Biology subjects

Irisson, J.-O.

Publications and source records attributed to Irisson, J.-O..

3 recordsLinked to original sources

bioRxiv2024

Standardizing marine habitat modelling practices to enhance inter-comparability across biological observations

In recent years, the volume of accessible marine pelagic observations has increased exponentially and now incorporates a wealth of new data types, including information derived from metagenomics and quantitative imaging. This calls for standardized modelling protocol across taxonomically harmonized observations, to better predict biogeographic patterns in space and time, and thus investigate marine ecosystem structure and functioning on a macroecological scale. In this context, we introduce CEPHALOPOD (Comprehensive Ensemble Pipeline for Habitat modelling Across Large-scale Ocean Pelagic Observation Datasets), a standardized and flexible framework to perform multi-species marine habitat modelling across data types and data sources. We built this new framework on observational data from federating initiatives such as AtlantECO, OBIS, GBIF, associated with already existing statistical and machine learning methods that enable to extract and model information from heterogeneous, scarce, and biased field observations. Here, we first document our statistical ensemble modelling approach and then assess its strength and limitations with a virtual ecologist approach. We show how our framework performs in reproducing a range of distributions from biased field samples. Then, we illustrate its performance and comparability across data types by investigating the global diversity patterns of coccolithophores from both abundance and metagenomic data. Our modelling framework serves as a foundation for the consistent generation of Essential Biodiversity and Ocean Variables (EBVs and EOVs) and carries the potential to significantly advance our comprehension of biodiversity and marine ecosystems functioning. Finally, it provides an unprecedented opportunity to foster collaborations in the field of marine science, sustainable ecological practices, and, ultimately, contribute to the preservation of global marine biodiversity.

ecology↗

bioRxiv2024

Key link between iron and the size structure of three main mesoplanktonic groups (Crustaceans, Rhizarians, and colonial N2-fixers) in the Global Ocean.

In marine ecosystems, critical services like fish production, carbon export, or the delivery of nutrients through N2-fixation rely heavily on the size spectrum of pelagic organisms, particularly mesoplankton (200-20,000 {micro}m). However, how environmental factors shape mesoplankton spectral biogeography remains largely unresolved, as so far only limited datasets exist to understand the large-scale shifts in mesoplankton size. Using global compilations of Rhizarian, colonial N2-fixer, and Crustacean images, we reveal the paramount role of iron in shaping the size structure and related biogeography of these groups. Our findings underscore the importance of atmospheric sources of iron for N2-fixers and Rhizarians while total iron, accounting for organic and inorganic compounds, appeared to explain most of the variance in Crustacean size structure via apparent recycling. With a comprehensive set of explanatory variables, our models reached high R2 (0.93, 0.61, and 0.69 respectively), providing robust predictions of mesoplankton size structure related to elemental cycling and ecosystem services. Our results suggest that future increases in global temperatures will have negative effects on mesoplankton size, possibly limiting carbon export from the productive layers to sequestration depth, that can be offset by expected increases in iron inputs that benefit N2-fixers, Rhizarians, and eventually Crustaceans.

ecology↗

bioRxiv2023

Picoeukaryotic photosynthetic potential is functionally redundant but taxonomically structured at global scale

Primary production, performed by RUBISCO, and often associated with carbon concentration mechanisms, is of major importance in the oceans. Thanks to growing metagenomic resources (e.g., eukaryotic Metagenome-Assembled-Genomes; MAGs), we provide the first reproducible machine-learning-based framework to derive the potential biogeography of a given function, through the multi-output regression of the standardized number of reads of the associated genes on environmental climatologies. We use it to study the genomic potential of C4-photosynthesis of picoeukaryotes, a diverse and abundant group of marine unicellular photosynthetic organisms. We show that the genomic potential supporting C4-enzymes and RUBISCO exhibit strong functional redundancy and an important affinity towards tropical oligotrophic waters. This redundancy is then structured taxonomically by the dominance of Mamiellophyceae and Prymnesiophyceae in mid and high latitudes. Finally, unlike the genomic potential related to most C4-enzymes, the one of RUBISCO showed a clear pattern affinity for temperate waters.

ecology↗