Environmental DNA (eDNA) analysis from water samples is a promising new method to identify both targeted species and whole communities of aquatic organisms. However, the current literature regarding ...eDNA shedding rates primarily focuses on fish and most decay rate constants are reported for warm sunlit waters. Here, we conducted experiments to investigate how eDNA shedding differs between animal forms and how long eDNA can persist in waters of varying temperature and light conditions. We designed quantitative PCR assays for one fish (mummichog, Fundulus heteroclitus), one crustacean (grass shrimp, Palaemon spp.), and two scyphomedusae (moon jelly, Aurelia aurita and nettle, Chrysaora spp.) to estimate eDNA shedding and decay rates. We found that shedding rates were highly variable for all organisms, but grass shrimp had the lowest shedding rate. We quantified eDNA decay rate constants at 6, 15, and 23°C and found that decay rate constants of mummichog and grass shrimp were larger at higher temperatures, while those of scyphomedusae did not show clear temperature dependence. We also found that higher‐order decay models with tails fit the data better than first‐order log‐linear models, suggesting temporal variability in eDNA decay rates. Results indicate that different animal forms shed different types of eDNA, impacting both shedding and decay rates. These findings fill critical knowledge gaps regarding variation in eDNA shedding and decay across animal forms under a range of realistic marine temperature conditions. These data will be useful for interpreting field studies that utilize eDNA to investigate ocean habitats that are otherwise difficult to access.
We conducted mesocosm experiments using a fish, a crustacean, and two scyphomedusae to investigate how environmental DNA (eDNA) shedding differs between animal forms and how long eDNA can persist in waters of different temperature and light conditions. We found that shedding rates were highly variable for all organisms, but grass shrimp had the lowest eDNA shedding rate and that decay rate constants of mummichog and grass shrimp were larger at higher temperatures, while those of scyphomedusae did not show clear temperature dependence. These findings fill critical knowledge gaps regarding variation in shedding and decay of eDNA across different animal forms under a range of realistic marine temperature and light conditions.
Summary
Environmental DNA (eDNA) analysis for detecting the presence of aquatic and terrestrial organisms is an established method, and the eDNA concentration of a species can reflect its ...abundance/biomass at a site. However, attempts to estimate the abundance/biomass of aquatic species using eDNA concentrations in large stream and river ecosystems have received little attention.
We determined the eDNA concentration and abundance/biomass of a stream fish, Plecoglossus altivelis, by conducting a snorkelling survey in the Saba River, Japan. Furthermore, we evaluated the relationship between eDNA concentrations and the estimated abundance/biomass of P. altivelis, and determined its spatial distribution within the river.
Across the three seasons from spring to autumn, we found significant correlations between the eDNA concentration of P. altivelis and its abundance/biomass at study sites within the river. We detected the eDNA at the sites where we found only feeding traces on stones (where P. altivelis was not directly observed), but not at sites without feeding traces. Additionally, we tested the optimal number of qPCR replicates needed for the eDNA evaluation of P. altivelis abundance and biomass; only a small number of replicates was required when the eDNA concentration was high.
Our findings suggest that eDNA analysis is a useful tool to estimate fish abundance/biomass as well as their spatial distribution in rivers.
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•Filtration-based eDNA sampling has many drawbacks.•Passive eDNA samplers were tested in biodiverse natural waters.•The two sampling methods yielded comparable fish ...biodiversity.•Passive samplers were superior in capturing a rare species.•Passive eDNA samplers show strong potential for eDNA biomonitoring.
Environmental DNA (eDNA) technology has revolutionized biomonitoring, but challenges remain regarding water sample processing. The passive eDNA sampler (PEDS) represents a viable alternative to active, water filtration-based eDNA enrichment methods, but the effectiveness of PEDS for surveying biodiverse and complex natural water bodies is unknown. Here, we collected eDNA using filtration and glass fiber filter-based PEDS (submerged in water for 1 d) from 27 sites along the final reach of the Yangtze River and the coast of the Yellow Sea, followed by eDNA metabarcoding analysis of fish biodiversity and quantitative PCR (qPCR) for a critically endangered aquatic mammal, the Yangtze finless porpoise. We ultimately detected 98 fish species via eDNA metabarcoding. Both eDNA sampling methods captured comparable local species richness and revealed largely similar spatial variation in fish assemblages and community partitions between the river and sea sites. Notably, the Yangtze finless porpoise was detected only in the metabarcoding of eDNA collected by PEDS at five sites. Also, species-specific qPCR revealed that the PEDS captured porpoise eDNA at more sites (7 vs. 2), in greater quantities, and with a higher detection probability (0.803 vs. 0.407) than did filtration. Our results demonstrate the capacity of PEDS for surveying fish biodiversity, and support that continuous eDNA collection by PEDS can be more effective than instantaneous water sampling at capturing low abundance and ephemeral species in natural waters. Thus, the PEDS approach can facilitate more efficient and convenient eDNA-based biodiversity surveillance and rare species detection.
