Abstract
Sediments receive a large amount of organic matter in eutrophic environment. Phosphorus is often responsible for this high primary production. This is why phosphorus become trapped into the sediment, organic matter bounded or not. The aim of this study is focused on the role of humic substances in the biogeochemistry of sediment phosphate. Phosphate was extracted in sediments from two Mediterranean lagoons. A fractionation scheme allows the separation of different inorganic fractions followed by the extraction and by the separation of humic and fulvic acids. 21 – 34% of total phosphorus was co-extracted with humic substances. Indeed, phosphorus might either be complexed with these compounds or be an integral part of their molecule. Humic substances therefore play an important role in the phosphate storage.