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See detailFrom seascape level to functional ecology: A case study over P. oceanica seagrass meadows in Calvi, Corsica
Lapeyra Martin, Jon ULg; Abadie, Arnaud; Richir, Jonathan ULg et al

in Actes du colloque Carhamb'ar 2017 (in press)

see long abstract

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See detailSTARECAPMED, des indices pour La Méditerranée
Leduc, Michèle; Abadie, Arnaud; Donnay, Annick et al

in Actes du colloque Carhamb'ar 2017 (in press)

Le projet STARECAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) a pour objectif (i) d’améliorer la compréhension du ... [more ▼]

Le projet STARECAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) a pour objectif (i) d’améliorer la compréhension du fonctionnement des différents écosystèmes marins côtiers présents en Méditerranée et (ii) de décrire l’influence des activités humaines sur les processus qui gouvernent ce fonctionnement. La baie de Calvi, par sa situation exceptionnelle, est un site de référence de la Directive Européenne Cadre sur l’Eau (DCE), du monitoring de l’eutrophisation et de la contamination par les éléments traces. La Station de recherches océanographiques STARESO, implantée dans la baie depuis près de 50 ans, possède un accès unique à la mer et de nombreuses facilités logistiques. Elle a développé au fil du temps une expertise scientifique reposant notamment sur l’acquisition de longues séries temporelles de données environnementales. Ensemble, Baie et Station s’intègrent en un site atelier dédié à l’évaluation de l’état de santé des écosystèmes marins côtiers de Méditerranée Nord-Occidentale. En particulier, différents indices et indicateurs y sont développés en collaboration avec de nombreux laboratoires partenaires. Ainsi, nous avons développé, d’une part, une version non destructive de l’indice PREI (Posidonia Rapid Easy Index) d’évaluation de la qualité des eaux côtières reposant sur le suivi des herbiers à Posidonia oceanica, et d’autre part, deux indices d’évaluation de l’impact des ancrages, puis testé   l’indice EBQI (Ecosystem Based Quality Index), une approche sur la diversité écologique. Les indices TEPI (Trace Element Pollution Index) et TESVI (Trace Element Spatial Variation Index) permettent d’évaluer la contamination par les éléments traces. Le BeMSI (BEnthic Methodology Simplification) est un nouvel indicateur de la qualité du milieu défini à partir de la composition des peuplements macrobenthiques des substrats meubles et plus généralement, l’indice LIMA traduit l’attrait paysager et la richesse patrimoniale du benthos méditerranéen entre 0 et –40 m. Quant à l’indice ICAR (Indice paysager CAulerpa Racemosa), il permet d’évaluer les niveaux de colonisation par l’algue invasive Caulerpa cylindracea. Enfin, une approche innovante reposant sur l’enregistrement des sons permet d’évaluer la qualité du milieu à partir d’un paysage acoustique sous-marin. En conclusion, le développement et l’application combinée de ces différents indices et indicateurs développés dans le cadre du programme pluridisciplinaire STARECAPMED fournissent une estimation globale des états du milieu côtier méditerranéen à différents niveaux d’organisation, depuis l’espèce jusqu’à l’écosystème. De plus, leur mise en œuvre dans ce même site atelier privilégié permet de les confronter, de les ajuster et de les intercalibrer pour à terme les proposer aux gestionnaires du milieu côtier. [less ▲]

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See detailEffects of an experimental resource pulse on the macrofaunal assemblage inhabiting seagrass macrophytodetritus
Remy, François ULg; Gobert, Sylvie ULg; Lepoint, Gilles ULg

in Belgian Journal of Zoology (in press)

Physical disturbances and resource pulses are major structuring drivers of terrestrial and aquatic ecosystems. The accumulations of exported dead leaves from the Neptune grass, Posidonia oceanica (L ... [more ▼]

