Environmental DNA最新文献

Urban coastal habitats experience substantial disturbances due to their proximity to human settlements and activities. Yet, despite the negative impact of urbanization on coastal environments, industrial structures can also provide artificial habitats. These are often easily accessible to regular surveys, including water sampling for environmental DNA (eDNA) analysis, an emerging and powerful tool for monitoring biodiversity in aquatic ecosystems. In this study, we utilized eDNA metabarcoding to investigate temporal and spatial trends in fish assemblages within urban coastal habitats between the Dee and Mersey estuaries (United Kingdom), historically one of the most anthropogenically impacted postindustrial coasts in the world. Over a 12-month period, we conducted nine water sampling trips at two locations: the Albert Docks in central Liverpool, and the Marine Lake in West Kirby. Illumina sequencing was used to analyze PCR amplicons generated using the fish-targeted Tele02-12S metabarcoding region. We found significant changes in fish community composition across the different months. Fish communities also significantly differed between the two sites, with the patterns of temporal changes varying substantially between them. Seasonal appearances/disappearances of specific taxa (e.g., European eel, sand smelt, flounder, and herring) shed light on important ecological and behavioral processes that may have management implications. Results also corroborate previous findings on the importance of “molecular bycatch” (nontarget sequences) in expanding our understanding of the anthropogenic influences on the natural environment. Overall, our findings emphasize the value of eDNA monitoring as a noninvasive, affordable, and sensitive approach for routine monitoring of temporal trends in fish assemblages, facilitating the stewardship of resilient urban coastal zones, and recognizing interventions that could increase biodiversity.

Understanding the dietary habits and trophic niches of species is crucial for the conservation and management of species and ecosystems. Science-based fisheries management requires large-scale data of prey and parasites of fish species that enables the analysis of multitrophic interactions in an ecosystem. Using one of the commercially exploited beaked redfish (Sebastes mentella) from the Barents Sea, our study aims to understand its diet composition and parasites. We used 12S and COI markers to analyze the stomach and intestine contents of uncleaned, water-cleaned, and bleach-cleaned fish samples to also trace how external contamination affects diet analysis of fishes. We detected 19 potential prey taxa each of vertebrates and invertebrates from the guts of beaked redfish. While invertebrates were the major food source of redfish, our analysis indicated only two taxa of vertebrates that significantly contributed to the diet composition. In addition, we also detected two jellyfish species which were among the dominant prey taxa. Several parasites that have been frequently reported from redfish by visual examination were also detected by metabarcoding of gut contents. As in metabarcoding studies in general, it is important to build the reference libraries of fish parasites to fully harness the power of molecular approaches in achieving multi-trophic interactions. We underscore that metabarcoding captures both the common prey as well as delicate taxa which may not be available for visual examinations such as jellyfishes or other cryptic taxa. Our study showcases the importance of gut metabarcoding in terms of simultaneous detection of diets and parasites.

Long-term biological monitoring and management depend on efficient protocols and methodology to characterize and precisely describe species distributions and diversity. In recent years, environmental DNA has progressively become a tool of choice in survey programs. However, the effect of variables such as sampling effort and sampling design still requires consideration. Simple random, grid, and transect-based sampling methods are widely used in ecological surveys to obtain an unbiased estimation of species richness and community structure. However, under certain conditions where spatial information is available, sampling design and sequencing depth can be optimized to reduce effort and cost. Here, we evaluate different subsampling approaches to identify sampling strategies that are both easily implemented in the field and provide optimal recovery of species diversity for a given sampling effort. With a homogeneous grid-based sampling (25–50 samples by lake) of 12 freshwater lakes in southeastern Québec, and using the 12S MiFish metabarcoding primer set, we demonstrate that random and stratified designs perform similarly to detect 90% and 95% of species. However, we found that, under certain circumstances, stratified sampling outperformed random sampling, requiring lower numbers of samples to detect the same species diversity. We also demonstrate that for the minimum sequence threshold and sample replication used in our study, a sequencing depth of 50K reads per sample is adequate to obtain a reliable portrayal of species richness. In this study, we contribute to the effort of eDNA sampling standardization by providing data for selecting the best sampling design, sequence depth, and sample size to detect 90%–95% of fish species found in temperate lakes.

