Brivaela Moriceau

• PhD
• Researcher at Université de Bretagne Occidentale

We investigated the influence of iron (Fe), phosphate (PO4), and silicic acid [Si(OH)4] concentrations on Si uptake rate by two strains of Synechococcus. Growth rates, cellular biogenic silica (bSi), and silicon uptake rates were measured and compared. Both strains showed significant Si cellular contents varying from 0.04 47 fmol cell⁻¹ to a maximu...

The paper aims to build seasonal silica budgets in two macrotidal estuaries, the Elorn and Aulne estuaries of the Bay of Brest (North-Western France), based on modeling and measurements, in order to increase our understanding of the silica (Si) cycle at land-sea interfaces. A diagenetic model was developed to quantify benthic Si fluxes, e.g. aSiO2...

Ba/Ca shell , Mo/Ca shell , and Li/Ca shell chronologies of Pecten maximus can provide information on past phytoplankton dynamics. Distinct Ba, Mo, and Li peaks in the shells are associated with algal blooms. This study evaluated the underlying hypothesis that respective element profiles reliably record variations in phytoplankton dynamics occurrin...

As part of the HIPPO (HIgh-resolution Primary Production multi-prOxy archives) project, environmental monitoring was carried out between March and October 2021 in the Bay of Brest. The aim of this survey was to better understand the processes which drive the incorporation of chemical elements into scallop shells and their links with phytoplankton d...

Chemical communication represents the most frequent mode of interaction in the living world. Although this mode of interaction is key to ecosystem functioning, our understanding of these interactions in plankton is limited. Some photosynthetic microorganisms can actively inhibit competitors (interaction called “allelopathy”) by releasing allelochem...

As part of the HIPPO (HIgh-resolution Primary Production multi-prOxy archives) project, an environmental monitoring was carried out between March and October 2021 in the Bay of Brest. The aim of this survey was to better understand the processes which drive the incorporation of chemical elements into scallop shells and their links with phytoplankto...

The Green Edge project was designed to investigate the onset, life, and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in Arctic Ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocea...

The Green Edge project was designed to investigate the onset, life and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of seawater, amongst other factors, have induced major changes in arctic ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocean...

In the last decades, the Arctic Ocean has been affected by climate change, leading to alterations in the sea ice cover that influence the phytoplankton spring bloom, its associated food web, and therefore carbon sequestration. During the Green Edge 2016 expedition in central Baffin Bay, the phytoplankton spring bloom and its development around the...

In the last decades, the Arctic Ocean has been affected by climate change, leading to alterations in the sea ice cover that influence the phytoplankton spring bloom, its associated food web, and therefore carbon sequestration. During the Green Edge 2016 expedition in the central Baffin Bay, the phytoplankton spring bloom and its development around...

We examined biogenic silica production and elementary composition (biogenic Si, particulate organic carbon and particulate organic nitrogen) of Rhizaria and diatoms in the upper 200 m along a transect in the Southwest Pacific sector of the Southern Ocean during austral summer (January-February 2019). From incubations using the 32 Si radioisotope, s...

The aim of this work was to determine the impact of sympagic (ice-associated) algal primary production on the quality of Arctic filter-feeding bivalves. For this purpose, we investigated the sea ice production of lipids (including omega−3 polyunsaturated fatty acids (n-3 PUFA) and highly branched isoprenoids (HBI)), as well as their subsequent inco...

The aim of this work was to determine the impact of sympagic (ice-associated) algal primary production on the quality of Arctic filter-feeding bivalves. For this purpose, we investigated the sea ice production of lipids (including omega−3 polyunsaturated fatty acids (n- 3 PUFA) and highly branched isoprenoids (HBI)), as well as their subsequent inc...

Diatoms in general, and Thalassiosira weissflogii (T. weissflogii) in particular, are among the most ubiquitous phytoplanktonic species while, phosphorus (P) is an essential nutrient that limits productivity in many oceanic regimes. To investigate how T. weissflogii cultures grown under different P regimes are chemically altered before and during t...

Phosphorus (P) limitation of phytoplankton growth is known to affect the accumulation and release of carbohydrates (CHO) by micro-algae. However, relatively little is known about the fate of algal exudates, notably their bacterial degradation. The CHO chemical characterization is also not exhaustive, especially in “functional” pools relevant for ph...

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Qikiq...

In marine ecosystems, carbon export is driven by particle flux which is modulated by aggregation, remineralization, and grazing processes. Zooplankton contribute to the sinking flux through the egestion of fast sinking fecal pellets but may also attenuate the flux by tearing apart phytoplankton aggregates into small pieces through swimming activity...

Numerical simulations of ocean biogeochemical cycles need to adequately represent particle sinking velocities (SV). For decades, Stokes' Law estimating particle SV from density and size has been widely used. But while Stokes' Law holds for small, smooth, and rigid spheres settling at low Reynolds number, it fails when applied to marine aggregates c...

The Arctic Ocean is particularly affected by climate change, with changes in sea ice cover expected to impact phytoplankton primary production. During the Green Edge expedition, the development of the late spring–early summer diatom bloom was studied in relation with the sea ice retreat by multiple transects across the marginal ice zone. Biogenic s...