Physical disturbances and resource pulses are major structuring drivers of terrestrial and aquatic ecosystems. The accumulations of exported dead leaves from the Neptune grass, Posidonia oceanica (L.) Delile are ephemeral and highly dynamic detrital habitats offering food sources and shelter for vagile macrofauna community. These habitats are frequently subject to wind and storms which can add “new” detrital material to previous accumulations; these can be defined as resource pulses and could potentially impact the associated macrofauna. This study assesses the impact of an experimental resource pulse on the macrofauna associated with exported P. oceanica litter accumulations. The experimental design consisted of two pulse treatments (the addition of dead leaves with and without the associated fauna), and two controls (one procedural, and one total control), where the added material was left underwater for 14 days. Invertebrates then present in the sampled detritus were all identified and counted. Our data suggest that the responses of these invertebrates to resource pulses present intermediate characteristics between aquatic and terrestrial ecosystems responses. Inputting a moderate amount of dead P. oceanica leaves into experimental mesocosms had a non-negligible impact and rapidly affected the macrofauna community. Specialist detritivores species were boosted while herbivore/detritivore species dramatically decreased. Predators also showed a modest but significant density increase, demonstrating the fast propagation of the pulse response throughout the entire community and through several trophic levels. Strict hypoxia-tolerant species were also only observed in the treated mesocosms, indicating the strong influence of resource pulses on physico-chemical conditions occurring inside litter accumulations. [less ▲]

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See detailCaractérisation des habitats et communautés benthiques en baie de Calvi (Corse) : évaluation du potentiel de l’imagerie ROV.
Sirjacobs, Damien ULg; Aguera Garcia, Antonio; Pelaprat, Corinne et al

in Bajjouk, Touria; Mahier, Marie; Piel, Steven (Eds.) et al Carhambar, 2017. Cartographie des habitats marins benthiques : de l’acquisition à la restitution. Actes de colloque. Édition Ifremer‐AFB. 161 p. (2017, March 15)

La Station de Recherches Sous-Marines et Océanographiques (STARESO) contribue à l’étude des habitats et communautés benthiques depuis de nombreuses années, notamment en baie de Calvi (Corse). Une campagne ... [more ▼]

La Station de Recherches Sous-Marines et Océanographiques (STARESO) contribue à l’étude des habitats et communautés benthiques depuis de nombreuses années, notamment en baie de Calvi (Corse). Une campagne d’acquisition d’image a été réalisée en juillet 2016 à l’aide d’un robot de type VideoRay afin d’évaluer les apports potentiels de cette approche dans certains des suivis environnementaux menés en baie de Calvi. Le robot a été équipé de caméras go-pro orientées vers le bas et vers l’avant (configurations d’acquisition en mode vidéo, vidéo stéréoscopique ou photos digitales). Le potentiel de certaines de ces approches sera évalué et illustré, notamment sur base de comparaison avec des observations produites en plongée. Ces exemples se focalisent tant sur des communautés globales et des indices paysagers (indice Lima) que sur des compartiments de ces communautés (macroalgues) ou encore sur la marge inférieure des habitats remarquables que constituent les herbiers de Posidonies. [less ▲]

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See detailPosidonies : Lire dans les prairies sous-marines
Abadie, Arnaud ULg; Gobert, Sylvie ULg; Pergent, Gérard

Article for general public (2017)

Les “feuilles” qui s’amoncèlent sur les plages de Méditerranée sont le souvenir échoué des luxuriantes prairies sous-marines qui tapissent les fonds. C’est un écosystème fragile dont dépend un grand ... [more ▼]

Les “feuilles” qui s’amoncèlent sur les plages de Méditerranée sont le souvenir échoué des luxuriantes prairies sous-marines qui tapissent les fonds. C’est un écosystème fragile dont dépend un grand nombre d’espèces : les chercheurs doivent apprendre à “lire” les fonds pour identifier les menaces qui pèsent sur la posidonie. [less ▲]

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See detailDepth-speci c Fluctuations of gene expression and protein abundance modulate the photophysiology in the seagrass Posidonia oceanica
Procaccini, Gabriele; Ruocco, Miriam; Marin-Guirao, Lazaro et al

in Scientific Reports (2017), 7(42890), 1-14

We present the results of a multiple organizational level analysis conceived to identify acclimative/ adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily uctuations in the light ... [more ▼]

We present the results of a multiple organizational level analysis conceived to identify acclimative/ adaptive strategies exhibited by the seagrass Posidonia oceanica to the daily uctuations in the light environment, at contrasting depths. We assessed changes in photophysiological parameters, leaf respiration, pigments, and protein and mRNA expression levels. The results show that the diel oscillations of P. oceanica photophysiological and respiratory responses were related to transcripts and proteins expression of the genes involved in those processes and that there was a response asynchrony between shallow and deep plants probably caused by the strong di erences in the light environment. The photochemical pathway of energy use was more e ective in shallow plants due to higher light availability, but these plants needed more investment in photoprotection and photorepair, requiring higher translation and protein synthesis than deep plants. The genetic di erentiation between deep and shallow stands suggests the existence of locally adapted genotypes to contrasting light environments. The depth-speci c diel rhythms of photosynthetic and respiratory processes, from molecular to physiological levels, must be considered in the management and conservation of these key coastal ecosystems. [less ▲]

