Experimental in situ exposure of the seagrass Posidonia oceanica (L.) Delile to 15 trace elements

in Aquatic Toxicology (2013)

The Mediterranean seagrass Posidonia oceanica (L.) Delile has been used for trace element (TE) biomonitoring since decades ago. However, present informations for this bioindicator are limited mainly to ... [more ▼]

The Mediterranean seagrass Posidonia oceanica (L.) Delile has been used for trace element (TE) biomonitoring since decades ago. However, present informations for this bioindicator are limited mainly to plant TE levels, while virtually nothing is known about their fluxes through P. oceanica meadows. We therefore contaminated seagrass bed portions at two experimental TE levels in situ with a mix of 15 TEs (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Ag, Cd, Pb and Bi) to study their uptake and loss kinetics by P. oceanica. Shoots immediately accumulated pollutants from the beginning of exposures. Once contaminations ended, TE concentrations came back to their original levels within two weeks, or at least showed a clear decrease. P. oceanica leaves exhibited different uptake kinetics depending on elements and leaf age: the younger growing leaves forming new tissues incorporated TEs more rapidly than the older senescent leaves. Leaf epiphytes also exhibited a net uptake of most TEs, partly similar to that of P. oceanica shoots. The principal route of TE uptake was through the water column, as no contamination of superficial sediments was observed. However, rhizomes indirectly accumulated many TEs during the overall experiments through leaf to rhizome translocation processes. This study thus experimentally confirmed that P. oceanica shoots are undoubtedly an excellent short-term bioindicator and that long-term accumulations could be recorded in P. oceanica rhizomes. [less ▲]

An adapted staining-destaining method to sort soft-bottom macrobenthos mixed with Posidonia oceanica fibers

in Mediterranean Marine Science (2013), 14(1), 92-94

Sorting   of   soft-­bottom   macrobenthos   entangled   with   Posidonia   oceanica fibers is time-consuming and tedious because of the weak of colour contrast .  This   paper   describes   a   staining ... [more ▼]

Sorting   of   soft-­bottom   macrobenthos   entangled   with   Posidonia   oceanica fibers is time-consuming and tedious because of the weak of colour contrast .  This   paper   describes   a   staining-­destaining   technique   that   produces   good   contrast   between   soft-­bottom   macrobenthos  and  Posidonia  oceanica fibers. The method has been tested on Corsican samples in oligotrophic areas characterized by small-size soft-bottom macrofauna. Our technique saves sorting time (-24%) and is simple to implement. [less ▲]

A study of Electra posidoniae Gautier (Cheleistomata, Anasca), a bryozoan strictly found as epiphyte of the seagrass Posidonia oceanica (L.) Delile.

Poster (2012, November 26)

Species living as epiphytes of marine macrophytes have often important role in ecosystem functioning, such as food web suppliers. Some animal or algae species may be considered as really specialised in ... [more ▼]

Species living as epiphytes of marine macrophytes have often important role in ecosystem functioning, such as food web suppliers. Some animal or algae species may be considered as really specialised in the colonization of plant substrate and often dominates epiphytic community, particularly, on long life-span seagrass and macroalgae species. Because epiphytic compartment dysfunction is often implied in seagrass human-induced declining, it is important to understand dynamics and life traits of its specific component in pristine area. In our study, colonization dynamics, biomass seasonality, diet composition of Electra posidoniae, an epiphytic bryozoa, strictly found on the leaves of the seagrass Posidonia oceanica and dominating the leaf epifauna, were assessed monthly at 10 metre depth in the Revellata Bay (Corsica, Mediterranean sea). Aiming to delineate their trophic role in the ecosystem, we have performed bulk stable isotopes measurements and gut content analysis. [less ▲]

An overview of the microbenthic loop in Posidonia oceanica meadows: the good, the bad and the ugly

in Creed, J.C.; Oigman-Pszczol, S.S. (Eds.) Proceedings of the 10th International Seagrass Biology Workshop (ISBW10), 25- 30 November 2012, Armação dos Búzios, Brazil (2012, November)

