DEVELOPMENT OF A CHRONIC SUBLETHAL SEDIMENT BIOASSAY USING THE ESTUARINE AMPHIPOD, LEPTOCHEIRUS-PLUMULOSUS (SHOEMAKER)

Based an the need for a test to evaluate chronic sublethal toxicity in estuarine sediments, a 28-d sediment bioassay with the estuarine amph ipod Leptocheirus plumulosus (Shoemaker) was developed. The test was i nitiated with animals less than 2 weeks old (i.e., 425-600 mu m sieved size class). Test endpoints included survival, growth (mu g dry weigh t/d), and reproduction (number of neonates/surviving female). Factors with the potential to influence test animal performance (i.e., nontrea tment factors) such as artificial sea salts, salinity, food ration, si ze 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 su rvival, growth, or reproduction. Similarly, L. plumulosus were toleran t of a wide range of sediment grain sizes with only extremely fine gra ined (e.g., >75% clay) or coarse grained (e.g., >75% sand) material si gnificantly affecting survival, growth, and reproduction. Test perform ance criteria included control survival (>80%) and reproduction (produ ction of offspring in all control replicates), and response to a refer ence toxicant test with cadmium chloride in a control chart format.