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See detailCopper toxicity on coral holobiont photosynthetic processes
Georges, Nadège; Richir, Jonathan ULg; Batigny, Antoine et al

Poster (2016, December 16)

Copper (Cu), an essential micronutrient to organisms, may become toxic when present at too high environmental concentrations. This metal remains an aquatic contaminant of concern, notably because of its ... [more ▼]

Copper (Cu), an essential micronutrient to organisms, may become toxic when present at too high environmental concentrations. This metal remains an aquatic contaminant of concern, notably because of its recent re-use as biocide in metal-based antifouling paints. The aim of this study was to monitor the physiological alterations in a zooxanthellate coral species and its endosymbionts (i.e. the coral holobiont) exposed to increasing Cu concentrations. Nubbins of Seriatopora hystrix were exposed for 8 days in 1 L intermittent respirometers to 5 nominal Cu concentrations: 0-2-5-15-50 ppb. Respirometers were maintained at 25.0±0.2°C with successive open/close cycles of 30 min. A 12/12 hours day-night light regime was applied with constant daylight intensity of 200 μmol photons m-2 s-1. Water renewal rate during the 30 min open cycles was 15 mL.min-1. The photosynthetic performances of coral endosymbionts were assessed daily with a fluorescence imaging system (imaging-PAM). At the end of the 8-days experiment, the maximal photochemical quantum yield (FV/FM) of coral nubbins had decreased by 12% and 38%, respectively, in the 15 ppb and 50 ppb treatments. This decrease was even greater for the effective photochemical quantum yield (ɸPSII) with values dropping by 41% and 54%, respectively. Cu exposure also affected the symbiosis between the coral host and its endosymbionts. Nubbins of the 15 ppb treatment slightly lightened from day 6, whilst nubbins exposed to the 50 ppb treatment lightened from day 3, and started to bleach from day 6. The analysis of nubbins’ primary productivity did not coincide with the above observations, the oxygen production within each respirometer remaining relatively constant during the overall experiment for all treatments. This unexpected observation may be the sign of a compensation mechanism. In conclusion, Cu affected the photosynthetic processes of S. histrix within 8 days from relevant environmental concentrations of 15 ppb. The exposure of corals to toxic chemicals thus has to be considered as an additional stressor to, e.g., ocean acidification or elevated temperature, which may disturb their ecophysiology and lead to bleaching. [less ▲]

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See detailExploring a Mediterranean mesozooplankton 13 year time-series.
Fullgrabe, Lovina; Richir, Jonathan ULg; Batigny, Antoine et al

Poster (2016, December 16)

Zooplankton plays diverse crucial roles within the marine ecosystem and can also be used as bio- indicator of climate changes since it is very sensitive to environmental changes. Therefore it is essential ... [more ▼]

Zooplankton plays diverse crucial roles within the marine ecosystem and can also be used as bio- indicator of climate changes since it is very sensitive to environmental changes. Therefore it is essential to consider long-term plankton series. Given the analysis of plankton samples is time- consuming, it requires an effective and rapid analytical method. We have used in this work a supervised learning approach adapted for the semi-automatic classification of digital images of the mesozooplankton of the Bay of Calvi (Corsica, France) by using the Zoo/PhytoImage software. Together with a 11-years long zooplankton time-series, a set of nine environmental variables were monitored in order to identify controlling factors and determine whether the communities were sensitive to global environmental changes. The main components of the mesozooplankton community were characterized by both seasonal and inter-annual variability. Additionally, variation of holoplankton and meroplankton differentiated one from each other. The holoplanktonic community could be split into two subgroups according to its variation in function of the environment: cladocerans and appendicularians, and to a lesser extent, copepods on one hand, and cnidarians, chaetognathes and thaliaceans, on the other hand. Regarding inter-annual variation, one year (2007) showed particularly low production of total zooplankton which was also the case for all the different holoplanktonic taxa. Accounting for that phenomenon were identified some potentially underlying environmental factors. Finally, although water temperature increased significantly over the last years along with the frequency of marine heat wave events, no evident change in the global zooplankton composition was observed yet. [less ▲]

