Biology subjects

Bonthond, G.

Publications and source records attributed to Bonthond, G..

6 recordsLinked to original sources

bioRxiv2026

Benthic macrofauna and microbiota mediate bottom trawling impacts on long-term carbon storage in marine sediments

The seafloor is the largest organic carbon sink on Earth. Its benthic fauna and microbiota jointly regulate long-term carbon storage by assimilating and degrading sedimentary organic matter (SOM). Bottom trawling threatens the long-term storage of organic matter by physical disturbance of the seafloor and remobilization of SOM. Trawling also impacts faunal and microbial communities and their diversity, but the implications of these ecological consequences for long-term carbon storage dynamics are poorly understood. Here, we combined datasets of paired faunal and microbial communities from the North Sea and used structural equation modeling to disentangle direct and biotically mediated effects of bottom trawling on SOM. One third of trawling-induced SOM loss is indirect and mediated by shifts in benthic faunal and microbial communities. Microbial community structure directly affected SOM and represented a key link in this pathway. Microbial effects on SOM were strongly tied to changes in metabolic traits. SOM loss coincides with increased microbial aerobic respiration potential, whereas SOM increases correlated with microbial assimilation processes, including dark carbon fixation. Benthic fauna impact SOM indirectly by shaping benthic microbial communities. Faunal diversity and species traits related to bioturbation promoted shifts in benthic microbiota that favor OM storage, corroborating their indirect but essential role in seafloor carbon dynamics. This study reveals that bottom trawling alters seafloor carbon storage not only through physical disturbance but also by disrupting faunal-microbial interactions that regulate sediment carbon dynamics. Taxonomic and functional shifts in benthic microbiota are a key, but underestimated, component of the processes regulating the seafloor carbon sink and warrant better integration of benthic biodiversity and ecological processes into assessments of seafloor carbon storage under anthropogenic pressures.

ecology↗

bioRxiv2025

Flatfish intestinal microbiota depend on various host traits, and vary with sediment type and bottom trawling effort

The intestinal microbiota of fishes support digestion, nutrient uptake and play an important role in the immune system, development and reproduction. Flatfish live in close contact with the seafloor, and are particularly exposed to anthropogenic disturbances such as bottom trawling. Bottom trawling impacts the ecosystem in various ways and it recent evidence indicates that the microbial composition and diversity in marine sediments varies with fishing intensity. It is presently unknown whether this trawling signal applies to the seafloor alone, or may also extend to microbiota of marine holobionts inhabiting it, such as flatfishes. Here, three flatfish species (Buglossidium luteum, Limanda limanda and Pleuronectes platessa) were sampled across the southeastern North Sea. We characterized the intestinal microbiota using 16S rDNA metabarcoding of 162 individuals, and disentangled how intestinal microbial composition and diversity are jointly shaped by various host traits (species, sex, age, weight, and condition factor) and environmental factors (sediment type and trawling intensity). Intestinal diversity varied among species and changed with age, weight and sediment type. Community composition was dependent on species, age, condition factor and sediment type. In addition, we found that trawling intensity explained shifts in intestinal microbial community composition, suggesting that the known impacts of bottom trawling on the benthic environment may cascade to intestinal microbiota of flatfish. Our findings provide important insight into host-microbiota interactions in marine ecosystems and highlight the interplay between host traits and environment as drivers of intestinal microbial diversity and community composition in flatfish. HighlightsO_LIFlatfish microbiota are shaped by host traits and environmental factors C_LIO_LIHost species and age affect intestinal microbial diversity and composition C_LIO_LIIntestinal microbiota vary along a bottom trawling intensity gradient C_LIO_LIBottom trawling impacts may cascade from sediments to fish intestinal microbiota C_LI

ecology↗

bioRxiv2024

Greater host influence and promiscuity: How an invasive seaweed host has advantages over co-occurring natives

