Last week we executed an experiment to begin to answer our new question: what is the relationship between nutrient concentration and uptake rate? As I explained in my last blog, we filled bladders with four different nutrient concentrations and deployed them at mid-estuary and lower-estuary marshes. My main task for the week was to be in charge of lab prep. Artificial sea water needed to be made, bladders needed to be filled, field supplies needed to be organized, nutrient samples needed to be taken, and so on. Besides being rather mundane and times, I enjoy being in the lab. As I have expressed before, field work tends to stress me out because there are so many variables. In the lab I have much more control over things. I also have lots of time to think and brainstorm about my life outside of EPA including grad school and other post undergrad opportunities. Often times I have to pause what I’m doing to write things down so I don’t forget!
One of the main difficulties of working on this project is that it involves a lot of man power as well as several different people taking charge of various aspects of the experiment. This can lead to problems because every part of the project needs to come together perfectly which sometimes does not happen due to lack of communication. Unfortunately, this was a rather large problem with our deployment last week. The tides were rather high, so we decided to deploy our chambers on low marsh benches. We do know at what tide elevation that a particular marsh floods, but we do not know elevations of all of the low marsh benches in the marsh itself. So, we decided to estimate, and our estimate happened to be rather off. On Monday, the chambers were deployed at Winant Marsh in mid-estuary. Using our calculations, we decided to add 10L of water to the bladders which will flood the chambers about two-thirds of the way. Upon Caitlin’s, return from deploying the chambers, she realized that she forgot to leave out the high tide sample bottle, so she and Stephanie went out to the marsh during high tide to collect a sample. When they got there, they were shocked to see that the tide was almost over topping the chambers – way higher than we thought it would go. This can cause problems because it can result in a pressure difference inside and outside the chambers which may lead to leakage. Leakage, especially from natural sea water infiltrating with our artificial sea water, can render our results useless.
That day, there was discussion and disagreement over how much water to add to the bladders for the subsequent day’s deployment. This is where several people thinking different things about the same project can lead to issues. Caitlin and I knew (or thought) that the low marsh bench at Hatfield flooded higher than it did at Winant. So we thought that our bladders for that deployment deserved little or no extra water. Ted on the other hand wanted to add 5L just to be safe. The problem with adding too much water is that it can greatly dilute the water that enters the chambers making it difficult to extrapolate out what the exact uptake rate actually is. I’m getting carried away… haha. Anyway in the end, we only added an extra 2L to each bladder because we realized that we didn’t have enough artificial sea water to add 5L and Jody found extra low sites to deploy the
chambers at (lower than our calculations were for). Again the tide came up really high and we didn’t have enough water as was needed leading to possible infiltration. The next day we made sure to add extra water and we found higher elevation sites, so we ended up having too much water! Ugh! It’s so difficult to get it just perfect.
After taking our salinity measurements and finding the final volumes, we compared our results to our initial measurements to see if they matched up (they should be the same if no water was gained or lost during the deployment). We found that a couple bladders may have had external leakage, but it is not as bad as it could have been. Hopefully we will have some usable data from UC Santa Barbara in a few weeks.
This week will be spent preparing for my presentations on Thursday and Friday as well as analyzing data. I can’t wrap my mind around the fact that this internship is almost over. I just hope that I can find a place to live before I move back to Hawaii!
Please feel free to read and enjoy my personal blog to learn about my summer outside of the EPA here: sarasoregonadventure.blogspot.com