The Arctic Ocean is particularly affected by climate change, with changes in sea ice cover expected to impact phytoplankton primary production. During the Green Edge expedition, the development of the late spring–early summer diatom bloom was studied in relation with the sea ice retreat by multiple transects across the marginal ice zone. Biogenic s...

The Arctic Ocean is particularly affected by climate change, with changes in sea ice cover expected to impact phytoplankton primary production. During the Green Edge expedition, the development of the late spring–early summer diatom bloom was studied in relation with the sea ice retreat by multiple transects across the marginal ice zone. Biogenic s...

The Green Edge initiative was developed to investigate the processes controlling the primary productivity and the fate of organic matter produced during the Arctic phytoplankton spring bloom (PSB) and to determine its role in the ecosystem. Two field campaigns were conducted in 2015 and 2016 at an ice camp located on landfast sea ice southeast of Q...

Within the marine realm, diatoms play a major role in carbon export mainly when they aggregate. Another efficient export pathway is zooplankton faecal pellets emission in the surface mixed layer or after vertical migration in the mesopelagic layers. When diatoms are grazed by large copepods their frustule may ballast the resulting faecal pellets an...

The potential presence of nanoplastics (NP) in aquatic environments represents a growing concern regarding their possible effects on aquatic organisms. The objective of this study was to assess the impact of polystyrene (PS) amino-modified particles (50 nm PSeNH2) on the cellular and metabolic responses of the diatom Chaetoceros neogracile cultures...

Diatom production is mainly supported by the dissolution of biogenic silica (bSiO2) within the first 200 m of the water column. The upper oceanic layer is enriched in dissolved and/or colloidal organic matter, such as exopolymeric polysaccharides (EPS) and transparent exopolymeric particles (TEP) excreted by phytoplankton in large amounts, especial...

The fraction of net primary production that is exported from the euphotic zone as sinking particulate organic carbon (POC) varies notably through time and from region to region. Phytoplankton containing biominerals, such as silicified diatoms have long been associated with high export fluxes. However, recent reviews point out that the magnitude of...

Diatom production is mainly supported by the dissolution of biogenic silica (bSiO2) within the first 200 meters of the water column. The upper oceanic layer is enriched in dissolved and/or colloidal organic matter, such as exopolymeric polysaccharides (EPS) and transparent exopolymeric particles (TEP) excreted by phytoplankton in large amounts, esp...

Diatoms sustain the marine food web and contribute to the export of carbon from the surface ocean to depth. They account for about 40% of marine primary productivity and particulate carbon exported to depth as part of the biological pump. Diatoms have long been known to be abundant in turbulent, nutrient-rich waters, but observations and simulation...

Silicifiers are among the most important organisms on planet Earth. Among them, diatoms play a key role in the trophic networks of the most productive coastal and open-ocean ecosystems, as well as in the biology-mediated transfer of CO 2 from the surface to the ocean interior. However, many gaps remain regarding their quantification at global scale...

Presentation of first results from the 2015 Qikiqtarjuaq Ice Camp - Green Edge Project

Presentation of first results from the Baffin Bay Expedition 2016 (NGCC Amundsen) - Green Edge Project

The marine ecosystem of Kongsfjorden experiences large variations in primary productivity due to pronounced seasonal variations in sunlight, glacier melt, and ice cover. The objective of this study was to assess spatial and seasonal variability in the downward export of biogenic matter in Kongsfjorden. Short-term sediment traps were deployed for pe...

We investigated the effects of iron (Fe) and copper (Cu) limitations on biogenic silica (bSiO2) dissolution kinetics of the marine diatom Pseudo-nitzschia delicatissima during a 3 week batch dissolution experiment. The dissolution of this species was faster during the first week than thereafter. Modeling results from four dissolution models and sca...

Fragments of microplastics are readily incorporated into groups of microscopic algae, altering the rate at which the plastics move through seawater, a recent study has found. In laboratory tests, polystyrene microbeads, which usually sink to the bottom of seawater at a rate of 4 mm a day, sank at a rate of several hundreds of metres a day when part...

Fragments of microplastics are readily incorporated into groups of microscopic algae, altering the rate at which the plastics move through seawater, a recent study has found. In laboratory tests, polystyrene microbeads, which usually sink to the bottom of seawater at a rate of 4 mm a day, sank at a rate of several hundreds of metres a day when part...

Fragments of microplastics are readily incorporated into groups of microscopic algae, altering the rate at which the plastics move through seawater, a recent study has found. In laboratory tests, polystyrene microbeads, which usually sink to the bottom of seawater at a rate of 4 mm a day, sank at a rate of several hundreds of metres a day when part...

Fragments of microplastics are readily incorporated into groups of microscopic algae, altering the rate at which the plastics move through seawater, a recent study has found. In laboratory tests, polystyrene microbeads, which usually sink to the bottom of seawater at a rate of 4 mm a day, sank at a rate of several hundreds of metres a day when part...

Plastic debris are resistant to degradation, and therefore tend to accumulate in marine environment. Nevertheless recent estimations of plastic concentrations at the surface of the ocean were lower than expected leading the communities to seek new sinks. Among the different processes suggested we chose to focus on the transport of microplastics fro...

