The Mesocosm or "Tank 1"
Monday arrived this past week, and with it came the dawn of the project I will be working on this summer. I collected 35 liters of water from 4 sites throughout Yaquina Bay. One of the sites, “OSU Dock” as the EPA calls it, is right outside the Hatfield Marine Science Center Visitor’s Center. The other sites are further up river around the city of Toledo, with one site being labeled as “Toledo” and the other sites “Cannon Quarry” and “Elk City.” So why on earth am I collecting 35 liters of water and lugging it back to the EPA labs? Excellent question. Let me explain.
The purpose of collecting these 140 liters of water combined is to examine the nutrient limitations of phytoplankton throughout the estuary. After these samples were collected, we divided them up into 48 two liter bottles. We measured the initial nutrient concentrations as well as the chlorophyll a concentrations, and then proceeded to “spike” them. Along with a control of plain water, these spikes consisted of treatments in which a Nitrogen spike, or “N”, was added as well as Phosphorous, or “P” spike. To further confirm whether a given spike had an effect an “N+P” spike was also a treatment. The result is 3 replicates of each treatment for each site, or 3 x 4 x 4, totaling 48 bottles. Complicated, I know, and they proved to be a little difficult to manage as the experiment progressed.
Once these bottles were spiked according to the given treatment, they were randomly placed in a mesocosm or in this case two tanks with pumped sea water and UV lights. These tanks produce the environmental conditions found throughout the estuary, so they are quite useful in conducting experiments. They were placed in these tanks starting Monday night, and there they remained till Friday morning. Every day, I measured the temperature of the water in the tanks, and the photosynthetically active radiation (PAR). More interestingly though, I also measured the relative fluorescence of each bottle, to get a sense of whether any given spike was having an effect. The result? The OSU Dock, or the site closest to the ocean, had a significant response for the “+N” and “N+P” treatments, suggesting that there wasn’t very strong upwelling prior to the sampling resulting in Nitrogen limitation. This may change as the summer progresses. The results further up river suggested “P” limitation, as the Toledo and Cannon Quarry sites showed significant results for the “+P” and “N+P” treatments. Elk City showed a significant response for the “+P” treatments, but mixed results for the “N+P” treatments. We believe that if given more time, the “N+P” treatments might further reflect the results from other sites. We will replicate this experiment several more times of the course of the summer so we will see how the results change as summer progresses. Regardless, from this week of the experiment it is evident that further up river phytoplankton appears to be limited by phosphorous concentrations. Keeping with my themes of leaving you hanging, I’ll get more into what this means next week! But I will say that I really enjoyed this week. Performing science at a high level, with the means and ability to conduct an experiment in a week is amazing, and I consider myself to be very, very lucky. Furthermore, it is a terrific feeling to know that the science you are doing is extremely pertinent to the state and the country in which I have largely spent my entire life. Alright, before I get too sentimental, I will say goodbye and remind you to look for next week’s post to learn more about what the results of my summer experiment mean for Oregon’s estuaries!