Fish communities in Baltic Sea coastal bays; using eDNA metabarcoding to assess vertical profile and traditional method comparison

Comparison of environmental DNA metabarcoding and bottom trawling for detecting seasonal fish communities and habitat preference in a highly disturbed estuary

Unraveling fish diversity and assembly patterns in a temperate river: Evidence from environmental DNA metabarcoding and morphological data

An environmental DNA (eDNA) metabarcoding approach has been widely used for biodiversity monitoring of fishes, although it has rarely been applied to tropical and subtropical aquatic ecosystems, where species diversity is remarkably high. This study examined the extent to which species richness can be estimated in a small coral reef lagoon (1,500 × 900 m) near Okinawa Island, southern Japan, where the surrounding waters are likely to harbor more than 1,500 species of fish. During 2015–2017, a total of 16 capture‐based surveys were conducted to create a faunal list of fish species, followed by eDNA metabarcoding based on seawater samples taken from 11 sites in the lagoon on a day in May 2019. We also tested whether eDNA metabarcoding could detect differences between adjacent fish communities inhabiting the offshore reef edge and shore‐side seagrass beds within the lagoon. A total of 217 fish species were confirmed by the capture‐based samplings, while 291 fish species were detected by eDNA metabarcoding, identifying a total of 410 species distributed across 119 families and 193 genera. Of these 410 species, only 96 (24% of the total) were commonly identified by both methods, indicating that capture‐based surveys failed to collect a number of species detected by eDNA metabarcoding. Interestingly, two different approaches to estimate species richness based on eDNA data yielded values close to the 410 species, including one that suggested an additional three or more eDNA surveys from 11 sites (36 samples) would detect 90% of the 410 species. In addition, nonmetric multidimensional scaling for fish assemblages clearly distinguished between the fish communities of the offshore reef edge and those of the shore‐side seagrass beds. This study demonstrates that an eDNA metabarcoding approach is useful for estimating species richness and detection of habitat segregation even in ecosystems with remarkably high species diversity.

New insights into biologic interpretation of bioinformatic pipelines for fish eDNA metabarcoding: A case study in Pearl River estuary

Fish diversity, an important indicator of the health of aquatic ecosystems, is declining sharply due to water pollution, overfishing, climate change, and species invasion. For protecting fish diversity, effective surveying and monitoring are prerequisites. In this study, eDNA (environmental DNA) metabarcoding and ground cages were used to survey the fish diversity of the Chaobai and Beiyun Rivers in Beijing. Based on the two methods, we identified 40 species, belonging to 35 genera, 18 families, and six orders. The richness of fish identified by eDNA metabarcoding was significantly higher than that captured by ground cages in both rivers. The fish captured by the ground cage method were all recognized by eDNA metabarcoding, except Squalidus wolterstorffi and Saurogobio dabryi, which were captured only in ground cages. The correlation of relative abundance between the two methods was affected by the properties of the rivers, such as the flow rate. Fish caught by ground cage in the Beiyun River were identified by eDNA, but not in the Chaobai River. Our results also suggest that the Chaobai River has higher fish diversity than the Beiyun River and different community assemblage. In addition to differences in the natural properties of the focal rivers, the development of urbanization is also an important contributor to different community structures overserved. eDNA metabarcoding as a new survey tool has great application prospects, it provides certain theoretical data and methodological references for the protection and management of river fish diversity.

