Thierry Thibaut

• PhD
• Professor at Aix-Marseille University

La création d’ouvrages maritimes sur les petits fonds côtiers a entraîné des régressions notables des herbiers de posidonie ces dernières décennies. Outre la destruction des herbiers par recouvrement, les impacts de ces aménagements peuvent être occasionnés lors de la phase travaux (turbidité, ancrages des engins de chantier…) et de la phase exploi...

Over historical time, Berre Lagoon (SE France, NW Mediterranean Sea) had undergone various changes. These became more significant, transforming and even disruptive since the 19th century when the channel connecting the lagoon to the sea was deepened and the surrounding areas were industrialized and urbanized. Pollution and anoxic crises were major...

The Mediterranean Sea, a biodiversity hotspot, faces significant threats from non-indigenous species (NIS), which drive biodiversity changes. Over the past century, the introduction of NIS has accelerated due to maritime traffic, aquaculture, and interoceanic canals, fostering biological invasions. Marine protected areas (MPAs), established to pres...

In the Mediterranean Sea, seaweed marine forests, one of the most important benthic assemblages for the coastal ecosystem functioning, are shaping the rocky reefs. Among the Fucales, Gongolaria barbata (syn. Cystoseira barbata) is a several years living species usually growing in very shallow, sheltered and well-lit marine reef habitats and in coas...

The red alga Bonnemaisonia clavata has rarely been reported in the Mediterranean Sea, perhaps because its very close resemblance to B. asparagoides. A relatively dense stand of B. clavata, with female and male individuals bearing cystocarps and androphores, respectively, has been observed at La Gabinière Island (Port-Cros Archipelago,

The study of the herbarium of the Domaine du Rayol has resulted in the determination of 30 taxa: 8 green algae (Ulvophyceae), 14 red algae (Rhodophyta) and 8 brown algae (Phaeophyceae). With the exception of Ericaria amentacea and E. crinita, all of them are first reported from Rayol-Canadel-sur-Mer. Laurenciella cf. marilzae is reported for the fi...

Infralittoral rocky reefs (IRR) are a coastal marine habitat subject to various anthropogenic pressures in the Mediterranean. An ecological assessment using an ecosystem-based approach appears essential to guide sustainable environmental management practices and meet the requirements of the European Union Marine Strategy and Habitats Directive. For...

Early-life stages play a key role in the dynamics of bipartite life cycle marine fish populations. Difficult to monitor, observations of these stages are often scattered in space and time. While Mediterranean coastlines have often been surveyed, no effort has been made to assemble historical observations. Here we build an exhaustive compilation of...

The specific identification of three major morphotypes of the tropical holopelagic Sargassum species causing massive strandings on the African and Caribbean coastlines was attempted by morphological characterisation as well as quantitative and qualitative analyses of several metabolites. Of the 25 morphological variables studied on 208 samples from...

Early-life stages play a key role in the spatio-temporal dynamics of marine populations due to their highly dispersive properties, their sensitivities to environmental factors and their influences on juveniles’ replenishment. However, these stages are difficult to monitor, so that in-situ observations are scarce and disparate, preventing a good und...

Since 2011, massive new strandings of holopelagic Sargassum have been reported on the coasts of the Caribbean, northern Brazil, Guiana, and West Africa, causing severe economic and ecological damage. Three common morphotypes (S. fluitans III, S. natans I, and S. natans VIII) were identified as responsible for these catastrophic events, with dominan...

Early-life stages play a key role in the dynamics of bipartite life cycle marine fish populations. Difficult to monitor, observations of these stages are often scattered in space and time. While Mediterranean coastlines have been highly surveyed, no effort was made to assemble historical observations. Here we build an exhaustive compilation of disp...

Since 2011, the Caribbean coasts have been subject to episodic influxes of floating Sargassum seaweed of unprecedented magnitude originating from a new area “the Great Atlantic Sargassum Belt” (GASB), leading in episodic influxes and mass strandings of floating Sargassum. For the biofilm of both holopelagic and benthic Sargassum as well as in the s...

The warming trend of the Mediterranean Sea is a long-term process. It has resulted in a northwards and westwards range expansion and abundance increase of thermophilic species, both native and non-indigenous, and in a shrinking of the range of cold-affinity species. Marine heatwaves (MHWs) are relatively short-term extreme episodes that are respons...

The blue shark (Prionace glauca) and the swordfish (Xiphias gladius) are two large apex predators in the Mediterranean Sea. The overlap of their ecological niche can lead to competition between the two species for the same food resources. Furthermore, their similar reproductive periods in the Mediterranean may intensify this competition. However, i...

Effective monitoring of non-indigenous seaweeds and combatting their effects relies on a solid confirmation of the non-indigenous status of the respective species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140...

