PRELIMINARY-STUDY TO COMPARE BODY RESIDUES AND SUBLETHAL ENERGETIC RESPONSES IN BENTHIC INVERTEBRATES EXPOSED TO SEDIMENT-BOUND 2,4,5-TRICHLOROPHENOL

Relationships between concentration of 2,4,5-trichlorophenol (TCP) in sediment, body residues of the chemical, and sublethal biological effe cts in three benthic invertebrates were studied. Uncontaminated lake s ediment was spiked with four concentrations (23-85 mu g/g dry sediment ) of TCP. Chironomid larvae (Chironomus riparius), oligochaete worms ( Lumbriculus variegatus), and sphaeriid bivalves (Sphaerium corneum) we re exposed to the sediment. The effect of chlorophenol on the rate of heat dissipation of animals was monitored by direct microcalorimetry. It appeared that both the behavior of the animals and their body resid ues explained the energetic response. Valve closure behavior of S. cor neum reduced the accumulation of toxicant (<0.3 mu mol/g) but was obse rved as a complex energetic response. Heat dissipation of L. variegatu s was at the same level in control animals and those with high body re sidues of TCP (>1.5 mu mol/g). Regardless of the amount of TCP accumul ated to C. riparius (0.1-0.6 mu mol/g), the rate of hear dissipation w as almost two times higher than that of the control animals, probably reflecting uncoupling of oxidative phosphorylation, which is the prima ry mode of toxic action of chlorophenols. However, when a threshold co ncentration was exceeded there was no concentration-response dependenc e until acute toxicity appears.