Ecological implications of molecular biomarkers: assaying sub-lethal stress in the midge Chironomus tentans using heat shock protein 70 (HSP-70) expression

Aquatic community structure is a reflection of the changes in constituent p opulations and the complex interactions between these organisms and environ mental stressors. Consequently, shifts in populations and community structu re can be used to assess water quality. However, these indicators only refl ect damage already sustained by an ecosystem and are not useful for predict ion of potential ecological impacts. Molecular/biochemical indicators, such as heat shock proteins, can provide early indication of environmental stre ss on aquatic communities. The heat shock protein response involves the syn thesis of an array of proteins that protect organisms from cellular damage resulting from exposure to a variety of stressors. Consequently, stress pro teins have the potential of being an important screening tool indicating ex posure to, and/or biological effects of environmental contaminants. The mid ge larva Chironomus tentans has been extensively used in bioassays of fresh water systems. However, investigations of stress proteins as environmental biomarkers in midges are lacking. To evaluate the potential use of HSP-70 a s a biomarker of environmental stress, we completed a preliminary character ization of the stress protein response in C. tentans upon exposure to heat shock. Western immunoblotting indicated an increase in a 72 kD protein afte r larvae were exposed to 33 degrees C, 35 degrees C, and 37 degrees C. The observed induction was rapid, appearing within 5-10 min, and persisted for over 24 h after removal of the stressor. The results are discussed with reg ard to the use of the HSP-70 biomarker as an environmental screening tool. It is proposed that the HSP-70 biomarker is most applicable as a sublethal toxicity test endpoint indicative of the presence of biochemically signific ant levels of stress.