Chronic toxicity of phenanthrene to the marine polychaete worm, Nereis (Neanthes) arenaceodentata.

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the environment. While environmental concentrations are generally below acutely lethal levels (Hyland and Schneider 1976), chronic, low level exposures may result in subtle sublethal effects. PAHs accumulate in bottom sediments and may represent a hazard to the benthos. Polychaetes are important members of this community (Officer and Lynch 1989). The objective of this study is to evaluate the chronic sublethal effects of one PAH, phenanthrene (PHN), on the polychaete worm, Nereis (Neanthes) arenaceodentata. PHN was selected because of its high toxicity to marine invertebrates relative to other PAHs (Neff 1979).

Chronic toxicity of Great Lakes sediments to Daphnia magna: elutriate effects on survival, reproduction and population growth.

: Seventeen Great Lakes sediments ranging in degree of expected toxicity were evaluated using a 21 day sediment elutriate bioassay with Daphnia magna. Sediments differed in their effects on survival, age at first reproduction, the number of broods produced and the total number of young produced per adult. Sediments producing low survivorship (50-60%) also had negative effects on reproduction. However, both positive and negative effects on reproduction were found among sediments producing high survivorship. To integrate all test end-points, a stochastic matrix population model was constructed and parameterized with survival and reproduction data from each sediment. By including estimates of variability in vital rates, the model output provided quantitative estimates of uncertainty in projected population size. Sediment effects on survival and reproduction translated into large differences in projected population growth; mean estimates of projected population size at day 28 of the simulations ranged over two orders of magnitude among the 17 sediments. Reproductive timing (e.g. age at first reproduction), followed by fecundity and survivorship, had the largest effect on population growth. Results of this study also indicate that the presence of suspended sediment in elutriates may confound toxicity evaluations using cladocerans. The concentration of total suspended solids was negatively correlated with age at first reproduction and positively correlated with measures of fecundity and population growth. In order to realize the potential benefits of chronic testing we must develop ecologically relevant ways of interpreting sediment bioassay results and expressing the uncertainty associated with our estimates of ecological risk.

Long-term storage of sediments: Implications for sediment toxicity testing.

Juvenile Nereis (Neanthes) arenaceodentata survival and growth were used to evaluate the effect of storage time on the toxicity of sediments with moderate PAH and metal contamination. Seven San Francisco Bay area sediments and a clean control sediment were stored (4 degrees C) and then periodically evaluated (up to two years after collection). During each test, juvenile worms (2-3 weeks post emergence) were exposed for 21 days. Test endpoints were survival and growth rate (mg dry weight/day). In general, survival was high (>75%) and long-term cold storage (740 days) did not significantly alter growth or survival. In half of the sediments a cyclical phenomenon was observed associated with the appearance of ammonia in the overlying water of bioassay beakers. The periodicity of this phenomenon was approximately one year. It was not associated with any geophysical characteristic of the test sediments (i.e. grain size, % TOC, % TKN). Significant mortality (0% survival on day 427) was associated with the largest of these peaks in overlying water ammonia concentration. Results of this study suggest that ammonia in stored sediments is an important, potentially confounding factor in sediment toxicity tests.

Trophic transfer and biomagnification potential of contaminants in aquatic ecosystems.

This review summarizes information obtained from published literature to determine to what degree biomagnification of organic compounds and metals occurs in freshwater and marine food webs. This review was conducted by: (1) examining data from studies conducted in laboratory experiments to establish body burden ratios between trophic levels (trophic transfer coefficients; TTCs); (2) comparing laboratory-derived TTCs with data obtained from field studies; and (3) comparing biomagnification predictions described by published aquatic food-web models with data obtained in this review. It was determined that: (1) the majority of chemicals evaluated (both organic and metals) do not biomagnify in aquatic food webs; (2) for many of the compounds examined, considerable trophic transfer does occur in aquatic food webs; (3) DDT, DDE, PCBs, toxaphene, methyl mercury, total mercury, and arsenic have the potential to biomagnify in aquatic systems; (4) the lipid fraction of receptors directly influences biomagnification of lipophilic compounds; (5) the food web model reviewed provided similar estimates for most of the organic compounds examined (log Kow values between 5 and 7), with model predictions falling within the range of values of all compounds except dieldrin; (6) for many organic compounds, lack of information precludes assessing the relative importance of biomagnification for these contaminants; and (7) even those compounds for which evidence for biomagnification is strongest show considerable variability and uncertainty regarding the magnitude and existence of food-web biomagnification in aquatic systems.

Toxicity and sublethal effects of No. 2 fuel oil on the supralittoral isopod Lygia exotica.

1. No. 2 fuel oil was of relatively low toxicity to the intertidal isopod Lygia exotica as indicated by the TLm values of over 100% for the WSF and 73 ppm at 24 and 48 hours and 36.5 ppm at 96 hours for the OWD. 2. Respiration was not significantly affected by short term exposure to several concentrations of No. 2 fuel oil prepared as either a WSF or OWD. 3. Lygia contamined by a spill of No. 2 fuel oil and Bunker C residual oil contained high concentrations of dibenzothiophenes. It is not known whether the dibenzothiophenes were accumulated by the Lygia tissues or absorbed to the exoskeleton. Therefore, the high mortality of Lygia following the spill cannot yet be attributed to the dibenzothiophenes.

Mercury and the estuarine marsh clam, Rangia cuneata Gray. I. Toxicity.

Mercury is relatively toxic to Rangia when exposed to initial high concentrations (1 to 6 ppm) followed by low sustained levels (0.013 to 0.432 ppm). Acclimation to low salinity (2 o/ooS) lessens the toxic effect of mercury. Actual concentrations of mercury causing 50% mortality (LC50) in 96 hr are 122 ppb in 2 o/ooS and 58 ppb in 15 o/ooS. Rangia's ability to survive acute mercury exposure (0.87 +/- 0.15 ppm) is enhanced by low level (8.56 +/- 2.54 ppb) contamination followed by a brief period (9 days) in clean sea water.

Spatial scales of current speed and phytoplankton biomass fluctuations in lake tahoe.

Spectral analysis of current speed and chlorophyll a measurements in Lake Tahoe, California and Nevada, indicates that considerably more variance exists at longer length scales in chlorophyll than in the current speeds. Increasingly, above scales of approximately 100 meters, chlorophyll does not behave as a simple passive contaminant distributed by turbulence, which indicates that biological processes contribute significantly to the observed variance at these large length scales.