I have spent an awful lot of time hunched over vats of acid washing bottles and syringes this week. Oddly, doing the dishes, whether with soap and water or 10% hydrochloric acid solution, is drudgery. The only excitement to be had was when my right glove began leaking. I expected the worst, but after rinsing with Milli-Q ultrapure water I was unharmed. I had the pleasure of throwing out the scary old gloves and donning a beautiful new pair that I can love and trust for the rest of the summer.

The experiment incubating pure water in plastic containers to look for an increase in the dissolved oxygen occurring as a result of leaching yielded interesting results. The 2 gallon ziplock bag showed quite a large increase in dissolved oxygen level in the ultrapure freshwater over several days. Unfortunately, the ziplock bag containing sterile seawater drained empty at some point during the incubation. The data on the logger from the drained bag showed a similar trend to the other bag, but the plot went wonky when the water started leaking. The five gallon carboys of pure water and sterile seawater showed much lower rates of leaching than the ziplock bags. Hmmm.

The glass BOD bottles are working out nicely. On Wednesday I went to Tillamook and collected water samples at low tide from several points in the bay that represent different mixing zones. I began incubating them on Thursday in BOD bottles. Temperature and light exposure have been difficult to control due to laboratory limitations, but wrapping the bottles in aluminum foil and storing them in a cooler in a dark room has helped keep them at a stable temperature and prevent light from triggering photosynthesis int he phytoplankton.

After 24 hours of incubation, we took oxygen readings and compared them to the oxygen levels in the water in the bay when the samples were taken. We noted significant decreases in oxygen, meaning the microbes were consuming oxygen at a rate that could be easily measured in a single day. This information answered key questions about the required size of bottle and length of incubation required to measure respiration rates in this environment. While biological oxygen demand has been measured in BOD bottles for many years and is a standard practice, measuring estuarine respiration rates in a complex system like Tillamook Bay is not the usual application. Knowing that we can use small samples of water and get results in a couple days is very helpful. If the oxygen decrease in the bottles levels off, it has been suggested that I add glucose to see if the microbes take off again and are carbon limited. Exciting!

Now I just need to prepare more BOD bottles. Back to the acid.