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See detailAssessing edge-effects in Posidonia oceanica seagrass meadows: A multidisciplinary approach
Lapeyra, Jon; Abadie, Arnaud; Lejeune, Pierre et al

Conference (2016, December)

Structural boundaries in ecosystems play an important role both in the context of seascape architecture, ecological processes and biodiversity. The Mediterranean Seagrass Posidonia oceanica (L.) Delile is ... [more ▼]

Structural boundaries in ecosystems play an important role both in the context of seascape architecture, ecological processes and biodiversity. The Mediterranean Seagrass Posidonia oceanica (L.) Delile is considered an ecosystem engineer species, forming habitats of great ecological value and providing many ecosystem services. This study aims to (1) determine whether there are differences between seagrass-sand corridors edges and the adjacent continuous meadow, and (2) investigate whether anthropogenic pressures can cause disturbances in the measured parameters along the edges and the meadow. We have developed a multidisciplinary approach combining plant physiology, faunal canopy community studies and seagrass structural parameters characterization. We performed in situ chlorophyll fluorescence measurements using a Pulse Amplitude Modulated (Diving-PAM) fluorometry in order to assess the photosynthetic rate of the shoots. Vagile macrofauna of the leaf stratum was sampled by a hand-towed net, and the major taxonomic groups were sorted, counted, and identified. Meadow’s biometric measurements and the epiphytic biomass were also determined. Regarding edge-meadow matrix, results have shown highest differences on matrix structural parameters such as shoot density and shoot type proportions. Shoot density was found to decrease in edges considerably. We found c.a to 60 % plagiotropic shoots on edges while in continuous meadow orthotropics were predominant (up to 90 %). Howerver vagile-fauna population densities and diversity did not differ significantly among stations studied, neither by sites. Photosynthetic rate and leaf surface values also did not show changes between edges and continuous meadow. However, results did show that plagiotropic shoots had higher photosynthetic rate than orthotropics, and also that epiphyte abundance sorted out to be much higher (up to 54 %) on edges. [less ▲]

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See detailRelationships between environmental parameters and the microbenthic loop of Posidonia oceanica meadows at small spatial scale
Pete, Dorothée ULg; Alvera Azcarate, Aida ULg; Gobert, Sylvie ULg

in Zoology 2016: 23rd Congress of Zoology (2016, December)

In these times of global change, understanding how carbon flows through ecosystems is of primary importance. In coastal Mediterranean regions, Posidonia oceanica meadows produce and store a lot of carbon ... [more ▼]

In these times of global change, understanding how carbon flows through ecosystems is of primary importance. In coastal Mediterranean regions, Posidonia oceanica meadows produce and store a lot of carbon, but most of it is described as refractory. As a step in the understanding of how organic matter degradation/storage happens in this ecosystem, this study focus on small scale relationships between the microbenthic loop (organic matter, microphytobenthos, bacteria and meiofauna) and environmental parameters (grain size, P. oceanica density, vegetal fibre biomass, pore water nutrient content, sediment total carbon (TC), organic carbon (TOC), nitrogen (TN) and phosphorous (TP) contents, phaeopigments and bacterial production (FDC)). Thus, a 1.25 m x 1.25 m frame was put in a pristine P. oceanica meadow and twelve points were randomly sampled in May 2008 for all the studied parameters. At such a small scale, every component of the microbenthic loop presented a heterogeneity, which was the highest for the microphytobenthos biomass and the lowest for total meiofauna abundance (TMA). No relationship was found between the components of the microbenthic loop but the abundances of Turbellaria and Ciliophora were correlated with total organic matter in the sediment (TOM). None of the environmental parameter was linked with the microphytobenthos biomass, suggesting that the high spatial variability observed did not depend on the measured parameters. Relationships were found between TOM and ammonium, total bacteria abundance and biomass (TBA and TBB) and sediment phaeopigments, TMA and TC, TN and TP. TBB variability was however explained by a combination of FDC and nutrient contents in pore water and sediment. Taking the microbenthic loop as a whole, pore water ammonium and nitrites + nitrates, FDC and phaeopigments were able to explain the observed variability. So, at small scale the variability in the microbenthic loop of a P. oceanica meadow is related with parameters linked with degradation processes and bacteria activities (phaeopigments, FDC, ammonium, nitrites + nitrates), except for meiofauna, which is related with the nutrient content of the sediment, especially TC. Those results underline the importance of the relationship between the microbenthic loop and degradation processes, even at a small scale. [less ▲]

