Last week’s water incubation experiment was useful. The plot of the dissolved oxygen levels over the weekend showed clear declines in all of the samples, but there was some strange “noise” at around the same point in the plots of both of the ziplock bags. There was no way to determine an accurate respiration rate from the data. Additionally, the magnitude of change in the dissolved oxygen was much greater in the ziplock bags than in the carboys. My mentor, Cheryl Brown, found an interesting paper in which similar methods were employed to determine respiration rates, and the researchers found that enough oxygen would leach out of the plastic containers and into the water to confound their results. They carried on using plastic containers for incubations, but incubated additional “blank” containers containing ultra purified water to determine a rate for the oxygen leaching from the plastic so that they could correct for it.

I am currently running several incubations of ultrapure water in carboys and ziplock bags to see if leaching could be the source of the noise in our dissolved oxygen plots. We also went to Tillamook and collected more water samples that are now incubating in glass BOD bottles, glass bottles specifically designed for the purpose of measuring biological oxygen demand through incubation. The oxygen sensor we are using for the bottles is optical like the HOBO loggers, but much smaller and designed to fit into the mouth of the bottles. The sensor does not take a time series of readings, and will be used to take only initial and final readings of dissolved oxygen.

The main purpose of this week’s Tillamook trip was not to collect water for incubation experiments, but as a trial run of the bi-weekly water sampling plan of Tillamook Bay and the tributaries that will take place over the summer. Two teams with boats went out on Friday and collected water samples to measure the carbonate chemistry and nutrients of the bay and the tributaries. I rode along with the team sampling the tributaries. We did a little boating in the lower end of a couple rivers and went out only a short way into the bay before pulling out the boat and driving to all five of the rivers to gather water samples both above and below the agricultural zone. It was a long day, and aside from the pungent smell of dairy cows, or “the smell of ice cream”, I saw juvenile salmon leaping out of the water eating bugs in the morning, green herons and pairs of bald eagles, and even one large juvenile chinook in a pool up the Miami River. We will be doing these sampling trips every two weeks for the rest of the summer and I hope to observe and learn more about the ecology of the Tillamook region as I continue to learn about the science of water.

Collecting water with a Van Dorn sampler.

Nutrient sampling on the boat.

A beautiful morning on the Trask River.