Photo: Benthic cyanobacteria are a type of photosynthetic bacteria that live on the bottom of aquatic environments, such as lakes, rivers, oceans, and wetlands. Some benthic cyanobacteria can produce toxins (cyanotoxins) that are harmful to aquatic life, animals, and humans. These blooms are exacerbated by nutrient pollution and warming temperatures. (Credit: USGS)
Bethany Lake is a man-made body of water located within housing developments and serves as a popular recreational area for hiking, fishing, and biking. Daily users have a higher risk of exposure to cyanotoxins but the sources of nutrient loading is unclear or unquantifiable, presenting a challenge to mitigating harmful algal blooms (HABs). Matt Yates, a USGS hydrologist and a recent graduate of PSU’s Environmental Science and Management (ESM) Master’s program, investigated the lake as part of his thesis which involved documenting nutrient sources, analyzing nutrient dynamics, understanding the hydrologic patterns between Bethany Lake and Rock Creek, and identifying the occurrence of HABs and cyanotoxins.
The UPP sat down with Matt to learn what inspired this topic, his resourcefulness amidst funding challenges, and next steps.
What inspired you to pursue this topic?
Clean Water Services conducted a preliminary study of Bethany Lake that showed signs of underwater or underground movement that affected the temperature of the stream reach as well as prevalence of E. coli and harmful algal blooms (HABs). Hyporheic exchange–the movement between subsurface water and stream–became a topic of interest. This phenomenon is particularly challenging to study in urban areas due to underground infrastructure creating complex water pathways. Bethany Lake is an example of this–it became apparent that the lake’s water flow is not as linear or clear cut as we thought and that it could be affecting HABs, dissolved oxygen, and other general water quality parameters.
How did the project’s scope change over time?
I had already collected a summer’s worth of data in Bethany Lake and Rock Creek. I monitored the water surface and subsurface flow, and I saw connections between subsurface flow, lake elevation, and potential nutrient loading that could trigger HABs. This factor and a new source of funding through USGS’s Harmful Algal Bloom (HAB) Cooperative Matching Funds Projects led to a successful proposal for more comprehensive research.
What unique approaches or methods are you using in your research?
Normally with groundwater-surface water interactions you can use a combination of flow and temperature to approximate how much water is entering or leaving the surface water system in relation to groundwater. Due to the low water flow in the summer, this was difficult to detect. As a result, the research uses isotope sampling as a tracer for groundwater, focusing on stable isotopes of nitrogen and oxygen in nitrate, which helps track water sources and potential wastewater signatures.
We also used specialized nitrate sensors that are able to capture data in 15-minute increments. This capability allows us to collect discrete water quality samples at a range of days, times, and conditions, connecting information from the lab to the sensor. We can then create a time series of data for nitrate as well as compare this data to other water quality parameters.
What surprising findings have emerged from this research?
We’ve seen more benthic algae growing later in the year than anticipated at the bottom of Rock Creek and in Bethany Lake, even in December. I was surprised to see that because it indicates adequate sunlight for algae growth.
The hydrology of the area is also interesting. Looking at a map of Rock Creek and Bethany Lake, you’d think this is a one-way interaction where all of the water flows into Rock Creek. However, our small study area indicates a substantial amount of flow from Rock Creek that enters Bethany Lake before returning into the creek. These water movement patterns differ from engineering diagrams and expectations due to, we think, an existing sewer line between the lake and the creek. We don’t fully understand this yet.
What challenges have you faced during the project?
The primary challenge was limited funding. I had asked for about $50,000 through the USGS’s Matching Funds Project but only received about half of that. I’m convinced I was a raccoon in my previous life because I was able to “dig through the trash” and borrow USGS equipment–both unclaimed or “broken”– and fixed them up.
Did you receive any PSU support or resources?
The biggest benefit from PSU has been Mary Munt, a PSU undergraduate student. In Summer 2024, Mary joined the project as part of an effort to create new pathways for PSU students to gain internship experience at USGS. The UPP worked with Jen Morse, an associate professor of ESM, and USGS to hire Mary to support data collection and data entry. She’ll continue to do this type of work and eventually take on a larger portion of field work.
What are the next steps for the project?
The project's second year will focus on final data collection, including extensive sampling for nutrients and stable isotopes. I also hope to secure additional funding to increase the number of samples that we can collect. Next year will be dedicated to preparing a peer-reviewed report for publication through USGS.
What advice would you give to a USGS employee who might be interested in going back to school?
It's definitely challenging. I would just make sure they understand that, but it's also something you can't really prepare for. I would encourage anyone who's seriously thinking about moving into a hydrologist position or a professional science position to consider grad school as an option, but to first set clear expectations of what you want to achieve from this experience.
For me, grad school became a safe place to explore different career paths and research topics. It reinvigorated my love for this type of work just by doing the coursework and being exposed to new ideas, people, and perspectives.
Visit the USGS webpage to learn more about Matt’s project.