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See detailCarbon dioxide dynamics in lake Kivu during the dry and wet seasons
Borges, Alberto ULg; Delille, Bruno ULg; Descy, J.-P. et al

Poster (2008)

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See detailLINK BETWEEN MARINE MAMMAL EXPOSURE TO PERFLUOROOCTANE SULFONATE (PFOS) AND STABLE-CARBON ISOTOPE RATIOS IN NERITIC AND OCEANIC WATERS OFF BRAZIL
Dorneles, Paulo; Lailson-Brito, José; Meyer, Johan et al

in Organohalogen Compounds (2008), 70

The main objective of the present study was to determine the current concentrations of PFOS in dolphins from neritic and oceanic waters of a region of high industrialization and urbanization in the ... [more ▼]

The main objective of the present study was to determine the current concentrations of PFOS in dolphins from neritic and oceanic waters of a region of high industrialization and urbanization in the Southern Hemisphere. Since stable carbon isotopes can be used to point out relative contributions to the diet of different potential primary sources in trophic networks, indicating for example the inshore versus offshore contribution to food intake 7,8, stable carbon isotope measurements were carried out in the same dolphins in order to clarify inter-species differences. [less ▲]

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See detailLactation effect on the trace element dynamics in northern elephant seals (Mirounga angustirostris)
Habran, Sarah ULg; Debier, Cathy; Lepoint, Gilles ULg et al

Conference (2007, November 30)

Northern elephant seals, Mirounga angustirostris, are exceptional mammals: females fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Females thus lose ... [more ▼]

Northern elephant seals, Mirounga angustirostris, are exceptional mammals: females fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Females thus lose approximately a third of body mass and produce energy-rich milk with a high fat content. Stable carbon and nitrogen isotope ratios (d13C and d15N used as diet markers) and total mercury concentrations (Hg) were measured in tissues (blood cells, serum, full blood, milk and blubber) from 20 mother-pup pairs on days 4 and 21 of lactation. A systematic difference was observed between isotopic values in blood cells and serum of the mothers, linked to diet and distinct biochemical composition between blood components. d13C differed between inner and outer blubber layers and were similar between inner blubber and milk. High Hg concentrations (up to 350 ng.g-1ww at the beginning of lactation) were found in the blood of mother elephant seals linked to their high d15N values in blood cells. Hg transfer through placenta and milk was observed between mothers and pups. A significant increase of blood Hg concentration in mothers (+285 ng.g-1ww) and a decrease in pups (-93 ng.g-1ww) were observed between days 4 and 21 of lactation. Both processes were explained by a remobilization of proteins and lipids during fasting and milk production in mothers and by a dilution of Hg in pups due to their high mass increase during this period. This study confirms that lactation modifies stable nitrogen isotope ratios in tissues, as well as mercury levels in blood from mothers and pups, and highlights the existence of a transplacental and transmammary transfer of mercury in northern elephant seals. Therefore, physiological processes and body condition should be considered carefully when interpreting stable isotope ratios and Hg concentrations in the framework of biomonitoring. [less ▲]

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See detailNocturnal vertical migrations by amphipods of the Posidonia oceanica (L.) Delile foliar stratum : Importance of the litter cover
Michel, Loïc ULg; Sturaro, Nicolas ULg; Lepoint, Gilles ULg et al

Poster (2007, November)

In seagrass meadows, several groups of vagile invertebrates are well known to perform a nocturnal rise from the lower layers of the meadow to the foliar stratum. This vertical migration is generally ... [more ▼]

In seagrass meadows, several groups of vagile invertebrates are well known to perform a nocturnal rise from the lower layers of the meadow to the foliar stratum. This vertical migration is generally regarded as a defense mechanism against predation by diurnal fishes, as well as a mean to maximize the exploitation of trophic resources offered by the meadow. Here, we focused on the amphipods from a Mediterranean Posidonia oceanica meadow. We sampled the community present in the meadows of Calvi Bay (NW Corsica) using two different techniques (hand-towed net and litter collecting). Samples were taken at two seasons, during both night and daytime. Our results confirm the nocturnal rise to the foliar stratum. Combined to an analysis of the recent literature, they also tend to show that amphipods spend the daytime not in the matte itself, as it has been proposed in the past, but in the thin layer of Posidonia litter present at the interface between the foliar stratum and the root/rhizome system. This would emphasize the role of the litter cover in the complexity of the habitat within the meadow, and therefore in the vagile invertebrate community structure and the functioning of the whole meadow as an ecosystem. [less ▲]

