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Element stocks and fluxes in the Posidonia oceanica ecosystem of the Mediterranean

Objective

The objective is to investigate the exchanges between and within the organic and inorganic compartments of the Posidonia seagrass ecosystem.
The research focussed on the exchanges that take place between and within the organic and inorganic compartments of the Posidonia ecosystem of the Mediterranean.
The spatial structures of 2 continuous meadows located off Lacco Ameno (Ischia) and off Stareso (Calvi) were investigated by means of the kriging technique.
The carbon dynamics in the Posidonia ecosystem were measured.^M
^M This^M involved assessing:
variations of the dial carbon budget of the Posidonia bed;
the carbon-13 carbon-12 ratio in plants and epiphytes;
the photosynthetic activity of Posidonia;
the role played by the detritic compartment in the carbon budget.

An assessment was made of mineral stocks and the role of nitrogen and phosphorus in the meadow structure. In terms of element stocks in the ecosystem the main compartment is by far the matte. Investigations on the effect of nutrient concentration on the meadow structure indicated that shallow water meadows appear to grow under limiting nutrient condition while deep water meadows are more likely to be light limited.

Measurements of litter decay rates showed a strong seasonality in the process with higher values in summer than in winter and in the shallow part of the bed than in the deep part. Also, concentrations of heavy metals were measured in Posidonia and Paracentrotus samples. Contamination experiments using cadmium showed that both Posidonia and Paracentrotus may be considered as valuable indicators of environmental contamination.
This project is complementing the ongoing project in the 4th environmental research and development programme concerning a functional approach to the Posidonia ecosystem in the Mediterranean (contract EV4V-0139-B). It will establish the important link between the biological functioning of the seagrass and benthos communities with their chemical environment, in particular regarding the nutrient, trace metal and carbon fluxes. In addition, it will develop a box flux model for predicting the carbon dynamics in benthic ecosystems and its exchange with the atmosphere (source, sink functions for carbon) and to predict changes of nitrogen and phosphorus stocks in the main compartments of the Posidonia ecosystem.

Detailed quantitative investigations will comprise :
spatial analyses of the microstructure of Posidonia beds;
monitoring of dissolved oxygen and inorganic carbon;
determination of carbon-12 to carbon-13 ratios;
carbon uptake and translocation at the plant level;
assessment of mineral stocks and of the role of nitrogen and phosphorus in the meadow structure;
biological activity of plant litter;
and assessment of pollution effects.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Université Libre de Bruxelles
Address
50,Avenue Franklin Roosevelt
1050 Bruxelles
Belgium

Participants (4)

STAZIONE ZOOLOGICA ANTON DOHRN
Italy
Address
Punta San Pietro
80077 Ischia Porto
UNIVERSITAT DE BARCELONA
Spain
Address
645,Avinguda Diagonal 645
08028 Barcelona
Université d'Aix-Marseille II
France
Address
113 Avenue De Luminy
13288 Marseille
Université de Liège
Belgium
Address
Sart Tilman
4000 Liège