Assessment of Copper Effects on a Diatom Species Through Multi-Scale Fractal Fourier Ptychographic Microscopy

Microalgae are actually considered as sentinel species to detect heavy metal (HM)- driven environmental pollution, since they usually show a dose-dependent response to these persistent pollutants. However, conventional techniques to determine signs of stress (such as evaluation of growth rates, visualization with electron microscopes, enzymatic assays to determine microalgal antioxidant response and molecular analyses aimed at evaluating the overespression of genes involved in HM stress) are time-consuming and do not provide in real time information regarding eventual phenomena of aquatic pollution. To overcome this problem, we settled a novel method: a multi-scale microscopy analysis based on Fourier Ptychographic Microscopy (FPM), choosing copper (Cu) as tested-contaminant for its high toxicity and a diatom species isolated from a seawater environment facing the Sarno River mouth. We combined FPM with a new multi-scale analysis method based on fractal geometry and were able to analyse the detrimental effects of Cu on Skeletonema pseudocostatum with this innovative approach.