Field Samples: How Humans Are Changing What’s in Our Water

Field Samples is a Q&A with presenters at our weekly Wednesday seminar. Today CFL grad student, Samantha Oliver, will talk about how humans changes to the landscape have drastically altered nutrient flows into lakes.
Sam Oliver is studying how human land use affects which nutrients end up in our lakes and how they get there. Photo courtesy Sam Oliver
Sam Oliver is studying how human land use affects which nutrients end up in our lakes and how they get there. Photo courtesy Sam Oliver
 Who are you, where are you from, and how did you get here?   

I’m Samantha Oliver, and I’m originally from Hackensack, MN – a small town in the northwoods. I got my undergraduate degree at UW and took Ecology of Fishes when I was a junior. At the time, I was sort of bouncing around the sciences to get a feel for what I liked. My TAs for the class were Jereme Gaeta and Matt Kornis (CFL alums), and they were advertising summer jobs at Trout Lake Station. I spent the summer there studying the spiny water flea, and I was hooked. After I got my master’s degree at the University of Minnesota Duluth, I wanted to come back to the CFL to study lakes. I reached out to Emily Stanley who was looking for someone to work on cross-scale interactions in lakes – and it was a good fit!

Pretend we just boarded an elevator and you only have one-minute to tell me about what it is you’re presenting on at seminar.  

A mid-October algae (or phytoplankton) bloom shows up on the Lake Mendota shoreline. Photo: Sam Oliver
A mid-October algae (or phytoplankton) bloom shows up on the Lake Mendota shoreline. Photo: Sam Oliver

Humans have drastically changed the distribution of nutrients (nitrogen and phosphorus) across the landscape through urbanization, food production and burning fossil fuels. This has come at a cost to water quality; excess nutrients are transported to surface waters where they can fuel toxic algal blooms, foul drinking water and disrupt the ecosystem. We’ve made progress on point source pollution like sewage discharge since the Clean Water Act was established in 1972. But diffuse nutrient sources like runoff from agricultural areas are difficult to manage and still plague surface waters. The United States spends billions of dollars on nutrient mitigation, and some national management efforts like the Clean Air Act are reducing nutrient loading. However, at the same time, new threats to water quality are emerging. Climate change is altering the timing and amount of precipitation, which will change the delivery of nutrients to surface waters. Given the patchwork of human impacts on the landscape, management strategies that vary in space and time, and ongoing threats to water quality, it is unclear if and how lake nutrient concentrations are changing across the U.S.. I’ll be talking about a study of 760 lakes across the U.S., where we assessed changes in nutrient concentrations from 1990-2011.

Why should someone not in the field of freshwater sciences care about your work? (The dreaded “So What?” question).  

Sam Oliver teaches young attendees at the Clean Lake Alliance's "Frozen Assets" festival, how to use a Secchi disk. Photo courtesy Sam Oliver.
Sam Oliver teaches young attendees at the Clean Lake Alliance’s “Frozen Assets” festival, how to use a Secchi disk. Photo courtesy Sam Oliver.

If you’re breathing, you care about water quality. Humans derive many benefits from clean lakes – whether they are drinking from them, eating from them, swimming in them, or looking at them. Additionally, we spend A LOT of money managing for clean water. It’s in our best interest to know if and when management works, where management efforts should be focused, and how forthcoming changes in the climate will impact our freshwater resources.
 What question did you answer or hope to answer? What other questions might your work lead scientists to ask?
How are lake nutrient concentrations changing? Are nitrogen and phosphorus changing in the same direction? What are the drivers of change?
Tell me about one funny, memorable, exciting or awesome moment from your work either in the field or in the lab.

The data we’re using for this project comes from many different data sources. We combined dozens of mostly state agency water quality datasets. Quality control is a big part of this effort, and we’re often making plots of “known” relationships (for example, the relationship between chlorophyll and phosphorus) to verify there is nothing funky going on with the data. On more than one occasion, we’ve been tricked by Iowa, which has such extreme values because there are a lot of nutrients in Iowa. The data seem like they simply can’t be real. It’s not a dream, you’re just in Iowa!

 

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