Fish diversity plays a critical role in maintaining the balance of water ecosystems, especially in the Chongqing section of the National Nature Reserve for Rare and Endemic Fishes in the upper Yangtze River, which serves as an important habitat for rare and endemic fish, as well as an important channel for the replenishment of fishery resources in the Three Gorges Reservoir. Under a 10-year ban on fishing in the Yangtze River basin, we investigate fish diversity and seasonal variation in the Reserve by using environmental DNA (eDNA) metabarcoding. We found fishes belonging to 85 genera, 24 families, and 8 orders in the Reserve. A comparison of eDNA metabarcoding results with the diversity of a recent fish catch revealed that eDNA metabarcoding not only enables rapid and efficient fish monitoring but also has a high sensitivity. Furthermore, the study demonstrates that eDNA metabarcoding can be used as a tool for monitoring seasonal variations of fish composition in freshwater ecosystems. The alpha and beta diversity analysis both showed compositional differences in the fish community in accordance with seasonal variations. In addition, changes in eDNA relative sequence abundance and the detection of fish species at different sampling sites may reflect shifts in habitat use and distribution. Thus, we provide detailed seasonal data on fish diversity in the Chongqing section of the Reserve. This will contribute to conservation and to the understanding of fish diversity and community dynamics in the Chongqing section of the Reserve.

Surveys of fish diversity in complex heterogeneous environments are highly challenging to perform using traditional survey methods. Although environmental DNA (eDNA) metabarcoding has been effectively used to evaluate fish diversity, studies exploring the spatial and temporal variability of fish communities in mosaic habitats and their connection to water quality after ecological project implementation are still scarce. Here, we evaluated the changes in water quality and fish assembles using the traditional method and environmental DNA (eDNA) metabarcoding after Ecological water replenishment (EWR) and the links between fish communities and water quality were established in the Baiyangdian (BYD) ecosystem in the North China Plain. All water quality variables including TN, NH3-N, CODMn and TP showed a conspicuous improvement pattern, and the number of fish species increased notably after EWR. In addition, 6 more introduced fish species were recorded when compared with the historical data before the implementation of the EWR project. Furthermore, the species richness showed a highly significant difference among the four habitats in the summer 2020 and spring 2021 (spring: P = 0.000; summer: P = 0.002), and obvious discrimination of fish communities across two seasons was observed (P = 0.001) with eDNA metabarcoding. The water quality variables driving the changes of fish communities during the same period varied significantly across different habitats, while not all showed noticeable discrepancy in driving cross-seasonal fish community changes. Thus, our study highlights that the continuous EWR improves the water quality and fish richness but potential ecological issues associated with introduced species should be carefully considered after EWR. Our results also confirm that eDNA is a reliable tool for assessing fish diversity and distinguishing spatiotemporal variability of fish communities in mosaic habitat ecosystems.

Objective Environmental DNA (eDNA) metabarcoding has become an important method for inventorying and monitoring biota in aquatic systems. The Texas Parks and Wildlife Department conducts regular fishery-independent sampling of biotic communities using traditional sampling gears, such as gill nets and bag seines, in all of the major estuaries of adjacent to the Gulf of Mexico in Texas. Previous studies have shown that eDNA approaches can complement traditional sampling methods. Methods We compared fish community structure data in the Cedar Lakes estuary system obtained with traditional sampling gears with data obtained using eDNA sampling using a small sequence of mitochondrial 12S ribosomal RNA gene and a validated taxonomic reference file. Result For spring and fall of 2022, eDNA metabarcoding detected a larger number of species than either bag seines or gill nets. Species richness detected via eDNA in two seasons in a single year was comparable with the species richness of agency’s historical record based on traditional gears for Cedar Lakes. Conclusion Seasonal and spatial variation in species richness was similar between traditional and eDNA sampling; however, eDNA metabarcoding allowed detection of several species that would be difficult or impossible to capture with either bag seines or gill nets. We observed two limitations of eDNA metabarcoding. Read depth was not a good index of relative abundance, which limits our ability to infer relative biomass using single samples. Secondly, we observed detection bias in our eDNA results. Specifically, eDNA failed to detect two species of elasmobranchs present when water sampling was performed and eDNA also performed poorly compared to traditional sampling gears for some species of bony fishes. Despite these limitations, eDNA metabarcoding proved to be an efficient and cost-effective alternative and compliment to traditional fisheries sampling gears for fishery-independent monitoring of community structure and composition in estuaries of the Gulf of Mexico.

