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Hydrolab MS5 with Hach LDO Helps Notre Dame Research Team Link Salmon to Healthy Forests
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Professor Gary Lamberti, Associate Professor Jennifer Tank, and Research Assistant Professor Dominic Chaloner from the University of Notre Dame's Department of Biological Sciences had a research team monitoring water quality this past summer in Alaska as part of a project to determine how the management of the nation's forests affects salmon production, and also how salmon affect the nation's forests.
Salmon have obvious recreational and economic value, but indigenous peoples of the Pacific Northwest have also viewed salmon with reverence and as an iconic symbol of healthy forests. Most people have heard that wild salmon are disappearing from many rivers in the Pacific Northwest, but nobody really knows exactly why that is happening. Considering that the pace of logging of the national forests has also declined, salmon are emerging as one of the most important economic “products” of the forest, especially in Oregon, Washington, and Alaska. What does it mean for forests, and society, if salmon disappear? |
“Salmon are intricately linked to the forest, because that is where they return from the ocean to spawn in rivers and lakes and then spend the critical first few months of their lives. We are taking a holistic approach to studying how forest management affects the quality of their freshwater habitats and then how the carcasses of dead salmon provide food and nutrients for stream and forest organisms” states Lamberti, the lead investigator on the project. “Until the past 10 years or so, few people realized that the nutrients from the bodies of spawned-out salmon may actually provide 'fuel' that helps to power the freshwater ecosystems where their young are born. We feel that this organic fuel may permeate many other areas of the forest because salmon are eaten by so many animals. We can even trace their nutrients into the trees growing along rivers and streams. It's sort of like 'CSI' with dead salmon.”
The Notre Dame research team uses Hydrolab MS5 sondes for their water quality data collection, and relies heavily on the Dissolved Oxygen data as an indicator of stream primary production and respiration which may be stimulated by the decomposition of dead salmon post-spawning. Meaningful changes in the DO are typically in the range of 2-3% saturation, so accuracy is absolutely critical to the quality of their work.
In the past, the team worked with Clark Cells, which provided a somewhat fuzzy picture of the events in the water. The team then applied tedious and time-consuming secondary processing to the data to develop the picture that they needed to understand. This year, however, the team was equipped with the new Hydrolab MS5 with Hach LDO, and they found their results to be dramatically clearer.
“The first thing that we noticed was the stability of the sensor. In the past, we could look at post-cal data, and expect to see drift of about 0.1 mg/L. With the LDO sensors, we consistently see post cal's that are within 0.01,” noted Dr. Jennifer Tank.
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The Hach LDO sensor also allowed the team to very clearly understand even subtle DO fluctuations without further processing. The graphs included show the difference between data collected from a Hach LDO sensor compared to data collected from a Clark Cell in a similar deployment. The crisp data and resulting graph provided by the Hach LDO sensor reduced the extrapolation and uncertainty that come with the Clark Cell, giving the researchers a robust estimate of whole-stream metabolism and even more confidence in their results.
“The data were so clear, we could even correlate changes in DO to intermittent changes in cloud cover, which is usually tough to do in well-aerated mountain streams” remarked Tank.
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The baseline information from the Notre Dame team's study is critical for restoring salmon populations where they have declined or been lost, or for preserving those populations that remain healthy. Limits set for the ocean harvest of salmon often allow just enough adults to return to rivers to lay enough eggs for the next generation. “That may not be enough,” notes Lamberti, because “the carcasses may be just as important as the eggs for the next generation to survive. The downward spiral from that type of fisheries management may doom salmon in many rivers, with consequences spreading throughout the forest.” Lamberti and his team hope to document the details of how salmon and the forest act as a cohesive, integrated unit to the benefit of both fish and trees alike.
Special thanks to Professor Gary Lamberti, Associate Professor Jennifer Tank, and Research Assistant Professor Dominic Chaloner for their contributions to this article.
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