Toxic Effect of Metal Doping on Diatoms as Probed by Broadband Terahertz Time-Domain Spectroscopy

The global marine environment is increasingly affected by human activities causing climate change, eutrophication, and pollution. These factors influence the metabolic mechanisms of phytoplankton species, such as diatoms. Among other pollutant agents, heavy metals can have dramatic effects on diatom viability. Detailed knowledge of the interaction of diatoms with metals is essential from both a fundamental and applicative point of view. To this aim, we assess terahertz time-domain spectroscopy as a tool for sensing the diatoms in aqueous systems which mimic their natural environment. Despite the strong absorption of terahertz radiation in water, we show that diatoms can be sensed by probing the water absorption enhancement in the terahertz range caused by the water-diatom interaction. We reveal that the addition of metal dopants affects this absorption enhancement, thus enabling the monitoring of the toxic effects of metals on diatoms using terahertz spectroscopy. We demonstrate that this technique can detect the detrimental effects of heavy metals earlier than conventional methods such as microscopy, enzymatic assays, and molecular analyses aimed at assessing the overexpression of genes involved in the heavy metal-stress response.

Automated summary

The global marine environment is being increasingly affected by human activities leading to climate change, eutrophication, and pollution. These factors impact the metabolic mechanisms of phytoplankton like diatoms. Heavy metals, among other pollutants, can significantly affect diatom viability. Understanding the interaction between diatoms and metals is crucial for both fundamental and applied purposes. Terahertz time-domain spectroscopy is evaluated as a method for sensing diatoms in aqueous systems resembling their natural environment. Despite the strong absorption of terahertz radiation in water, diatoms can still be detected by the enhancement of water absorption in the terahertz range caused by the water-diatom interaction. The addition of metal dopants affects this absorption enhancement, enabling the use of terahertz spectroscopy to monitor the toxic effects of metals on diatoms. This technique is shown to detect the harmful effects of heavy metals earlier than conventional methods like microscopy and molecular analyses.