Saturday, 15 July 2006

P-dynamics in the Hypersaline Ponds Used for Cultivation of Artemia Franciscana in the Mekong Delta of Vietnam.

Khoi Chau Minh1, Guong Vo Thi1, Margriet Drouillon2, Pieter Pypers2, and Roel Merckx2. (1) Soil Science and Land Management Dept, Can Tho Univ, Campus II, 3/2 Street , Ninh Kieu District, Can Tho, Vietnam, (2) Division of Soil and Water Management, Dept of Land Management, K.U. Leuven, Kasteelpark Arenberg 20, Heverlee, 3001, Belgium

Artemia production occurs in hypersaline condition and depends on adequate algal growth. In turn, algae proliferation uses mineral nutrients derived from sediment or soil in the culture system. Managing Artemia production hence depends on understanding and controlling the dynamics of Phosphorus (P) (and nitrogen) among others in the soil-water system. To this purpose, we set up the P equilibrium and incubation experiments to investigate the dynamics of P in the hypersaline ponds used for Artemia cultivation in the coastal area of the Mekong Delta, Vietnam. The results showed that the concentrations of Dissolved Reactive P (DRP) and Total Dissolved P (TDP) were higher in hypersaline conditions (EC 97 dS cm-1) than in less saline conditions (EC 11-23 dS cm-1) (P < 0.0001). In a standing water column, there was a large amount of dissolved P immobilized by soil microorganisms; however, daily raking the pond bottom soils to feed Artemia offered a favorable condition for the release and maintenance of dissolved P. During the early stage (4 days) of submergence and while disturbing soils by forced aeration for Artemia culture, the concentrations of DRP were linearly correlated with Olsen-P (R2 = 0.64, P < 0.001), while its relationship with DRP present after equilibrating the soils for 24 hours followed a logarithmic pattern (R2 = 0.84, P < 0.001). In conclusion, Olsen-P and/or DRP measurements after a 24 h-P equilibrium test allow predicting the availability of P in those conditions. Key words: P equilibrium, dissolved reactive P, total dissolved P, hypersaline, Artemia, coastal area.

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