The use of environmental DNA (eDNA) metabarcoding to analyze fish species diversity across different aquatic ecosystems is well documented. Nonetheless, there is a gap in validating eDNA metabarcoding studies on the diversity and structure of fish communities in coastal ecosystems, particularly in comparing these findings with bottom trawl catch data. In this study, we employed eDNA metabarcoding to explore species composition and relative abundance in fish communities, taxonomic-level diversity variations, and the interplay between community structures and environmental factors in the Yellow Sea and compared these results with those obtained from bottom trawl catches. In addition, we compared the various methods used to estimate the distributions of taxonomic, phylogenetic, and functional diversity factors. We found that eDNA metabarcoding detected a greater number of species (86 vs. 41), genera (73 vs. 37), and families (42 vs. 25) than bottom trawl results at each sampling station. eDNA metabarcoding provided higher Shannon, Simpson, and Chao1 alpha diversity indices than the bottom trawl results. The PCoA results showed that eDNA metabarcoding samples could be more clearly separated at the sampling sites in the Zhuanghe (ZH) and Lianyungang (LYG) areas than bottom trawling samples. The RDA analysis indicated that temperature, along with NO3- and NH4+ concentrations, were pivotal in shaping the geographical patterns of fish communities, as identified through eDNA metabarcoding, echoing findings from bottom trawling studies. Furthermore, our findings suggest that eDNA barcoding surpasses bottom trawling in detecting taxonomic and phylogenetic diversity, as well as in uncovering greater functional diversity at the local level. Conclusively, eDNA metabarcoding emerges as a valuable complement to bottom trawling, offering a multifaceted approach to biodiversity monitoring that not only boosts efficiency but also reduces environmental impact on coastal ecosystems.

The sampling of environmental DNA (eDNA) coupled with cost-efficient and ever-advancing sequencing technology is propelling changes in biodiversity monitoring within aquatic ecosystems. Despite the increasing number of eDNA metabarcoding approaches, the ability to quantify species biomass and abundance in natural systems is still not fully understood. Previous studies have shown positive but sometimes weak correlations between abundance estimates from eDNA metabarcoding data and from conventional capture methods. As both methods have independent biases a lack of concordance is difficult to interpret. Here we tested whether read counts from eDNA metabarcoding provide accurate quantitative estimates of the absolute abundance of fish in holding ponds with known fish biomass and number of individuals. Environmental DNA samples were collected from two fishery ponds with high fish density and broad species diversity. In one pond, two different DNA capture strategies (on-site filtration with enclosed filters and three different preservation buffers versus lab filtration using open filters) were used to evaluate their performance in relation to fish community composition and biomass/abundance estimates. Fish species read counts were significantly correlated with both biomass and abundance, and this result, together with information on fish diversity, was repeatable when open or enclosed filters with different preservation buffers were used. This research demonstrates that eDNA metabarcoding provides accurate qualitative and quantitative information on fish communities in small ponds, and results are consistent between different methods of DNA capture. This method flexibility will be beneficial for future eDNA-based fish monitoring and their integration into fisheries management.

Environmental DNA (eDNA) integrated with metabarcoding is a promising and powerful tool for species composition and biodiversity assessment in aquatic ecosystems and is increasingly applied to evaluate fish diversity. To date, however, no standardized eDNA-based protocol has been established to monitor fish diversity. In this study, we investigated and compared two filtration methods and three DNA extraction methods using three filtration water volumes to determine a suitable approach for eDNA-based fish diversity monitoring in the Pearl River Estuary (PRE), a highly anthropogenically disturbed estuarine ecosystem. Compared to filtration-based precipitation, direct filtration was a more suitable method for eDNA metabarcoding in the PRE. The combined use of DNeasy Blood and Tissue Kit (BT) and traditional phenol/chloroform (PC) extraction produced higher DNA yields, amplicon sequence variants (ASVs), and Shannon diversity indices, and generated more homogeneous and consistent community composition among replicates. Compared to the other combined protocols, the PC and BT methods obtained better species detection, higher fish diversity, and greater consistency for the filtration water volumes of 1 000 and 2 000 mL, respectively. All eDNA metabarcoding protocols were more sensitive than bottom trawling in the PRE fish surveys and combining two techniques yielded greater taxonomic diversity. Furthermore, combining traditional methods with eDNA analysis enhanced accuracy. These results indicate that methodological decisions related to eDNA metabarcoding should be made with caution for fish community monitoring in estuarine ecosystems.

