Nicolas Savoye

University of Bordeaux · Environnements et Paléoenvironnements Océaniques et Continentaux (UMR 5805)

Despite 20 years of control on eutrophication, episodes of summer hypoxia still occur in the Loire estuary, impacting water quality and posing a key scientific and management challenge. This work aimed to quantify the contribution of the benthic compartment to hypoxia in the Loire estuary by direct measurement of water-sediment fluxes and an in-dep...

Along with their important diversity, coastal ecosystems receive various amounts of nutrients, principally arising from the continent and from the related human activities (mainly industrial and agricultural activities). During the 20th century, nutrients loads have increased following the increase of both the global population and need of services...

Arcachon Bay is a prominent oyster production area on the coast of Western Europe, and is subject to chemical contamination including by trace metals. Recently, the national “mussel-watch” monitoring network – using local bivalves as semi-quantitative bioindicators of coastal chemical contamination – highlighted a significant increase in copper (Cu...

Large amounts of nutrients have been released to the coastal ecosystems during the 20th century. Since then, management policies have been implemented and these amounts decreased in the economically developed countries. We examined the bi-decadal changes in nutrients (nitrate + nitrite, ammonium, orthophosphate and silicic acid) in the Arcachon bay...

A better understanding of growth drivers in shellfish populations including the common cockle Cerastoderma edule is essential, as their future is challenged by unsustainable fishing practices and climate change. In this study the spatial and temporal variabilities in common cockle growth across latitudes were assessed and compared with historical d...

Coastal marine ecosystems, which play a crucial role in the biogeochemical and ecological functioning of the Earth, are highly sensitive to the combined effects of climate and human activities. Because of their location, coastal ecosystems are directly influenced by human activities, but it remains challenging to assess the spatial and temporal sca...

The consistency of satellite and in situ time series of Chlorophyll-a (Chl-a), Turbidity and Total Suspended Matters (TSM) was investigated at 17 coastal stations throughout the year 2017. These stations covered different water types, from relatively clear waters in the Mediterranean Sea to moderately turbid regions in the Bay of Biscay and the sou...

Particulate organic matter (POM) in coastal systems is a mixture of different organic matter (OM) sources originating from land and sea. Among sources, bacterial biomass plays a large role in OM processing and carbon recycling in the ocean and is often neglected as a source in common approaches. The present study proposes to use elemental and isoto...

The functional diversity of two planktonic functional compartments, the nano-microphytoplankton and the mesozooplankton was used in order to better understand i) the drained marshes functioning and their related ecological functions, ii) the impacts of human control (replenishment) and human activities on the catchment basin (urbanization and catch...

Autochthonous organic material, not organic matter from the watershed, compose fluffy sediments of shallow Aquitaine lakes Pierre ANSCHUTZ; Céline CHARBONNIER; Léna ROSSI; Damien BUQUET; Nicolas SAVOYE Shallow lakes often contain fluffy sediments that are very rich in organic matter (OM). These sediments represent a sink of carbon, but they also ac...

To understand and predict the physical, chemical, and biological processes at play in coastal and nearshore marine areas requires an integrated, interdisciplinary approach. The case study of the French structuration of coastal ocean and nearshore observing systems provides an original overview on a federative research infrastructure named ILICO. It...

Marine mucilage has been described as worldwide phenomena occurring sporadically, or frequently in certain coastal areas. They are transitory phenomena that can remain in the photic zone for several days or weeks. Their occurrence has been more frequent and persistent, and their magnitude has increased during the last decades. Their formation typic...

Primary consumers play a key role in coastal ecosystems by transferring organic matter from primary producers to predators. Among them, suspension-feeders, like bivalve molluscs are widely used in trophic web studies. The main goal of this study was to investigate variations of C and N elemental and isotopic ratios in common bivalves (M. edulis, M....

Marine mercury (Hg) concentrations have been monitored in the French coastline for the last half a century using bivalves. The analyses presented in this study concerned 192 samples of bivalves (mussels: Mytilus edulis and Mytilus galloprovincialis and oysters: Crassostrea gigas and Isognomon alatus) from 77 sampling stations along the French coast...

What is the temporal variability of the elemental stoichiometry of marine microbial communities across ocean regions? To answer this question, we present an analysis of environmental conditions, particulate organic carbon, nitrogen, and phosphorus concentrations, and their ratios across 20 time-series (3 – 25 years duration) representing estuarine,...

Precise indices based on n-alkane signatures were developed in order to determine the sources and composition of sedimentary organic matter (SOM) in coastal systems. The Arcachon Bay (France), a well-studied temperate lagoon, was used as an example of a complex coastal system sheltering a wide diversity of OM sources. Three main groups of sources w...

Although stable isotope ratios are increasingly used to investigate the trophic ecology of marine organisms, their spatial variations are still poorly understood in the coastal environment. In this study, we measured the stable isotope composition (δ13C, δ15N) of suspended particulate organic matter (SPOM) (primary producer), a suspension feeder, t...

