Key Expoitable Results (KERs)

Life history traits influence marine species dispersal and habitat colonization. Medusozoans (jellyfish and siphonophores) exhibit diverse life cycles, evolved from an ancestral cycle alternating between a benthic polyp and a pelagic medusa. Despite their ecological importance, factors shaping medusozoan distribution remain poorly understood. By integrating metabarcoding and environmental data from the Tara Oceans expedition with life history traits, we provide global evidence supporting the longstanding hypothesis that benthic polyp presence/absence is a key factor influencing the distribution and abundance of planktonic medusozoans in the surface ocean. We inferred on a time-calibrated phylogeny of Medusozoa multiple transitions to a fully planktonic (holoplanktonic) life cycle, either through polyp loss, acquisition of drifting polyps, or development of polyps parasitizing pelagic organisms. We could associate each transition with a shift toward offshore habitats and the emergence of globally dominant Operational Taxonomic Units (OTUs), whose abundance far exceeds that of any nonholoplanktonic medusozoans in the planktonic realm. The prevalence of holoplanktonic medusozoans in terms of abundance and diversity is broadly observed in coastal and offshore environments, peaking over greater bathymetric depths in tropical and subtropical regions. We show that holoplanktonic and nonholoplanktonic groups interact with distinct yet compositionally similar planktonic communities. Holoplanktonic OTUs occupy more peripheral positions in a plankton interactome, suggesting greater flexibility in biotic interactions, an adaptive trait in rapidly changing planktonic ecosystems. These findings highlight how life cycle evolution shaped the global distribution of medusozoans and suggest that variations in life history may significantly influence how medusozoans respond to global environmental changes.

Spatial synchrony, the tendency for temporal fluctuations in an ecological variable to be positively associated in different locations, is a widespread and important phenomenon in ecology. Understanding of the nature and mechanisms of synchrony, and how synchrony is changing, has developed rapidly over the past two decades. Many recent developments have taken place through the study of long-term datasets. Here, we review and synthesize some important recent advances in spatial synchrony, with a focus on how long-term data have facilitated new understanding. Longer time series do not just facilitate better testing of existing ideas or more precise statistical results; more importantly, they also frequently make possible the expansion of conceptual paradigms. We discuss several such advances in our understanding of synchrony, how long-term data led to these advances, and how future studies can continue to improve the state of knowledge.

This work combines ecological and macroeconomic approaches to assess the economic costs of climate change impacts on Net Primary Production in the Atlantic Ocean by 2050. The novelty of this study lies in introducing ecological limits in the fishery sector of the Computable General Equilibrium model used for macroeconomic assessment. To control socio-economic and climate uncertainties, we include projections from three CMIP6 climate models under two Shared Socioeconomic Pathways. Our results suggest a substantial economic loss by 2050 in Western African regions higher than 1% of Gross Domestic Product in most of the scenarios. This is the consequence of the impact on Net Primary Production and the strong increase in global fishery prices, which will affect the future economic structure. Economic losses and increases in fish prices are strongly amplified when biophysical constraints on fishery expansion are introduced in the macroeconomic model.

Non-cyanobacteria diazotrophs (NCDs) are shown to dominate in surface waters shifting the long-held paradigm of cyanobacteria dominance. This raises fundamental questions on how these putative heterotrophic bacteria thrive in sunlit oceans. The absence of laboratory cultures of these bacteria significantly limits our ability to understand their behavior in natural environments and, consequently, their contribution to the marine nitrogen cycle. Here, via a multidisciplinary approach, we identify the presence of NCDs within the phycosphere of the model diatom Phaeodactylum tricornutum (Pt), which sustain the survival of Pt in nitrogen-depleted conditions. Through bacterial metacommunity sequencing and genome assembly, we identify multiple NCDs belonging to the Rhizobiales order, including Bradyrhizobium, Mesorhizobium, Georhizobium, and Methylobacterium. We demonstrate the nitrogen-fixing ability of PtNCDs through in silico identification of nitrogen fixation genes and by other experimental assays. We show the wide occurrence of this type of interactions with the isolation of NCDs from other microalgae, their identification in the environment, and their predicted associations with photosynthetic microalgae. Our study underscores the importance of microalgae interactions with NCDs to support nitrogen fixation. This work provides a unique model Pt-NCDs to study the ecology of this interaction, advancing our understanding of the key drivers of global marine nitrogen fixation.

Microbial communities are essential to marine ecosystem functioning, yet much of their metabolic potential remains hidden within unassigned sequence space, the ocean’s functional dark matter. Analyzing 1,379 sunlit-ocean metagenomes, we developed a protein-centric framework that clusters 147 million predicted proteins into Operational Protein Units (OPUs), sequence-based groups encompassing both known and uncharacterized proteins. This approach captures the full breadth of microbial functional diversity, extending beyond genome- or pathway-centric views. Using machine learning on OPU profiles, we identified ten Ocean Microbiome Signatures (OMSs), functional groups that represent dominant metabolic strategies of marine microbial communities. Each OMS displays distinct spatial patterns, taxonomic composition, and functional repertoires. By integrating functional dark matter into ecosystem-level analyses, this protein-centric framework expands current models of the ocean microbiome. It uncovers fundamental principles linking protein repertoires to environmental structure, revealing how conserved ecological strategies underpin the potential metabolic architecture of the global ocean.