Reference : Effects of shading and sediment alterations on Posidonia oceanica meadows: in situ exper...
Scientific congresses and symposiums : Unpublished conference
Life sciences : Environmental sciences & ecology
Life sciences : Aquatic sciences & oceanology
http://hdl.handle.net/2268/81194
Effects of shading and sediment alterations on Posidonia oceanica meadows: in situ experiments
English
Pete, Dorothée mailto [Université de Liège - ULg > Département des sciences et gestion de l'environnement > Océanologie >]
Velimirov, Branko mailto [Medizinische Universität Wien > General Microbiology, Molecular Biology and Virology > > >]
Lepoint, Gilles mailto [Université de Liège - ULg > Département des sciences et gestion de l'environnement > Océanologie >]
Gobert, Sylvie mailto [Université de Liège - ULg > Département des sciences et gestion de l'environnement > Océanologie >]
24-Nov-2010
No
No
International
2010 World Seagrass Conference
21-25 novembre 2010
World Seagrass Association
Faculty of Science, Prince of Songkla University
Princess Maha Chakri Sirindhorn Natural History Museum, Prince of Songkla University
Excellence Centre for Biodiversity of Peninsular Thailand
Patong, Phuket
Thaïlande
[en] Ecology ; Sediment ; Seagrass ; in situ experiments ; shading ; sediment alterations
[en] In the Mediterranean Sea, the seagrass Posidonia oceanica is affected by many threats from anthropogenic sources. One of them is the increasing development of fish farming, which is responsible of the destruction of some meadows. Within troubles cause by those fish farms on the surrounding environment, the increase of phytoplankton biomass in the water column (leading to a shading effect) and a modification of the sediment are often cited as a reason of seagrass disappearance.

To understand how those troubles are affecting P. oceanica and its sedimentary compartment, in situ experiments were led during three months, from the end of May til the end of August 2009, in STARESO (STAtion de REcherches Sous-marines et Océanographiques, Corsica, France), at a depth of 10 meters.
The shading was mimicked by three replicated shading frames (3 x 1 m), which stopped around 50 % of the incident light. To modify the sedimentary compartment, some sediment was taken from under the fish farm of Calvi (Corsica, France) and added once a week on marked zones in the seagrass meadow. Those sites were compared with a control site, situated in the same meadow.
Samples were taken once a month and consisted in pore water, sediment cores and shoots of P. oceanica. An estimation of the density of the meadow in every sampling zones was also performed.
Measured parameters are the concentration of nutrients in pore water, grain size, redox potential discontinuity (RPD), biomass of bacteria, organic matter, meiofauna and microphytobenthos within the sediment, total carbon and nitrogen in the sediment and leaves, the length, width and biomass of leaves and shoots, the biomass of epiphytes and the content of chlorophyll a in leaves.

During those experiments, Posidonia oceanica was not very affected. However, some parameters of the sedimentary compartment were modified (RPD, biomass of bacteria, organic matter, nutrients in pore water,…), suggesting a modification in the functioning of the ecosystem. These results are important because they show that the sedimentary compartment reacts more rapidly to threats then the seagrass itself. So, it could be an interesting tool in quality assessments.
Laboratoire d'Océanologie, ULg
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS ; Programme ARC.RACE 0510/333 ; Université de Liège, Subsides "Missions scientifiques" du Patrimoine
Utilisation de l'exergie pour mesurer et détecter les effets des perturbations affectant les herbiers à Posidonia oceanica (L.) Delile: caractérisation au sein du compartiment sédimentaire.
Researchers ; Professionals ; Students
http://hdl.handle.net/2268/81194
This is the abstract presented in the conference abstract book.

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