Every inch of the environment that surrounds us. . .potentially contains genetic information from other organisms that inhabit our world. But until recently, researchers lacked the tools needed to make use of that information, which comes in the form of environmental DNA (eDNA) or environmental RNA (eRNA). While scientists have begun to explore uses for eDNA in recent years, fewer have tackled its fickler, more elusive sister eRNA.

Along with eDNA, organisms also shed eRNA. However, while eDNA has become a valuable tool for ecosystem ecologists in recent years, eRNA hasn’t received the same attention. According to Robert Masaki Hechler, an aquatic ecologist at the University of Toronto and a coauthor of the preprint research, this is because RNA is generally less stable than DNA, degrading so swiftly that many scientists assumed it would be difficult or impossible to harvest and analyze it quickly enough to get any results. However, ecologists and eDNA scientists had long speculated that, if possible, analyzing eRNA could provide insights into ecosystem health that eDNA cannot. Ironically, eRNA’s rapid degradation could allow it to provide a more accurate snapshot of what organisms are currently in a system, scientists posit. Moreover, the RNA an organism sheds can change throughout its life whereas its DNA remains fixed over time.

Setting up eight tanks of artificial lake water in the lab, Hechler and Cristescu along with other scientists cultivated populations of Daphnia (Daphnia pulex), a water flea that is commonly used in ecology experiments. They then set the temperature of half of the tanks at 20°C, which is normal for Daphnia, and the other half at 28°C, which is almost hot enough to kill the crustacean. The team then took tissue samples, which contain organismal RNA (oRNA), and water samples, which contain eRNA, from each tank, and immediately put them into -80°C freezers in order to prevent the RNA from degrading. oRNA samples, Hechler explains, are the gold standard for measuring an organism’s health status and response to stress. By comparing them to the eRNA samples, he and Cristescu hoped they would be able to tell whether the latter provided useful information.