The aim of this study is to compare the azole synergy across an insect, Chironomus riparius, and a crustacean species, Daphnia magna. We use a combination of in vivo measurements of cytochrome P450 monooxygenase (CYP) biotransformation potential and toxicokinetic (TK) and toxicodynamic (TD) modeling to understand the mechanism behind the synergy of two azole fungicides: the imidazole prochloraz and the triazole propiconazole on the pyrethroid insecticide α-cypermethrin. For both species, the synergistic effect of prochloraz was well-described by its effect on in vivo CYP activity, which corresponded to the biotransformation rate of the TK model parameterized on the survival data of the mixture experiment. For propiconazole, however, there were 100-fold and 50-fold differences between the 50% effect concentration of in vivo CYP activity and the modeled biotransformation rate for C. riparius and D. magna, respectively. Propiconazole, therefore, seems to induce synergy through a mechanism that cannot be quantified solely by the CYP activity assay used in this study in either of the two species. We discuss the differences between prochloraz and propiconazole as synergists across the two species in the light of the type and time dynamics of affected biotransformation processes.

Copepods are considered high quality live feed for fish larvae due to their large within species size span, swimming pattern triggering hunting behaviour, and complete biochemical profile. In a continuous cultivation system aiming at the planktonic calanoid Acartia tonsa an intruding harpacticoid frequently appears. We experimentally evaluate how the interaction from the semi-benthic Tisbe holothuriae is affecting our cultures and ask whether the two copepod-species are expected to pose competitive exclusion or co-exist long-term. This is pursued by establishing 40 days mono-and mixed copepod cultures reared in a stationary setup (S) theoretically advantageous for T. holothuriae and a rotating setup (R) with organisms kept in suspension by use of a plankton wheel, theoretically advantageous for A. tonsa. The carrying capacities of A. tonsa in either mono-or mixed cultures are not affected whether the copepods are subject to S or R treatment. Only exception is the S-setup containing mixed culture were A. tonsa obtains a significantly lower carrying capacity compared with A. tonsa alone in R-setup. The mono-and mixed cultures of T. holothuriae are, however, highly negatively affected by the R setup compared with S setup. A long-term solution to limit the presence of T. holothuriae is to apply turbulence level in a classical stagnant tank setup to an extend that suppress T. holothuriae and simultaneously allow algae in suspension as food for A. tonsa, make their eggs sediment as well as minimize risk of benthic-predation on eggs. K E Y W O R D Sco-existence, culture contamination, logistic population development, niche differentiation, polyculture