Diatom aggregates contribute significantly to the vertical sinking flux of particulate matter in the ocean. These fragile structures form a specific microhabitat for the aggregated cells, but their internal chemical and physical characteristics remain largely unknown. Studies on the impact of aggregation on the Si cycle led to apparent inconsistenc...

The recycling of biogenic silica (bSiO(2)) produced by diatoms is a vital process sustaining a significant fraction of primary production in the oceans. The efficiency with which bSiO(2) dissolves controls the availability of nutrient silicon in the water column, and modulates the export of organic carbon to the deep sea. Environmental conditions d...

Interactions between carbon and silica in the diatom frustule play an important role in carbon export through their impact on diatom remineralization (carbon degradation and biogenic silica dissolution). To ameliorate model prediction of the fate of Si and organic matter during sedimentation, there is a need to first understand the origin and natur...

Silicon (Si), in the form of dissolved silicate (DSi), is a key nutrient in marine and continental ecosystems. DSi is taken up by organisms to produce structural elements (e.g., shells and phytoliths) composed of amorphous biogenic silica (bSiO2). A global mass balance model of the biologically active part of the modern Si cycle is derived on the b...

To elucidate the origin of the silicic acid (DSi) anomaly observed along the 4000 isobath on the Congo margin, we have established a benthic Si mass balance and performed direct measurements of biogenic silica (bSiO(2)) dissolution in the deep waters and in the sediments. Results strongly suggest that the anomaly originates from the sediments; the...

A fully transient, 2-dimensional physical and biological model has been developed to quantify the seasonal cycle of silica in the estuaries-coastal zone continuum of the Bay of Brest (France). The numerical model includes an explicit representation of the benthic-pelagic coupling, which is stimulated by the increasing density of an invasive megaben...

About a decade ago, the OPALEO community has evaluated the advantages and difficulties of using the mass accumulation rate of biogenic silica (opal MAR) in marine sediments, as a proxy for paleoproductivity (Ragueneau et al., 2000). On the one hand, diatoms play a major role in carbon export, biogenic silica is relatively well preserved compared to...

While a relationship between ballast and carbon in sedimenting particles has been well-documented, the mechanistic basis of this interaction is still under debate. One hypothesis is that mineral ballast protects sinking organic matter from degradation. To test this idea, we undertook a laboratory experiment using the diatom Skeletonema marinoi to s...

Knowing which fraction of a phytoplankton population is viable would often be helpful in answering ecological or physiological questions. However, viability stains (1) often do not function properly, especially with diatoms, (2) are rarely used, and (3) frequently appear to give ambiguous results. Here, we investigate the performance of the FDA via...

The particles sinking out of the ocean's surface layer are made up of a mixture of living and dead algal cells, fecal pellets, and aggregates, while the parameters used to describe the behavior of biogenic silica (bSiO2) in today's models are experimentally determined on freely suspended diatoms (FC). In a simple advection-reaction model we combine...

Settling particles were collected from the Ligurian Sea in the northwestern Mediterranean Sea in May 2003 and separated by elutriation into different settling velocity classes (.230, 115–230, 58–115, and ,58 m d21). Particles of the different classes were incubated for 5 d to study their biodegradability. Particulate opal content and organic compou...

Because aggregated diatoms sink rapidly through the water column, leaving little time for dissolution, aggregation influences the balance between recycling of biogenic silica (bSiO2) and its sedimentation and preservation at the seafloor. Additionally, aggregation may directly impact dissolution rates of opal. Laboratory experiments were conducted...

Despite recent progress in understanding the ocean's role in the global carbon cycle, we are not yet able to predict the response of ecosystems to climate change and feedbacks of the ocean onto atmospheric CO2. In particular, particle flux dynamics must be represented more faithfully in ocean models. We know that particulate organic carbon (POC) fl...

Diatoms play a major role in carbon export from surface waters, but their role in the transport of carbon to the deep sea has been questioned by global analyses of sediment trap fluxes which suggest that organic carbon fluxes and transfer efficiencies through the mesopelagic are tightly correlated with CaCO3 (Klaas and Archer, 2002; François et al....

Diatoms are key species that strongly participate to primary production and to carbon export out of the surface layer. During this PhD, the role of diatoms and the impact of aggregation on the biological pump were investigated using direct measurement of bSiO2 dissolution rates in aggregates and freely suspended diatoms during laboratory experiment...

Biodeposition is a process that strongly affects physical, chemical and biological properties near the sediment–water interface, and mollusks have been shown to influence the cycling of many biogenic elements. In the Bay of Brest ecosystem, the invasive benthic suspension feeder Crepidula fornicata has been proliferating for 50years, and its influe...

Les échanges entre le carbone de l'atmosphère et les autres réservoirs (océan, biosphère terrestre...) étaient équilibrés jusqu'à l'ère industrielle. Depuis 1850, les activités anthropiques telles que la déforestation, l'élevage intensif et surtout la combustion d'énergies fossiles émettent en grande quantité CO2 et CH4 dans l'atmosphère. L'équilib...