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See detailImportance de l’océan pour la régulation du climat de nos régions
Gobert, Sylvie ULg

Scientific conference (2016, November 29)

Mise en évidence des rôles de l'océan dans notre climat et conséquences des changements actuels

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See detailEcoNum, a research unit devoted to marine environment monitoring
Richir, Jonathan ULg; Batigny, Antoine; Georges, Nadège et al

Conference (2016, October 27)

The monitoring of coastal environments remains a research domain of great interest and concern. Coastal ecosystems are threatened by natural and human-induced stressors and are, as transitional ... [more ▼]

The monitoring of coastal environments remains a research domain of great interest and concern. Coastal ecosystems are threatened by natural and human-induced stressors and are, as transitional environments, particularly sensitive to disturbances. EcoNum first research thematic revolves around hermatypic corals, calcifying organisms, and their adaptation potentials to environmental changes including by using original and patented chemostats. The studied organisms are grown and maintained in artificial mesocosms that simulate environmental conditions of a natural system. This infrastructure allows to perform long-term experiments, giving time to organisms to adapt to the tested conditions (e.g., increased temperature or lowered pH). Longer-term studies have demonstrated that many organisms are more resistant to environmental stressors than previously observed on the short-term. EcoNum also studies coastal plankton abundance and diversity. Plankton is particularly sensitive to physicochemical changes of water bodies. The classification and the enumeration of planktonic organisms require specialized tools in order to analyse time series of multiple samples. EcoNum has developed a software for the semi-automatic classification of planktonic organisms called Zoo/PhytoImage. This software has been used to study a 10-year time series of coastal Mediterranean zooplankton samples. The concomitant analysis of environmental parameters registered at high frequency with specific statistical tools such as the R package pastecs allows to understand the processes governing the changes observed in plankton assemblages. The use and the development of statistical tools in R (e.g., Zoo/Phytoimage, pastecs) is a priority of EcoNum to favour open access knowledge and reproductive sciences. EcoNum research topics also focus on coastal ecotoxicology. Chemicals, including trace elements, remain contaminants of concern, mainly in coastal environments that are the final sink of inland pollution sources. The chemical integrity of coastal ecosystems thus has to be accurately monitored. The partitioning of chemicals between their dissolved, particulate and sedimentary phases does not provide information on their bioavailability. EcoNum thus monitors coastal waters using bioindicator species such as seagrasses, mussels or sand worms. A global map of the contamination of the Mediterranean by trace elements has been drawn using seagrasses has bioindicator species. EcoNum also studies trace element ecology and toxicology. For instance, it has demonstrated the toxicity of copper on the coral Seriatopora hystrix and it's symbiont's photosynthetic processes, or its bioaccumulation and basipetal translocation towards rhizomes in the seagrass Posidonia oceanica as reserve nutrient for subsequent leaf growth. Finally, coastal vegetated systems are potential carbon thinks (or sources) in the global carbon cycle. Therefore, EcoNum studies the primary productivity of seagrass meadows, from the individual to the community, with measuring techniques as diverse as PAM-fluorometry or biomass production determination. To conclude, EcoNum is a research unit devoted to marine environment monitoring. It develops research thematics on major coastal communities such as coral reefs, seagrass beds or plankton assemblages and studies their natural dynamics and the effects of stressors on their global functioning. [less ▲]

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See detailA one year survey of seagrass primary productivity using the diving-PAM technique
Richir, Jonathan ULg; Abadie, Arnaud; Grosjean, Philippe et al

Poster (2016, October 18)

Marine magnoliophytes are major primary producers in coastal benthic habitats worldwide. They play a crucial role in the global carbon cycle (one of the more efficient blue carbon wells). Hence, it is ... [more ▼]

