Water quality at Wild Basin: It’s complicated

 

Maria and I started the summer research season with the goal of collecting a boatload of data to support our very reasonable hypothesis: water quality in Bee Creek improves very soon after it enters Wild Basin, and there are very low levels of contaminants in Bee Creek until it leaves the wilderness preserve. For this study we are primarily using the ratio of E. coli to the total number of microorganisms as indicators of contamination and water quality. This made sense to us because the primary sources of contamination should be coming from outside of Wild Basin. For example, stormwater run-off from neighborhood lawns and roads. Also, Maria had previously collected data that supported our hypothesis. Sounds straightforward, right?

Well, science had its own ideas. What we have found so far is much more complicated and interesting, but provides many more questions than answers at this point.

MariaR_BeeCreekFieldworkMaria during field sampling last week. She is surprisingly happy despite the 100 degree air temperatures!

Surprise 1: There are sources of E. coli within Wild Basin

Based on the data so far, it appears that there are multiple sources of E. coli to Bee Creek within Wild Basin. Some of the sources are banks of sediments adjacent to the stream. These sediments were deposited last May during a flood that transported stormwater from a construction site upstream into Wild Basin. Either the sediments originally harbored high levels of E. coli or they are currently acting as sites for the accumulation and proliferation of E. coli. There also seem to be two other groundwater-fed seeps that flow into Bee Creek and harbor high levels of E. coli. This is really surprising because generally groundwater has lower levels of E. coli. These results suggest that there are some contaminant sources affecting shallow groundwater in the Bee Creek watershed.

Surprise 2: Spatial patterns in water quality shift over time

Originally we expected to see a gradual decline in E. coli cell concentrations in Bee Creek as it flows through Wild Basin. We didn’t find that, but we also found that the pattern in E. coli concentrations changes considerably within even a week. This is partly due to changes in stream flow and precipitation, however these factors don’t seem to explain all of the differences we observe.

Stay tuned – Maria is still processing samples and analyzing data so we will (hopefully) have more info soon! Also we will be submitting samples for characterizing the microbial community through gene sequencing (16S rRNA gene sequencing) which should help us address some of the questions around the sources of E. coli to Bee Creek. We’ll write a lot more on that in the next post.

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