Abstract-Based on the need for a test to evaluate chronic sublethal toxicity in estuarine sediments, a 28-d sediment bioassay with the estuarine amphipod Leptocheirus plumulosus (Shoemaker) was developed. The test was initiated with animals less than 2 weeks old (i.e., 425-600 m sieved size class). Test endpoints included survival, growth (g dry weight/d), and reproduction (number of neonates/surviving female). Factors with the potential to influence test animal performance (i.e., nontreatment factors) such as artificial sea salts, salinity, food ration, size at test initiation, intraspecific density, sediment grain size, and diet were evaluated. For example, intraspecific densities between 10 and 60 animals/beaker (i.e., 0.18-1.4 animals/cm 2 ) did not affect survival, growth, or reproduction. Similarly, L. plumulosus were tolerant of a wide range of sediment grain sizes with only extremely fine grained (e.g., Ͼ75% clay) or coarse grained (e.g., Ͼ75% sand) material significantly affecting survival, growth, and reproduction. Test performance criteria included control survival (Ͼ80%) and reproduction (production of offspring in all control replicates), and response to a reference toxicant test with cadmium chloride in a control chart format.

Abstract-This article describes the selection process used to identify optimal measures of growth and reproduction for the proposed 28-d sublethal sediment bioassay with the estuarine amphipod Leptocheirus plumulosus. We used four criteria (relevance of each measure to its respective endpoint, signal-to-noise ratio, redundancy relative to other measures of the same endpoint, and cost [i.e., of labor, training, and equipment]) to evaluate nine growth and seven reproductive measures. Optimal endpoint measures were identified as those receiving relatively high scores for all or most criteria. Measures of growth scored similarly on all criteria, except for cost. The cost of the pooled (female plus male) growth measures was substantially lower than the cost of the female and male growth measures because the latter required more labor (by approx. 25 min per replicate). Pooled dry weight was identified as the optimal growth measure over pooled length because the latter required additional labor and nonstandard software and equipment. Embryo and neonate measures of reproduction exhibited wide differences in labor costs but yielded similar scores for other criteria. In contrast, brooding measures of reproduction (females carrying embryos in the brood pouch) scored relatively low on endpoint relevance, signal-to-noise ratio, and redundancy criteria. We recommend neonates/survivor as the optimal measure of L. plumulosus reproduction because it exhibited high endpoint relevance and signal-to-noise ratios, was redundant to other reproductive measures, and required minimal time.

Based on the need for a test to evaluate chronic sublethal toxicity in estuarine sediments, a 28‐d sediment bioassay with the estuarine amphipod Leptocheirus plumulosus (Shoemaker) was developed. The test was initiated with animals less than 2 weeks old (i.e., 425–600 μm sieved size class). Test endpoints included survival, growth (μg dry weight/d), and reproduction (number of neonates/surviving female). Factors with the potential to influence test animal performance (i.e., nontreatment factors) such as artificial sea salts, salinity, food ration, size at test initiation, intraspecific density, sediment grain size, and diet were evaluated. For example, intraspecific densities between 10 and 60 animals/beaker (i.e., 0.18–1.4 animals/cm2) did not affect survival, growth, or reproduction. Similarly, L. plumulosus were tolerant of a wide range of sediment grain sizes with only extremely fine grained (e.g., >75% clay) or coarse grained (e.g., >75% sand) material significantly affecting survival, growth, and reproduction. Test performance criteria included control survival (>80%) and reproduction (production of offspring in all control replicates), and response to a reference toxicant test with cadmium chloride in a control chart format.

This article describes the selection process used to identify optimal measures of growth and reproduction for the proposed 28‐d sublethal sediment bioassay with the estuarine amphipod Leptocheirus plumulosus. We used four criteria (relevance of each measure to its respective endpoint, signal‐to‐noise ratio, redundancy relative to other measures of the same endpoint, and cost [i.e., of labor, training, and equipment]) to evaluate nine growth and seven reproductive measures. Optimal endpoint measures were identified as those receiving relatively high scores for all or most criteria. Measures of growth scored similarly on all criteria, except for cost. The cost of the pooled (female plus male) growth measures was substantially lower than the cost of the female and male growth measures because the latter required more labor (by approx. 25 min per replicate). Pooled dry weight was identified as the optimal growth measure over pooled length because the latter required additional labor and nonstandard software and equipment. Embryo and neonate measures of reproduction exhibited wide differences in labor costs but yielded similar scores for other criteria. In contrast, brooding measures of reproduction (females carrying embryos in the brood pouch) scored relatively low on endpoint relevance, signal‐to‐noise ratio, and redundancy criteria. We recommend neonates/survivor as the optimal measure of L. plumulosus reproduction because it exhibited high endpoint relevance and signal‐to‐noise ratios, was redundant to other reproductive measures, and required minimal time.

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).