Physiological effects of copper on the freshwater alga Closterium ehrenbergii Meneghini (Conjugatophyceae) and its potential use in toxicity assessments

Abstract

Although green algae of the genus Closterium are considered ideal models for testing toxicity in aquatic ecosystems, little data about the effects of toxicity on these algal species is currently available. Here, Closterium ehrenbergii was used to assess the acute toxicity of copper (Cu). The median effective concentration (EC 50) of copper sulfate based on a dose response curve was 0.202 mg L-1 , and reductions in photosynthetic efficiency (F v / F m ratio) of cells were observed in cultures exposed to Cu for 6 h, with efficiency significantly reduced after 48 h (p < 0.01). In addition, production of reactive oxygen species significantly increased over time (p < 0.01), leading to damage to intracellular organelles. Our results indicate that Cu induces oxidative stress in cellular metabolic processes and causes severe physiological damage within C. ehrenbergii cells, and even cell death; moreover, they clearly suggest that C. ehrenbergii represents a potentially powerful test model for use in aquatic toxicity assessments.

Small heat shock protein genes of the green algae Closterium ehrenbergii: Cloning and differential expression under heat and heavy metal stresses

“…In details, the effect of different concentrations of CuCl 2 presented shows that decrease of the auto‐fluorescence (red color) is accompanied with the increase of the production of ROS (green color; Figure A), indicating that CuCl 2 could trigger oxidative stress, even at lower concentrations. The observed effect of CuCl 2 matches with previous reports on C. ehrenbergii and also other species, about the increase ROS production during oxidative stress . In addition, the effect of K 2 Cr 2 O 7 , at 2 and 4 mg/L concentrations, and the increase of fluorescence (ROS production) was proportional to the increasing concentrations.…”

“…Additionally, increasing concentration of potassium dichromate has shown to be inducing a general decline in cell densities in the green alga Pseudokirchneriella subcapitata . Moreover, recent study by Wang et al on the effect of copper on C. ehrenbergii showed that F v /F m was considerably affected by copper toxicity and also declined with increasing copper concentration and exposure time, indicating that chlorophyll content and/or photosynthetic electron transport might be inhibited by exposure to the metal …”

“…32 In addition, it has been used in toxicity evaluations and bioassays for detecting the deleterious effects of hazardous substances on aquatic systems, due to its sensitivity to a wide range of surfactants. [33][34][35] More recently, we found a considerable increase of antioxidant enzyme activities in C. ehrenbergii exposed to environmental stressors. [35][36][37] These findings have supported that it might be used as an ideal organism for eco-toxicological assessment, in terms of physiological and biochemical perspective.…”

“…The doses effect of toxicants (CuSO 4 , CuCl 2 , and K 2 Cr 2 O 7 ) on CeHSPs transcriptional expression were tested using C. ehrenbergii cultures treated with a series of concentrations of each toxicant. The different concentrations were chosen to consider the EC 50 values of the biocides . The treated and untreated cultures were harvested at 24 hours for the analysis.…”

“…Relatively larger size (~300 μm in length) and particular shape (long, curved, and tapered at both ends) of the species make it the perfect candidate for the observation of morphological and cellular changes . In addition, it has been used in toxicity evaluations and bioassays for detecting the deleterious effects of hazardous substances on aquatic systems, due to its sensitivity to a wide range of surfactants . More recently, we found a considerable increase of antioxidant enzyme activities in C. ehrenbergii exposed to environmental stressors .…”