Biology subjects

Gehlen, M.

Publications and source records attributed to Gehlen, M..

4 recordsLinked to original sources

bioRxiv2026

Salinity exposure in early-life drives genomic adaptation to climate change in Antarctic toothfish (Dissostichus mawsoni)

Antarctic marine ecosystems are undergoing rapid physical change, yet the capacity of long-lived polar fishes to adapt genomically remains poorly understood. Antarctic toothfish (Dissostichus mawsoni) are an exploited top fish predator whose early life stages develop beneath the sea-ice edge, where salinity, temperature and circulation are being reshaped by climate change. Using whole-genome resequencing data, we investigated how environmental exposure, particularly during early life, structures patterns of local adaptation in D. mawsoni. We analysed 2.4 million unlinked SNPs from 24 adults sampled across the circumpolar distribution of D mawsoni, and compared variability in putatively-adaptive loci with variation in environmental parameters from the ORAS5 global ocean reanalysis, including salinity, temperature, mixed-layer depth, sea-ice concentration and thickness, and surface currents. To capture uncertainty in ontogenetic exposure, we constructed three environmental scenarios differing in their spatial and temporal representation of conditions: Point of Capture-Time of Capture (POC-C), Spawning Ground-Time of Birth (SG-B), and Point of Capture-Time of Birth (POC-B). Genotype-environment association (GEA) was performed using redundancy analysis conditioned on fishing pressure and latent-factor mixed models, with high-confidence GEA loci being defined as SNPs jointly detected by both approaches and robust to random-predictor tests. The scenario that best explained genomic variation was SG-B, in which environmental variables were averaged over hypothesised spawning grounds during the egg incubation period of D. mawsoni (August - October). Within this scenario, the significant environmental axis, dominated by salinity, was strongly associated with 854 high-confidence GEA loci. Functional enrichment revealed over-representation of gene ontology terms linked to monoatomic ion transport, ion channel complexes and calcium signalling, consistent with salinity-driven selection on osmoregulatory pathways during early development. Our results provide genomic evidence that early-life salinity exposure is a key driver of local adaptation in D. mawsoni, underscore the importance of correctly representing life-stage-specific environments in climate genomics, and highlight a concrete pathway by which climate-induced freshening and sea-ice change may alter recruitment and stock resilience.

ecology↗

bioRxiv2022

Changes in functional composition and gene expression in eukaryotic plankton at the Atlantic-Arctic Polar front

In the Arctic Ocean, phytoplankton communities, dominated by eukaryotes, sustain the marine food web and influence biogeochemical cycles. While many are endemic, some are transported by currents from the Atlantic Ocean along an environmental gradient that steepens at the polar front. Despite these distinct biogeographies, the functional characteristics of these communities remain poorly characterized. Here, we analyzed twenty metatranscriptomes from a North Atlantic-Arctic environmental gradient considering ocean currents transport times. Functions related to the regulation of gene expression and cold acclimation were more abundant in Arctic metatranscriptomes. Using the PHATE dimensionality reduction algorithm, reconstructed transcriptomes of Bacillariophyta, Mamiellales, Pelagophyceae, and Phaeocystales revealed different gene expression patterns, including photosynthesis regulation. All groups showed upregulation of numerous key temperature-associated functions and a subset of shared functions, supporting a convergence in transcriptomic changes under polar conditions. This study, based on a new resource of reconstructed transcriptomes, addressed the functional differentiation of eukaryotic phytoplankton across the North Atlantic and Arctic Ocean. It evidenced both differential and convergent changes in gene expression across the polar front in widespread phytoplankton types. These results advance our understanding of the functional dynamics of phytoplankton along environmental gradients.

genomics↗

bioRxiv2021

Insights into biotic and abiotic modulation of ocean mesopelagic communities

For decades, marine plankton have been investigated for their capacity to modulate biogeochemical cycles and provide fishery resources. Between the sunlit (epipelagic) layer and the deep dark waters, lies a vast and heterogeneous part of the ocean: the mesopelagic zone. How plankton composition is shaped by environment has been well-explored in the epipelagic but much less in the mesopelagic ocean. Here, we conducted comparative analyses of trans-kingdom community assemblages thriving in the mesopelagic oxygen minimum zone (OMZ), mesopelagic oxic, and their epipelagic counterparts. We identified nine distinct types of intermediate water masses that correlate with variation in mesopelagic community composition. Furthermore, oxygen, NO - and particle flux together appeared as the main drivers governing these communities. Novel taxonomic signatures emerged from OMZ while a global co-occurrence network analysis showed that about 70% of the abundance of mesopelagic plankton groups is organized into three community modules. One module gathers prokaryotes, pico-eukaryotes and Nucleo-Cytoplasmic Large DNA Viruses (NCLDV) from oxic regions, and the two other modules are enriched in OMZ prokaryotes and OMZ pico-eukaryotes, respectively. We hypothesize that OMZ conditions led to a diversification of ecological niches, and thus communities, due to selective pressure from limited resources. Our study further clarifies the interplay between environmental factors in the mesopelagic oxic and OMZ, and the compositional features of communities.

ecology↗

bioRxiv2020

Restructuring of genomic provinces of surface ocean plankton under climate change

The impact of climate change on diversity, functioning and biogeography of marine plankton remains a major unresolved issue. Here, niche theory is applied to plankton metagenomes of 6 size fractions, from viruses to meso-zooplankton, sampled during the Tara Oceans expedition. Niches are used to derive plankton size-dependent structuring of the oceans south of 60{degrees}N in climato-genomic provinces characterized by signature genomes. By 2090, assuming the RCP8.5 high warming scenario, provinces would be reorganized over half of the considered ocean area and quasi-systematically displaced poleward. Particularly, tropical provinces would expand at the expense of temperate ones. Sea surface temperature is identified as the main driver of changes (50%) followed by phosphate (11%) and salinity (10%). Compositional shifts among key planktonic groups suggest impacts on the nitrogen and carbon cycles. Provinces are linked to estimates of carbon export fluxes which are projected to decrease on average by 4% in response to biogeographical restructuring.

ecology↗