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See detailField measurements of inorganic nitrogen uptake by epiflora components of the seagrass Posidonia oceanica (Monocotyledons, Posidoniaceae)
Lepoint, Gilles ULg; Jacquemart, Julien; Bouquegneau, Jean-Marie ULg et al

in Journal of Phycology (2007), 43(2), 208-218

Crustose corallines, crustose and erect brown algae, and sessile animals are major components of the epiphytic community of the Mediterranean seagrass Posidonia oceanica (L.) Delile. Production, biomass ... [more ▼]

Crustose corallines, crustose and erect brown algae, and sessile animals are major components of the epiphytic community of the Mediterranean seagrass Posidonia oceanica (L.) Delile. Production, biomass, and specific composition of this epiphyte-seagrass association are impacted by anthropogenic increase of nutrient load in this oligotrophic area. In this context, nitrogen uptake by P. oceanica and its epiflora was measured using the isotope N-15 at a 10 m depth in the Revellata Bay (Corsica, Mediterranean Sea). Epiflora components showed various seasonal patterns of biomass and abundance. The epiphytic brown algae appeared at the end of spring, later than the crustose corallines, and after the nitrate peak in the bay. Because of their later development in the season, epiphytic brown algae mostly rely on ammonium for their N needs. We hypothesize that the temporal succession of epiphytic organisms plays a crucial role in the N dynamics of this community under natural conditions. The epiphytic brown algae, which have a growth rate one order of magnitude greater than that of crustose corallines, showed lower N-uptake rates. The greater N-uptake rates of crustose corallines probably reflect the greater N requirements (i.e., lower C/N ratios) of red algae. We determined that the epiflora incorporated ammonium and nitrate more rapidly than their host. Nevertheless, when biomass was taken into account, P. oceanica was the most important contributor to N uptake from the water column by benthic macrophytes in this seagrass bed. [less ▲]

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See detailEvaluation of the usefulness of bird feathers as a non-destructive biomonitoring tool for organic pollutants: A comparative and meta-analytical approach
Jaspers, V. L. B.; Voorspoels, S.; Covaci, Adrian et al

in Environment International (2007), 33(3), 328-337

In this study, we investigated whether bird feathers can be used as a non-destructive biomonitor for organic pollutants. We analysed the outermost tail feathers of 8 terrestrial and aquatic bird species ... [more ▼]

In this study, we investigated whether bird feathers can be used as a non-destructive biomonitor for organic pollutants. We analysed the outermost tail feathers of 8 terrestrial and aquatic bird species from Belgium (8 species, n = 108) for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs). Every compound class could be quantified in one single tail feather of the birds under study (sum PCBs ranging from 5.5 to 5 10 ng/g feather, sum PBDEs from 0.33 to 53 ng/g feather, sum DDTs from 1.5 to 730 ng/g feather), except for PBDEs in feathers of the common moorhen (Gallinula chloropus). Further, we calculated Pearson correlations between concentrations of organic pollutants in feathers and concentrations in corresponding muscle or liver tissue from the birds. Correlations were found significant in half of the cases of the terrestrial species, but were found not significant for the aquatic species, with the exception of a significant correlation of sum PCBs in the common moorhen. Only for the common buzzard (Buteo buteo) (n=43) all correlations were found significant (0.32 < r < 0.77). In order to cope for low statistical power, we performed a meta-analysis on all bird species together. This led to significant correlations between levels in feathers and corresponding levels in muscle or liver for all terrestrial birds (p < 0.05 in all cases, effect size 0.59 (p,p'-DDE) to 0.71 (Sigma PCB) for levels in feather and muscle). When correlations were recalculated excluding the birds that had died due to starvation, correlation coefficients for the terrestrial birds were found even higher (effect size up to 0.83 (Sigma PCB)). These results have important implications for non-destructive and retrospective biomonitoring. Although our results suggest that exact concentrations in the body cannot be predicted using feathers, bird feathers can give a good estimate of contamination levels in a population and as such are a potential non-destructive biomonitoring tool for organic pollutants. Outermost tail feathers and muscle tissue were also examined for nitrogen (delta N-15) and carbon (delta C-13) stable isotope content in the different bird species. However, delta N-15/delta C-13 signatures in feather or muscle were not significantly correlated with the corresponding levels of organic pollutants in these tissues. Various confounding factors (such as habitat, condition, age, sex) may have masked a relationship between delta N-15 values and organic pollutant levels in the birds under study. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailEarly colonization of Posidonia oceanica (L.) Delile by epiphytes: Comparison between natural and artificial seagrass leaves
Pete, Dorothée ULg; Gobert, Sylvie ULg; Lepoint, Gilles ULg et al

in Pergent-Martini, Christine; El Asmi, Souha; Le Ravallec, Célia (Eds.) Proceedings of the third Mediterranean symposium on marine vegetation (2007, March)

