Temporal variations of manganese in the haemolymph and tissues of the Norway lobster, Nephrops norvegicus (L.).

The Norway lobster, Nephrops norvegicus, lives on sediments rich in manganese (Mn) and any dissolved Mn(2+) can readily be taken up by the animal. To investigate temporal fluctuations of bioavailable Mn, a N. norvegicus fishing ground on the Swedish west coast was repeatedly sampled every 2 months from September 1992 to November 1994. The lobsters collected contained on average 91.7 µg Mn g(-1) dry wt. (S.E. 4.2, n=156). The oxygen saturation of the bottom water proved to be negatively correlated with both the temperature of the water and the Mn (concentration and total content) of the animal's haemolymph. The temporal fluctuations in animal Mn load were however, small compared to spatial differences found in an earlier study. There was an increase in the Mn concentration of the lobster exoskeleton (from 56 to 340 µg Mn g(-1) dry wt. exoskeleton) and gills (from 34 to 160 µg Mn g(-1) dry wt. gill) in postmoult animals compared to premoult. The Mn concentrations of the lobsters' hepatopancreas and muscle tissue remained relatively constant throughout the moult cycle and appear to be more conservative in their Mn concentration and less affected by exposure to Mn.