DNAqua-Net conference unites participants from around the world with the quest to standardize and implement DNA-based aquatic biomonitoring

The EU COST Action DNAqua- Net has since its start in 2016 gathered European researchers with the quest to standardize and implement DNA- based aquatic biomonitoring. On March 9– 11, 2021, their work culminated in their first conference. Here, an astounding 1500 participants from around the world gathered virtually to share their research on DNA- based aquatic biomonitoring encompassing DNA reference databases, field and laboratory protocols, data analyses and storage, implementation strategy and legal issues, and biotic indices and metrics. The overwhelming interest in DNA- based aquatic bioassessment and monitoring strongly underlines its relevance and timeliness.


| INTRODUC TI ON
We have all heard the saying "water is the giver of life." However, aquatic ecosystems are under pressure, and there is an urgent need to develop and implement methods to monitor their biodiversity. In recent years, DNA-based methods have proved to be a powerful tool to reveal the diversity of freshwater and marine ecosystems , and there has been growing interest in standardization and implementation to complement existing monitoring methods.
To this end, the EU COST Action DNAqua-Net was established in 2016. To disseminate the latest results in DNA-based aquatic biodiversity monitoring, DNAqua-Net held its first international conference, DNAQUA2021, on March 9-11, 2021. The 3-day conference was initially to be held in Evian, France -a place known for its mineral water spring, which would have befitted the theme of this conference. However, due to the COVID-19 pandemic, the conference was held virtually, allowing a large number of researchers and stakeholders from around the globe to participate.
The conference had five sessions on DNA-based aquatic biomonitoring with themes ranging from field and laboratory protocols to strategies for implementation, and participants from around the world had the opportunity to connect virtually to present and discuss their research with the ultimate aim of standardizing and implementing DNA-based aquatic biomonitoring.

| DNAqua-NE T
Just as the largest rivers begin as small streams, DNAqua-Net began as a small idea from a team centered around Professor Florian Leese, University of Duisburg-Essen, and Dr Agnès Bouchez, Research Director of the French National Institute for Agriculture. As others joined, the idea grew into an EU COST (European Cooperation in Science and Technology) Action (CA15219), and today, the DNAqua-Net stream has become a deep river of discovery and collaboration as researchers from all over Europe have joined to develop new genetic tools for the biomonitoring of aquatic ecosystems in Europe (Leese et al., 2016).
"As the managing team of DNAqua-Net, we could have hardly imagined the impact of DNAqua-Net back in 2015, when we wrote the proposal", says the DNAqua-Net managing team in Leese et al., (2021).
Since the formation of DNAqua-Net in 2016, the managing team has led the network of over 400 members from 49 countries to work toward the goal of establishing a gold standard means of molecular biodiversity assessment for European waters (Deiner, 2021). To achieve this, members of DNAqua-Net are working in close collaboration with stakeholders to develop a legally binding conceptual framework for the standardization of DNA-based tools used in assessments. The progress of DNAqua-Net has been extremely fruitful, with more than 100 publications since its inception. Going beyond scientific impact, DNAqua-Net is a platform for capacity building by training the next generation of researchers to continue this crucial work. It has also acted as a springboard for the launch of various applied studies (Leese et al., 2021). Most importantly, the establishment of a DNA and environmental DNA-based methods working group within the European Standardisation Organisation CEN (CEN/TC230/WG28) is a marked testament to the impact of DNAqua-Net. One can only hope that the success and achievements of DNAqua-Net will inspire the establishment of EU COST Actions within related areas, such as DNA-based biomonitoring of terrestrial arthropods and vertebrates, fostering equally inclusive, open, and dynamic networks, and importantly giving us all an opportunity to stand on each other's shoulders to strengthen our collective research and work toward common goals.
To celebrate the achievements of DNAqua-Net and the researchers who use DNA-based methods for assessing biodiversity, researchers and stakeholders came together in the first DNAqua-Net international conference for three days of remarkably interactive talks and insights. Following the conference, on March 12, 2021, DNAqua-Net members offered 13 stakeholder workshops for endusers and policymakers, bridging the gap from academic progress to application. This attracted over 900 participants from 15 European countries.