Posidonia oceanica is an important marine Magnoliophyta of the Mediterranean coastal zone that can form dense meadows. The leaves of this seagrass are colonized by a lot of organisms, from bacteria to ... [more ▼]

Posidonia oceanica is an important marine Magnoliophyta of the Mediterranean coastal zone that can form dense meadows. The leaves of this seagrass are colonized by a lot of organisms, from bacteria to polychaetes and algae. However, the early stages of colonization are not well known. A preliminary is proposed to examine the nine first days of colonization by epiphytes on natural leaves and on Artificial Seagrass Units (ASUs). Aims of this work were to understand which species are the first to set up, to compare colonization on both leaves and to determine the interest of ASUs in ecological studies. It was shown that the setting up of epiphytes on the bases of both leaves is rapid (first algae on the second day) but the number of organisms increases quicker on ASUs than on natural leaves and on the smooth faces than the rough ones. Shannon-Wiener diversity and evenness were higher for the P. oceanica leaves and the use of Bray-Curtis similarity index showed that colonisation is not similar (between 20 and 30 % similarity) on both leaves for the same day. It can be explained by the lower colonization rate of natural leaves. This lower rate is probably due to a less developed biofilm on natural leaves than on ASUs, to a difficult access to the bases of P. oceanica leaves for epiphytes and microoganisms, and the production of phenol compounds by the plant. Even if ASUs used here do not seem to be similar to natural leaves in early stages of colonization, they could be used in ecological studies thanks to their rapid covering by epiphytes. [less ▲]

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See detailLong-Term Feeding Ecology and Habitat Use in Harbour Porpoises Phocoena Phocoena from Scandinavian Waters Inferred from Trace Elements and Stable Isotopes
Fontaine, Michael ULg; Tolley, K. A.; Siebert, U. et al

in BMC Ecology (2007), 7

BACKGROUND: We investigated the feeding ecology and habitat use of 32 harbour porpoises by-caught in 4 localities along the Scandinavian coast from the North Sea to the Barents Sea using time-integrative ... [more ▼]

BACKGROUND: We investigated the feeding ecology and habitat use of 32 harbour porpoises by-caught in 4 localities along the Scandinavian coast from the North Sea to the Barents Sea using time-integrative markers: stable isotopes (delta13C, delta15N) and trace elements (Zn, Cu, Fe, Se, total Hg and Cd), in relation to habitat characteristics (bathymetry) and geographic position (latitude). RESULTS: Among the trace elements analysed, only Cd, with an oceanic specific food origin, was found to be useful as an ecological tracer. All other trace elements studied were not useful, most likely because of physiological regulation and/or few specific sources in the food web. The delta13C, delta15N signatures and Cd levels were highly correlated with each other, as well as with local bathymetry and geographic position (latitude). Variation in the isotopic ratios indicated a shift in harbour porpoise's feeding habits from pelagic prey species in deep northern waters to more coastal and/or demersal prey in the relatively shallow North Sea and Skagerrak waters. This result is consistent with stomach content analyses found in the literature. This shift was associated with a northward Cd-enrichment which provides further support to the Cd 'anomaly' previously reported in polar waters and suggests that porpoises in deep northern waters include Cd-contaminated prey in their diet, such as oceanic cephalopods. CONCLUSION: As stable isotopes and Cd provide information in the medium and the long term respectively, the spatial variation found, shows that harbour porpoises experience different ecological regimes during the year along the Scandinavian coasts, adapting their feeding habits to local oceanographic conditions, without performing extensive migration. [less ▲]

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See detailFatty acids and stable isotopes in fish and harbour porpoises (Phocoena phocoena) from the North Sea: further insights in their trophic relationships
Drouguet, Olivier; Caut, Stéphane; Haelters, Jan et al

Poster (2007)

Recent observations revealed an increased abundance of the harbour porpoise in the southern part of the North Sea. Concomitant to sightings of living individuals, the number of stranded porpoises ... [more ▼]

