Temperature determines the rate at which retene affects trout embryos, not the concentration that is toxic.

The toxicity of waterborne retene (7-isopropyl-1-methyl phenanthrene) to post-hatch embryos of rainbow trout (Oncorhynchus mykiss) was assessed at 5 and 11 °C. Survival times of retene-exposed embryos were 70 % longer at 5 °C than at 11 °C, but survival times and LC50 s did not vary when time was expressed as degree-days (thermal units), i.e., at a common stage of development. The size of survivors decreased with increasing retene concentrations, but not with temperature. Retene did not bioconcentrate to any extent (bioconcentration factors < 2) at either temperature, indicating effective biotransformation by embryos. However, concentrations of retene metabolites were slightly higher at 5 °C, suggesting slower excretion rates than at 11 °C. The relative expression of cytochrome P450 proteins (CYP1A) did not vary with temperature but increased with retene concentration, as indicated by cyp1a mRNA concentrations. The induction of CYP1A protein by retene exposure was evident in the vasculature of eye, brain, heart, kidney, liver, gill, mouth, intestine, muscle, and yolk-sac. However, immunohistochemical staining was greater at 5 than at 11 °C for all tissues except liver and muscle. Overall, temperature effects on retene toxicity disappeared when the duration of embryo development and retene exposure were expressed as thermal units (degree-days). Temperature controlled the rate of embryo development and the rate of toxicity (time to a toxic endpoint), but not the concentrations that were toxic.

Bioaccumulation of phenanthrene and benzo[a]pyrene in Calanus finmarchicus.

With petroleum exploration and development expanding in the Arctic (AMAP, 2007) there is a need to obtain additional information on the ecotoxicology of Arctic organisms. Here we perform 192 h laboratory exposure experiments on the keystone Arctic zooplankton species, Calanus finmarchicus. We trace the accumulation and depuration of two polycyclic aromatic hydrocarbons (PAHs): phenanthrene and benzo[a]pyrene (B[a]P) using (14)C labeled PAH compounds. Copepods were not fed during the experiment, limiting uptake to diffusion processes alone. The lighter PAH compound, phenanthrene, accumulated rapidly in C. finmarchicus, reaching steady state within 96 h. The heavier PAH compound, B[a]P, accumulated more slowly and steady state was not reached within the 192 h exposure period. As expected, the bioconcentration factor (BCF) for B[a]P was higher than for phenanthrene in accordance with a higher octanol/water partition coefficient for B[a]P (log K(ow)=6.04) compared to phenanthrene (log K(ow)=4.53). However, for both compounds, log BCF was lower than log K(ow) that may indicate active biotransformation and excretion of the selected PAH compounds. These findings on the bio-uptake kinetics for petroleum hydrocarbons are essential for evaluating the potential consequences of an oil spill in the Arctic.

Inhibition of pyrene biotransformation by piperonyl butoxide and identification of two pyrene derivatives in Lumbriculus variegatus (Oligochaeta).

Using the freshwater annelid Lumbriculus variegatus (Oligochaeta), the presence of cytochrome P450 (CYP) isozymes was investigated by analyzing metabolites of the polycyclic aromatic hydrocarbon (PAH) pyrene in treatments with and without the CYP inhibitor piperonyl butoxide (PBO). The results show a low biotransformation capability of L. variegatus (7% of total pyrene body burden as metabolites at 168 h). Addition of PBO resulted in a significant reduction of metabolites, suggesting the presence of a CYP in L. variegatus. Besides 1-hydroxypyrene, three peaks representing unknown metabolites were detected in LC-FLD (liquid chromatography with fluorescence detection) chromatograms of L. variegatus. Deconjugations showed that sulfonation and glucosidation are involved in the formation of these unknowns. Further studies with the time of flight mass analyzer provided the identification of the glucose-sulfate conjugate of 1-hydroxypyrene. The same metabolites were detected in the solvent-nonextractable fraction by incubation of the tissue residues with proteinase K, suggesting that part of these metabolites are bound to proteins. Overall, the slow biotransformation of pyrene by L. variegatus (involving CYP) supports the use of this species in standard bioaccumulation tests; however, the tissue-bound metabolite fraction described in the current study deserves further investigation for its toxicity and availability to upper trophic levels through diet.

Environmental temperature changes uptake rate and bioconcentration factors of bisphenol a in tadpoles of Rana temporaria.

Toxicokinetics of radiolabeled (14C) bisphenol A was studied in the common frog (Rana temporaria) at two experimental temperatures (7 and 19 degrees C). The growth rate of the tadpoles during the 96-h experiment was very slow at 7 degrees C, but the weight of tadpoles almost tripled at 19 degrees C. At all tested exposure concentrations (0.2, 1.5, 10, and 100 microg/L), conditional uptake rate constants (ku) were 69 to 82%, and elimination rates (ke) 79 to 90% lower, at 7 degrees C than at 19 degrees C. On the contrary, bioconcentration factors (BCFs) were higher at 7 degrees C than at 19 degrees C. Total accumulated bisphenol A per individual was higher at 19 degrees C, which is in agreement with higher k, at 19 degrees C. Exposure concentrations did not have any constant effect on BCFs at the two temperatures. The results of the current experiment suggest that higher temperature increases uptake and total amount of chemical in frog tadpoles but does not necessarily lead to higher BCFs. High temperature may have increased the growth rate more than the uptake rate, resulting in a net dilution of bisphenol A in tadpole tissues. The observed difference in BCFs also could be a result of temperature-induced changes in allometric relationships (increased surface area to volume ratio) and/or more effective elimination in more developed tadpoles at high temperature.

Bisphenol A induces yolk-sac oedema and other adverse effects in landlocked salmon (Salmo salar m. sebago) yolk-sac fry.

Accumulation and toxicity of waterborne bisphenol A were studied in landlocked salmon (Salmo salar m. sebago) yolk-sac fry. In a short-term (96 h) exposure to five bisphenol A concentrations yolk-sac fry had higher accumulation rates and bioconcentration factors (BCF96) than earlier studies have shown for salmon eggs. Furthermore, the conditional uptake rate constant tended to decrease as exposure concentration increased. Fry were also exposed to bisphenol A for 42 days at three concentrations (10, 100 and 1000 microg/l), and changes in behaviour, morphology and histological structure were observed. After 6 days of exposure, the highest concentration (1000 microg/l) of bisphenol A caused fluid accumulation (oedema) in the yolk sac and haemorrhages in the front part of the yolk sac and in the head around the gill arches. Later on, the fry at 1000 microg/l showed phlegmatic behaviour and had darker skin coloration than the fry in the other treatments. At the two highest concentrations (100 and 1000 microg/l) histological changes were seen in liver cell nuclei, where strongly stained fragments were observed. In the control fry and the fry exposed to 10 microg/l the nucleolus was clearly visible and spherical in shape and no strongly stained fragments were present. This study shows that high concentrations of bisphenol A may have both morphological and histological effects on salmon yolk-sac fry.