Marine magnoliophytes are major primary producers in coastal benthic habitats worldwide. They play a crucial role in the global carbon cycle (one of the more efficient blue carbon wells). Hence, it is necessary to characterise the eco-systemic services seagrass meadows provide. Posidonia oceanica (L.) Delile, the main Mediterranean seagrass species, has high foliar and belowground biomass production. Several methods have been used so far to measure its primary production (e.g., using incubation bells, optodes, biomass and elementary content measurements). A less used method relies on chlorophyll fluorescence measurements through the Pulse Amplitude Modulated (PAM) fluorometry method (Diving - PAM). In the framework of the STARECAPMED project, this study aimed to determine weekly to bimonthly over a one-year period the photosynthetic responses (Yield, relative Electron Transfer Rate, Rapid Light Curve) of P. oceanica. The survey was performed at 10m depth in a pristine meadow (Calvi, Corsica, France). To obtain reliable and comparable data, the protocol was standardized: measurements were performed on the convex middle part of the third leaf, at zenith, during shiny and calm weather days. Results showed that the plant displayed a well-marked seasonality. The mean ETR (μmol e- m-2 s-1 ) of the plant ranged from 2.17 in winter to 21.9 in summer and was linearly correlated throughout the year with the in situ irradiance (PAR irradiance taken perpendicularly to the surface, in the average leaf orientation). The ETR plateaus of the RLCs, ranging from 10.9 to 35.0, and their corresponding maximum PAR intensities evolved similarly. These results demonstrated both the adaptation and the seasonal plasticity of the meadow’s photosynthetic system. Overall the non-destructive PAM technique is a powerful and cost-effective tool to assess the primary productivity of seagrass meadows where other techniques (e.g. optodes) cannot be used and when direct sampling (e.g. biomass measurements) is not allowed. [less ▲]

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See detailDiversity, dynamics and trophic ecology of animal communities associated to Posidonia oceanica (L.) Delile macrophytodetrital accumulation: synthesis of a ten year study
Lepoint, Gilles ULg; Borges, Alberto ULg; Champenois, Willy ULg et al

Poster (2016, October 17)

In the Mediterranean, Neptune grass Posidonia oceanica, produces a huge quantity of detrital biomass. These macrophytodetritus may accumulate in shallow waters, forming litter accumulations colonised by ... [more ▼]

In the Mediterranean, Neptune grass Posidonia oceanica, produces a huge quantity of detrital biomass. These macrophytodetritus may accumulate in shallow waters, forming litter accumulations colonised by abundant, yet understudied, animal communities. These accumulations are especially foraged by juvenile and adult fishes. Here, we aim to synthesize results obtained over the last ten years regarding diversity, dynamics and trophic ecology of associated meio- and macrofauna. Accumulations are found throughout the year but important seasonal and short-term variability in composition, quantity and physico-chemical parameters inside the accumulation is observed. Accumulations are dominated by respiration (litter degradation), however, primary production occurs at exposed surfaces (epiphytic production). Meio- and macrofauna have distinct traits in comparison to adjacent habitats (seagrass meadows or epilithic algae communities). A physico-chemical gradient occurs inside accumulations which partially defines assemblage composition and distribution. Meiofauna, in particular harpacticoid copepods, is diverse, abundant and composed of species from seagrass meadows, water column and sediment. In contrast, macrofaunal assemblages are simplified compared to the ones occurring in the seagrass meadows and are dominated by amphipods. Litter accumulations display a lower macrofaunal diversity than do seagrass meadows, but a higher abundance and animal biomass. Meio- and macrofauna show a high trophic diversity, dominated by ingestion and assimilation of epiphytes (macroalgae and, probably, detrivorous microbiota). Moreover, direct or indirect assimilation of carbon originating from seagrass detritus is demonstrated for many species. Although diverse trophic niches were observed, the assemblage showed a simplified trophic web structure compared to the seagrass meadows. Detritivorous organisms dominate this assemblage and are more abundant in the litter than in the living meadows. Consequently, according to its abundance and the fact it consumes directly and indirectly seagrass material, fauna associated to litter accumulation may play a significant role in the degradation and transfer to higher trophic level of detrital seagrass carbon. [less ▲]

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See detailInvestigating the potential of Cymodocea nodosa (Ucria) Ascherson as a coastal carbon sink coupling marine habitat cartographies and in situ nondestructive sampling
Abadie, Arnaud ULg; Richir, Jonathan ULg; Pieraccini, Riccardo ULg et al

Poster (2016, October)

Seagrass meadows are major carbon sinks, trapping about 10% of the total CO2 sequestrated in the oceans. In the Mediterranean, a major focus has been made on the climax species Posidonia oceanica (L ... [more ▼]

