[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/07/EW-08-09-12-Fish-Leaves.mp3|titles=EW 08-09-12 Fish-Leaves]
Most of us learned about the aquatic food web in high school. Using a sealed aquarium, teachers explained that plants form the base of the web, with the organic carbon they create supporting aquatic life—from invertebrates to sport fish.
But just because an aquarium functions as a sealed ecosystem doesn’t mean lakes behave this way. Research by Cary Institute of Ecosystem Studies scientist Jon Cole and colleagues has revealed that algae and duckweed are getting a little help from the watershed.
Scientists have long suspected that aquatic food webs were subsidized by leaves, pine needles, and other organic carbon that washes in from the watershed. Cole and colleagues were among the first to prove this theory in a series of large-scale lake experiments.
Terrestrial and aquatic carbon are virtually identical. To determine the percent of aquatic life supported by the two types of carbon, a tracer was used.
The results? More than a quarter of zooplankton—small animals that live in the water column—were derived from land-grown plant material. Bottom-dwelling invertebrates and fishes received an even larger terrestrial subsidy—50 to 80% of their diet came from the watershed. Jon Cole explains…
“When you look at your fish, it’s not necessarily the result of a simple algae-zooplankton-fish food chain, it’s much more complicated than that with dissolved in particulate organic matter coming from the watershed, fueling microbes that are eaten by other things, that are ultimately eaten by the invertebrates and small fish that the big prize fish you catch are eaten by, so it changes our understanding of how the food web works.”
When you reel in a fish this summer, remember that some of it is derived from last year’s maple leaves.
Web Extra
Jon Cole, a scientist at the Cary Institute of Ecosystem Studies, shares his thoughts on why the terrestrial influence in watersheds remained a mystery for so long…
[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2012/07/cole_web_extra.mp3|titles=cole_web_extra]