Ref ID : 6105
Armin Peither, Ingrid Juttner, Antonius Kettrup, and Jan-Peter Lay; A pond mesocosm study to determine direct and indirect effects of lindane on a natural zooplankton community. Environmental Pollution 93(1):49-56, 1996
Reprint
In File
Notes
We assessed the threshold concentrations for toxic effects by lindane on a zooplankton community using mesocosms in a natural pond. Enclosures (1000 litres) were treated to give mean concentrations of 0, 2, 6, 12, 18, 24 and 50 µg litre-1 over a test period 39 days. Larvae of the phantom midge Chaoborus flavicans showed a high susceptibility to lindane and were virtually eliminated from enclosures with >/_12 µg litre-1 4 days after application. Populations of cyclopoid nauplii (Eucyclops serrulatus) were reduced at a lindane concentration of 2 µg litre-1 and showed high mortality after 11 days exposure to >/_6 µg litre-1. No lindane-induced effects could be seen in the cladoceran species Daphnia longispina and Chydorus sphaericus. Rotifer species were probably not directly affected by lindane; however, loss of the principal predator Chaoborus was accompanied by an increase in the numbers of Asplanchna priodonta. A simultaneous decrease in Keratella quadrata possibly reflected predation since its decline showed no dose-response relationship with lindane and it is among the major prey of Asplanchna. Such complex secondary effects, occurring through trophic interactions between a predator and two co-occurring prey, would not have been predicted from single-species toxicity tests. These, and effects on cyclopoid populations that occurred predominantly through the mortality of nauplii, demonstrate the value of toxicological studies on natural communities. We conclude that a combination of laboratory and field investigations, coupled with mono-species and community assessments, provide the best route for understanding the effects of toxicants such as lindane for regulatory purposes.