The genomic revolution has fundamentally changed how we survey biodiversity on earth. High-throughput sequencing ("HTS") platforms now enable the rapid sequencing of DNA from diverse kinds of environmental samples (termed "environmental DNA" or "eDNA"). Coupling HTS with our ability to associate sequences from eDNA with a taxonomic name is called "eDNA metabarcoding" and offers a powerful molecular tool capable of noninvasively surveying species richness from many ecosystems. Here, we review the use of eDNA metabarcoding for surveying animal and plant richness, and the challenges in using eDNA approaches to estimate relative abundance. We highlight eDNA applications in freshwater, marine and terrestrial environments, and in this broad context, we distill what is known about the ability of different eDNA sample types to approximate richness in space and across time. We provide guiding questions for study design and discuss the eDNA metabarcoding workflow with a focus on primers and library preparation methods. We additionally discuss important criteria for consideration of bioinformatic filtering of data sets, with recommendations for increasing transparency. Finally, looking to the future, we discuss emerging applications of eDNA metabarcoding in ecology, conservation, invasion biology, biomonitoring, and how eDNA metabarcoding can empower citizen science and biodiversity education.

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Environmental DNA metabarcoding: transforming how we survey animal and plant communities

Mitochondrial genome (mitogenome) plays important roles in evolutionary and ecological studies. It becomes routine to utilize multiple genes on mitogenome or the entire mitogenomes to investigate phylogeny and biodiversity of focal groups with the onset of High Throughput Sequencing (HTS) technologies. We developed a mitogenome toolkit MitoZ, consisting of independent modules of de novo assembly, findMitoScaf (find Mitochondrial Scaffolds), annotation and visualization, that can generate mitogenome assembly together with annotation and visualization results from HTS raw reads. We evaluated its performance using a total of 50 samples of which mitogenomes are publicly available. The results showed that MitoZ can recover more full-length mitogenomes with higher accuracy compared to the other available mitogenome assemblers. Overall, MitoZ provides a one-click solution to construct the annotated mitogenome from HTS raw data and will facilitate large scale ecological and evolutionary studies. MitoZ is free open source software distributed under GPLv3 license and available at https://github.com/linzhi2013/MitoZ.

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MitoZ: a toolkit for animal mitochondrial genome assembly, annotation and visualization.

https://scholarworks.utrgv.edu/cgi/viewcontent.cgi?article=1077&context=eems_fac

Past, present, and future perspectives of environmental DNA (eDNA) metabarcoding: A systematic review in methods, monitoring, and applications of global eDNA

Environmental DNA (eDNA) metabarcoding has emerged as a potentially powerful tool to assess aquatic community structures. However, the method has hitherto lacked field tests that evaluate its effectiveness and practical properties as a biodiversity monitoring tool. Here, we evaluated the ability of eDNA metabarcoding to reveal fish community structures in species-rich coastal waters. High-performance fish-universal primers and systematic spatial water sampling at 47 stations covering ~11 km2 revealed the fish community structure at a species resolution. The eDNA metabarcoding based on a 6-h collection of water samples detected 128 fish species, of which 62.5% (40 species) were also observed by underwater visual censuses conducted over a 14-year period. This method also detected other local fishes (≥23 species) that were not observed by the visual censuses. These eDNA metabarcoding features will enhance marine ecosystem-related research, and the method will potentially become a standard tool for surveying fish communities.

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Environmental DNA metabarcoding reveals local fish communities in a species-rich coastal sea

The future of biotic indices in the ecogenomic era: Integrating (e)DNA metabarcoding in biological assessment of aquatic ecosystems

Comparison of environmental DNA metabarcoding and conventional fish survey methods in a river system

