Behaviour of environmental iron, manganese and aluminium in relation to brown/black gill syndrome in Penaeus monodon cultured in ponds on acid sulphat
J.M.P.K. JAYASINGHE*, M.J. PHILLIPS AND M.U.M. ANAS
Acid sulphate soils are marginally acceptable soils for aquaculture and brown/black gill syndrome is one of the common problems associated with shrimp culture in acid sulphate soils. Unusually high concentrations of iron (up to 1588 μg g-1 dry wt) and manganese (up to 93.2 μg g-1 dry wt) were observed in Penaeus monodon cultured on acid sulphate soils in the west coast of Sri Lanka exhibiting concomitant colour changes in gills. A steady increase in iron and manganese levels was observed in gills of the cultured shrimp with culture time. Statistically significant differences were observed for levels of iron (p <. 001) and manganese (p <. 05) in the gills of shrimp showing normal gill colour (2 to 5 weeks) and shrimp showing high incidence of brown gills (6 to 10 weeks). Iron in the gills of the shrimp appears to be in the form of hydrated oxides while manganese appears to be in a co-precipitated form with iron oxides.