The dictionary definition of serendipity is: n. 1. Making a fortunate discovery by accident. 2. Good fortune. Want to hear how serendipity at Togiak National Wildlife Refuge in southwestern Alaska led to new insights in global science? Read on.
Togiak Refuge biologist Mark Lisac and I collaborated with an international team of scientists to detect human–produced nitrogen in remote lakes throughout the Northern Hemisphere—from Alaska to the Rocky Mountains to Norway. In doing so, we helped reveal that the impact of human activities since late–19th–century industrialization is evident in even the most isolated ecosystems on the planet.
The research was published in the international journal Science on Dec. 16, 2011, and is available at http://www.sciencemag.org.
To a large degree, the findings were serendipitous. They were incidental to a study with very different objectives. Working with colleagues from the University of Washington, Lisac and I were studying prehistoric sockeye salmon runs in order to understand natural variability in modern–day runs. This is important because Togiak Refuge is located in the salmon capital of the world.
Reconstructing ancient salmon runs required our research team to collect sediment from lakes, date sediment layers and analyze the nitrogen isotope ratios found at various dates. All nitrogen sources to lakes are characterized by a mixture of light and heavy isotopes of nitrogen. Nitrogen sources that come from saltwater, especially those represented by migrating salmon, have a relatively high ratio of heavy isotopes to light isotopes compared with nitrogen produced in watersheds and delivered to lakes via freshwater streams. Thus, the relative enrichment of lake nitrogen isotopes can be used to infer quantities of salmon present at various points in history.
However, to make that inference it was necessary to collect and analyze sediments from reference lakes that were not accessible to migrating salmon, including High Lake and Nagugun Lake at Togiak Refuge.
At one point, a member of our team, Gordon Holtgrieve of the University of Washington, noticed a subtle–but–distinct change in the heavy–isotope proportion in the most recent 115 years in High and Nagugun Lakes. This led to a review of sediment data from 34 other lakes studied by other researchers throughout the Northern Hemisphere, and the same change was observed elsewhere. This change in isotope composition could not be explained by changes in climate, normal chemical processes, salmon runs or other natural sources of nitrogen.
Other studies have demonstrated that human activities that burn fossil fuels and use agricultural fertilizers can elevate nitrogen levels in the atmosphere and that the nitrogen is then deposited back on Earth through rain and snow. These studies have demonstrated local and regional nitrogen deposition, but not global deposition—until now. Given the remote location of the Togiak Refuge lakes (on the edge of the Bering Sea 350 miles from the nearest connecting road) and the other study lakes across the Northern Hemisphere, atmospheric deposition was the inescapable conclusion.
Although nitrogen is necessary for life, and often is viewed positively as a fertilizer, at high levels it is considered a pollutant, causing a variety of ecological responses. This study demonstrates an ecologically significant increase in deposition of human–derived nitrogen to even the most remote watersheds of the world. The ecological ramifications of this increase are not known.
What is known is that the insights that emerged from this work would not have occurred without the original salmon study at Togiak Refuge— and that, sometimes with a touch of serendipity, National Wildlife Refuge System science is contributing to global science.
Patrick Walsh is a supervisory biologist at Togiak National Wildlife Refuge in Alaska.
