Risk assessment of the National Institute of Standards and Technology petroleum crude oil standard water accommodated fraction: further application of a copepod-based, full life-cycle bioassay.

The U.S. National Institute of Standards and Technology (NIST) petroleum crude oil was used to generate NIST water-accommodated hydrocarbon fractions (WAFs) for standardized assessment of crude oil effects on the copepod Amphiascus tenuiremis. Effects were assessed using a 96-well microplate, full life-cycle test. Briefly, nauplii (age, 24 h) were reared individually to adults (n > or =120 nauplii/treatment) in microplate wells containing 200 microl of treatment solution (seawater control [0%] or 10, 30, 50, or 100% NIST-WAF). Nauplii were monitored through development to adulthood, and mature virgin male:female pairs mated in wells containing original treatments (<30 d). A second bioassay using 0, 10, 30, and 50% WAFs (n > or =60 nauplii/treatment) was conducted to assess the effects of ultraviolet (UV) light on naupliar endpoints (<16 d). In the first experiment, nauplius-to-copepodite survival in exposures to 100% WAF was 27% +/- 6% lower than in controls (92% +/- 1%), but copepodite-to-adult survival was greater than 90% across all treatments. Analysis of development curves showed that nauplii in the 10% WAF developed into copepodites 25% faster, whereas nauplii in the 50 and 100% WAFs developed 17% slower, than controls. Copepodite development into male and female copepods was significantly delayed (2 and 4 d, respectively) in the 100% WAF compared to controls. Although none of the WAF exposures had significant effects on fertilization success or total viable production (p > 0.05), embryo hatching in the 100% WAF was significantly less (70.0% +/- 21.2%) than that in controls (87.0% +/- 19.4%). Results from the UV bioassay showed that relatively short exposures (<14 d) to 30 and 50% WAFs in the presence of UV light caused negative effects on copepod survival and development. Naupliar-stage survival and developmental endpoints were the most sensitive indicators of exposure to the NIST crude oil WAF