Four different microalgae species were addressed, and their motility recorded with a camera after 2h exposure to the toxicants.

Another microfluidic device was based on a digital microfluidic diluter chip forming single droplets containing the microalgae and polluted seawater with different concentration gradients. tsingtaoensis fell approximately 2.4 and 5.3 μmol L −1 for Cu(II), respectively. Drastic changes in phytoplankton motility was observed after 2 h, and the EC 50 values for motility inhibition of P. One of these chips was formed by four different units, generating a concentration gradient, connected to downstream diffusion chambers in which the phytoplankton is confined The concentration gradient generator allows testing of eight different concentration of toxic agents on the same chip. Microfluidic chips have also been exploited to assess pollutant toxicity in the marine environment through observation of the motility change of phytoplankton exposed to heavy metal ions (Cu, Pb, Hg) or phenol. Other fluorescence techniques used to evaluate Cu(II) toxicity are flow cytometry and fluorescence microscopy using both autofluorescence and staining with fluorescent labels. In particular, changes in the fluorescence intensity following pulsed excitation (PAM: pulse amplitude modulated fluorescence), allow exploration of the way in which the photosynthetic cycle is affected by Cu(II). Many studies have been devoted to this last topic, and the observation of changes in the spontaneous fluorescence of chlorophylls in the photosystems allows evaluation of the insurgence of stress in the cell.

However, high doses of this metal induce adverse effects, such as ROS (Reactive Oxygen Species) production, which, in turn, affects many metabolic pathways and the photosynthetic efficiency of the microalgae.

Cu(II) is always present in culture media as well as in the natural environment because it is an essential micronutrient. Among toxicants, the metal ion Cu(II) has a strong effect on the growth and viability of aquatic microorganisms, in particular, microalgae.

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