Seagrass meadows are major carbon sinks, trapping about 10% of the total CO2 sequestrated in the oceans. In the Mediterranean, a major focus has been made on the climax species Posidonia oceanica (L.) Delile, while other species remained little studied. In the framework of the STARECAPMED project, we thus chose to study Cymodocea nodosa (Ucria) Ascherson, a pioneer species with a rapid turnover and an expected high stocking capacity. Furthermore, the area covered by that species has been largely underestimated. In order to fill these two knowledge gaps, we first mapped all seagrass habitats within a Mediterranean bay (Calvi, Corsica, France) using side scan images, aerial photographs and ground truths. This cartography was followed by seasonal in situ density measurements and non-destructive shoot sampling (leaf cutting). Samplings were performed at different depths (5 to 23 m depth) in 6 contrasted stations (small patchy meadows to continuous beds) in order to cover all the existing facies of the bay. Elementary contents (carbon, nitrogen and stable isotope ratios) were measured in laboratory. This first work shows that C. nodosa meadows in Calvi Bay cover an area of 0.498 km2. Carbon stocks of the leaves reached 0.25 tons in winter and 2.72 tons in summer. Their nitrogen contents showed a marked seasonality with a maximum value of 0.020 mgN.m-2 in July and a minimum value of 0.005 mgN.m-2 in March. Some modifications in the trophic conditions of the water column at several stations were put in an obvious through the N stable isotopes values, mostly during the summer period. The actual underestimation of the area covered by that species in Calvi Bay has been properly mapped thanks to side scan sonar techniques revealing, together with elementary content analysis, its importance in the carbon balance of coastal areas. [less ▲]

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See detailTrophic interactions between two neustonic organisms: insights from Bayesian stable isotope data analysis tools
Lepoint, Gilles ULg; Laurent, Bernard; Gobert, Sylvie ULg et al

in Belgian Journal of Zoology (2016), 146(2), 123-133

The by-the-wind sailor Velella velella (Linnaeus, 1758) and its predator, the violet snail Janthina globosa (Swainson, 1822) are both floating neustonic organisms. Despite their global oceanic ... [more ▼]

The by-the-wind sailor Velella velella (Linnaeus, 1758) and its predator, the violet snail Janthina globosa (Swainson, 1822) are both floating neustonic organisms. Despite their global oceanic distribution and widespread blooms of V. velella in recent years, many gaps remain in our understanding about prey/predator interactions between these two taxa. Using stable isotope ratios of carbon and nitrogen, we aimed to study the trophic relationship between V. velella and J. globosa and investigate diet variation of V. velella and J. globosa in relation to individuals’ size. Bayesian approaches were used to calculate isotopic niche metrics and the contribution of V. velella to the J. globosa diet. Our data showed that the isotopic niche of V. velella differed markedly from that of J. globosa. It was larger and did not overlap that of the J. globosa, indicating a more variable diet but at a lower trophic level than J. globosa. The isotopic niche of V. velella also varied according to the size class of the individual. Small individuals showed a larger isotopic niche than larger animals and low overlap with those of the larger individuals. J. globosa displayed very low isotopic variability and very small isotopic niches. In contrast, there were no isotopic composition nor isotopic niche differences between J. globosa of any size. This very low isotopic variability suggested that J. globosa is a specialist predator, feeding, at least in this aggregation, principally on V. velella. Moreover, outputs of a stable isotope mixing model revealed preferential feeding on medium to large (> 500 mm2) V. velella colonies. While our isotopic data showed the trophic relationship between V. velella and J. globosa, many questions remain about the ecology of these two organisms, demonstrating the need for more fundamental studies about neustonic ecosystems. [less ▲]

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See detailEnvironmental monitoring: between science and decision-making
Richir, Jonathan ULg; Gobert, Sylvie ULg; Lejeune, Pierre et al

Scientific conference (2016, April 13)

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See detailDes indices scientifiques pour la gestion et la protection de milieu marin
Gobert, Sylvie ULg

Scientific conference (2016, March 24)

En 1972, L’Université de Liège inaugure STARESO: une station pour les recherches sous-marines et océanographiques. Posée sur la presqu’île de La Revellata, la station accueille depuis plus de 40 ans, des ... [more ▼]

En 1972, L’Université de Liège inaugure STARESO: une station pour les recherches sous-marines et océanographiques. Posée sur la presqu’île de La Revellata, la station accueille depuis plus de 40 ans, des scientifiques de notre Université et du monde entier. La Méditerranée est considérée comme un mini océan, modèle pour comprendre l’océan mondial. Elle abrite une très grande biodiversité terrestre et marine mais c’est aussi une des mers les plus touristique au monde, zone subissant la littoralisation, la surpêche, la pollution... Les indices pour la détection de la pollution et pour la gestion des milieux marins permettent de visualiser, de montrer de manière synthétique et rapide, l’état des écosystèmes. A partir de STARESO, zone encore protégée de l’activité humaine, des indices définissant l’état des écosystèmes (DCE), des indices paysagers (qualité et valeur patrimoniale), des indices de pollution (teneur en éléments traces) et de colonisation par des espèces envahissantes ont été mis au point, validés scientifiquement et proposés aux gestionnaires du milieu marin. Après une description du site d’étude, du contexte écologique, cet exposé présente ces indices, les limites et les champs d’application en milieu marin. [less ▲]