Environmental DNA (eDNA) integrated with metabarcoding is a promising and powerful tool for species composition and biodiversity assessment in aquatic ecosystems and is increasingly applied to evaluate fish diversity. To date, however, no standardized eDNA-based protocol has been established to monitor fish diversity. In this study, we investigated and compared two filtration methods and three DNA extraction methods using three filtration water volumes to determine a suitable approach for eDNA-based fish diversity monitoring in the Pearl River Estuary (PRE), a highly anthropogenically disturbed estuarine ecosystem. Compared to filtration-based precipitation, direct filtration was a more suitable method for eDNA metabarcoding in the PRE. The combined use of DNeasy Blood and Tissue Kit (BT) and traditional phenol/chloroform (PC) extraction produced higher DNA yields, amplicon sequence variants (ASVs), and Shannon diversity indices, and generated more homogeneous and consistent community composition among replicates. Compared to the other combined protocols, the PC and BT methods obtained better species detection, higher fish diversity, and greater consistency for the filtration water volumes of 1 000 and 2 000 mL, respectively. All eDNA metabarcoding protocols were more sensitive than bottom trawling in the PRE fish surveys and combining two techniques yielded greater taxonomic diversity. Furthermore, combining traditional methods with eDNA analysis enhanced accuracy. These results indicate that methodological decisions related to eDNA metabarcoding should be made with caution for fish community monitoring in estuarine ecosystems.

ABSTRACTEnvironmental DNA (eDNA) metabarcoding has been widely used in freshwater systems, contributing to the advancements in the monitoring of fish diversity and community species composition. Nevertheless, the accuracy and reliability of eDNA metabarcoding in assessing functional structures and revealing the mechanisms underlying fish community assembly remain unclear. In this study, we combined a traditional survey method (electrofishing) and eDNA metabarcoding to conduct fish stock monitoring in the upper reaches of the Huishui stream. We assessed taxonomic and functional structures, as well as community assembly mechanisms, during dry and wet seasons. The results revealed that, compared with electrofishing surveys, eDNA metabarcoding detected a greater number of species and higher functional richness in both seasons. Despite significant differences in fish taxonomic composition between the seasons, both eDNA and traditional methods indicated that environmental filtering dominated the process of fish community assembly in both dry and wet seasons. We showed that eDNA metabarcoding is comparable to the electrofishing method in monitoring the community composition of stream fish and can accurately and reliably determine fish community assembly mechanisms. Combining functional traits and eDNA is a robust approach for monitoring stream fish community compared to taxonomic uncertainty.

Environmental deoxyribonucleic acid (eDNA) metabarcoding offers advantages over physical capture for identifying and quantifying animals in monitoring programs. In this study, the fish community was sampled at three stations (inner, middle, and outer estuary) in three estuaries in August 2020, and four estuaries in June and August 2021 (Prince Edward Island, Canada) using both beach seining and eDNA metabarcoding. Two 12S primer sets, 12S-160 and 12S-248F, with different amplicon lengths, yielded similar results. eDNA metabarcoding consistently detected species captured by 186 co-located beach seines and revealed additional species. It also detected monthly (June–August), interannual (2020–2021), and spatial shifts in the fish community, distinguishing stations separated by as little as 0.4 km. Positive correlations existed between eDNA metabarcoding species reads and beach seining captures. These findings suggest eDNA metabarcoding complements physical capture methods for characterizing nearshore fish communities in Prince Edward Island’s estuaries. While eDNA techniques lack certain population parameter information provided by physical methods, such as size, sex, and age structure, they offer a more comprehensive diversity assessment and presence–abundance insights, especially in inaccessible environments.

The future of biodiversity monitoring and conservation utilizing environmental DNA