Climate and the Evolution of the Ocean: The Paleoceanographic Data
The idea of reconstructing the history of oceans and climates in the past using marine sediment cores arrived quite late after the beginnings of oceanography. It was initiated in the twentieth century, well after the first attempts to measure variations in seawater temperature down the water column, which date back to the eighteenth century with the great circumnavigation expeditions. Land geologists were the first to propose paleoceanographic reconstructions from exposed marine series, limiting the collected information to former coastal waters.
(pp. 225-254, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, IFREMER, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LGO, UBS, IFREMER, UBO EPE, CNRS
Seasonal Variations in the Biodiversity, Ecological Strategy, and Specialization of Diatoms and Copepods in a Coastal System With Phaeocystis Blooms: The Key Role of Trait Trade-Offs
Although eutrophication induced by anthropogenic nutrient enrichment is a driver of shifts in community composition and eventually a threat to marine biodiversity, the causes and consequences on ecosystem functioning remain greatly unknown. In this study, by applying a trait-based approach and measuring niche breadth of diatoms and copepods, the drivers and underlying mechanisms of the seasonal species succession of these ecological communities in a coastal system dominated in spring by Phaeocystis blooms were explored. It is suggested that the seasonal succession of diatoms and copepods is the result of several trade-offs among functional traits that are controlled by the seasonal abiotic and biotic pressure encountered by the plankton communities. The results of this study highlight that a trade-off between competition and predator, i.e., weak competitors are better protected against predation, plays an important role in promoting plankton species richness and triggers the Phaeocystis bloom. As often observed in eutrophicated ecosystems, only the biotic homogenization of the copepod community and the shift in the diet of copepods toward Phaeocystis detrital materials have been detected during the Phaeocystis bloom. The diatom and copepod communities respond synchronously to fluctuating resources and biotic conditions by successively selecting species with specific traits. This study confirms the key role of competition and predation in controlling annual plankton succession.
(Frontiers in Marine Science. vol. 8, n° 2296-7745, pp. Article 656300, 21/06/2026)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, UCA Faculté Médecine, UniCA, OOB, SU, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE
The mid-Cretaceous Natih Formation in northern Oman: a model for platform-intrashelf basin depositional systems and associated petroleum habitat
The Late Albian – Early Turonian Natih Formation in Oman and its stratigraphic equivalents in the Middle-East correspond to a wide carbonate platform that developed on the Arabian plate along the passive margin of the Neotethys Ocean. It is composed of rudist-rich shallow marine deposits grading laterally to organic-rich deposits accumulated in intrashelf basins of relatively limited water depth. Consequently, this formation corresponds to a prolific petroleum system isolated below and above by effective regional seals. This formation, largely exploited in subsurface in the Middle-East, is spectacularly exposed in the Oman mountains thanks to the tectonic deformation of the Neotethys palaeomargin. These outcrops provide an excellent data set to construct a high-resolution sequence stratigraphic model for this type of carbonate system. The stratal architecture and the facies distribution clearly reveal how the platform evolution can be related to the ratio between accommodation rate and carbonate production during cycles at different scales. The cyclic evolution of this ratio is responsible for the gradual transition from a very flat platform with minor lateral facies and thickness variations to a low angle depositional profile from platform to intrashelf basin illustrated by clinoform geometries and pronounced lateral facies changes. Tectonic deformations have minor if no effect on the development of these intrashelf basins. Numerous additional interpretative key points will be addressed during this field trip: the location of shale deposits restricted to very shallow marine environment and implications on the inner platform sequence interpretation, the strong asymmetry of these transgressive sequences related to volumetric partitioning, the lack of pronounced rudist build-ups, the heterogeneities associated to subaerial exposure surfaces; and the hierarchy and fractal character of depositional sequences. This depositional model of the Natih Formation can be useful for the prediction of reservoir and source rock distribution and heterogeneity in this type of carbonate system.
