If we are what we eat, some lake fish, it turns out, are made of maple leaves. These fallen leaves play an integral role in the food webs of lakes.

It has long been thought that aquatic plants form the base of a lake's food web. The energy they contain supports life, from invertebrates to the largest sport fish. Now, a study funded by the National Science Foundation's (NSF) Biological Sciences Directorate shows that aquatic plants are receiving a little help from trees along the shoreline.

Scientists Michael Pace and Jonathan Cole of the Institute for Ecosystem Studies in Millbrook, New York, found that a significant part of the aquatic food chain is supported by organic matter ("food") that originates on shore.

A building block of life, organic carbon is essential to aquatic food webs. In lakes, aquatic plants produce this carbon by harnessing the sun's energy through photosynthesis. Some of the carbon supports the growth of fish and invertebrate populations.

In Lakes Peter and Paul at the University of Notre Dame Research Center, scientists conducted tests to determine whether lake plant production was enough to support resident aquatic life.

The short answer: it's not. Test results show that aquatic plants don't produce nearly enough food to support lake animals. Therefore, to survive and thrive, the lake animals are dependent on inputs from the surrounding shores.

Leaves and other organic matter that enter lakes, it turns out, are ultimately incorporated into aquatic animals. That maple leaves may eventually become perch, and that the vegetation around a lake can have profound impacts on the animal life within that lake, blur the boundaries between aquatic and land-based ecosystems.

As naturalist John Muir once wrote, tug on one strand of nature, and you'll find it connects to all others.

So it is, biologists are discovering, with life itself.

Back to Overview [Next]