Friday, March 7, 2014

If optical brighteners are in the Talek, shouldn't the water be "whiter and brighter"?

After spending two great weeks with us, David had to return to the US, but we had one more week in the field with Emma. During this time, we spent some more time investigating the Talek River and its tributaries. A lot of Emma's research is focused on understanding the impact of humans on river ecosystems, and she is working with us to untangle the role of urban developments vs. tourism facilities vs. hippo inputs in the Talek River and its tributaries. This is an important river system to understand because it is the main tributary in the middle reaches of the Mara, and it enters the Mara River in the middle of the reserve. However, water quality in the Talek can be very poor, which may have a big impact on the water quality we see in the downstream portion of the Mara.

Build-up of rotting hippo feces and in a tributary of the Talek
As one tool in our toolbox, we worked on a new method that can be used to detect something called "optical brighteners" in river water. I had never heard of optical brighteners until recently, but they are in many kinds of laundry detergent, and are what make your clothes look "whiter and brighter." It's not that optical brighteners are necessarily bad for the river, but if they are detectable in a river, they indicate the presence of large human inputs of other kinds, like nutrients and sewage. 

Emma and Chris collecting water samples in the Ntiaktiak River
We collected water samples along a transect down the Talek River and its tributaries and into the Mara. Then we compared the fluorescence of the water samples at a certain wavelength to a solution made completely of Omo (the most popular detergent in Kenya). Then, because optical brighteners degrade in UV light, we exposed the water samples to UV light and tested them again. The samples with declining fluorescence after UV exposure were positive for optical brighteners.

Sure enough, we did find optical brighteners present at certain sites in the river, but not necessarily where we expected them. This is an exciting new tool to have, but as usual with new methods, it only raised more questions for us.

Emma testing for optical brighteners
After we finished that round of surveys, we started some hippo pool surveys. Because river flows are so lo right now, it's a great time to do them, and we could get Emma's insight on our methods.

Collecting hippo feces from hippo pool surveys
With all this exciting stuff going on, we were actually in the field working until one hour before Emma's flight departed out of the Mara. I think that was a record! We had such a great visit with both Emma and David, and feel very fortunate they were both able to spend so much time in the field with us this year. Looking forward to many years ahead!

Amanda and Emma at the Mara Serena airstrip

Post a Comment