(pp. 515-586, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, KAUST
Fluvial sand, Amazon mud, and sediment accommodation in the tropical Maroni River estuary: Controls on the transition from estuary to delta and chenier plain
The Maroni River, South America, is a tropical estuary encased in a narrow lower valley with a limited area of estuarine tidal flat development, and displays a channel with large downstream-migrating sandy bedforms linked to a large sand-filled shallow mouth. The sand-rich nature of the lower Maroni River reflects significant fluvial bedload supply, and the Maroni is among rivers with the lowest suspension-sized sediment load in the world. During the dry season, the estuary shows high suspended sediment concentrations near the bottom (several g/l) that are due to the ingress of mud streaming alongshore from the Amazon River delta. However, Amazon mud is expelled from the estuary during the high-discharge rainy-season, and seems to be essentially restricted to this seasonal intrusion along the main channel with little net estuarine sedimentation because of limited chan- nel overbank sediment accommodation space. Sand actively supplied by the Maroni River to the coast has been diverted by wave-generated longshore transport westwards, towards the Suriname coast. This has resulted in the construction of numerous sandy cheniers within a muddy coastal plain built from Amazon mud. This sedi- ment-source dichotomy is an important original feature of the Guiana Shield estuaries. The asymmetric prograda- tion at the mouth of the Maroni fingerprints the westward growth, in the vicinity of river mouths, of the muddy, chenier-studded, coastal plain of the Guianas. The propensity for these rivers to supply sand to the coast, even- tually evolving into deltas, depends on the ability of their estuaries to limit westward (downdrift) deflection by long-term updrift coastal sedimentation. The Maroni estuary has tended to evolve towards a delta built from both Maroni river sand and Amazon mud, a stage, among the Guiana Shield Rivers, that only the large Essequibo River estuary in Guyana has achieved. Further studies will be needed in order to constrain the infill pattern of the Maroni River estuary and its mouth.
(Regional Studies in Marine Science. vol. 41, n° 2352-4855, pp. 101548, 21/06/2026)
LEEISA, IFREMER, UG, CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, IEPA, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Peer Community In… A free recommendation process of preprints based on peer reviews
(21/06/2026)
UMR CBGP, Cirad, UM, IRD [Occitanie], IRD, INRAE, Institut Agro, ISA, UNS, CNRS, INRAE, UniCA, DipSO, INRAE, ECOSYS, INRAE, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Shift from short‐term competition to facilitation with drought stress is due to a decrease in long‐term facilitation
Disentangling short- and long-term neighbour effects, using both removal and observational methods within a single experiment, has strongly improved our understanding of the driving mechanisms of plant–plant interactions. However, there has been no attempt to assess two important underlying processes of their changes along gradients, either environmental-severity (changes in target performance without neighbours) or neighbour-traits (changes in performance with neighbours) effects, the former previously shown in alpine communities to be involved in competition and the latter in facilitation. We addressed this goal in an experiment conducted in continental saline depressions (sebkhas) from the Mediterranean arid climate of central Tunisia. We quantified short- and long-term effects of dominant shrubs, transplanting three target grass species in open, nurse and removed-nurse microhabitats of two habitats of different salinity levels in height sebkhas. The design extended greographically from central Tunisia to the Libyan border, 500 km southeastward. We used the relative interaction index to calculate short- and long-term effects before and after the dry summer seasons and environmental-severity and neighbour-trait effects. Short-term effects were slightly negative and long-term effects strongly positive before the dry summer season in the two habitats. Short-term effects switched to positive with increasing drought stress, due to an environmental-severity effect, whereas long-term effects decreased due to a neighbour-trait effect. Salinity did not affect neither short- nor long-term shrub effects. Soil moisture measurements showed that both changes were due to vanishing shrub soil engineering-effects during the summer drought. We conclude that an increase in short-term facilitation with increasing drought stress through time, apparently supporting the stress gradient hypothesis, might be due to a decrease in long-term facilitation. Thus, we recommend using, as much as possible, both the removal and observational methods in experiments assessing changes in plant–plant interactions along stress gradients to avoid wrong conclusions.
(Oikos. vol. 130, n° 0030-1299, pp. 29-40, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The Terebelliformia-Recent Developments and Future Directions
(Diversity. vol. 13, n° 1424-2818, pp. 60, 21/06/2026)
IO-USP, USP, USP, LECOB, SU, CNRS, OOB, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Transgenerational epigenetic sex determination: Environment experienced by female zebrafish affects offspring sex ratio
Sex determination is a complex process that can be influenced by environment in various taxa. Disturbed environments can affect population sex ratios and thus threaten their viability. Emerging evidences support a role of epigenetic mechanisms, notably DNA methylation, in environmental sex determination (ESD). In this work, using zebrafish as model and a transgenerational experiment comprising 4 successive generations, we report a strength link between the promotor methylation level of three genes in female gonads and population sex ratio. One generation of zebrafish was exposed throughout its lifetime to cadmium (Cd), a non-essential metal, at an environmentally relevant concentration. The subsequent generations were not exposed. At the first and the third generation a subset of individuals was exposed to an elevated temperature, a well-known masculinizing factor in zebrafish. While heat was associated to an increase in the methylation level of cyp19a1a gene and population masculinization, foxl2a/dmrt1 methylation levels appeared to be influenced by Cd and fish density leading to offspring feminization. Ancestral Cd exposure indeed led to a progressive feminization of the population over generations and affected the sex plastic response of zebrafish in response to heat. The effect of Cd on the methylation level of foxl2a was observed until the third generation, supporting potential transgenerational inheritance. Our results support (i) a key role of cyp19a1a methylation in SD in zebrafish in response to environmental cues and (ii) the fact that the environment experienced by parents, namely mothers in the present case, can affect their offspring sex ratio via environment-induced DNA methylation changes in gonads.
