A building block of life, organic carbon is essential to aquatic food webs. In lakes, aquatic plants produce organic carbon by harnessing the sun's energy (photosynthesis); some of this carbon supports the growth of fish and invertebrate populations. Scientists have long suspected that organic carbon from land is also significant to aquatic life, but the idea is difficult to demonstrate.
By tracing the fate of carbon through large-scale lake manipulations, Pace, Cole, and their colleagues have revealed that in some waters terrestrial organic carbon significantly subsidizes the aquatic food web.
"These scientists have found an ingenious method of teasing apart the carbon cycle of lakes," says James Morris, program director in the National Science Foundation (NSF)'s division of environmental biology, which funded the research. "Their study reveals a surprising degree of dependence of lake food webs on sources of organic matter transported into the lakes from the surrounding watershed. These findings reinforce the concept that the ecology of lake ecosystems is tightly coupled with that of the surrounding terrestrial landscape."
That maple tree leaves many eventually become perch, and that the vegetation around a water body can have profound impacts on the animal life within the body of water blur the perceived ecological boundaries between aquatic and terrestrial systems.