The diet of different macrozoobenthic trophic groups was investigated in the Arcachon Bay — a semi-enclosed macrotidal ecosystem that shelters the largest Z. noltei seagrass meadow in Europe — in early spring and late summer 2009, using stable isotopes and fatty acids. Fatty acid profiles and literature information about the biology and physiology...

River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle1. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems2. It is generally assumed that inland waters emit c...

Coastal and estuarine nursery grounds are essential habitats for sustaining flatfish stocks since only these shallow and productive areas provide the high food supply that allows maximizing juvenile growth and survival in most flatfish species. However, the main organic matter sources at the basis of benthic food webs might differ drastically betwe...

Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncerta...

We measured spatial and temporal variations in carbon concentrations, isotopic compositions and exports during a complete hydrological cycle in nine watercourses draining a lowland forested podzolized catchment, flowing into the Arcachon lagoon (France). In addition, integrated fluxes of CO2 across the water-atmosphere interface were estimated to a...

This work studied the impact of a small estuary (a 4 km-long estuary, at the interface between the Leyre River and the Arcachon lagoon, SW France) with a short flushing time on continental nutrient loads to a coastal lagoon. While large estuaries are known to modify the nutrient load of rivers to the coast, the impact on continental fluxes of a sho...

The origin and composition of sediment organic matter (SOM) were investigated together with its spatial dis-tribution in the Arcachon Bay – a macrotidal lagoon that shelters the largest Zostera noltii meadow in Europe – using elemental and isotopic ratios. Subtidal and intertidal sediments and primary producers were both sampled in April 2009. Thei...

Surface δ15NPON increased 3.92 ± 0.48‰ over the course of 20 days following additions of iron (Fe) to an eddy in close proximity to the Antarctic Polar Front in the Atlantic sector of the Southern Ocean. The change in δ15NPON was associated with an increase in the >20 μm size fraction, leading to a maximal difference of 6.23‰ between the >20 μm and...

Les sources de matières organiques, à la base des réseaux trophiques des juvéniles de poissons plats, diffèrent selon le système hydrique considéré. Au sein des nourriceries estuariennes, le réseau trophique repose principalement sur la matière organique particulaire d'origine terrigène. En revanche, dans les zones non estuariennes et notamment les...

We studied the evolution of the isotopic composition of dissolved Si (d 30 Si DSi) and biogenic Si (d 30 Si BSi) during a diatom bloom induced by an iron fertilization experiment in a Southern Ocean (SO) eddy. Dissolved Si (DSi) consumption was clearly boosted as a result of iron addition. We estimate an apparent Si isotopic fractionation factor of...

Estimation of the silicon (Si) mass balance in the ocean from direct measurements (Si uptake-dissolution rates …) is plagued by the strong temporal and spatial variability of the surface ocean as well as methodological artifacts. Tracers with different sensitivities toward physical and biological processes would be of great complementary use. Silic...

Spatial changes in the dietary regime of Ruditapes philippinarum from intertidal sediments of Arcachon Bay were depicted by analyzing stable isotope ratios in both its adductor muscles and potential trophic sources. Manila clams were collected from 50 sites in May to June 2006. Dietary reconstruction was based on the IsoSource mixing model, conside...

Spatial changes in the dietary regime of Ruditapes philippinarum from intertidal sediments of Arcachon Bay were depicted by analyzing stable isotope ratios in both its adductor muscles and potential trophic sources. Manila clams were collected from 50 sites in May to June 2006. Dietary reconstruction was based on the IsoSource mixing model, conside...

The stable carbon and nitrogen isotopic composition of digenean trematode parasites and their marine mollusc hosts was investigated to describe the potential influence of parasites on their host and its different tissues, and to obtain further insight into their trophic relationships. Four parasite-host systems were studied: Labratrema minimus-Cera...

The Arcachon lagoon is a preserved site, but eutrophication may develop as a consequence of low buffer capacity and slow turnover of waters inside the lagoon.. The aim of this study was to determine the fate and transformation of N, P, and C compounds between river mouths and the lagoon, in order to better describe their dynamics. Macrotidal estuar...

The stable carbon and nitrogen isotopic composition of digenean trematode parasites and their marine mollusc hosts was investigated to describe the potential influence of parasites on their host and its different tissues, and to obtain further insight into their trophic relationships. Four parasite–host systems were studied: Labratrema minimus–Cera...

Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1594-1604, doi:10.1016/j.dsr2.2008.04.013. This paper presents resul...

This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22°45′N, 158°W; Hawaii; studied during June–July 2004) and the mesotrophic Subarctic Pacific K2 site (47°N, 161°W; studied during July–August 2005). Earlier work has shown that non-lithoge...

We report on the distribution of excess, non-lithogenic particulate barium (Ba), a proxy for twilight-zone remineralization of organic matter (OM), in the Kerguelen Plateau area during the late austral summer of 2005. This study was part of a broader investigation focusing on natural iron fertilization controlling the characteristic and recurrent p...

