Accumulation of trace metals in aquatic insect Stenopsyche marmorata Navas transferred in streams

Instar V larvae of the aquatic insect Stenopsyche marmorata were transferred between a noncontaminated site and a contaminated site and changes in the accumulation of nickel (Ni), copper (Cu), zinc (Zn), and lead (Pb) in larvae were monitored for 30 days. Concentrations of the four metals rapidly increased or decreased within 10 days in the transferred larvae and approached concentrations of the native larvae living in the transfer sites. The accumulation of Ni and Cu in the larval body was very noticeable. The decreased Ni concentrations are represented by two exponential rate formulas, suggesting a biological half-life of 1.4 and 12.1 days. Under laboratory conditions, routes of Ni and Cu uptake were examined and Ni uptake was found to be mainly from food. However, larvae accumulated Cu from both food and water sources. In this case, the amount of metal uptake from food was more than that from water. The results of this indoor experiment are discussed and compared with the results of the transfer field experiment. Active biomonitoring of trace metal in transferred larvae is useful since it enables rapid and easy assessment of metal contamination.