•Environmental DNA (eDNA) can be obtained from ancient and modern environments.•Coupled to DNA metabarcoding, eDNA is a powerful means of biodiversity monitoring.•eDNA has short degradation time in ...contemporary ecosystems.•We review main findings of eDNA studies and discuss limitations and perspectives.•We focus specifically on eDNA for biodiversity monitoring and conservation.
The continuous decline in Earth’s biodiversity represents a major crisis and challenge for the 21st century, and there is international political agreement to slow down or halt this decline. The challenge is in large part impeded by the lack of knowledge on the state and distribution of biodiversity – especially since the majority of species on Earth are un-described by science. All conservation efforts to save biodiversity essentially depend on the monitoring of species and populations to obtain reliable distribution patterns and population size estimates. Such monitoring has traditionally relied on physical identification of species by visual surveys and counting of individuals. However, traditional monitoring techniques remain problematic due to difficulties associated with correct identification of cryptic species or juvenile life stages, a continuous decline in taxonomic expertise, non-standardized sampling, and the invasive nature of some survey techniques. Hence, there is urgent need for alternative and efficient techniques for large-scale biodiversity monitoring. Environmental DNA (eDNA) – defined here as: genetic material obtained directly from environmental samples (soil, sediment, water, etc.) without any obvious signs of biological source material – is an efficient, non-invasive and easy-to-standardize sampling approach. Coupled with sensitive, cost-efficient and ever-advancing DNA sequencing technology, it may be an appropriate candidate for the challenge of biodiversity monitoring. Environmental DNA has been obtained from ancient as well as modern samples and encompasses single species detection to analyses of ecosystems. The research on eDNA initiated in microbiology, recognizing that culture-based methods grossly misrepresent the microbial diversity in nature. Subsequently, as a method to assess the diversity of macro-organismal communities, eDNA was first analyzed in sediments, revealing DNA from extinct and extant animals and plants, but has since been obtained from various terrestrial and aquatic environmental samples. Results from eDNA approaches have provided valuable insights to the study of ancient environments and proven useful for monitoring contemporary biodiversity in terrestrial and aquatic ecosystems. In the future, we expect the eDNA-based approaches to move from single-marker analyses of species or communities to meta-genomic surveys of entire ecosystems to predict spatial and temporal biodiversity patterns. Such advances have applications for a range of biological, geological and environmental sciences. Here we review the achievements gained through analyses of eDNA from macro-organisms in a conservation context, and discuss its potential advantages and limitations for biodiversity monitoring.
Biofilm formation is important for establishing plants-microbe associations. The role of calcium on biofilm formation has been studied in many bacteria except rhizobia. In this study, we investigated ...the role of calcium for biofilm formation in
Azorhizobium caulindans
, which forms nodules in the stem and root of its host plant
Sesbania rostrata
. We found that calcium is essential for
A. caulindans
biofilm formation, in addition to the presence of extracellular matrix components, eDNA and proteins. Also, calcium-mediated biofilm formation was tested with chemotaxis, motility, cyclic di-GMP synthesis, and quorum sensing mutants. Finally, calcium was found to promote
S. rostrata
root colonization of
A. caulinodans
. In total, these results show that calcium is essential for
A. caulindans
biofilm formation, and it affects the interaction between
A. caulinodans
and host plant.
Abstract
Environmental DNA (eDNA) technology potentially improves the monitoring of marine fish populations. Realizing this promise awaits better understanding of how eDNA relates to fish presence ...and abundance. Here, we evaluate performance by comparing bottom trawl catches to eDNA from concurrent water samples. In conjunction with New Jersey Ocean Trawl Survey, 1-l water samples were collected at surface and depth prior to tows at about one-fourth of Survey sites in January, June, August, and November 2019. eDNA fish diversity from 1 l was same as or higher than trawl fish diversity from 66 M litres swept by one tow. Most (70–87%) species detected by trawl in a given month were also detected by eDNA, and vice versa, including nearly all (92–100%) abundant species. Trawl and eDNA peak seasonal abundance agreed for ∼70% of fish species. In log-scale comparisons by month, eDNA species reads correlated with species biomass, and more strongly with an allometric index calculated from biomass. In this 1-year study, eDNA reporting largely concorded with monthly trawl estimates of marine fish species richness, composition, seasonality, and relative abundance. Piggybacking eDNA onto an existing survey provided a relatively low-cost approach to better understand eDNA for marine fish stock assessment.
