In the past few weeks, things have sped up quite a bit as my time in Idaho is coming to a close. My supervisor Jack and I spent a lot of time in the lab processing my samples of particulate organic matter (POM), that I’ve collected over the past weeks by standing in the rivers of our different sites for 15 minutes and trapping suspended POM in a repurposed macroinvertebrate net. My project goal in explicit terms is to determine the amount, and size of suspended particulate organic matter being transported in the river. We used a sieve, and vacuum filter, to separate the POM into different size fractions – coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), and very fine particulate organic matter (VFPOM). We then dried and ashed these different categories of POM in a high heat oven. I learned how to use an analytical balance to weigh the samples before and after ashing them, to determine how much organic material lie within each sample. This amount organic material, aka the “ash-free dry mass,” was analyzed using statistical tests and graphing tools to gain an understanding of the nutrient cycling and energy budgets in the Upper Henrys Fork River. This related to Jack’s bigger picture project by helping us understand if macrophyte growth is limited by a lack of nutrients. We found that most of the nutrients and organic material was travelling down the river in the form of large clumps or rafts POM, not small particles.
We also found that the Last Chance stretch had the highest amount of POM in the water column, while Flat Rock had the least.
We also found that a large amount of material, and thus nutrients, is being transported downstream in the form of very big rafts of plant or algae, called VBOM. After some basic observatory data we took each week, we were able to estimate the amount of very big organic material going by per day, per site. Some sites had as much as 86 lbs of VBOM going by per day like our Harriman site!
We observed an overall trend of increased POM levels in our spring-fed sites Buffalo River and Flat Rock, due to macrophytes growing abundantly then senescing and being released into the water column during the high productivity of summer months. We believe that the Last Chance/Harriman site didn’t follow this trend of steadily increasing POM levels due to the influence of the Island Park Dam altering natural flow patterns.
I presented my work and findings at HFF’s weekly summer seminar series, and was very excited to share the data and its implications!
After working hard on my project, I was super excited to go backpacking with my friend Frances in Grand Teton National Park. We hiked in Granite Canyon and slept at a backcountry camping site, explored the beautiful lake about a mile up, and hiked out the next day and got smoothies in Jackson!