Effect of salinity on the toxicity of diclofenac, ibuprofen and naproxen toward cyanobacterium Synechocystis salina.

Aquatic species are continuously exposed to pharmaceuticals and changeable water conditions simultaneously, which can induce changes in the toxicity of pollutants. Cyanobacterium are an organism for which less ecotoxicological tests have been performed compared to green algae. In this study, we decided to check how selected non-steroidal anti-inflammatory drugs (NSAID) affect the grow of Synechocystis salina, picocyanobacterium isolated from the Baltic Sea, with salinity as potential modulator of toxicity. S. salina was exposed to diclofenac (DCF), ibuprofen (IBF) and naproxen (NPX) (nominal 100 mg L-1) in BG11 medium and sea salt supplemented BG11 medium (38 PSU) over 96 h in continuous light at 23 °C. No acute toxicity was found in both tested salinity levels. The comparable grow rate in exposed culture compared to control culture over 4 days indicate lack of stress for several generations which need to be overcome with substantial energy consumption. S. salina was found to be halotolerant and can be species for ecotoxicology test where salinity in an additional stressor. Furthermore, resistant of S. salina to target NSAIDs provide a competitive advantage over other phytoplankton species.

Unicellular cyanobacteria degrade sulfoxaflor to its amide metabolite of potentially higher aquatic toxicity.

Sulfoxaflor (SFX) is a fourth-generation neonicotinoid used widely in modern agriculture. Due to its high water solubility and mobility in environment, it is expected to occur in water environment. Degradation of SFX leads to formation of corresponding amide (M474), which in the light of recent studies may be much more toxic to aquatic organisms than the parent molecule. Therefore, the aim of the study was to assess the potential of two common species of unicellular bloom-forming cyanobacteria (Synechocystis salina and Microcystis aeruginosa) to metabolize SFX in a 14-day-long experiment, using elevated (10 mg L-1) and predicted highest environmental (10 µg L-1) concentrations. The results obtained support the occurrence of SFX metabolism in cyanobacterial monocultures, leading to release of M474 into the water. Differential SFX decline in culture media, followed by the presence of M474, was observed for both species at different concentration levels. For S. salina, SFX concentration decreased by 7.6% at lower concentration and by 21.3% at higher concentration; the M474 concentrations were 436 ng L-1 and 514 µg L-1, respectively. Corresponding values for M. aeruginosa were 14.3% and 3.0% for SFX decline; 282 ng L-1 and 317 µg L-1 for M474 concentration. In the same time, abiotic degradation was almost non-existent. Metabolic fate of SFX was then studied for its elevated starting concentration. Uptake of SFX to cells and amounts of M474 released to water fully addressed the decrease in SFX concentration in M. aeruginosa culture, while in S. salina 15.5% of initial SFX was transformed to yet unknown metabolites. The degradation rate of SFX observed in the present study is sufficient to produce a concentration of M474 that is potentially toxic for aquatic invertebrates during cyanobacterial blooms. Therefore, there is a need for more reliable risk assessment for the presence of SFX in natural waters.

Review of warming and acidification effects to the ecotoxicity of pharmaceuticals on aquatic organisms in the era of climate change.

An increase in the temperature and the acidification of the aquatic environment are among the many consequences of global warming. Climate change can also negatively affect aquatic organisms indirectly, by altering the toxicity of pollutants. Models of climate change impacts on the distribution, fate and ecotoxicity of persistent pollutants are now available. For pharmaceuticals, however, as new environmental pollutants, there are no predictions on this issue. Therefore, this paper organizes the existing knowledge on the effects of temperature, pH and both stressors combined on the toxicity of pharmaceuticals on aquatic organisms. Besides lethal toxicity, the molecular, physiological and behavioral biomarkers of sub-lethal stress were also assessed. Both acute and chronic toxicity, as well as bioaccumulation, were found to be affected. The direction and magnitude of these changes depend on the specific pharmaceutical, as well as the organism and conditions involved. Unfortunately, the response of organisms was enhanced by combined stressors. We compare the findings with those known for persistent organic pollutants, for which the pH has a relatively low effect on toxicity. The acid-base constant of molecules, as assumed, have an effect on the toxicity change with pH modulation. Studies with bivalves have been were overrepresented, while too little attention was paid to producers. Furthermore, the limited number of pharmaceuticals have been tested, and metabolites skipped altogether. Generally, the effects of warming and acidification were rather indicated than explored, and much more attention needs to be given to the ecotoxicology of pharmaceuticals in climate change conditions.