Posidonia oceanica is an endemic seagrass of the Mediterranean Sea. The ecosystem based on this plant is essential from an ecological and economical point of view (commercial species, touristic activities ... [more ▼]

Posidonia oceanica is an endemic seagrass of the Mediterranean Sea. The ecosystem based on this plant is essential from an ecological and economical point of view (commercial species, touristic activities, oxygen production), though very sensitive to environmental perturbations. To detect those perturbations, scientists are trying to find more efficient ecological indicators. Most of the time, those indicators are based on the plant itself. Unfortunately, this seagrass does not react very quickly to perturbations so, when a reaction is noticed, it is often too late to prevent irremediable damages to the ecosystem. The sedimentary compartment of P. oceanica meadows has been less studied than the canopy level. However, it could be a good source of ecological indicators because it is the final container of all the pollution. In this framework, the microbenthic loop has been studied. It is a major subsystem of those meadows and encompasses organic matter, bacteria, microphytobenthos and meiofauna. As those organisms have a rapid turnover and stay almost all their life inside the sediment, they seemed good potential indicators. This presentation will show what is useful or not inside the sediment and more specifically inside the microbenthic loop. Results of a comparison between a fish farm and a reference location will be used, as well as in situ experiments (shading and sediment loading) and small spatial scale variations. At the end of this presentation, you will know what are the good, the bad and the ugly in the sedimentary compartment of a P. oceanica meadow. [less ▲]

Trophic tracers reveal considerable diversity among diets of dominant amphipods from Posidonia oceanica seagrass meadows

Poster (2012, August 20)

Mediterranean Posidonia oceanica meadows shelter a high biomass and an important biodiversity of amphipod crustaceans. In other temperate meadows, the amphipods play an important part in the functioning ... [more ▼]

Mediterranean Posidonia oceanica meadows shelter a high biomass and an important biodiversity of amphipod crustaceans. In other temperate meadows, the amphipods play an important part in the functioning of the ecosystem, notably in organic matter transfers from producers to higher level consumers. However, the situation in Posidonia oceanica meadows remains unclear, and little is known about the trophic ecology of amphipods, which are generally regarded as generalist herbivores/detritivores despite the lack of precise studies. Here, we combined gut content examination and trophic markers (fatty acids, stables isotopes of C and N) to delineate the diet of the dominant species of amphipods from Posidonia oceanica seagrass meadows and to highlight trophic diversity among this community. Our results indicate that contribution of microepiphytic diatoms and of benthic and suspended particulate organic matter to the diet of amphipods were anecdotal. On the other hand, all dominant species heavily relied on macroalgal epiphytes, suggesting a certain extent of overlapping in the diets of the dominant species. Considerable interspecific differences nonetheless existed, notably concerning grazing preferences towards epiphytes from leaves or litter fragments vs. epiphytes from rhizomes. In addition, the use of the SIAR isotopic mixing model showed that most species had a mixed diet, and relied on several food items. None of the examined species seemed to graze on their seagrass host, but Gammarus aequicauda partly relied on seagrass leaf detritus. Overall, our findings demonstrate that amphipods have the potential to be key-items in trophic and functional interactions occurring among Mediterranean Posidonia oceanica meadows. [less ▲]

Seasonal and depth-related distributions of epiphytic Bryozoa in a Mediterranean seagrass meadow

Poster (2012, May 31)

Although biofouling on Posidonia oceanica (L.) Delile is thought to be driven by the variability of environmental parameters and phenology of the plant, effect of these parameters on sessile animal ... [more ▼]