The surface microbiome of seaweed hosts is a multi-domain biofilm regulated by host-microbe and microbe-microbe interactions. The extent to which hosts influence these interactions, and potentially affect their resilience and invasion success, remains unclear. We experimentally tested whether hosts with invasion history exert more influence over their biofilms than native hosts. Biofilm formation on proxy surfaces adjacent to one invasive (Gracilaria vermiculophylla) and two native (Fucus serratus, Fucus vesiculosus) co-occurring hosts was monitored and compared to mature epiphytic biofilms of the same hosts. Only Gracilarias proxy biofilms were significantly different in community composition compared to control surfaces. Gracilarias proxy biofilms also showed the highest similarity to their adjacent algae sharing certain bacterial taxa that were absent in control treatments, indicating that colonization of the proxy surface was influenced by the host. Gracilaria and its proxy biofilm showed highest similarity in microbial network variables, suggesting a higher ability of the invader to influence connectivity and microbial associations within its biofilm. Meanwhile Gracilarias mature biofilm also showed higher variability in its prokaryotic composition over experiments, which was also reflected in a less robust microbial network in both Gracilaria and its proxy biofilms. This suggests that in addition to stronger influence in the invasive host, it was also more promiscuous towards potential symbionts from the environment. Ultimately, through examining microbial interactions, in line with previous research we found that host influence and promiscuity may play an important role in seaweed hosts to acclimate to different environmental condition and successfully thrive in new ecosystems.

molecular biology↗

bioRxiv2024

Seasonal cycles in a seaweed holobiont: A multiyear time series reveals repetitive microbial shifts and core taxa

Seasonality is an important natural feature that drives cyclic environmental changes. Seaweed holobionts, inhabiting shallow waters such as rocky shores and mud flats, are subject to seasonal changes in particular, but little is known on the influence of seasonality on their microbial communities. In this study, we conducted a bi-monthly, three-year time series to assess the seasonality of microbial epibiota in the seaweed holobiont Gracilaria vermiculophylla. Our results reveal pronounced seasonal shifts that are both taxonomic and functional, oscillating between late winter and early summer across consecutive years. While epibiota varied taxonomically between populations, they were functionally similar, indicating that seasonal variability drives functional changes, while spatial variability is more redundant. We also identified seasonal core microbiota that consistently (re)associated with the host at specific times, alongside a permanent core that is present year-round, independent of season or geography. These findings highlight the dynamic yet resilient nature of seaweed holobionts and demonstrate that their epibiota undergo predictable changes. Therewith, the research offers important insights into the temporal dynamics of seaweed-associated microbiota, and demonstrates that the relationship between seaweed host and its epibiota is not static, but naturally subject to an ongoing seasonal succession process.

ecology↗

bioRxiv2023

From microbial communities to regional biogeography: Unraveling patterns, determinants and the influence of bottom trawling in benthic microbiota

Microbial composition and diversity in marine sediments are shaped by environmental, biological, and anthropogenic processes that operate on different scales. However, our understanding of benthic microbial biogeography remains limited. Here, we study how benthic microbiota vary at a regional scale in the North Sea with sediment characteristics, temperature, organic matter content, shear bed stress and bottom trawling intensity, a prevalent industrial fishing practice which heavily impacts benthic ecosystems. Using 16S rDNA amplicon sequencing, we characterized benthic microbiota from the top centimeter of 349 sediment samples and used uni-and multivariate statistical models, accounting for spatial autocorrelation, to disentangle the effects of the different predictors. Fitted models demonstrate how the geographic interplay of different environmental anthropogenic drivers shapes the structure and functioning of benthic microbial communities. Sediment properties were the primary determinants, with diversity increasing with sediment permeability but at the same time increasing with mud content, highlighting different underlying processes. Alpha diversity also increased nonlinearly with total organic matter content and temperature and showed a more complex relationship with bottom shear stress but decreased with bottom trawling intensity. These trawling associated diversity changes were accompanied by shifts in functional groups related to energy metabolism. Specifically, with increasing trawling intensity, we observed a transition toward more aerobic heterotrophic and less denitrifying metabolism. Our findings provide first insights of benthic microbial biogeographic patterns on a large spatial scale and illustrate how anthropogenic activity such as bottom trawling may influence the distribution and abundances of microbes and overall benthic metabolism at macroecological scales.

ecology↗

bioRxiv2023

THE RHODOEXPLORER PLATFORM FOR RED ALGAL GENOMICS AND WHOLE GENOME ASSEMBLIES FOR SEVERAL GRACILARIA SPECIES

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales are highly diverse and widely distributed order whose species can serve as ecosystem engineers in intertidal habitats, including several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensis and G. gracilis), a draft genome assembly of G. caudata, and genome annotation of the previously published G. vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

genomics↗