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See detailEstimating carbon fluxes in a Posidonia oceanica system: Paradox of the bacterial carbon demand
Velimirov, Branko; Lejeune, Pierre; Kirschner, A. et al

in Estuarine Coastal & Shelf Science (2016), 171

A mass balance ecosystemic approach, based on bacterial carbon demands and primary production data, was used to investigate if the bacterial community (freewater bacterioplankton and benthic bacteria of ... [more ▼]

A mass balance ecosystemic approach, based on bacterial carbon demands and primary production data, was used to investigate if the bacterial community (freewater bacterioplankton and benthic bacteria of the oxygenated sediment layer) could be sustained by the main primary producers (Posidonia oceanica and its epiphytes, adjacent macroalgae and phytoplankton communities; hereafter called the P. oceanica system) of a non-eutrophic Mediterranean bay. Unexpectedly, the findings of this study differed from previous works that used benthic incubation chamber and O2 optode methods. In this study, data were grouped in two categories, corresponding to two time periods, according to the seawater temperature regime (<18 °C or >18 °C): from May to October and from November to April. Between May and October, the produced benthic macrophyte tissues could not provide the carbon required by the bacteria of the oxygenated sediment layer, showing that the balance production of the investigated bay was clearly heterotrophic (i.e. negative) during this time period. In contrast, between November and April, benthic bacteria respiration nearly equated to carbon production. When integrating the open water carbon dynamics above the meadow in the model, a negative carbon balance was still observed between May and October, while a slight carbon excess was noticed between November and April. In the light of these findings, the carbon balance being negative on an annual basis, alternative carbon sources are required for the maintenance of the bacterial carbon production. [less ▲]

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See detailDistribution of inorganic and organic contaminants in the intertidal surface sediments along the Hugli River Estuary, eastern part of India
Das, Krishna ULg; Sarkar, Santosh; Thomé, Jean-Pierre ULg et al

Conference (2016, February 17)

Hooghly estuary and coastal environment in north east coast of India has been strongly affected by the rapid human settlements, intensive boating and tourist activities, deforestation and ongoing ... [more ▼]

Hooghly estuary and coastal environment in north east coast of India has been strongly affected by the rapid human settlements, intensive boating and tourist activities, deforestation and ongoing agricultural and aquacultural practices. The present work investigated trace elements (TEs, T-Hg, Al, V, Cr, Fe, Mn, Cu, Zn, Co, Ni, Ca, Sr, Li, Be, P, Mo, Ag, Cd, Sn, Sb, Ba, Pb, Bi, U, As, Se) and organohalogen compounds in surface sediment (top 0-10cm) considering 8 sampling sites along the Hugli River Estuary (HRE), India. The studied organic compounds include polychlorobiphenyls (PCBs), hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane and metabolites (DDTs) and polybromodiphenyl ethers (PBDEs). Textural analyses of the sediment reveal an overall dominance of mud. All trace elements could be detected at variable concentrations in the following descending order: Al>Fe>Ca> P>Mn> Cu> Zn> Ba >V >Cr>Sr>Ni> Li >Co >Pb>As >Se >U >Be >Sn>Bi >Ag >Mo >Cd >Sb. A synchronous enrichment of majority of the elements were observed at the site Gangasagar (~100 km south megacity Calcutta), situated at the confluence of Hugli River and Bay of Bengal, which might be attributed to cumulative impact of the physicochemical processes and multiple anthropogenic sources. It is revealed that PCBs and DDTs were the dominant compounds among the organic pollutants accounting concentrations up to 23.5 ng.g-1 and 4.4 ng.g-1 respectively at the site Babughat, adjacent to the megacity Calcutta. The results have implications for pollution in complex estuarine environment in a meso-macrotidal setup where there is significant influx of sediments carrying huge load of inorganic and organic pollutants mainly due to rapid urbanization and industrialization. [less ▲]

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