Biogeochemistry study in mangrove ecosystem sediments using dialysis porewater sampler

I. Sakho (1) , V. Mesnage (1) , N. Lecoq (1) , Julien Deloffre (1) , A. Vennin , R. Lafite (1)

1 M2C - Morphodynamique Continentale et Côtière

This chapter deals with the biogeochemistry of sediment in coastal ecosystem as mangrove and detailed the dialysis porewater sampler in order to evaluate nutrients fluxes at the sediment-water interface. The chapter is structured in three different part: (i) Several porewater techniques are detailed and their advantages-disadvantages are discussed. Conventional methods of porewater sampling such as centrifugation or squeezing, present some limitations that is an over-estimation of dissolved substances owing to the highest pressure imposed to the sediment. Then other sampler designs (DET, Dialyser), with a dialysis membrane insert into the sediment, waiting for its equilibration without sediment coring are discussed. They allow to obtain continuous profiles of the sediment-water interface with high vertical resolution. (ii) The dialysis technique (type Hesslein) is described and adapted for mangrove sediments (Somone, Senegal). Its provides concentration gradient of nutrients, useful to quantify the nutrients fluxes released from sediment compartment. However, this technique required an equilibration time, which has been determine with an in situ experiment, detailed in the chapter. (iii) The equilibration time has been also determine with a numerical model of diffusion. The principle, sensibility tests and physical parameters of the diffusion model, are detailed. Furthermore, the diffusion model is calibrated with real data sets in order to fit the model.

Mots clés: diffusion model; Somone; Senegal; mangrove; porewater; dialysis sampler

Domaines: Planète et Univers [physics]

I. Sakho, V. Mesnage, N. Lecoq, Julien Deloffre, A. Vennin, et al.. Biogeochemistry study in mangrove ecosystem sediments using dialysis porewater sampler. Gleason, G. and Victor, T.R. Mangrove Ecosystems: Biogeography, Genetic Diversity and Conservation Strategies, Nova Science Publishers, pp.167-190, 2013, Environmental Research Advances, 978-1-62808-719-2. ⟨hal-01222284⟩