Acute and chronic bioassays with New Zealand freshwater copepods using pentachlorophenol

The suitability for laboratory culture and comparative sensitivity of three species of New Zealand freshwater copepod (Calamoecia lucasi Brady, Boecke lla delicata Percival, and Mesocyclops cf. leuckarti,ti Claus) to pentachlo rophenol (PCP) was assessed. Acute bioassays used two life stages (nauplii and adults). Acute 48-h lethality tests were conducted at 22 degrees C with laboratory cultured animals of all species and at varying temperatures wit h seasonally collected C. lucasi adults. Mean 48-h median lethal concentrat ion values for nauplii ranged from 52 to 227 mu g/L PCP for C. lucasi and B . delicata, respectively, and from 106 to 173 mu g/L for adult C. lucasi an d M. leuckarti, respectively. The survival rate in controls was greater tha n or equal to 95% in acute tests, with the exception of C. lucasi nauplii, in which it was 60%. Mean 48-h median lethal concentration values for seaso nally collected C. lucasi adults were significantly higher in summer than i n all other seasons. Chronic sublethal tests starting with nauplii <24 h ol d measured time to metamorphosis. Pentachlorophenol delayed metamorphosis i n all species. Chronic toxicity values were 14, 61, and 104 mu g/L PCP for C. lucasi, B. delicata. and M. leuckarti, respectively. The mortality rate in controls was also high in C. lucasi sublethal tests (65%), and of the th ree species, they were the most difficult to culture.