Environmental DNA (eDNA) approaches contributing to species identifications are quickly becoming the new norm in biomonitoring and ecosystem assessments. Yet, information such as age and health state ...of the population, which is vital to species biomonitoring, has not been accessible from eDNA. DNA methylation has the potential to provide such information on the state of a population. Here, we measured the methylation of eDNA along with tissue DNA (tDNA) of Lymnaea stagnalis at four life stages. We demonstrate that eDNA methylation varies with age and allows distinguishing among age classes. Moreover, eDNA was globally hypermethylated in comparison to tDNA. This difference was age‐specific and connected to a limited number of eDNA sites. This differential methylation pattern suggests that eDNA release with age is partially regulated through DNA methylation. Our findings help to understand mechanisms involved in eDNA release and shows the potential of eDNA methylation analysis to assess age classes. Such age class assessments will encourage future eDNA studies to assess fundamental processes of population dynamics and functioning in ecology, biodiversity conservation and impact assessments.
Environmental DNA sampling (eDNA) has emerged as a powerful tool for detecting aquatic animals. Previous research suggests that eDNA methods are substantially more sensitive than traditional ...sampling. However, the factors influencing eDNA detection and the resulting sampling costs are still not well understood. Here we use multiple experiments to derive independent estimates of eDNA production rates and downstream persistence from brook trout (Salvelinus fontinalis) in streams. We use these estimates to parameterize models comparing the false negative detection rates of eDNA sampling and traditional backpack electrofishing. We find that using the protocols in this study eDNA had reasonable detection probabilities at extremely low animal densities (e.g., probability of detection 0.18 at densities of one fish per stream kilometer) and very high detection probabilities at population-level densities (e.g., probability of detection >0.99 at densities of ≥3 fish per 100m). This is substantially more sensitive than traditional electrofishing for determining the presence of brook trout and may translate into important cost savings when animals are rare. Our findings are consistent with a growing body of literature showing that eDNA sampling is a powerful tool for the detection of aquatic species, particularly those that are rare and difficult to sample using traditional methods.
•We used multiple experiments and an observational field study to estimate eDNA production rates and its downstream persistence from brook trout in streams•We used our empirical data in models to estimate false negative probabilities for eDNA when animals are rare, and compare these with traditional sampling•We found that eDNA was substantially more sensitive than traditional electrofishing for detecting rare brook trout
The assessment of fish stocks is often dependent on scientific trawl fisheries surveys, which are both invasive and costly. The analysis of environmental DNA (eDNA) from water samples is regarded as ...a non-invasive and cost-effective alternative, but meaningful performance evaluations are required for a wider application. The goal of this study was to comparatively analyze a newly developed, more sensitive real-time PCR based eDNA approach with bottom trawl fisheries catches to locally detect and quantify Atlantic cod (
Gadus morhua)
in the North and Baltic Seas. With a species-specificity of the qPCR assay of 100%, a minimal limit of 15 Cytochrome b eDNA copies was determined for the detection of cod. In addition, a Gaussian processing regression proved a significant correlation (95%) between eDNA (copies per L of water) and cod biomass (CPUE/Ha) found by bottom trawling. The results presented here prove the potential of eDNA analyses for quantitative assessments of commercial fish stocks in the open ocean, although additional comparative analyses are needed to demonstrate its performance under different oceanographic conditions.
Environmental DNA (eDNA) detection has emerged as a powerful tool for monitoring aquatic organisms, but much remains unknown about the dynamics of aquatic eDNA over a range of environmental ...conditions. DNA concentrations in streams and rivers will depend not only on the equilibrium between DNA entering the water and DNA leaving the system through degradation, but also on downstream transport. To improve understanding of the dynamics of eDNA concentration in lotic systems, we introduced caged trout into two fishless headwater streams and took eDNA samples at evenly spaced downstream intervals. This was repeated 18 times from mid‐summer through autumn, over flows ranging from approximately 1–96 L/s. We used quantitative PCR to relate DNA copy number to distance from source. We found that regardless of flow, there were detectable levels of DNA at 239.5 m. The main effect of flow on eDNA counts was in opposite directions in the two streams. At the lowest flows, eDNA counts were highest close to the source and quickly trailed off over distance. At the highest flows, DNA counts were relatively low both near and far from the source. Biomass was positively related to eDNA copy number in both streams. A combination of cell settling, turbulence and dilution effects is probably responsible for our observations. Additionally, during high leaf deposition periods, the presence of inhibitors resulted in no amplification for high copy number samples in the absence of an inhibition‐releasing strategy, demonstrating the necessity to carefully consider inhibition in eDNA analysis.
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