An increase in frequency of epizootic events and mass mortalities have been related with the warming trend of the NW Mediterranean. The present study focuses on Spongia officinalis, a commercial sponge species particularly threatened by the sea warming. The aim of this work was to acquire fundamental data about the biology of this sponge and the mechanisms of health alteration. The stress level of sponges was revealed by measuring Heat Shock Proteins (HSP) expression, a protein family involved in maintaining homeostasis. In parallel, we studied the expression of indicators of the sponge chemical defences. These indicators result from the secondary metabolism and are measured by assessing the sponge natural toxicity and then searching the expression level of certain secondary metabolites