Toward our first objective to ‘close the marine biodiversity and ecosystem knowledge gap’, we have generated, during the first 18 months of the project, arguably the most complete set of biological samples and contextual data across marine ecosystems and biomes to date. In May 2023, the TREC/Tara EUROPA expedition had holistically sampled marine waters, sediments, aerosols, and holobionts across >100 Land-Sea transects along the European coastline from Finland to Italy. >150 standard protocols were systematically applied to sample life, from viruses to animals, across biocomplexity scales (molecular, subcellular, to organismal and community) together with key contextual parameters including pollutants. This has generated >35,000 samples stored and registered at the EMBL Planetary Biology Biobank. Furthermore, 60 1m-sediment cores were collected at 12 sites along the way, covering time periods ranging from the early 20th century to the 18th century, and providing >10,000 samples for various chemical and paleoecological analyses including paleo-DNA sequencing. Data and biomass samples from weekly or bi-weekly ecosystem time series performed in Naples, Banyuls, Blanes, Azti, Roscoff and Plymouth over the last 2-3 decades, were assembled and partly re-sequenced for cross time-series comparisons. Marine waters and sediments across land-sea transects were also sampled along seasons in Roscoff and Naples, using TREC-compatible protocols, with 10 sampling campaigns achieved since April 2023. Finally, 80% of the planned samples from 15 keystone holobionts were collected across critical ecological dimensions of their habitats, including plankton, kelp forests, seagrasses, shallow and deep sea reefs.
To understand the drivers and mechanisms of marine biodiversity structure and dynamics, and determine which element of biodiversity are key for marine ecosystems functions and services, the first 18 months of the project were mainly spent on developing new theoretical models, assembling large-scale meta-datasets to develop statistical indicators and models to monitor and predict marine biodiversity changes, and building associated softwares. On the one hand, we have explored various novel ways of modeling marine biodiversity across levels of biological organization: (i) based on biological and physiological traits, (ii) integrating population drift, neutral heritable variation, and dispersal across the seascape, (iii) assembling comprehensive metabolic knowledge from metagenomes and metatranscriptomes, (iv) linking eco-evolutionary mechanisms of species interactions to ecosystem functions. On the other hand, we have compiled and completed large datasets - e.g. eDNA metabarcoding, fish-catch, phytoplankton microscopy, soundscapes, etc., together with environmental metadata - to build up statistical indicators and models of marine ecosystems status and health. Integrating across inclusive spatial, temporal, and/or organismal/biological dimensions, these data-driven models are used as new tools to quantify the impact of local (aquacultures, fisheries, invasive species) and global (natural versus anthropogenic climate and environmental changes) drivers on marine biodiversity and ecosystem functions.
