The effects of biocides on the growth of aerophytic green algae (Chlorella sp.) isolated from a cave environment

Lampenflora communities of bacteria, cyanobacteria, algae, mosses and lichens colonize illuminated show-caves as a consequence of disturbances to the caves’ ecological equilibrium. These communities have unesthetic impacts and can cause the biodeterioration of limestone. A 15% hydrogen peroxide solution was proposed for use as an ecological agent for the safe removal of these microorganisms. This study tested the effects of three different biocides (hydrogen peroxide, a commercial solution containing salicylic acid and a product containing chlorine dioxide as the active component), on the growth of green algae (Chlorella sp.), which are frequently encountered in lampenflora communities. Chlorella sp. was treated with the biocides under laboratory condition, and chlorophyll a (Chl a) concentrations were measured 1 h, 3 days, 7 days and 10 days after treatment. The change in Chl a concentration was compared to the untreated control group at each time point. All three biocides prevented the growth of green algae and the product containing chlorine dioxide appeared to be the most effective growth inhibitor. Hydrogen peroxide is known to suppress lampenflora growth in caves, and further studies on other biocides remain necessary to identify a solution that is both ecologically safe and economically feasible