Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

FP5

BASICS Résumé de rapport

Project ID: EVK3-CT-2002-00078
Financé au titre de: FP5-EESD
Pays: France

Data set on carbon biogeochemistry in the Bay of Villefranche (NW Mediterranean Sea)

The role of the activity of microorganisms on carbon biogeochemistry was investigated during a 1.5 year period in the Bay of Villefranche. DOC concentrations ranged from 56 to 108 µmol per liter. DOC concentration was lowest in winter and increased during the after the spring bloom, which was therefore as expected in the relative oligotrophic and deep bay the major source of organic matter. The ratio of gross primary production (GPP) to respiration was > 1 during the first half year of the study period and < 1 afterwards.

This indicates a shift from autotrophy to heterotrophy of the system in the study period with no clear seasonal pattern. One of the conclusions from this study is that the metabolic balance and its effect on carbon biogeochemsirty are difficult to predict. Across the study period, bacterial production represented between 18% and 70% of gross primary production and reached highest values (ca. 40-70%) during the phytoplankton blooms investigated.

There were also differences in bacterial production and respiration between two consecutive blooms. Highest respiration was measured in association to forest fires, which introduced black carbon and nutrients (NO3 and PO4) into the water column.

A Sahara dust wet depostion events also caused bacterial respiration to increase by 60-90%. The data suggest that the effects of short-term events such as forest fires, local upwelling, rain fall and Sahara dust events on carbon biogeochemistry have not been appreciated sufficiently.

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Markus WEINBAUER, (Research scientist)
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