The substances found most often in the gammarids were the antidepressant Citalopram, the UV filter Benzophenon, the metal-corrosion protection agent Benzotriazol and the insecticide Thiacloprid. The latter substance is known to have a toxic effect on gammarids and other invertebrates.
In addition to Thiacloprid, Munz found three other insecticides: Imidacloprid, Acetamiprid und Clodthianidin. Although these were only present in the water samples in low concentrations, or not at all, they were surprisingly prevalent the gammarids – indicating that the organisms accumulate the substances in their bodies.
In order to gain a more precise understanding of this accumulation process, Munz collected additional gammarids in nearly natural, uncontaminated waters. She placed the animals in an artificial channel system in order to ascertain how many trace substances would be accumulated by the gammarids within one month. Using this experiment with semi-realistic conditions she obtained data comparative to the field samples and thus gained a better understanding of the accumulation process.
The results do not, however, explain how the significant accumulation of insecticides in the gammarids arises. Juliane Hollender intends to investigate this question through further research. “It is possible that the gammarids take in these materials not only through water but also in their food,” says Hollender. “They eat fallen autumn leaves, for example, which could also be a factor.” For this reason, so-called biomonitoring, which measures the accumulation of substances in living things, becomes ever more important in aquatic risk management. According to Hollender the method developed by Munz is a major factor in showing how water pollution affects organisms.