Coupling biogeochemical analysis, environmental DNA and ecological network analysis of sediment cores to reconstruct environmental history and ecosystem changes in Posidonia oceanica meadows.

Project Information

POSIDONIArXiv

Grant agreement ID: 101105307

DOI

10.3030/101105307

Project closed

EC signature date 24 April 2023

Start date 1 May 2024

End date 31 May 2026

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 181 152,96

Coordinated by

AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Spain

Periodic Reporting for period 1 - POSIDONIArXiv (Coupling biogeochemical analysis, environmental DNA and ecological network analysis of sediment cores to reconstruct environmental history and ecosystem changes in Posidonia oceanica meadows.)

Reporting period: 2024-05-01 to 2026-05-31

Summary of the context and overall objectives of the project

POSIDONIArXiV’s main objective was to generate new knowledge on how molecular approaches can be applied to monitor biodiversity in seagrass ecosystems through space and time. These ecosystems are the foundation of marine foodwebs and are vitally important for coastal communities worldwide, yet they are under threat from anthropogenic impact. Therefore, we need to develop novel methods to accurately monitor these ecosystems, both to determine present day biodiversity, but also how this has changed historically in response to human and environmental factors. This project explored the use of environmental DNA (eDNA) technologies to monitor seagrass associated biodiversity through space and time in the Balearic Islands, Spain. This project successfully completed nearly all of the objectives with only slight deviations to ensure the best possible results and based on learnings gathered during the project. The first objective was to assess whether surface sediment eDNA could be a viable source of biodiversity information in seagrass habitats comparing to traditional survey methods – visual surveys and sediment infauna. It was found that surface sediment eDNA successfully characterised seagrass associated biodiversity but that this should use as a complementary monitoring approach rather than standalone, as species detected in visual surveys were not captured in eDNA but eDNA detected far greater species than the other two methods. This is important for ongoing monitoring of seagrass ecosystems as this project had generated evidence that surface sediment eDNA can now be integrated as a standard monitoring tool. The second objective characterised historical biodiversity in seagrass ecosystems through the collection, subsampling and analysis of sediment cores. This objective is near completion and preliminary results show eDNA could be extracted from these historical sediment cores and multi trophic taxa detected. The geochemical data reveals a stable environment for the past millennia until recent anthropogenic impact in the past 200 years. This reveals seagrass habitats have been an integral part of the study site for thousands of years, reiterating the importance of protecting these habitats for the future. Further analysis will elucidate exactly how the marine community has changed over this time and this will enable objective 3 to be completed. This objective seeks to assess how ecosystem structure and function has changed over the study time period. This data will yield important insights into historical changes at the study sites but also showcase the utility of eDNA data. The impacts of this project are being explored through scientific publications, communications at workshops and conferences but also in the collaborations developed through secondments at the University of Copenhagen and the University of Zurich. In addition, the results of this work have been applied to inform additional projects that are using eDNA to monitor biodiversity in seagrasses both in Europe and Australia.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The main activities for this project was the field campaign to the study site in the Balearic Islands, Spain. Here, surface sediment samples were collected for eDNA analysis, sediment was also collected for the infauna analysis and visual surveys were conducted to assess the associated biodiversity and these were used in objective 1. Sediment cores were also collected on this trip for objectives 2 and 3. From here, the samples for objective 1 were extracted for DNA and sent for analysis. Then, the sediment cores were subsampled for eDNA and biogeochemical analyses. The latter involved carbon and lead210 dating, processing samples for organic and inorganic carbon and sediment grain size, as well as scanning one half of each core using XRF to obtain detailed mineralogical composition. This data was then modelled with the help of researchers form the host institution to obtain age-depth profiles and characterise the sediment composition. The eDNA samples from the sediment cores were then extracted and sent for analysis. To process all the eDNA data, a custom analysis was written in collaboration with researchers from the University of Copenhagen. Several workshops were run at the host institution (CEAB) to transfer this knowledge and teach the lab how to process and analyse eDNA data. In addition, a workshop was also held at the University of Copenhagen to discuss eDNA methods, particularly hybridisation capture as this was initially proposed to be used in the framework of POSIDONIArXiV. This resulted in a open access publication that describes a roadmap to using hybridisation capture on ancient eDNA samples, including when this should be used and what kind of information can be obtained. Within the framework of objective 1, the supervision of a masters student project occurred and led to publication nearly ready for submission. The results of this objective were also presented at the Ocean Sciences Meeting in Glasgow 2026. While the data for objective 2 is still being processed, so far the results are promising and the secondment stay at the University of Zurich enabled the exploration of this data and how it can be used in objective 3. In addition to the main objectives of POSIDONIArXiV, collaboration with researchers at the host institution has led to participation in three additional research publications related to seagrass ecology, and the co-supervision of masters students on related topics.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The results of POSIDONIArXiV support sediment eDNA as a biodiversity monitoring tool in seagrass ecosystems. These environments can be difficult to survey if water clarity is poor and hence this work has shown a viable method to document biodiversity, especially in cases where other approaches cannot be used. Furthermore, obtaining eDNA from historic sediments in seagrass ecosystems has not been achieved for marine organisms. As this work is the first of its kind, it shows it is possible to generate data on historical biodiversity in seagrass ecosystems. In addition, we were able to detect the influence of modern human impact, however, there is further analysis that needs to be done here to characterise how the marine community responded to this impact. The results of this work have demonstrated what is possible with eDNA, yet this needs to be tested in additional environments and ideally over extended timeframes than was able to be achieved in this project.