The impact of iron fertilization on mesopelagic carbon (C) remineralization was assessed during the European Iron Fertilization Experiment (EIFEX) in the Southern Ocean by following the temporal change of excess particulate barium (also called biogenic or Baxs) in the mesopelagic waters of a mesoscale eddy. Before the iron infusion the site was alr...

Five iron-fertilization experiments in the Southern Ocean have clearly demonstrated that adding iron increases primary production, but the implications for carbon export to the ocean interior have been less clear. This reflects both observational limitations of short-term experiments and their uncertain relevance to quantifying ecosystem level proc...

In this article, we show how a disease could bias stable isotope analyzes of trophic networks and propose a strategy in the choice of tissues to be analyzed. In the past few years, a new pathology (brown muscle disease or BMD) affecting the posterior adductor muscle of Ruditapes philippinarum has emerged in Arcachon Bay. BMD induces a necrosis of m...

Variations of phytoplankton assemblages were studied in November–December 2001, in surface waters of the Southern Ocean along a transect between the Sub-Antarctic Zone (SAZ) and the Seasonal Ice Zone (SIZ; 46.9°–64.9°S; 142°–143°E; CLIVAR-SR3 cruise). Two regions had characteristic but different phytoplankton assemblages. Nanoflagellates(<20μm) and...

1] Particulate biogenic Ba, Sr and Ca and barite crystal contents from suspended matter were compared with acantharian water column distributions and individual Ba/Sr acantharian skeletal ratios during the European Iron Fertilization Experiment (EIFEX) in the Southern Ocean. In the upper 150 m, results indicate that the particulate biogenic Ba xs s...

We determine Southern Ocean diatom silicon isotopic signatures and compare them with the previously published data for dissolved silicic acid from the same locations. Five stations distributed along the WOCE SR-3 transect (Australian Sector of the Southern Ocean) in different biogeochemical provinces are presented: Polar Front and Inter-Polar Front...

This paper provides pieces of advice on the practices of quality assurance and quality control in assessing production and dissolution rates of biogenic silica in marine waters with stable isotope techniques. The objective is to make a rigorous contribution to the interpretation of 30Si isotopic measurements including modelling and uncertainty anal...

Spring and summer profiles of dissolved and particulate barium (Ba) from WOCE SR3 line (145°E) in the Southern Ocean are compared and seasonal evolutions discussed. Fluxes are estimated from mass conservation equations and from differences in reservoir contents between seasons. Subtraction of barium is observed at mesopelagic depths (upper 600 m) a...

The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the ro...

The short-lived thorium isotope 234Th (half-life 24.1 days) has been used as a tracer for a variety of transport processes in aquatic systems. Its use as a tracer of oceanic export via sinking particles has stimulated a rapidly increasing number of studies that require analyses of 234Th in both marine and freshwater systems. The original 234Th meth...

234Th is an extremely useful radiotracer of particle dynamics in aquatic systems. Its utility, however, has yet to be realized by many within the aquatic science community. The reasons for this may in part be due to a lack of knowledge of how this nuclide has been used in the past as well as how and where 234Th might be profitably applied in future...

Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the 234Th activity distribution (in order to calculate 234Th fluxes) and an estimate of the C / 234Th ratio on sinking particles, to empirically derive C...

Over the past few decades, the radioisotope pair of 238U / 234Th has been widely and increasingly used to describe particle dynamics and particle export fluxes in a variety of aquatic systems. The present paper is one of five review articles dedicated to 234Th. It is focused on the models associated with 234Th whereas the companion papers (same iss...

We present water column profiles of excess particulate Ba (Baxs, an estimate of biogenic Ba from total particulate Ba after small corrections for lithogenic Ba) along a transect in the Australian sector of the Southern Ocean from the Subantarctic Zone (SAZ) to the Sea Ice Zone during spring (October–December 2001). Surface water Baxs contents appea...

We analyzed d 29 Si of dissolved silicate for eight water column profiles across the Southern Ocean (south of Australia in spring 2001) from the Seasonal Ice Zone (SIZ) north to the Subantarctic Zone (SAZ), including the first isotopic compositions measured for Si-depleted seawaters. All profiles display mixed layer enrichments in heavy Si isotopes...

The isotopic composition of silicic acid and biogenic Si along the WOCE SR3 transect (142-144 ̊E; spring 2001) was analysed by MC-ICP-MS, following Cardinal et al. (2003). We sampled the Subantarctic Zone (SAZ), the Subantarctic Front (SAF), the Polar Front Zone (PFZ), the Interpolar Front Zone (IPFZ), the southern Antarctic Zone (AZ-S) and the Sea...

Measurement of biogenic silica (BSi) in the suspended matter of estuarine and coastal waters is not trivial because of the interference of lithogenic silica (LSi) that can represent up to 90% or more of the total particulate silica within the water column. Till date, no method has provided a satisfying way to correct this mineral interference when...

Radon-222 is a good natural tracer of groundwater discharge and other physical processes in the coastal ocean. Unfortunately, its usefulness is limited by the time consuming nature of collecting individual samples and traditional analysis schemes. We demonstrate here an automated multi-detector system that can be used in a continuous survey basis t...