Recent observations revealed an increased abundance of the harbour porpoise in the southern part of the North Sea. Concomitant to sightings of living individuals, the number of stranded porpoises displaying lesions linked to fishing nets has also increased this last decade. The increased abundance of porpoises together with the increase in numbers of bycaught animals raised the question of possible competition between porpoises and fishermen in the North Sea. Therefore, a detailed view on harbour porpoise trophic ecology in this region is crucial for their conservation. Stomachs of the washed ashore porpoises were often empty and provided limited information on their recent diet. Another way of looking into the diet of marine mammals is the analysis of blubber. Stable isotopes ratio (d13C and d15N, SI) and fatty acid composition (20 fatty acids, FA) were analyzed in muscle and blubber of 10 freshly stranded harbour porpoises and in 60 potential prey fish from 10 species collected in the North Sea. The SI ratio and FA composition of these fish enabled a clear classification in different trophic levels and different trophic niches. The FA composition was very similar between harbour porpoise blubber and demersal fish, underlining a preferential predation on that resource for the porpoises investigated. A bias might exist for the porpoises: most of the animals were juveniles, and washed ashore during spring. Porpoises might display other feeding habits in other life stages, other periods of the year. These preliminary results however indicate the enhanced accuracy of crossing these biomarker approaches. [less ▲]

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See detailAssessment of trophic relationships between symbiotic tropical ophiuroids using C and N stable isotope analysis
Fourgon, Didier; Lepoint, Gilles ULg; Eeckhaut, Igor

in Journal of the Marine Biological Association of the United Kingdom (2006), 86(6), 1443-1447

Analyses of the natural abundance of carbon and nitrogen stable isotopes were performed to investigate the feeding habits of two ophiurolds, Ophiomastix venosa and Ophiocoma scolopendrina, and to assess ... [more ▼]

Analyses of the natural abundance of carbon and nitrogen stable isotopes were performed to investigate the feeding habits of two ophiurolds, Ophiomastix venosa and Ophiocoma scolopendrina, and to assess the potential benefit obtained by the symbiotic Ophiomastix venosa juveniles. A tracer experiment was also carried Out to clarify the contribution of algae to the nitrogen uptake amongst the tested ophiurolds. Our results suggest that Ophiocoma scolopendrina adults occupy a higher position in the food web than Ophiomastix venosa and mainly feed on neuston. In contrast, O. venosa adults feed on the alga Sargassum densifolium, and on organic matter associated with sediment. Free juveniles and symbiotic juveniles of O. venosa have intermediate PC values between both adult species. The high proportion of C-13 in the symbiotic juveniles compared to the one in their conspecific adults indicates that their diet slightly differs from the latter and is closer to that of Ophiocoma scolopendrina. This raises the hypothesis that symbiotic juveniles steal neuston front their associated host, O. scolopendrina. [less ▲]

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See detailLactation effect on stable isotope ratios and mercury levels in the blood of northern elephant seals
Habran, Sarah ULg; Debier, Cathy; Lepoint, Gilles ULg et al

Poster (2006, October 27)

Female northern elephant seals, Mirounga angustirostris, fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Stable carbon and nitrogen isotope ratios ... [more ▼]

Female northern elephant seals, Mirounga angustirostris, fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Stable carbon and nitrogen isotope ratios (d13C and d15N used as diet markers) and total mercury concentrations (Hg) were measured in tissues (blood cells, serum, full blood, milk and blubber) from 20 mother-pup pairs on day 4 and 21 of lactation. A systematic difference was observed between isotopic values in blood cells and serum of the mothers, linked to diet and distinct biochemical composition between blood components. d13C differed between inner and outer blubber layers and were similar between inner blubber and milk. High Hg concentrations (up to 350 ng.g-1 ww at the beginning of lactation) were found in the blood of mother elephant seals linked to their high d15N values in blood cells. Hg transfer through placenta and milk was observed between mothers and pups. A significant increase of blood Hg concentration in mothers (+285 ng.g-1ww) and a decrease in pups (-93 ng.g-1ww) were observed between days 4 and 21 of lactation. Both processes were explained by a remobilization of proteins and lipids during fasting and milk production in mothers and by a dilution of Hg in pups due to their high mass increase during this period. To conclude, physiological processes and body condition should be considered carefully when interpreting stable isotope ratios and Hg concentrations in the framework of biomonitoring. [less ▲]

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See detailDiet of Damselfishes (Pomacentridae): a multidisciplinary approach
Fabri, Grégory ULg; Parmentier, Eric ULg; Lepoint, Gilles ULg et al

