Silver nano-particles, or nanosilver, are tiny globules of silver about 1/1000th the diameter of a human hair. Since silver is toxic to bacteria, nanosilver is widely used as an antibacterial and is found in over 400 products, including: underwear, socks, towels, carpets, cosmetics, baby bottles, stuffed animals, refrigerators, and washing machines.
Because of how common it is, the release of nanosilver into aquatic systems is inevitable and could influence fish and other animals that live in these environments. To study this emerging concern, researchers from Trent University and Lakehead University spent two years adding nanosilver to an entire lake in northwestern Ontario. The study was conducted at the IISD-Experimental Lakes Area, a world-renowned research facility made up of 58 pristine lakes, which are set aside for this type of whole-ecosystem research that simply isn’t possible in most other areas.
Researchers then studied each level of the food chain, to determine how nanosilver influenced the lake’s food-web. The main interest of my study was to examine the effects of nanosilver on Yellow Perch and to determine whether their feeding behaviour, growth, and activity changed during nanosilver exposure. Yellow Perch are a popular target for anglers, who prize this fish for it’s delicious taste. Many predatory fish also like to eat Yellow Perch, so they are an important part of lake ecosystems.
By catching, measuring and dissecting over 500 fish, and using some mathematical models, I was able to estimate the effects of nanosilver on this species. So far, my initial results suggest there was no significant effect of the nanosilver additions on Yellow Perch. These fish grew and behaved just as well as Yellow Perch from another lake that did not have nanosilver added. Instead, Yellow Perch were more affected by season, with a predictable decrease in body condition (how fat they are) over the winter and spring, and an increase in the summer.
This result was unexpected because nanosilver is known to be toxic to bacteria and organisms lower in the food chain. Additionally, the Yellow Perch I studied were found to contain nanosilver, with significant quantities building up in the gills, liver, and muscle tissues over the course of the experiment. But despite accruing nanosilver in their body, we didn’t observe any change in the population size of Yellow Perch, or in the population size of Northern Pike, their main predator.
While we found that adding low levels of nanosilver didn’t seem to impact Yellow Perch in my study, it is important to note that the level of nanosilver used was based on 2012 concentrations of the contaminant. Current estimates of the level of nanosilver are much higher than they were in 2012, and we are still adding lots of nanosilver to the environment through wastewater effluent. So, while nanosilver probably isn’t a huge current issue for fish, it is something we should keep an eye on for the future.
*This article was written by Lauren Hayhurst, a Graduate Student in the Community Ecology and Energetics Lab at Lakehead University (ceelab.ca). Find Lauren on Twitter @Laur_Danielle.