The worldwide decline of macroalgal forests is raising major concerns for the potentially negative consequences on biodiversity and ecosystem functions, pushing for the definition of specific conservation and restoration measures. Protecting and restoring these habitats requires detailed information on their distribution, ecological status, and dri...

RESUME En réponse à des enjeux d’intégration écologique, différentes approches d’éco-conception des ouvrages maritimes ont été développées ces dernières années ; l’objectif étant d’apporter des fonctions écologiques complémentaires aux fonctions techniques premières de ces ouvrages (digues, quais, pontons, corps-morts, émissaires...). En fonction d...

The analysis of biological and ecological traits has a long history in evolutionary and ecological research. However, trait data are often scattered and standardised terminology that transcends taxonomic and biogeographical context are generally missing. As part of the development of a global trait database of marine species, we collated trait info...

The calcified red macroalga Lithophyllum byssoides, a very common midlittoral species in the western Mediterranean Sea, is a significant ecosystem engineer capable, under exposed and dim light conditions, of building wide and solid endemic bioconstructions near the mean sea level: the L. byssoides rims or 'trottoirs à L. byssoides'. Although the gr...

Effective monitoring and combatting the effect of non-indigenous seaweeds relies on a solid confirmation of the non-indigenous status of the species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140 species whose...

The lower mid-littoral and shallow subtidal communities were studied in the district of Vlora (Albania), three years after the establishment of a Marine Protected Area, with particular attention to the long-lived species. The bioconstructions built in the mid-littoral zone by the calcified rhodobiont Lithophyllum byssoides were in poor condition an...

Introduction Coastal detrital bottoms (CDB) are one of the most extensive habitats of the continental shelf worldwide, in the upper levels of the circalittoral zone. Hosting a diverse community structured by sediment grain size, trophic interactions and calcified organisms, CDB exhibit important ecological functions. In the Mediterranean Sea, CDB a...

Since 2011, the proliferation of brown macro-algae of the genus Sargassum has considerably increased in the North Tropical Atlantic Sea, all the way from the Gulf of Guinea to the Caribbean Sea and the Gulf of Mexico. The large amount of Sargassum aggregations in that area cause major beaching events, which have a significant impact on the local ec...

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The analysis of biological and ecological traits has a long history in evolutionary and ecological research. However, trait data are often scattered and standardised terminology that transcends taxonomic and biogeographical context are generally missing. As part of the development of a global trait database of marine species, we collated trait info...

In the Mediterranean Sea, Coastal Detrital Bottoms (CDB) are one of the most extensive habitats of the continental shelf. The EU Marine Strategy Framework Directive has embraced the concept of a socio-ecosystem-based approach to consider the functioning of marine habitats and their related services. We propose an ecosystem-based quality index (EBQI...

We document for the first time, the spatial distribution at basin scale (North tropical Atlantic Ocean) of As, P and trace metal (TM) concentrations in the three morphotypes belonging to the two holopelagic species Sargassum natans and S. fluitans and three morphotypes: S. natans VIII, S. natans I and S. fluitans III. These samples collected in the...

The Port-Cros National Park (PCNP), established in 1963, was one of the earliest terrestrial and marine parks in the Mediterranean Sea. From 2012, it engaged in a major redefinition and extension of its territory (N-PCNP—New Port-Cros National Park). This case is particularly interesting insofar as the protected area has been competently and effici...

Sargassum natans and Sargassum fluitans are uniquely holopelagic macroalgae, providing open ocean nursery and foraging habitat for commercially and ecologically important species. Recent basin‐wide changes in pelagic Sargassum diversity and distribution have manifested in proliferation of a previously rare morphotype, Sargassum natans VIII, to riva...

The Red Sea and Indian Ocean seagrass Halophila stipulacea entered the Mediterranean in the late 19th century via the Suez Canal. Here, we report on the discovery of a population of H. stipulacea covering 16.5 ha off the harbour of Cannes, French Riviera, France. This represents the northernmost locality of the species and a jump of 350 km to the n...

The temperate Northwest Pacific brown alga Rugulopteryx okamurae (Dictyotales, Phaeophyceae) was first discovered in 2002 in the Mediterranean Sea in the Thau coastal lagoon (Occitania, France) and then again in 2015 along the southern side of the Strait of Gibraltar, where it was assigned with invasive status. We report here on the first occurrenc...

The restoration of algal marine forests has been developing for about thirty years. In the Mediterranean, this work has only focused on Fucales of the genus Ericaria and Gongolaria (synomym Cystoseira). In France, three large-scale restoration projects have been carried out on Ericaria amentacea to re-vegetate areas where the species had disappeare...

