Daphnia (water flea)
Researchers at U of T Scarborough have found that the ‘chemical conversations’ tiny species rely on to find food and mates can be affected by even small amounts of pollution (iStock photo)
Thursday, March 4 - 2021
Don Campbell

Researchers at U of T Scarborough have for the first time shown that pollution can disrupt the ‘chemical conversations’ water fleas rely on to communicate with other species.

Daphnia, commonly referred to as water fleas, live in all sorts of aquatic environments from swamps to freshwater lakes and ponds. They’re crucial to the aquatic food chain, feeding on algae, while also serving as food for insects, water mites and small fish. They navigate their environment by releasing bio-molecules (info-chemicals) that interact with other species, helping them detect prey or potential mates.

“It’s these info-chemicals that species use to communicate with each other – they’re basically like messengers,” says Professor Myrna Simpson, a Canada Research Chair and professor in the department of physical & environmental sciences who co-authored the research.

It’s been thought that ‘chemical conversations’ between species are disrupted when one of the species is affected by pollution, but this is the first time this disruption between two species have been observed as a result of exposure to such low levels of pollution. 

The study, by Simpson and former postdoc Tae-Yong Jeong, now an assistant professor at Hankuk University of Foreign Studies in South Korea, found that info-chemicals between water fleas and algae could be disrupted by a small amount of fenoxycarb (200 nanograms per one litre of water), a type of pesticide. Fenoxycarb is also an endocrine disruptor – one that can mimic or disrupt hormones in the body – which is important because the endocrine system is believed to play a big role in producing these info-chemicals in water fleas.

Myrna Simpson and Tae-Yong Jeong
Professor Myrna Simpson and former postdoc Tae-Yong Jeong from the Department of Physical and Environmental Sciences discovered that 'info-chemicals' used by water fleas were affected by even small amounts of a pollutant (photo by Don Campbell)

What’s more, Simpson says these disruptions may cascade throughout the entire food web. If water fleas can’t reproduce or find food it means there will be less of them. Fewer water fleas mean less food for larger predators, but also more algae, which can lead to algae blooms that can harm fish and deteriorate water quality.


“Daphnia are an excellent indicator of aquatic ecosystem health,” says Simpson, whose research program focuses on the effect of environmental change in water and soil at the molecular-level. “If they’re unhealthy, other organisms living in that ecosystem are also likely unhealthy as well.”  

Simpson and Jeong used a novel technique they previously developed that relies on a powerful instrument called a tandem mass spectrometer to detect the info-chemical disruption. They pioneered a method using something called metabolomics that’s able to detect rapid changes in tissues and cells almost instantaneously. This approach is not only fast, it’s also highly sensitive to any stress or biochemical changes within an organism.

Simpson says the fact the info-chemicals of Daphnia and algae were disrupted so quickly and at such a low concentration of exposure shows these pollutants may pose a greater ecological risk than is currently recognized. She adds that most water monitoring focuses on how relatively large amounts of a toxin will affect a water flea’s ability to reproduce.

“This shows we may need to look at things more broadly because there is this disruption taking place, and we know that these types of pollutants are commonly found in the environment at these low levels.”

The research, which was published in the journal Environmental Science & Technology and received funding from U of T Scarborough’s Faculty Research Excellence Scholar award, offers the potential of developing a rapid way of assessing the health of an ecosystem. Simpson says the overall goal is to create a framework where these novel techniques can be easily used in environmental monitoring programs.

“Currently water pollution tests are time consuming and they analyze only a certain number of pollutants, but there are many pollutants and by-products that are undocumented. By using metabolomics to study how Daphnia are affected, it can offer a rapid way of assessing water quality through this critically important organism.