Nutrient dynamics at the sediment-water interface in a Mediterranean lagoon (Thau, France): influence of biodeposition by shellfish farming activities.
The Thau Lagoon, a French Mediterranean shallow lagoon, is a site where extensive shellfish farming occurs. The aim of the present work is to evaluate the role of this activity on nutrient exchange at the sediment-water interface in relation to organic matter (OM) sedimentation and degradation. Two stations inside (C5) and outside (C4) of the shellfish farming areas were sampled at three seasons. Porewater chemistry surveys and calculated diffusive fluxes were used to evaluate the trophic status of the Thau lagoon. Quantitative (Particulate Organic Carbon) as well as qualitative OM (Hydrogen Index, Carbohydrates) analyses were performed on sediments to assess OM characteristics. Results emphasized that surficial sediments at C5 are always more enriched in OM. Porewater nutrient concentrations are 10-20 times higher at C5 than at C4. In June 2003, the porewater profiles exhibit a sharp gradient at the bottom waters, indicating a hypereutrophic status, leading to an anoxic crisis.
Mesnage
Valérie
V
UMR CNRS 6143 M2C, Université de Rouen, 76 821 Mont-Saint-Aignan, France. valerie.mesnage@univ-rouen.fr
Ogier
Sylvie
S
Bally
Gabriel
G
Disnar
Jean-Robert
JR
Lottier
Nathalie
N
Dedieu
Karine
K
Rabouille
Christophe
C
Copard
Yoann
Y
D017756:Aquaculture / Q000379:methods*; D002241:Carbohydrates / Q000032:analysis; D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring; D005602:France; D019015:Geologic Sediments / Q000032:analysis*; D006859:Hydrogen / Q000032:analysis; D008522:Mediterranean Sea; D010758:Phosphorus / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012623:Seawater / Q000032:analysis*
D002241:Carbohydrates; D000644:Quaternary Ammonium Compounds; D010758:Phosphorus; D002244:Carbon; D006859:Hydrogen