Dauby, Patrick

Lepoint, Gilles

Mascart, Thibaud

Remy, François

English

Ghent University Academic Bibliography

0.0 0.2 0.4 0.6 0.8 1.0024681012Proportion densitiesproportiondensityLitterLiving.leavesEpiphytes0.0 0.2 0.4 0.6 0.8 1.0024681012Proportion densitiesproportiondensityLitterLivingleavesEpiphytesLeaf fall impact on diversity and trophic ecology of vagile macrofauna associated with exported P.oceanica litter.   Remy F1, Mascart T12, Dauby P3, Lepoint G1   1 MARE Centre, Laboratory of Oceanology, University of Liège, B6c, 4000 Liège, Belgium  2 Marine Biology, Gent University 281 S8, 9000 Gent, Belgium  3 MARE Centre, Laboratory of Sytematics and Animal Diversity, University of Liège, B6c, 4000 Liège, Belgium Contact: francois.remy@ulg.ac.be  Introduction Methods Posidonia oceanica seagrass meadows produce a huge amount of detritus (300 to 2000 g.dry.wt.m-2yr-1). P. oceanica ecosystem presents similar traits with tempered deciduous forest ecosystem (eg: important leaf fall event in the autumn period). Leaf fall in P. oceanica ecosystem is a major event which influences the exported detritic compartment and its associated macro-invertebrates. We tried to assess the influence of leaf fall on the biodiversity and trophic diversity of P. oceanica exported litter macro-invertebrates. - Revellata Bay (STARESO)  - 2 sampling sites, 2 seasons  - Standardized samples  - Evaluation of biodiversity  - Isotopic measurements (IRMS)  - SIAR Bayesian mixing model Results Discussion A) Biodiversity Poster presented in Brest for the 8th International Conference on Applications of Stable Isotope Techniques to Ecological Studies «ISOECOL » -  August 2012 Fig 1 : location of the sampling sites in Revellata Bay (Calvi, Corsica) 1: STARESO, 2: Oscelluccia Proportionally more crustaceans at site 2 before leaf fall, and proportionally more crustaceans at site 1 after leaf fall. Proportionally more Annelids than Molluscs before leaf fall and this pattern is inverted after leaf fall. Higher global abundance before leaf fall. Higher biodiversity before leaf fall (H’=2,71 and 100 species) than after leaf fall (H’=1,38 and 37 species).  Higher biodiversity at site 1 before leaf fall, and this pattern is inverted after leaf fall. Fig 2 : number of individuals (ind.m-2) of each taxa at each sampling site before and after leaf fall. B : before leaf fall, A: after leaf fall. δ15N (‰) δ15N (‰) δ13C (‰) Fig 3 : graphs showing the isotopic signatures for 13C and 15N of the most common macro-invertebrates  and the major potential food sources of P. oceanica litter (delta form in « per mil », ‰). B: before leaf fall, A: after leaf fall. After After Before Before EP L.L L EP L.L L EP = Epiphytes L.L = Living leaves L = litter Density Litter Living leaves Epiphytes Proportion Density Proportion Litter contribution : [0 - 18%] Living leaves contribution : [3 - 49%] Epiphytes contribution : [47 - 81%] Litter contribution : [0 – 28%] Living leaves contribution : [0 – 80%] Epiphytes contribution : [21 – 99,5%] After Before Litter Living leaves Epiphytes B) Trophic diversity Fig 4 : graphs showing the respective contribution proportion of the 3 major potential food sources to the diet of G.fucicola . The contribution values are the CI 95%. B: before leaf fall, A: after leaf fall. Custom TEF used were 0.2 ± 0.6 ‰ for Δ13C and 1.2 ± 0.5 ‰ for Δ15N (from Michel 2011). Focus: Gammarella fucicola (crustacean  amphipod). We here show a somewhat diverse community (more than 115 species) where crustaceans are dominant, and more precisely, the amphipod G. fucicola representing up to 55% of the litter macro-fauna. We also show a community with low δ15N primary consumers, carnivorous species with higher δ15N, and omnivorous species with intermediate δ15N . With the SIAR results, we can see that even if the dominant crustacean species ingest litter leaves, it seems not to assimilate the major part of it’s carbon from this food source. G. fucicola seems to assimilate it’s carbon mainly from epiphytes and to a lesser degree, from living P. oceanica leaves. We can also highlight major abundance and biodiversity differences between summer (before leaf fall) and autumn (after leaf fall). It’s important to see that these huge community modifications don’t seem to affect the diet of most of the litter macro-invertebrates as the general isotopic signatures pattern remains quite constant.   Potential food sources: The authors warmly thank the STARESO field station staff for their support during the sampling campaign. The first author acknowledges a PhD F.R.I.A. grant (Fund for Research Training in industry and in agriculture) of the Belgian National Fund for Scientific Research (FRS-FNRS). This study was conducted within the frame of FRS-FNRS research project FRFC 2.4511.09 (University of Liège). Acknowledgements 

Leaf fall impact on diversity and trophic ecology of vagile macrofauna associated with exported Posidonia oceanica litter

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Leaf fall impact on diversity and trophic ecology of vagile macrofauna associated with exported Posidonia oceanica litter

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