Selection of Optimal Measures of Growth and Reproduction for the Sublethal Leptocheirus Plumulosus Sediment Bioassay

Abstract

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.

A comparison of acute and chronic toxicity methods for marine sediments

“…The RM estimated the relative amount of response between test endpoints due to sediment exposure by taking the grand mean of inter-treatment reductions compared to the control (modified from Gray et al, 1998) …”

“…The response of different endpoints (e.g., survival vs. growth) may reflect differing modes of action (Kuhn et al, 2002), inherent sublethal endpoint variability (McGee et al, 2004;Pinza et al, 2002), or different procedures applied in the test methods (Table 1). Although intra-treatment variation may be reduced through increased replication or expression of neonates produced as a function of number of sexually mature females, the increased labor of such approaches may not be cost effective (Gray et al, 1998). Also, the addition of supplemental food to the sediment matrix in chronic toxicity test methods for marine or estuarine sediments may reduce chemical bioavailability (McGee et al, 2004) relative to organisms in acute tests that receive no supplemental food (Lotufo et al, 2001).…”

Review and comparison of available testing approaches and protocols for testing effects of chemicals on sediment‐dwelling organisms with potential applicability to pesticides

“…After extensive studies in the USA, a chronic whole sediment bioassay/toxicity test has been developed using the estuarine amphipod L. plumulosus (Schlekat et al 1992;McGee et al 1993;DeWitt et al 1996;Emery et al 1997;Moore et al 1997;Gray et al 1998). The US EPA published a protocol for conducting a 28-day chronic sublethal sediment bioassay using this species (USEPA, 2001).…”

Measuring sublethal impacts of pollution on reproductive output of marine Crustacea

“…Amphipod models are used extensively in lethal (USEPA 1994, ASTM 1997, Bat & Raffaelli 1998, Roddie & Thain 2002 and sublethal toxicity tests employing a variety of endpoints, including growth, reproduction, behaviour and morphology (Malbouisson et al 1995, Nelson & Brunson 1995, Blockwell et al 1996, Gray et al 1998, Ingersoll et al 1998. These endpoints can sometimes demonstrate effects at population and community levels that may be occurring at more marginally contaminated sites in the field (Ingersoll et al 1998).…”