Poster (2006, October)

Coral reefs are the marine ecosystem showing the greatest fish diversity. Damselfishes (Pomacentridae) represent, with more than 340 species, one of the most important families in the coral reef ... [more ▼]

Coral reefs are the marine ecosystem showing the greatest fish diversity. Damselfishes (Pomacentridae) represent, with more than 340 species, one of the most important families in the coral reef environment. Currently their diet is understudied. This work has 2 aims: (i) to characterize the diet of 13 pomacentrid species of the reef of Toliara (Madagascar) and (ii) to investigate if the specific diversity of this family would result from a strong trophic segregation. A multidisciplinary approach including morphological data (teeth, lower jaw-lever mechanics and intestine length), stomach contents and stable isotope analysis were used. The morphological approach and the stomach contents show that each studied species is able to capture small planktonic preys (e.g. copepods). However, the 13 species can be divided into two trophic guilds: alguivores and planktivores (respectively species where the filamentous algae and the planktonic preys count for more than 60% of their diet). Within these two principal classes, the analysis of the stomach contents and stable isotopes permit to define sub-groups : (1) the species having a food behaviour exclusively alguivore or planktivore (> 90% of their diet) (2) species showing a more varied diet by also eating other types of preys such as vagiles and/or sessiles invertebrates. The diet would contribute but could not explain all diversity in Pomacentridae. Some species show a very similar diet. Consequently other ecological factors should be responsible for the reduction of interspecific competitions and for the existence of such diversity. [less ▲]

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See detailFood sources of two detritivore amphipods associated with the seagrass Posidonia oceanica leaf litter
Lepoint, Gilles ULg; Cox, Anne-Sophie; Dauby, Patrick ULg et al

in Marine Biology Research (2006), 2(5), 355-365

This study focused on the ingestion and assimilation of Posidonia oceanica (L.) Delile litter by Gammarella fucicola Leach and Gammarus aequicauda Martynov, two dominant detritivore amphipods of the P ... [more ▼]

This study focused on the ingestion and assimilation of Posidonia oceanica (L.) Delile litter by Gammarella fucicola Leach and Gammarus aequicauda Martynov, two dominant detritivore amphipods of the P. oceanica leaf litter. Scanning electron microscope observations indicated that leaf litter is highly colonized by diverse diatoms, bacteria and fungi, which may constitute a potential food source for the litter fauna. Gut content observations demonstrated that these species eat P. oceanica litter, and that this item is an important part of their ingested diet. Stable isotope analyses showed that the species do not experience the same gains from the ingested Posidonia. Gammarella fucicola displayed isotopic values, suggesting a major contribution of algal material (micro- and macro-epiphytes or drift macro-algae). On the other hand, the observed isotopic values of G. aequicauda indicated a more important contribution of P. oceanica carbon. The mixing model used agreed with this view, with a mean contribution of P. oceanica to approximately 50% (range 40-55%) of the assimilated biomass of G. aequicauda. This demonstrated that the two species, suspected to be detritus feeders, display in reality relatively different diets, showing that a certain degree of trophic diversity may exist among the detritivore community of the seagrass litter. [less ▲]

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See detailTrophic diversity and potential role of detritivorous crustaceans in Posidonia oceanica litter
Sturaro, Nicolas ULg; Gobert, Sylvie ULg; Cox, Anne-Sophie et al

Conference (2006, June)

Detrivorous crustaceans are pivotal components of the trophic food webs and are found to be the main constituents of the macrofauna in Posidonia oceanica litter. The coexistence of many of these species ... [more ▼]

Detrivorous crustaceans are pivotal components of the trophic food webs and are found to be the main constituents of the macrofauna in Posidonia oceanica litter. The coexistence of many of these species in the same biotope raises the question of trophic diversity and of its role in litter degradation process. Diet composition of five common species of detrivorous crustaceans in P. oceanica litter (i.e. the gammarid amphipods Gammarella fusicola and Gammarus aequicauda and the isopods Idotea baltica, Idotea hectica and Zenobiana prismatica) were studied using a combination of gut content and stable isotopes analysis. Despite the common food supply (i.e. Posidonia dead leaf, Posidonia epiphytes or drift macroalgae), there were considerable interspecific differences in diet composition. Gut content observations indicate that P. oceanica leaf litter is an important part of the ingested food of all the species. Algae material (macroepiphytes and drift macroalgae) inhabiting the litter is mainly found in G. fusicola, I. hectica and I. baltica. I. baltica displays a high proportion of crustacean fragments. Isotope ratios showed that most of the species do not assimilate much of the ingested Posidonia. Application of a mixing model using isotopic values to estimate the contribution of the potential different food sources confirms this view. On one hand, the tissue of G. aequicauda could be constituted by more than 50 % of P. oceanica carbon. On the other hand, for the other species studied, P. oceanica represented a minor contribution (10 - 30 %), although it is a major component of the gut contents. This could imply that micro-organism (diatoms, bacteria and fungi) living on the Posidonia detritus is a major food source of detrivorous. Moreover, I. baltica, Z. prismatica and G. fusicola have a diversified diet composed mainly of algae. Crustaceans are an important food source for I. baltica. By contrast, I. hectica indicated a major contribution of algae material. Our results demonstrate the trophic diversity existing between the detrivorous crustaceans species in P. oceanica litter. This trophic diversity is probably one of the factors that allows these species to coexist in the same biotope. The results also underline the potential role of these species in the degradation of P. oceanica litter by fragmenting mechanically the Posidonia detritus and by assimilating directly Posidonia carbon and transferring it to higher trophic level (i.e. coastal fishes). Moreover, it allows us to think that micro-organisms (diatoms, bacteria and fungi) colonising leaf litter may constitute an important food source for litter fauna. [less ▲]

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See detailIn situ sampling of pore waters from seagrass meadows
Gobert, Sylvie ULg; Lepoint, Gilles ULg; Biondo, Renzo ULg et al

in Biologia Marina Mediterranea (2006), 13

A routine and low cost method to collect pore water in a seagrass meadow in situ and underwater is here proposed. The method consists of direct-suction filtered sampling allowing the determination of ... [more ▼]

A routine and low cost method to collect pore water in a seagrass meadow in situ and underwater is here proposed. The method consists of direct-suction filtered sampling allowing the determination of nutrient concentrations in the sampled water. Data ranges of nutrient (NO2-+NO3-; HPO4 2- and NH4+) concentrations in a P. oceanica meadow are also discussed [less ▲]

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See detailTrace Metal Concentrations in Posidonia Oceanica of North Corsica (Northwestern Mediterranean Sea): Use as a Biological Monitor?
Gosselin, Marc; Bouquegneau, Jean-Marie ULg; Lefèbvre, Frédéric et al

in BMC Ecology (2006), 6

BACKGROUND: Within semi-closed areas like the Mediterranean Sea, anthropic wastes tend to concentrate in the environment. Metals, in particular, are known to persist in the environment and can affect ... [more ▼]

BACKGROUND: Within semi-closed areas like the Mediterranean Sea, anthropic wastes tend to concentrate in the environment. Metals, in particular, are known to persist in the environment and can affect human health due to accumulation in the food chain. The seagrass Posidonia oceanica, widely found in Mediterranean coastal waters, has been chosen as a "sentinel" to quantify the distribution of such pollutants within the marine environment. Using a technique similar to dendrochronology in trees, it can act as an indicator of pollutant levels over a timeframe of several months to years. In the present study, we measured and compared the levels of eight trace metals (Cr, Ni, Cu, Zn, As, Se, Cd, and Pb) in sheaths dated by lepidochronology and in leaves of shoots sampled from P. oceanica meadows collected from six offshore sites in northern Corsica between 1988 and 2004; in the aim to determine 1) the spatial and 2) temporal variations of these metals in these areas and 3) to compared these two types of tissues. RESULTS: We found low trace metal concentrations with no increase over the last decade, confirming the potential use of Corsican seagrass beds as reference sites for the Mediterranean Sea. Temporal trends of trace metal concentrations in sheaths were not significant for Cr, Ni, Cu, As or Se, but Zn, Cd, and Pb levels decreased, probably due to the reduced anthropic use of these metals. Similar temporal trends between Cu levels in leaves (living tissue) and in sheaths (dead tissue) demonstrated that lepidochronology linked with Cu monitoring is effective for surveying the temporal variability of this metal. CONCLUSION: Leaves of P. oceanica can give an indication of the metal concentration in the environment over a short time period (months) with good accuracy. On the contrary, sheaths, which gave an indication of changes over long time periods (decades), seem to be less sensitive to variations in the metal concentration in the environment. Changes in human consumption of metals (e.g., the reduction of Pb in fuel) are clearly reflected in both organs. These results confirm that P. oceanica is a good bioindicator of metals and a good biomonitor species for assessing Cu in the environment. [less ▲]

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