(Environmental Pollution. vol. 277, n° 0269-7491, pp. 116864, 21/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, CNRS
Cell and tissue level responses in mussels Mytilus galloprovincialis dietarily exposed to PVP/PEI coated Ag nanoparticles at two seasons
Silver nanoparticles (Ag NPs) are present in numerous consumer products due to their antimicrobial and other unique properties, thus concerns about their potential input into aquatic ecosystems are increasing. Toxicity of Ag NPs in waterborne exposed aquatic organisms has been widely investigated, but studies assessing the potential toxic effects caused after ingestion through the food web, especially at low realistic concentrations, remain scarce. Moreover, it is not well known whether season may influence toxic effects of Ag NPs. The main objective of this study was to determine cell and tissue level responses in mussels Mytilus galloprovincialis dietarily exposed to poly-N-vinyl-2-pirrolidone/polyethyleneimine (PVP/PEI) coated 5 nm Ag NPs for 1, 7 and 21 days both in autumn and spring. Mussels were fed every day with microalgae Isochrysis galbana exposed for 24 h to a low dose (1 μg Ag/L Ag NPs) in spring and to a higher dose (10 μg Ag/L Ag NPs) in spring and autumn. Mussels fed with microalgae exposed to the high dose accumulated Ag significantly after 21 days in both seasons, higher levels being measured in autumn compared to spring. Intralysosomal metal accumulation measured in mussel digestive gland and time- and dose-dependent reduction of mussels health status was similar in both seasons. DNA strand breaks increased significantly in hemocytes at both exposure doses along the 21 days in spring and micronuclei frequency showed an increasing trend after 1 and 7 days of exposure to 1 μg Ag/L Ag NPs in spring and to 10 μg Ag/L in both seasons. Values decreased after 21 days of exposure in all the cases. In conclusion, PVP/PEI coated 5 nm Ag NPs ingested through the food web were significantly accumulated in mussel tissues and caused adverse cell and tissue level effects both in autumn and in spring.
(Science of the Total Environment. vol. 750, n° 0048-9697, pp. 141303, 21/06/2026)
UPV / EHU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Latitudinal influence on gametogenesis and host–parasite ecology in a marine bivalve model
Reproduction and parasites have significant impacts on marine animal populations globally. This study aimed to investigate the associative effects of host reproduction and a host–parasite interplay on a marine bivalve, along a geographic gradient of latitude. Cockles Cerastoderma edule were sampled from five European sites (54°N to 40°N), between April 2018 and October 2019. A histological survey provided data on trematode (metacercaria and sporocyst life stages), prevalence, and cockle stage of gametogenesis to assess the influence of a latitudinal gradient on both interplays. Sex ratios at the northernmost sites were skewed toward females, and spawning size was reduced at the lower latitudes. Trematode infection did not follow a latitudinal gradient. Localized site-related drivers, namely seawater temperature, varied spatially, having an impact on cockle–trematode interactions. Spawning was related to elevated temperatures at all sites. Prolonged spawning occurred at southern latitudes, where seawater temperatures were warmer. Trematode prevalence and the impact of trematodes on gametogenesis were found to be spatially variable, but not latitudinally. Therefore, it is not possible to determine the likelihood of boom and bust events in cockles, based on the latitudinal location of a population. In terms of sublethal impacts, it appeared that energy was allocated to reproduction rather than somatic growth in southern populations, with less energy allocated to reproduction in the larger, northern cockles. The demonstrated spatial trend of energy allocation indicates the potential of a temporal trend of reduced cockle growth at northern sites, as a result of warming sea temperatures. This awareness of the spatially varying drivers of populations is crucial considering the potential for these drivers/inhibitors to be exacerbated in a changing marine environment.
(Ecology and Evolution. vol. 11, pp. 7029-7041, 21/06/2026)
UCC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS