by Richard Manning
I had spent the day with biologist Brian Fransen, wading in a creek that fed into Willapa Bay in western Washington. It was a stream where salmon spawned, but he was collecting and examining other species of fish. His real target was not the fish, but a simple element, carbon – that building block shared by all living things.
Not all carbon is alike: Carbon from the ocean has a distinct signature. Fransen took tissue samples from young fish that had never seen the ocean, yet he found that 60 percent of the carbon in their bodies was ocean-derived.
The young fish acquired the ocean's carbon by feeding on carcasses of spawned-out salmon that had died in that creek the season before. Salmon are born, leave the stream as a pencil-sized fish, spend a few years fattening on ocean's bounty, then return with a gift to the natal stream, as much as 60 pounds of body mass made of not just carbon, but of the other nutrients the entire system needs. They import nutrients to landlocked life. This is the measure of the power of salmon.
Scientists now estimate that the Columbia River system once gained about 400 million pounds of nutrients from each year's salmon runs, before the dams broke the cycle.
Not only small fish contain ocean carbon. Samples of salmonberry bushes growing streamside reveal as much as 18 percent of their nutrients are ocean-derived, making it one of the more aptly named plants around. The same is true of trees. Plants are fed when carcasses decay and fertilize the soil, or when the dead salmon enter the food chain and eventually return to the soil as droppings. The faunal section of the chain contains at least 20 vertebrate species, including, of course, bears, but also surprisingly, deer and elk, which during spawning season are known to feed directly on salmon carcasses.
Salmon depend on healthy streams that in turn depend on healthy streamside vegetation to shelter them and preserve water quality and flows. The vegetation, in turn, depends on bears' fertilizer, which, in turn, depends on salmon. We humans, in turn, depend on them all.
That last point can be driven home by a negative example. Scientists are beginning to find that the salmon's almost magical ability to concentrate nutrients also works for pollutants. Research on lakes in Alaska, published in the journal Nature, found that salmon had accumulated deadly PCBs dumped in the oceans. When the salmon spawned and died by the thousands in the lakes, they increased PCB concentrations in those waters sevenfold. The pollutant, of course, will not remain in those lakes; it will cycle through the food web and, finally, into us.
We think we have thrown these pollutants away, but there is no "away" when life is woven together. Salmon teach us a hard lesson: Dump in the ocean and we'll bring it right back to you.
The unique, wandering ways of salmon make their example dramatic, but the truth is, all of life works this way. Life feeds on a great cycle and flow of nutrients. To those who presume to decide which of the links in the food chain can be sacrificed, there is only one reply: No form of life is dispensable; there is no expendable link. Just as there is no "away," there is no "other." All of us – salmon, bear, person, tree and stream – are made of the same matter and are in this life together.