long-term study based on eDNA monitoring in an MPA in the north-western Mediterranean Sea that includes areas with various protection levels. Specifically, from June 2021 to January 2023, we collected eDNA samples during the summer, fall, and winter seasons from shallow water (20 m depth), at 40 m depth, and from the mesophotic zone (80 m depth) in a Fully Protected Area (FPA) and in a nearby Lightly Protected Area (LPA) in the Riou archipelago (France). In this short period and relatively small area, we detected a total of 113 actinopterygian and chondrichthyan taxa. Species with high fishing vulnerability had higher detection rates in the FPA than in the LPA, suggesting a positive impact of FPAs on the conservation of these threatened species. A marked seasonal signal in species detections, including significantly lower detections of several species in winter, indicated a combined effect of species biological changes and migration behavior. The seasonality trend was stronger in the FPA than in the LPA, indicating that such areas may modify sub-yearly patterns in communities and ecosystem processes. Fish composition was associated with water depth, with marked species dissimilarities between shallow waters and the mesophotic zone, implying that multiple depths should be considered in MPA monitoring to fully capture the response of biodiversity to management. Our results point to the importance of temporal information combined with extensive sampling across depths and protection levels to fully understand the ecological dynamics and structure of coastal fish communities.

Biodiversity and community structures across the Magellan seamounts and abyssal plains in the western Pacific Ocean revealed by environmental DNA metabarcoding analysis

Seamounts within deep-sea ecosystems are recognized as biodiversity hotspots, yet they are increasingly threatened by anthropogenic activities such as overfishing, resource exploitation, and climate change. To establish environmental baseline data and assess the impacts of current or future anthropogenic activities, we conducted environmental DNA (eDNA) metabarcoding analyses to comprehensively characterize prokaryotic and eukaryotic diversity across various water depths of the Magellan seamounts and the adjacent abyssal plains. Metabarcoding analysis revealed higher richness and diversity in both prokaryotic and eukaryotic communities within the seamounts compared to the abyssal plains. Overall, the analysis identified 9,068 prokaryotic amplicon sequence variants (ASVs), representing 39 phyla and 47 classes. Similarly, 4,569 eukaryotic ASVs were identified, spanning 34 phyla and 93 classes. Furthermore, our results revealed distinct community structures between the seamounts and abyssal plains, with turnover across different water depths. These findings are crucial as they indicate the unique ecological roles and potential vulnerability of seamount communities, emphasizing the need for targeted conservation strategies. Our study underscores the importance of conducting comprehensive long-term environmental assessments of the impacts of anthropogenic activities on seamount ecosystems and highlights the potential of eDNA metabarcoding as a powerful tool for guiding conservation and management efforts in remote and challenging marine environments.

Testing the applicability of environmental DNA metabarcoding to landscape genetics.

Landscape genetics is a field dealing with local genetic differences and contributes to strategic conservation planning. Recently, environmental DNA (eDNA) metabarcoding has proven useful not only for detecting species but also for assessing genetic diversity and genetic structure on a large scale such as in phylogeography. However, it remains unclear whether eDNA analysis also has sufficient power to perform the landscape genetics, which focuses on a local scale. To reveal the applicability of eDNA to landscape genetics, we conducted an eDNA metabarcoding analysis of the mitochondrial DNA D-loop region of the fluvial sculpin Cottus nozawae in the upper Sorachi River in Japan and compared the results with inferences based on traditional tissue-based approaches by the same D-loop region and genome-wide SNP data. As a result, the spatial distribution of haplotypes was generally consistent between the eDNA- and tissue-based approaches. In addition, the genetic differentiation statistics calculated using eDNA and tissue samples were highly correlated when comparing both in the D-loop region. The removal of low-frequency reads or the conversion to semi-quantitative rankings of eDNA data did not alter the correlation of genetic diversity and differentiation statistics with tissue-based approaches much. Finally, we confirmed that analyses using eDNA data can reveal patterns such as isolation-by-distance shown in previous studies on this species, indicating the applicability of eDNA to basic landscape genetics. Even though some limitations remain, eDNA may have great potential for conducting basic landscape genetics.