Drinking water assessments use a variety of microbial, physical, and chemical indicators to evaluate water treatment efficiency and product water quality. However, these indicators do not allow the complex biological communities, which can adversely impact the performance of drinking water distribution systems (DWDSs), to be characterized. Entire bacterial communities can be studied quickly and inexpensively using targeted metagenomic amplicon sequencing. Here, amplicon sequencing of the 16S rRNA gene region was performed alongside traditional water quality measures to assess the health, quality, and efficiency of two distinct, full-scale DWDSs: (i) a linear DWDS supplied with unfiltered water subjected to basic disinfection before distribution and (ii) a complex, branching DWDS treated by a four-stage water treatment plant (WTP) prior to disinfection and distribution. In both DWDSs bacterial communities differed significantly after disinfection, demonstrating the effectiveness of both treatment regimes. However, bacterial repopulation occurred further along in the DWDSs, and some end-user samples were more similar to the source water than to the postdisinfection water. Three sample locations appeared to be nitrified, displaying elevated nitrate levels and decreased ammonia levels, and nitrifying bacterial species, such as Nitrospira, were detected. Burkholderiales were abundant in samples containing large amounts of monochloramine, indicating resistance to disinfection. Genera known to contain pathogenic and fecal-associated species were also identified in several locations. From this study, we conclude that metagenomic amplicon sequencing is an informative method to support current compliance-based methods and can be used to reveal bacterial community interactions with the chemical and physical properties of DWDSs.

Using Amplicon Sequencing To Characterize and Monitor Bacterial Diversity in Drinking Water Distribution Systems.

Biological surveys are needed to monitor and assess the health of ecosystems and the species within them. However, morphology-based biodiversity surveys can be invasive, time consuming and financially expensive. Recently, environmental (e)DNA sequencing has been demonstrated as a potential alternative to morphological-based surveys because it enables the rapid and inexpensive detection of multiple taxa from DNA present in the environment. Numerous studies have shown that eDNA-based biodiversity surveys can provide considerable information about aquatic ecosystem function and health. Therefore, this molecular method has the potential to improve how current aquatic biological surveys are conducted. Currently, most eDNA literature is aimed at an audience with a moderate to advanced knowledge of DNA sequencing, creating a barrier for many ecologists who lack DNA sequencing expertise but wish to apply such methods to their research. The aim of this review is to provide guidance to non-geneticists regarding sequencing eDNA for aquatic biodiversity surveys and to highlight the requirements that need to be considered before the technique can be effectively incorporated into biomonitoring programs. Specifically, we provide details and recommendations on some of the major principles, from sample collection to bioinformatic analyses. For those areas where specific recommendations cannot be given, we have provided references to suitable literature.

Using environmental (e)DNA sequencing for aquatic biodiversity surveys: a beginner’s guide

Assessing the impact of water treatment on bacterial biofilms in drinking water distribution systems using high-throughput DNA sequencing

Microalgal bloom events can cause major ecosystem disturbances, devastate local marine economies, and endanger public health. Therefore, detecting and monitoring harmful microalgal taxa is essential to ensure effective risk management in waterways used for fisheries, aquaculture, recreational activity, and shipping. To fully understand the current status and future direction of algal bloom distributions, we need to know how populations and ecosystems have changed over time. This baseline knowledge is critical for predicting ecosystem responses to future anthropogenic change and will assist in the future management of coastal ecosystems. We explore a NGS metabarcoding approach to rapidly identify potentially harmful microalgal taxa in 63 historic and modern Australian marine port and ballast tank sediment samples. The results provide a record of past microalgal distribution and important baseline data that can be used to assess the efficacy of shipping guidelines, nutrient pollution mitigation, and predict the impact of climate change. Critically, eDNA surveys of archived sediments were able to detect harmful algal taxa that do not produce microscopic fossils, such as Chattonella, Heterosigma, Karlodinium, and Noctiluca. Our data suggest a potential increase in Australian harmful microalgal taxa over the past 30 years, and confirm ship ballast tanks as key dispersal vectors. These molecular mapping tools will assist in the creation of policies aimed at reducing the global increase and spread of harmful algal taxa and help prevent economic and public‐health problems caused by harmful algal blooms.

Jennifer L. A. Shaw

Papers

Comparison of environmental DNA metabarcoding and conventional fish survey methods in a river system

Using Amplicon Sequencing To Characterize and Monitor Bacterial Diversity in Drinking Water Distribution Systems.

Using environmental (e)DNA sequencing for aquatic biodiversity surveys: a beginner’s guide

Assessing the impact of water treatment on bacterial biofilms in drinking water distribution systems using high-throughput DNA sequencing

Retrospective eDNA assessment of potentially harmful algae in historical ship ballast tank and marine port sediments.