What constitutes fish food is a matter of debate. A high-profile study a few years ago suggested that fish get almost 50 percent of their carbon from trees and leaves, evidence for a very close link between the terrestrial and aquatic ecosystems.
But new research from the University of Washington shows this is not likely to be true. Algae provide a much richer diet for fish and other aquatic life, according to research published this week in the Proceedings of the National Academy of Sciences.
"Are the fish made of maple? Our argument would be no, they're not, they're made of algae," says Michael Brett, a UW professor of civil and environmental engineering. "Other scientists have said that up to 50 percent of the carbon was coming from this terrestrial source. We're saying that's very unlikely."
The results could be important not just to fish but to people seeking to boost fish populations.
"In terms of fishery production this means you've really got to focus on the algae," Brett said. "The terrestrial environment is still important, but for other reasons such as habitat."
The new paper shows that algae are necessary ingredients for healthy zooplankton, the animals at the base of the aquatic food web. Brett's lab studies omega-3 fatty acids, the same ones touted in health studies. Fish can't produce the heart-healthy lipids, they just accumulate them from their diet. Brett's group looks at where exactly the omega-3's are coming from, largely from several groups of phytoplankton that can make these fats.
After reading the fish food study published in 2004 in the journal Nature, "we were furrowing our brows and saying 'This doesn't make sense,'" Brett said, "because the terrestrial plants aren't producing these omega-3 molecules. Those results completely conflicted with the perspective that was coming out of our own area of research."
The earlier study by the Institute for Ecosystem Studies
|Contact: Hannah Hickey|
University of Washington