Accumulation of manganese in selected links of food chains in aquatic ecosystems

anglais. The accumulation of elements in biocenoses of aquatic ecosystems depends primarily on the forms of elements in the environment. The bioaccumulation coefficient (BC) is a measure of the intensity of an elements uptake of trace by living organisms. Manganese is an essential element for both plant and animal organisms. However, its excess may cause a toxic effect, i.e. it disturbs the activity of synapses, thus leading to an impaired functioning of the central nervous system. This study focused on the accumulation of manganese in individual links of an aquatic ecosystem food chain under conditions of extensive carp farming. The BC values were computed and the pollution degree of the fish pond was estimated. The investigations were conducted in a fish pond situated in Mydlniki and fed with water from the Rudawa River. Water, bottom sediment, benthic organisms (Diptera Chironomidae larvae) and carps were sampled from the pond. Organs most strongly involved in the metal metabolism (gills, gonads, liver and muscles) were prepared from sampled carps. Manganese concentrations were determined in all samples using atomic emission spectroscopy after wet mineralization of samples in a closed system in a microwave mineralizer. The concentrations of manganese in the abiotic elements of pond ecosystems were low and should not pose any threat of its excessive accumulation in living organisms. However, the manganese concentrations in the benthic organisms and in the analyzed carp organs were high. Similarly, other authors found high manganese concentration in fish living in the environments polluted with this element. The value of manganese enrichment coefficient for the bottom sediments in relation to its water concentration was high. The biggest manganese content was assessed in gills, then in the liver and gonads, and the smallest one - in carp muscles. Manganese BCs in the gills of carps in relation to its content in water and bottom sediments were 176.6 and 0.08, respectively. The BC values in relation to the manganese concentration in water were much higher, but lower in comparison to its content in bottom sediments than reported elsewhere. This confirms that the BC for manganese in gills varies depending on the water pollution level.

anglais. manganese, bioaccumulation, food chain, aquaculture

15

945-956

4