Reviewing: Franzitta, Marco, et al. “Toxicity Going Nano: Ionic Versus Engineered Cu Nanoparticles Impacts on the Physiological Fitness of the Model Diatom Phaeodactylum tricornutum.” Frontiers in Marine Science (2020). (https://doi.org/10.3389/fmars.2020.539827)
Before heading to the beach and diving into the ocean, you pull out a tube of sunscreen and put it on your face and your body. But were you aware that the sunscreen you just lathered up is washing off and releasing large amounts of nanoparticles into the ocean?
Nanoparticles are very tiny particles that range from 1 – 100 nanometers. A million nanoparticles aligned side by side would be as large as the size of a head of a pin. While nanoparticles are very common in nature – in sand, dust, soot, volcanic ash, clouds, and ocean spray – humans started designing and producing nanoparticles in the last few decades. These engineered nanoparticles can now be found almost everywhere, such as in medicines, electronics, cosmetics, automobiles, and energy industries.
With increasing use of engineered nanoparticles in our everyday lives, we are not only releasing nanoparticles as we use them, but we are also producing domestic and industrial wastes along the way. And even though engineered nanoparticles have been increasingly making their way into the ocean, it is still largely unknown what effects these engineered nanoparticles may have on marine organisms.
A group of scientists were particularly interested in finding out the impact of engineered copper nanoparticles on marine algae, which are tiny relatives of plants. Algae are essential to marine ecosystem, not only because they can use sunlight, carbon dioxide and water to produce oxygen (a process which we commonly refer to as “photosynthesis”), but also because they form the base of marine food webs by becoming food to larger invertebrates and fish. While algae require copper to keep healthy, and too little copper would prevent them from growing, too much copper can also adversely affect their growth. So, the scientists intended to find out if copper coming from engineered nanoparticles can affect marine algae. They grew Phaeodactylum tricornutum, a very common marine diatom (type of marine alga composed of silica) in low, medium and high concentrations of either natural ionic copper or engineered copper nanoparticles.
The scientists found that copper from engineered nanoparticles is more easily accessible by diatoms (up to a hundred times) and cause more damage to their growth than ionic copper, which is the natural form of copper. This is because copper from nanoparticles negatively affected the diatom’s ability to photosynthesize. Specifically, diatoms supplied with engineered copper nanoparticles were found to be substituting magnesium, a central atom in chlorophyll (a pigment used for photosynthesis), for copper from nanoparticles. This copper-substituted chlorophyll is much less efficient in absorbing and trapping light energy, so diatoms with copper-substituted chlorophyll cannot produce as much energy as diatoms with ordinary chlorophyll, which reduces their growth. In addition, diatoms growing with engineered copper nanoparticles also included lower amounts of polyunsaturated fatty acids (chemicals you can commonly find in nuts and cooking oil) in their cells. Since polyunsaturated fatty acids are used to build the walls of chloroplast (a site where photosynthesis happens inside a cell), a decrease in polyunsaturated fatty acids suggest that these chloroplast walls were damaged.
Why should we care about these results? Photosynthesis by marine algae like diatoms provide us with every other breath we take, and copper engineered nanoparticles can potentially reduce their ability or efficiency to produce oxygen. In addition, marine algae also form the base of marine food web. As copper engineered nanoparticles reduce the amount of polyunsaturated fatty acids in these algal cells, these algae essentially become poor quality food, and may affect larger organisms up in the food chain and eventually us. While nanoparticles have become inseparable from our lives, engineered nanoparticles can potentially harm the marine ecosystem.
I am a PhD student in chemical oceanography at University of Washington. I am studying how different forms of metals in the ocean are shaping microbial communities in the North Pacific Ocean. When not working, I like going for a walk, visiting farmers’ markets and playing keyboard.