Environmental DNA (eDNA) is a complex mixture of DNA, varying in particle sizes and distributed heterogeneously in aquatic systems. Optimizing eDNA sampling is crucial for maximizing species detection, particularly in high-risk scenarios like invasive species management. In this study, we compare two eDNA sampling methods - namely tow net and grab sample, where the tow nets process large volumes of water (3500–7000 L) through a 64 μm pore size and the grab samples process 1 L sample at a single point through 0.45–1.2 μm pore size membranes. We compared these methods to ascertain what most influences (1) the detection of invasive species (Dreissena mussels and Burmese pythons) using qPCR or ddPCR and (2) total diversity monitoring of metazoan, protist, and fungi community using a COI marker and plant communities using the ITS marker. Sampling was conducted across a wide geography and diverse aquatic environments in Minnesota and Florida, USA, and Switzerland. The tow net samples had significantly higher eDNA yield compared to grab samples; however, they exhibited equal or lower alpha diversity of OTUs (Operational Taxonomic Units). The two sampling methods measured different beta diversity of communities detected with the COI marker across all three regions, highlighting the impact of the sampling method on the diversity of eDNA captured. In comparison, the beta diversity of plant eDNA was less impacted by the sampling method. We found no clear difference in detection for the invasive species targets based on the eDNA sampling method. These results underscore the need for pilot studies before conducting biodiversity inventory and monitoring, and a need for a greater understanding of not just how much, but also what, eDNA is captured depending on method choice, considering both spatial and particle size heterogeneity.

Comprehensive assessments of coastal biodiversity in complex coral communities are crucial but challenging, particularly under unfavorable conditions such as poor underwater visibility in urbanized and eutrophic environments. Here we aim to examine the scope of underwater diversity detection and community shifts across habitat transitions spanning different geographic regions in Hong Kong SAR, a highly urbanized coastal city with limited underwater visibility of 3.93 ± 1.25 m during the sampling period. We employ and compare two methods: 12S rRNA eDNA metabarcoding coupled with custom built reference database and simultaneous extensive underwater visual census (UVC) surveys. eDNA detected a higher species richness per site. Yet, each survey method featured a distinct species profile with associated trophic guilds, where 98 (32.3%) species found exclusively by UVC and 120 (39.6%) species detected only by eDNA. eDNA featured species from diverse habitats and evolutionary distances, including cryptic and large mobile fishes, offering enhanced prediction on local ecosystem functions. eDNA also recorded 90 putative species that had never been recorded in additional seven yearlong UVC dataset, with seven prospective new occurrence records to the territorial waters. UVC on the other hand was more efficient in documenting reef-associated species. Both methods captured similar patterns of community spatial structure along the habitat transitions while only eDNA detected more large fish species in offshore compared to sheltered inshore environments, This may suggest inshore overfishing and incapability of UVC in surveying large mobile species in turbid environments. Considering the discrepancies between two methods, we highlight the importance of complementing both UVC and eDNA metabarcoding survey for a complete overview of local biodiversity under unfavored underwater conditions in an urbanized seascape.

The success of amplicon sequencing studies of environmental DNA (eDNA) depends on the choice of primer pairs used to select taxa-specific regions of DNA for amplification then sequencing to characterize sample composition. This paper presents practical methods to visualize the extent to which different primer pairs can differentiate taxonomic groups, enabling researchers to assess which primers might be best suited for a study or environment of interest. These methods can also be used to review taxonomic annotations in genomic reference sequence databases. We apply the concept of DNA barcoding gaps to metabarcoding of multiple species in environmental DNA to leverage reference data on the amplicon sequences of previously characterized specimens. Since reference data sets are large and complex, we provide a simple and intuitive method to navigate subsets of reference sequence data containing conflicting or ambiguous relationships between genomic information and taxonomic classification. We demonstrate how to use gap visualization and taxonomic segmentation in comparing how well different primer pairs discriminate species of interest, and in detecting anomalies in reference sequence annotation. We show how these visualization methods can enable amplicon survey study design and make fundamental molecular resources more accessible to a wider research audience beyond bioinformaticians and data scientists.

Estuaries are a key component of the land-sea continuum, and their microbial diversity depends on the connection with terrestrial ecosystems. This work aimed to demonstrate that the terrestrial matter carried by rivers influences the structuration of microeukaryote communities of superficial (0–3 cm) sediments collected at the interface between the land and marine coastal areas. To demonstrate this hypothesis, we have chosen the main island of New Caledonia as a study site, a French overseas territory located in the South West Pacific. Using amplicon sequencing of the 18S-V4 rDNA extracted from sediments, we analyzed microeukaryote community composition in relation to numerous environmental parameters. Samples were collected in five bays influenced by riverine inputs and corresponding to distinct geological features of the watersheds, as revealed by high variations in metal concentrations released from specific minerals in the sediment. Particularly, the influence of ultramafic soils was highlighted by higher nickel concentration (correlated to Co, Cr, Mn, and Fe). Diatoms were the dominant taxonomic group, especially the classes of Bacillariophyceae and Mediophyceae. Then Apicomplexa, Ciliophora, Dinoflagellata, and Cercozoa followed. The metallic composition of the sediment explained 18.46% of the community spatial variability. The selection of ASVs based on their contribution to beta diversity and their correlation with metallic concentrations enabled us to identify spatial patterns. This information could lead to identifying microeukaryote bioindicators of terrestrial influences, particularly of ultramafic origin. We hypothesized that the association between microeukaryotes and metallic compositions is linked to selection processes, given the resistance of some microeukaryotes to some high metallic concentrations. In vitro experiments are needed to confirm this hypothesis. Our results emphasized the role of terrestrial inputs in shaping estuarine diversity and the need to consider the entire land–sea continuum for studying these ecosystems.