In the Mediterranean Sea, shallow rocky reefs and the associated three-dimensional (3D) structure support rich and abundant communities; they are therefore of functional importance, in particular for the renewal of fish stocks. However, these habitats and their functions are likely to be altered by anthropogenic pressures inducing habitat transform...

Coastal zones are ecosystems of high economic value but exposed to numerous disturbances, while they represent nurseries for many fish species, raising the issue of the preservation of their functions and services. In this context, the juvenile fish assemblages of all types of habitats present in shallow coastal zones were studied on the south-east...

Within the frame of a natural environment impacted by anthropogenic activities, assessing and quantifying their related pressures are essential to its management and are linked to its status. However, there are no, or very few, geographical areas where thorough knowledge of human uses and sources of impact is available as a basis to quantify these...

The tropical Atlantic has been facing a massive proliferation of Sargassum since 2011, with severe environmental and socioeconomic impacts. The development of large-scale modeling of Sargassum transport and physiology is essential to clarify the link between Sargassum distribution and environmental conditions, and to lay the groundwork for a season...

Dispersal is a central process that affects population growth, gene flow, and ultimately species persistence. Here we investigate the extent to which gene flow occurs between fragmented populations of the deep-water brown algae Ericaria zosteroides (Turner) Greville (Sargassaceae, Fucales). These investigations were performed at different spatial s...

Ce rapport présente les fiches descriptives des 32 unités d’habitats de niveau 3 (biocénose) et 119 unités de niveau 4 (faciès et associations) de la typologie des biocénoses benthiques de Méditerranée version 2, pour servir d’outil d’aide à l’identification et la conservation des habitats. Les habitats ont été décrits sur la base des descriptions...

Some species of seagrasses (e.g., Zostera marina and Posidonia oceanica) have declined in the Mediterranean, at least locally. Others are progressing, helped by sea warming, such as Cymodocea nodosa and the non-native Halophila stipulacea. The decline of one seagrass can favor another seagrass. All in all, the decline of seagrasses could be less ex...

The Tropical Atlantic is facing a massive proliferation of Sargassum since 2011, with severe environmental and socioeconomic impacts. As a contribution to this proliferation, an increase in nutrient inputs from the tropical rivers, in response to climate and land use changes or increasing urbanization, has been often suggested and widely reported i...

The development of population genomic approaches in non‐model species allows for renewed studies of the impact of reproductive systems and genetic drift on population diversity. Here, we investigate the genomic signatures of partial clonality in the deep water kelp Laminaria rodriguezii, known to reproduce by both sexual and asexual means. We compa...

Partial clonality, mode of reproduction, heterozygote excess, population genomics, kelp The development of population genomic approaches in non‐model species allows for renewed studies of the impact of reproductive systems and genetic drift on population diversity. Here, we investigate the genomic signatures of partial clonality in the deep water k...

Average Sargassum beaching distribution after one year of drift.

Kelp species (Laminariales, Phaeophyceae) are globally widespread along temperate to Polar rocky coastal lines. Here we analyse the mitochondrial and chloroplast genomes of Laminaria rodriguezii, in comparison to the organellar genomes of other kelp species. We also provide the complete mitochondrial genome sequence of another endemic kelp species...

Ce rapport présente les fiches descriptives des 32 unités d’habitats de niveau 3 (biocénose) et 119 unités de niveau 4 (faciès et associations) de la typologie des biocénoses benthiques de Méditerranée version 2, pour servir d’outil d’aide à l’identification et la conservation des habitats. Les habitats ont été décrits sur la base des descriptions...

The Tropical Atlantic is facing a massive proliferation of Sargassum since 2011, with severe environmental and socioeconomic impacts. The development of Sargassum modelling is essential to clarify the link between Sargassum distribution and environmental conditions, and to lay the groundwork for a seasonal forecast on the scale of the Tropical Atla...

Coastal zones are ecosystems of high economic value but exposed to numerous disturbances, while they represent nurseries for many fish species, raising the issue of the preservation of their functions and services. In this context, the juvenile fish assemblages of all types of habitats present in shallow coastal zones were studied on the south-east...

Since 2011, huge amounts of Sargassum algae are detected in the equatorial Atlantic, causing large strandings events on the coasts of the West Indies, Brazil and West Africa. The distribution of this stock shows strong annual and interannual variability, whose drivers are not settled yet. Here we use satellite Sargassum observations from MODIS and...

The direct and indirect impact of fish farms, shellfish aquaculture, and extensive forms of aquaculture such as seeding of juvenile sea urchins, on macrophytes (seaweeds and seagrasses), is reviewed in Mediterranean benthic ecosystems. Fish farms constitute a source of organic matter and nutrients (food and fecal pellets) that causes the extirpatio...