| THECONFEREN CE
The DNAQUA2021 conference offered an opportunity for scientists and stakeholders alike to get up to date with the latest re-

| HI G HLI G HTSFROMDNAqua2 021
The conference was kicked off by Agnès Bouchez and Florian Leese, who warmly welcomed the conference participants, gave a short presentation about the achievements of DNAqua-Net, and introduced the first two keynote speakers. Both keynote speakers presented their research regarding improvements in eDNA methods and touched upon the need for protocol standardization. The first keynote was by a member of DNAqua-Net, Assistant Professor Kristy Deiner, ETH Zurich (Switzerland), who presented an overview of eDNA, outlined key knowledge gaps, and shared her view on the future and the direction of the field (Deiner, 2021). The second keynote lecturer, Associate Professor Hideyuki Doi, University of Hyogo (Japan), presented a range of studies using different eDNA sources, such as water and sediment cores, to demonstrate methodological and fundamental advances for understanding the distribution and abundance of aquatic species (Doi, 2021). These two keynotes set a welcoming tone for the following sessions.
The first session of the conference was on DNA barcode refer- The second session, held on day two of the conference, concerned field and laboratory protocols and was chaired by Dr Kat Bruce, founder and Chief Technical Officer of NatureMetrics (UK), and Associate Professor Emre Eskin, Ankara University Agricultural Faculty (Turkey). Ultimately, the protocols used in field and laboratory work make or break our sequence data, and if not carried out properly, even the best bioinformatician would struggle to make sense of the data. Therefore, work toward standardization and implementation of DNA-based aquatic biomonitoring requires solid groundwork with respect to protocol development and validation.
The session was entitled "The search for one (or none) protocol to rule them all!", and the first of the two keynotes was given by gave an interesting talk on how predictive machine learning models can be used to assess river quality using molecular data derived from diatoms. Her work gives promising insights for the future of bioassessment in rivers, but critically noted that further studies would be required to test the accuracy of this approach on other taxa such as invertebrates (Feio, 2021). The following 17 talks and 51 posters highlighted how advances in high-throughput sequencing have presented new opportunities for biodiversity monitoring and the assessment of ecological status. Following the sessions, 13 prizes of 500 € were awarded to students and early-career researchers, 11 selected by expert reviewers and 2 selected by the audience. Hosting a virtual conference with a large number of participants runs the risk of technical disaster or long lonely days in front of the computer. Instead, the positive, dynamic, and inclusive atmosphere from the DNAqua-Net network carried over into the conference, everything ran without technical issues, and people from across the world shared their knowledge as a community. Thereby, the conference opened the door for synergy and collaboration between research groups. As the DNAqua-Net managing team says in the welcome statement in the abstract book:

| VIRTUALTAK E-HOMEME SSAG E S
"The implementation of (e)DNA-based methods into bioassessment and monitoring programs of our rivers, lakes, oceans and the groundwater, will be particularly successful if we sustainably stay connected across countries, generations, cultures and disciplines" (Leese et al., 2021).
Following the DNAQUA2021 conference, it became clear that the participants agreed: a community vote resulted in an overwhelming majority in favor of having another international conference in 2023. The broad support for maintaining this community is a testament to the significant methodological progress that has been made since the inception of DNAqua-Net, and it will be exciting to see the progress toward standardization and implementation of DNA-based aquatic biomonitoring at the next conference. With more biomonitoring experts now connected across Europe and beyond, the impact of the work contributed by everyone, no matter the research background, will be felt for years to come.  DNAqua-Net is the EU COST Action CA15219: Developing new genetic tools for bioassessment of aquatic ecosystems in Europe.

ACK N OWLED G EM ENTS
The DNAQUA2021 conference was organized by members of the DNAqua-Net, with the support of local and international committees and several sponsors.

CO N FLI C TO FI NTE R E S T
The authors of this meeting report are not part of DNAqua-Net.
Chair of DNAqua-Net Florian Leese and DNAqua-Net member and WP3 leader Kat Bruce have read and approved the meeting report.

AUTH O RCO NTR I B UTI O N S
KB led the work. All authors contributed to writing and editing.

DATAAVA I L A B I L I T YS TAT E M E N T
Data sharing is not applicable to this article as no new data were created or analyzed.