Sheepshead minnows (Cyprinodon variegatus) were continuously exposed to two concentrations of polycyclic aromatic hydrocarbons (PAHs) dissolved in seawater (sigma PAH = 7.57 and 72.31 microg/L) for 36 d, followed by 8 d of depuration. The PAHs studied were naphthalene (NPH or C0-NPH), phenanthrene (PHE or C0-PHE), pyrene (PYR), 2-methylnaphthalene (C1-NPH), 1,3-dimethylnaphthalene (C2-NPH), 2-isopropylnaphthalene (C3-NPH), 9-methylphenanthrene (C1-PHE), and 9-ethylphenanthrene (C2-PHE). Uptake rate constants (k1) for NPHs increased with increasing degree of alkylation and log value of the octanol/water partition coefficient (Kow), whereas k1 values for three- and four-ring PAHs were lower despite their high log Kow values. Elimination rate constants (k2) for the homologue series of NPHs and PHEs generally increased with decreasing degree of alkylation and log Kow values. However, the depuration time did not directly correlate with the molecular size for nonalkylated PAHs. Bioconcentration factors (BCFs) were estimated from the ratio of k1 to k2 and also directly from PAH concentrations in fish tissue and water samples, and the factors generated by the two methods were very similar. A significant positive correlation was determined between log BCFs and log Kow values for the series of C0- through C3-NPH at both low (r2 = 0.985, p = 0.0077) and high (r2 = 0.956, p = 0.022) exposures, although this correlation was not determined for all the PAHs studied. As a result of increased metabolism and/ or reduced bioavailability with increasing lipophilic character, the estimated BCFs for C0- through C2-PHE and PYR were generally lower than those for C0- through C3-NPH. The two exposure levels revealed minor variations in k1 and k2 values for parent PAHs and in the temporal pattern of PAH metabolite concentrations in bile. The present results indicate that the presence and nature of alkyl groups have a significant influence on the kinetics and metabolism of PAHs in fish.

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Ocean acidification (OA) resulting from anthropogenic emissions of carbon dioxide (CO(2)) has already lowered and is predicted to further lower surface ocean pH. There is a particular need to study effects of OA on organisms living in cold-water environments due to the higher solubility of CO(2) at lower temperatures. Mussel larvae (Mytilus edulis) and shrimp larvae (Pandalus borealis) were kept under an ocean acidification scenario predicted for the year 2100 (pH 7.6) and compared against identical batches of organisms held under the current oceanic pH of 8.1, which acted as a control. The temperature was held at a constant 10°C in the mussel experiment and at 5°C in the shrimp experiment. There was no marked effect on fertilization success, development time, or abnormality to the D-shell stage, or on feeding of mussel larvae in the low-pH (pH 7.6) treatment. Mytilus edulis larvae were still able to develop a shell in seawater undersaturated with respect to aragonite (a mineral form of CaCO(3)), but the size of low-pH larvae was significantly smaller than in the control. After 2 mo of exposure the mussels were 28% smaller in the pH 7.6 treatment than in the control. The experiment with Pandalus borealis larvae ran from 1 through 35 days post hatch. Survival of shrimp larvae was not reduced after 5 wk of exposure to pH 7.6, but a significant delay in zoeal progression (development time) was observed.

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