Biouptake experiments were carried out on the marine species Neanthes arenaceodentata and Leptocheirus plumulosus and the freshwater oligochaete Lumbriculus variegatus using 28-day sediment toxicity protocols as outlined in the SI. Tissues and digestive fluids were sonicated according to USEPA method 3550B and the lipid content of organisms was measured by spectrophotometric analysis. PCB concentrations in biolipids were reported based on duplicate or triplicate analysis.