Although biofouling on Posidonia oceanica (L.) Delile is thought to be driven by the variability of environmental parameters and phenology of the plant, effect of these parameters on sessile animal colonization is still poorly understood. This study aims to document the seasonality and the bathymetric variability of epiphytic Bryozoa diversity and abundance on this seagrass Posidonia shoots were collected in the Revellata bay (Corsica, Mediterranean) in five seasons from 7 to 30 m depth. Colony densities may reach more than 87000 colonies. m-2 at 10 m depth in spring; this probably implies an important contribution of Bryozoa larvae to spring plankton where P. oceanica meadows are present. The Bryozoa specific distribution and abundance appeared to be determined by the seasonality of both the environmental parameters and the plant phenology. However, depth and associated environmental gradients played a structuring role. Based on our data and on the literature, we propose a classification of epiphytic Bryozoa in four categories from hyper-epiphytic specialist to accidental epiphytes and underline the necessity to protect seagrass systems on their full depth range to maximize biodiversity conservation. [less ▲]

Stare-Capmed : Présentation générale du projet et exemple d'une action : "Impact de l'ancrage sur la dynamique des herbiers de posidonies".

Conference (2012, May 16)

STARE-CAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) est un projet de recherche mis en place par Stareso S.A.S. depuis ... [more ▼]

STARE-CAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) est un projet de recherche mis en place par Stareso S.A.S. depuis janvier 2012. Il a pour objectif d’établir un site de référence à long terme pour la compréhension, par la recherche fondamentale, des processus de l’évolution des écosystèmes méditerranéens côtiers et océaniques en réponse aux changements actuels globaux et locaux des pressions anthropiques. Centré sur la Baie de Calvi et le proche large, il vise à fournir un référentiel basé sur des mesures à haute fréquence qui doivent pouvoir complémenter les réseaux de surveillance basse fréquence et de recherches existants et ainsi faire progresser la compréhension des processus. En outre, le projet doit fournir aux utilisateurs finaux (collectivités locales et régionales, administrations nationales, ...) des orientations de gestion basées sur l’analyse étayée des processus en jeux. Financé par l’Agence de l’eau RMC et la Collectivité Territoriale de Corse, le projet, multidisciplinaire, se décline actuellement selon 10 axes de travail : • Suivi du cadre hydrographique et physico-chimique • Suivi et quantification des pressions anthropiques • Ecosystème planctonique • Benthos de substrat meuble • Benthos de substrat dur et faune vagile • Phanérogames marines et écosystèmes associés • Mouillages et processus d’altération des herbiers de posidonies • Ecotoxicologie et polluants émergents • Bilan CO2 et métabolisme des écosystèmes • Zones protégées, espèces nouvelles, recrutement Pour chacun de ces axes, la stratégie d’échantillonnage est basée sur la comparaison de données obtenues durant des périodes où l’impact anthropique est faible (octobre-avril) avec celles obtenues durant des périodes de pression intense (mai-septembre), et sur la comparaison de données issues de sites de référence peu impactés avec celles provenant de sites où l’impact anthropique est reconnu. A titre d’exemple, le but de l’action "Mouillages et processus d’altération des herbiers de posidonies" est de mettre en évidence les conséquences des altérations liées à l’arrachage de faisceaux de posidonies sur la vitalité de l’herbier. Des zones où la pression de mouillage est reconnue seront définies sur base des travaux de cartographie de l’herbier, également réalisés dans le cadre du projet STARE-CAPMED. Elles seront comparées avec des zones d’herbiers sains témoins par la caractérisation du sédiment (mesures de compacité in situ, mesures des concentrations en O2 et nutriments et du pH de l’eau interstitielle, granulométrie et teneur en matière organique du sédiment, proportions de rhizomes et morts) ainsi que par la définition de l’état physiologique des faisceaux de posidonies (mesures biométriques classiques, analyses des contenus élémentaires en carbone, azote et phosphore) et par l’application d’indices écologiques définis par la DCE (PREI, BIPO, …). Les résultats obtenus permettront d’avoir une vue d’ensemble des processus par lesquels l’impact physique des mouillages de bateaux de plaisance occasionne des dégâts aux herbiers de posidonies. Ils pourront ainsi fournir une base de connaissances solide aux gestionnaires soucieux de limiter cet impact. [less ▲]

