Structure-function relationships for monitoring cellular stress and recovery responses with Selenastrum capricornutum

Recovery responses to toxicants are neglected in screening and hazard assessment studies which use primary producers as test microorganisms. In this study both structural and functional biotic variables of Selenastrum capricornutum populations are proposed to diagnose cellular stress and to predict recovery responses. The industrial effluent had greater short-term effects on both photosynthetic efficiency (P/B ratio) and adenylate energy charge (EC A ) than did cadmium. With both toxicants high P/B ratios and EC A are observed at the end of the experiment when cell densities are still low, suggesting that these functional parameters can be useful in the detection of recovery responses to toxicants. EC A appears to remain low only under conditions of acute stress. The variation of ATP/cell during the 96 h of the exposure experiment is proposed as an indicator tool for predicting short-term recovery in hazard assessment studies.