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Do fish eat trees?

An FoS ecologist finds out

By Megan O'Connor

Michael Arts stands next to lab equipment

Professor Michael Arts, aquatic ecologist, Ryerson University


New research into boreal lakes – containing more than 60% of the world’s freshwater – shows that fish gain mass from the nearby trees.

Ryerson’s Michael Arts, an aquatic ecologist, worked on the team that studied the biomass production of organisms living in such environments.  Their work has been published in Nature Communications – a high impact journal that caters to multidisciplinary research.

Their conclusion, that “forests fuel fish growth,” is based on an analysis of carbon data. Forests produce organic matter, or “terrestrial carbon”; this matter get washed into streams that feed the lakes. The team found that the biomass of secondary consumers – such as fish – contained large amounts of terrestrial (rather than algal-produced) carbon. Fish, in particular, derive at least 34 percent of their biomass from forest matter; and the number goes up to 66 percent in more densely forested areas.  

Arts, a Professor in Ryerson’s Department of Chemistry and Biology, is an expert on using lipid-based biochemical tracers (e.g., fatty acids) to assess how organisms respond to stress and also to reveal how food webs function. This expertise was key to explaining how human land use affects the quality (essential fatty acids) of zooplankton that fuel fish production in boreal lakes. Recently he has also been involved in field studies in the Canadian Arctic on copepods, Greenland Sharks and polar bears. “My goal is to understand how lipids can be used to understand food web dynamics in a changing world,” Arts explains, “and how they can be used to map the fate and distribution of contaminants in freshwater and marine food webs” – food webs that are, increasingly, being affected by climate change.

The paper’s first author, Andrew Tanentzap, is also a Canadian, now based at Cambridge University. The six authors have paid for Open Access so that everyone can download a PDF of their paper for free.

Its title is a tongue twister: “Forests Fuel Fish Growth in Freshwater Deltas.” Yet the gravitas is all in the data – and in the implications for human activities. The boreal forest is Canada’s largest ecosystem. It contains over 200 petagrams (200,000,000,000 metric tons) of terrestrial carbon (see “The Carbon the World Forgot”) and the majority of the planet’s fresh water. Our management of the region is critical; and this team of researchers has given us much-needed insight.

As our Faculty of Science Dean Imogen Coe remarked, “It’s a very Canadian paper.”

See the news release for more details.

CBC Radio One interview (June 30, 2014)


Andrew J. Tanentzap, Erik J. Szkokan-Emilson, Brian W. Kielstra, Michael T. Arts, Norman D. Yan & John M. Gunn

“Forests fuel fish growth in freshwater deltas.” Nature Communications 5, Article number: 4077 doi:10.1038/ncomms5077. Received 29 November 2013. Accepted 09 May 2014. Published 11 June 2014.

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