Our research aims to target mangroves (trees and shrubs that grow in saline coastal habitats in the tropics and subtropics) and their subsequent production of volatile organic compounds (VOCs) through plant respiration. In particular, we are aiming to measure concentrations of isoprene, dimenthyl sulfide (DMS), and various terpenes. These particular chemical compounds released by plants are reactive with hydroxyl radicals (OH-) and contribute to the formation of harmful atmospheric ozone. These compounds also help to form biogenic acid rain and are important in the overall tropospheric chemistry. My question upon arriving to the Bahamas was "why are the mangroves important to study." I later came to the conclusion: while trees produce more VOCs, the majority are coniferous and do not produce a significant amount during fall and winter. By looking at the mangroves which photosynthesize yearly, we will be able to calculate concentration of VOCs during the entire year and subsequently their overall impact in the yearly atmospheric chemistry budget.
Collection of the VOCs is a fairly simple, yet time consuming process. This morning myself along with my mentor Tracey located a small, slightly removed mangrove bush and placed a 4 x 5 foot Teflon drawstring bag over the mangrove completely enclosing the bush. Then, by placing a small Teflon tube into the mangrove we pumped in clean air for a twenty minute duration to flush any accumulated VOCs out of the bag. Then, we sit and wait for an hour while the VOCs collect within the bag.
The key word is WAIT! There is a lot of down time. And often times to keep ourselves entertained we resort to funny jokes, childhood letter games (thanks mom!), and music. While we waited today, we noticed the fish kept jumping strangely out of the water nearby. As we examined closer, we noticed a small lemon shark swimming in the shallow waters just an arms throw away. With the quickly approaching rising tide, this did not comfort the both of us. The rising tide forced us to finish our collection wading in the water. The mass of minnows swimming around our toes however was quite amusing as they followed our shadows to stay out of the intense sun. It was fun to play with them to help the time collecting the samples pass. The next part of the collection pulls air from inside the enclosed bag into a narrow "trap" that is about four inches long and filled with a compound that captures chemical compounds. Keeping track of the elapsed time of collection and analysis of the traps back home, we can then compute the concentrations using complicated computer programs.
I might compare our field research here in Bimini to your favorite shampoo. Lather. Rinse. Repeat. We brought with us forty-two traps to use within the mangroves. This means forty-two samples, forty-two collections, and a lot of time. Each collection takes roughly two and a half hours. We managed to dodge the tide and find two other locations that did not require us to stand in water. However, we could not escape the quickly rising sun which soon left no shade in sight. The thought of escaping the intense sun and the buggy area near the mangroves couldn't come soon enough.
After many applications of bug spray and sun screen, a bottle of water, a much needed cool afternoon rain, and some fun along the way, we packed up for the day and began walking back to the condo. After a long day in the field, we fantasized about ice cream, cheeseburgers, and lemonade. Overall, it was an exciting and exhausting day.
I am excited to finish taking samples and get back to the lab where we can begin analyzing our traps. Bimini has been a treat and I very much look forward to the next week and a half to discover more about mangroves, marine ecosystems, and self. The best part of field research (next to the science of course…) in the Bahamas, the snorkeling is great!
By Steven Curtis
Penn State
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