. Advances in marine environmental research : proceedings of a symposium. Marine ecology -- Research; Marine ecology. • NO MUD PROVIDED O MUD PROVIDED SUMMER. 50 Figure 11-2. Survival of adult N. obsoletus exposed to "; ppm in the presence or absence of sediment. NOTE: Winter exposures were initiated 10/22/76 (50 snails/treatment). Sunn- mer exposures were initiated 7/12/77 (25 snails/treatnnent). Control mortal- ities less than 5 percent. Mean oil hydrocarbon concentrations ± (N) were: ppm ± (25), winter; ppm ± (23), summer. Larval mortality of N. obsoletus
. Advances in marine environmental research : proceedings of a symposium. Marine ecology -- Research; Marine ecology. • NO MUD PROVIDED O MUD PROVIDED SUMMER. 50 Figure 11-2. Survival of adult N. obsoletus exposed to "; ppm in the presence or absence of sediment. NOTE: Winter exposures were initiated 10/22/76 (50 snails/treatment). Sunn- mer exposures were initiated 7/12/77 (25 snails/treatnnent). Control mortal- ities less than 5 percent. Mean oil hydrocarbon concentrations ± (N) were: ppm ± (25), winter; ppm ± (23), summer. Larval mortality of N. obsoletus was high in four to eight day experiments at "; ppm, and relatively low at lesser concentrations (Table 11-1). Substantial batch variability in larval tolerance was observed (Figure 11-3). Whereas 50 percent mortality was recorded at "; ppm after three-days in experiment "A", the 50 percent level was not exceeded until day eight in a second experiment using a different hatch of larvae. Indeed, no mortality occurred until day four in experiment "B". All C. inoratus larvae exposed to "; ppm died witliin four days. At "; ppm and "; ppm, about 33 percent of the larvae were still living after three weeks (Figure 11-4). Survival to the megalops stage, attained after 25-28 days, was: control, 58%; "; ppm, 34%; "; ppm, 30%; "; ppm, 0%. 140. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Environmental Research Laboratory (Narragansett, R. I. ); Jacoff, Francine Sakin. Narragansett, R. I. : Environmental Research Laboratory, Office of Research and Development, U. S. Environmental Protection Agency
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