Search

Massive storage of dihydrogen (H 2) in underground geological storage (UGSs) will be necessary to meet future H 2 production ambitions. Such storage in deep aquifers was simulated in a high-pressure reactor, and the evolution of the 3 phases (natural gas/H 2 , formation water and rock) with autochthonous microorganisms was monitored over several weeks. These results show that methanogens do not necessarily dominate the community, but that sulfate-reducing activity and formate bioproduction are systematically present. The experimental data were fed into a biochemical model in PHREEQC to better understand the interplay between the phenomena observed. In particular, it was shown that the microbial activities associated with H 2 consumption led to alkalinisation, which could explain, at least in part, the slower rate at which H 2 disappeared, even if sufficient CO 2 and sulfate remained in the system. Combined with a supposed local nutrient depletion, these results are encouraging for H 2 storage in deep aquifers. • Injection of H 2 in three deep aquifers was studied in a high-pressure reactor. • Multidisciplinary approach including experiment analyses and biochemical modeling. • Low sulfate content sites should be favored for H 2 storage in deep aquifers. • Storage behavior needs to be studied site-specifically. [ABSTRACT FROM AUTHOR]

Despite the popularity of stable isotope analysis (Carbon and Nitrogen), the drivers of species isotopic niches and their consequences on food web functioning remained poorly described, especially in estuaries. Here, we hypothesised that species niche characteristics are influenced by ecosystem hydro-morphological features and the functional structure of fish assemblages. The trophic niches of four fish species (Dicentrarchus labrax, Pomatoschistus minutus, Sprattus and Platichthys flesus) and overlap between them were compared during two consecutive autumns in eight estuarine ecosystems of the northeast Atlantic Ocean. Our findings demonstrated a relative steadiness of trophic positions of fish in estuaries, despite a high level of interspecific variability. The seabass generally occupied the higher trophic position, followed by the sand goby, while the flounder and sprat were at the lowest position in the food web. Species isotopic niches and overlap were mediated by some estuarine features, including estuary size and intertidal extent, but also by biotic interactions at the intra- and inter-specific levels, as reflected by the influence of fish abundance and functional diversity metrics. Our results support the statement that the intertidal area is a pivotal factor in regulating trophic interactions, by promoting niche partitioning and diversification of trophic resources between species. Moreover, niche size and dietary divergence of species decreased with increasing regularity of trophic strategies within assemblages, suggesting that species occupied more restricted trophic niches when they were less subjected to competition for the same food resources. These findings emphasize the importance of local conditions and the functional composition of assemblages in modulating the trophic resources consumed by fish in estuarine environments. [Display omitted] • Trophic niches of four fishes were investigated across eight estuaries. • Species isotopic niches were influenced by functional diversity of assemblages. • Niche size and divergence decreased with functional divergence and evenness. • Intra- and inter-specific interactions affect species niches and overlap. • Intertidal area promote niche partitioning and diversification of trophic resources. [ABSTRACT FROM AUTHOR]