Macroalgae are a key component of benthic coastal ecosystems. They are sensitive to natural and anthropogenic disturbances. In the Mediterranean Sea, macroalgae can be used by environmental managers (i) to delineate biogeographic provinces (on the basis of their range), (ii) as indicators of global warming (based on changes in their distribution ar...

The present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggregations...

The present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggregations...

The release of emerging organic contaminants is identified among the most critical hazards to the marine environment, and plastic additives have received growing attention due to their worldwide distribution and potential deleterious effects. Here we report dissolved surface water concentrations of two important families of plastic additives (organ...

Coastal detrital sandy bottoms are an ecosystem (CDE) widespread over the continental shelf from 30 down to 100 m depth in the Mediterranean Sea. Despite the extensive surface area it covers on the continental shelf, this key ecosystem has not been considered as a habitat of European interest by the Habitat Directive of the European Union (Natura 2...

Canopy-forming seaweeds constitute marine forests that deliver ecosystem services. The worldwide range shift, sharp decline or loss of many of these forests, caused by the cumulative impact of increasing human pressure and climate change, have been widely documented. Contrasting examples, reflecting higher than expected resilience, have been more r...

Should be cited as : BLANFUNÉ A., BOUDOURESQUE C.F., THIBAUT T., VERLAQUE M., 2016. The sea level rise and the collapse of a Mediterranean ecosystem, the Lithophyllum byssoides algal rim. In : The Mediterranean region under climate change. A scientific update. Thiébault S., Moatti J.P. (eds.), AllEnvi, IRD éditions publisher, Marseille : 285-289.

Nine species of the genus Sargassum (Phaeophyceae; kingdom Stramenopiles) are currently accepted in the Mediterranean Sea: S. acinarium, S. desfontainesii, S. flavifolium, S. furcatum, S. hornschuchii, S. muticum, S. ramentaceum, S. trichocarpum and S. vulgare. Sargassum desfontainesii and S. furcatum, are Atlantico-Mediterranean species. Sargassum...

L’EBQI (Ecosystem-Based Quality Index – indice de qualité basé sur l’écosystème) est un indice basé sur une approche écosystémique. Son principe est de prendre en compte de nombreux compartiments fonctionnels de l’écosystème afin de caractériser son état écologique. Un écosystème est le siège de nombreuses relations entre individus de la même espèc...

Sandy beaches, together with the foredune and the dune, form a morphological, functional and ecological complex, the beach-dune complex. This complex provides ecosystem services which have by far the highest value in the coastal areas, both marine and terrestrial habitats considered; it requires an overall management approach. Sandy beaches are oft...

The Mediterranean coralligenous and the intertropical coral reef ecosystems are similar in several aspects, such as their ability to thrive in nutrient-poor waters and the communities associated with them. For example, these ecosystems encompass communities ranging from bioconstructions by calcified blade-forming coralline macroalgae, bioconstructi...

Biodiversity means the variety of life, encompassing levels of complexity from within species to across ecosystems. Biodiversity therefore includes several dimensions: evolutionary scale (genetic, species, higher taxonomic levels and phylogenetic diversity), functional scale, organizational scale (patch, ecosystem, landscape/seascape diversity), sp...

Cystoseira montagnei J. Agardh and C. spinosa Sauvageau (Phaeophyceae, Sargassaceae): a taxonomic reappraisal of misused names, with the proposal of Cystoseira michaelae Verlaque et al. nom. et stat. nov. Abstract – Cystoseira granulata C. Agardh var.

The European Red List of Habitats provides an overview of the risk of collapse (degree of endangerment) of marine, terrestrial and freshwater habitats in the European Union (EU28) and adjacent regions (EU28+), based on a consistent set of categories and criteria, and detailed data and expert knowledge from involved countries1. A total of 257 benthi...

Species of the genus Sargassum are large canopy-forming marine brown algae (engineer species) found worldwide from tropical to cold-temperate latitudes. Among this very diversified genus (335 taxa accepted taxonomically), only 9 species (including the invasive S. muticum) have been reported from the Mediterranean Sea. We have analysed the changes o...

The brown alga Cystoseira amentacea (Phaeophyceae, kingdom Stramenopiles) constitutes an extensive belt in the shallowest horizon of the infralittoral (the infralittoral fringe), in the Mediterranean Sea. Hydrodynamic modelling was used to infer connectivity between populations of C. amentacea of the Bay of Marseille (Provence, France, NW Mediterra...

The necromass of the Posidonia oceanica seagrass meadow: fate, role, ecosystem services and vulnerability

In the Mediterranean Sea, Fucales, and in particular the species of the genus Cystoseira C. Agardh, are habitat-forming species dominating several benthic assemblages from the littoral fringe down to 70–80 m depth in the clearest waters. They generate high primary production involved in the maintenance of diversified trophic levels, they provide sh...