Use of semi-quantitative kit methods to study the heterotrophic bacterial community of Posidonia oceanica meadows: Limits and possible applications

in Estuarine Coastal & Shelf Science (2012), 109

Rapid, easy and low cost semi-quantitative methods were tested to study the heterotrophic bacterial community of Posidonia oceanica meadows and were compared to techniques commonly used in microbial ... [more ▼]

Rapid, easy and low cost semi-quantitative methods were tested to study the heterotrophic bacterial community of Posidonia oceanica meadows and were compared to techniques commonly used in microbial ecology. Free and pore-water bacterial densities were estimated by luminescence, and principal enzymatic activities, metabolic capabilities and benthic mineralisation processes were studied with microtitration methods: ApiZym galleries, Biolog microplates and BART tests. Bacterial densities varied little throughout the year and were around 5.0 10^5 and 6.0 10^6 cells ml -1 of free and pore-water, respectively. The combined use of the ApiZym gallery and the Biolog microtitration plate permitted highlighting bacterial enzymatic activities susceptible to degrade principal organic polymers present in the Posidonia meadow, and to correlate these enzymatic activities to the subsequent potential utilization of resulting monomeric products. Levels of enzymatic activities (1.80-8.36 nmoles substrates h -1 ml- 1) and energetic bacterial metabolism (1.80-6.42 nmoles substrates h -1 ml- 1) presented seasonality relying on the temperature regime and on the primary production (Posidonia and phytoplankton). Main mineralization processes of buried organic matter through sulfate and iron reduction activities were successfully detected. Despite the complexity of the studied ecosystem, results obtained by this semi-quantitative approach, compared to studies applying commonly used methods in microbial ecology, highlighted the same bacterial dominant key processes. Their low cost, rapid and easy use, and the low level of expertise and sophistication they require means that these techniques are of use to many employed in environmental surveys. [less ▲]

Chemical contamination along the Mediterranean French coast using Posidonia oceanica (L.) Delile above-ground tissues: a multiple trace element study

in Ecological Indicators (2012), 18

Levels of Be, Al, V, Mn, Co, As, Se, Mo, Ag, Sn, Sb, Bi as well as of Cr, Fe, Ni, Cu, Zn, Cd and Pb in Posidonia oceanica (L.) Delile from the Mediterranean French coast were analysed using DRC ICP-MS ... [more ▼]

Levels of Be, Al, V, Mn, Co, As, Se, Mo, Ag, Sn, Sb, Bi as well as of Cr, Fe, Ni, Cu, Zn, Cd and Pb in Posidonia oceanica (L.) Delile from the Mediterranean French coast were analysed using DRC ICP-MS. The first twelve elements have not been well studied and can be considered to be potential pollutants as a result of potentially increased levels resulting from anthropogenic activities. Spatial variation and/or compartmentalization were found for all trace elements. Except for Al, Cr, Fe, Cu and Ag, most trace elements were preferentially accumulated in photosynthetic tissues, suggesting uptake from the water column. Moreover, for Be, V, Mn, Co, Ni, As, Mo, Sb, Sn and Pb, adult leaves had higher levels than intermediate leaves, suggesting low kinetics of accumulation. Levels in the third intermediate leaf were representative of the average levels of the integral shoot, and thus can be used alone in chemical biomonitoring. For most of the twelve little-studied trace elements, the background levels of the northwestern Mediterranean Sea can be measured, and their spatial variation can be related to anthropogenic activities. Levels of the seven widely studied trace elements seem to decrease or stabilize over time, probably due to their reduced anthropogenic use. These observations show that P. oceanica is a sensitive bioindicator for the monitoring of chemical contamination of a large number of trace elements. [less ▲]

Posidonia oceanica, a usefull tool to biomonitor the pollution of Mediterranean coastal areas by trace elements

Scientific conference (2011, December 02)