Environmental DNA (eDNA) sampling is a powerful method for detecting aquatic species at low densities. However, eDNA may remain close to the source in lentic systems, decreasing the effectiveness of eDNA surveys. We conducted cage experiments with salamanders and simultaneous detailed hydrologic and wind measurements to investigate the influence of the physical environment on detection patterns of eDNA in ponds. We found much higher detection rates in the surface layer than at depth, and that aquatic vegetation reduced detection of eDNA produced in open water by 80%–94%. Within the surface mixed layer, detection rates were highest close to the source in the direction of water flow in the bottom half of the layer, and detections farthest from the source occurred when velocities in this sublayer were high. Detections were near zero even close to the source when this sublayer was flowing fast and away from the sampling point. The direction of water flow in this lower half of the surface mixed layer was negatively correlated with wind direction for most of the study. These spatial and temporal dynamics indicate that eDNA transport processes in ponds are highly complex. Sampling away from aquatic vegetation, in the surface mixed layer, and upwind of potential sources, in addition to sampling at many locations within a pond and considering temporal patterns, may improve detection of rare pond species. This work contributes to a growing body of literature characterizing the variability of eDNA detection in lentic systems.

Freshwater mussels are traditionally monitored by visual observations which is time-consuming and can be difficult depending on water conditions. Environmental DNA (eDNA) is an attractive alternative since it can detect a species in the water without visual observations. Furthermore, since the DNA can potentially travel downstream in the river systems, presence of a species can be detected even away from the population of mussels. In this paper, we evaluate and describe how dPCR (digital PCR) technique can be used to efficiently monitor four freshwater mussel species: the freshwater pearl mussel Margaritifera margaritifera from Margaritiferidae family and three species from Unionidae family: the depressed river mussel Pseudanodonta complanata, the painter's mussel Unio pictorum, and the thick shelled river mussel Unio crassus, which are all regarded endangered in many regions worldwide. dPCR assays for the four mussel species were developed and tested in silico before conducting field surveys. The verification step in the field was carried out in two Swedish rivers with confirmed populations of the freshwater pearl mussel (M. margaritifera). Furthermore, two other rivers with unknown presence of the endangered freshwater mussels were surveyed for occurrence of the four mussel species, using the capacity to multiplex several species simultaneously in a dPCR reaction. We furthermore showed that the target DNA concentrations probably depend on the season and water level, which may largely affect the detection probability and interpretation of the results in terms of population size.

Worldwide, freshwater vertebrate populations are declining with increasing pressure on rivers due to numerous environmental and climatic threats. Environmental DNA (eDNA) could potentially provide a more efficient and non-invasive mechanism to monitor freshwater systems, either as a complement or in replacement to traditional methods to accurately assess species' distributions. Here, we utilize a hierarchical multispecies N-mixture model to compare three fish sampling methods: traditional fyke netting and active and passive environmental DNA sampling along a 30 km stretch of the Canning River in Western Australia. We used the fitted model to compare capture probabilities among sampling methods and reveal the sampling effort required to describe the species assemblage. Results indicated that while all methods could detect fish, combined eDNA methodologies detected one more fish species than those caught by fyke netting. In addition, active eDNA sampling produced the highest capture probabilities and more consistently described the entire fish assemblage at any given site. Fyke netting and passive eDNA did not show significant differences in their average capture probabilities, and both methods had lower abilities to capture individual species than active eDNA. Active eDNA also required fewer replicate samples to detect the expected observed richness, and fyke netting required the most replicates. Additionally, a hierarchical multispecies abundance model showed that active environmental DNA (eDNA) sampling is the most effective method for monitoring freshwater fish populations. This study contributes to our understanding of eDNA in aquatic systems and demonstrates that, at least under current conditions, active sampling is still the preferred method in freshwater systems with low flow compared to both passive sampling and fyke netting.