-by Shiyu Rachel Wang
“Get out of the way!” Chuck shouted. The motor's sound trailed off, and we had to stop our boat in the middle of the creek to let the dolphins pass. “You know people pay hundreds of dollars in Savannah to watch the dolphins?” I pointed out the irony. “Yeah, they are cool, but not when we need to finish this CO2 sampling by sunrise.” Chuck grumbled. I looked at my watch, we just lost 5 minutes of sampling time.
This is the third CO2 transect sampling for this summer. Chuck, my advisor, was concerned about the sampling time because we need to catch the CO2 level in the marsh creek at sunrise before all the plants and phytoplankton “wake up” to do photosynthesis- a CO2 uptake process that requires sunlight. At sunset, we will measure the CO2 level in the water again before photosynthesis stops as the sun goes down. By capturing the difference in CO2 level at sunrise and sunset, we can evaluate the metabolic activities
happening in the water and the carbon exchange across the air-water surface.
The CO2 level in the atmosphere has risen from 280 ppm prior the industrial revolution to 400 ppm at present. The ocean has been removing CO2 from the air, acting as a buffer pool. In other words, the CO2 in the air will be much higher if the ocean doesn’t do its job. However, on this giant oceanic carbon sink, there are hot spots that are actually releasing CO2 to the atmosphere. Marsh tidal creeks are one of them. Our study focuses on how much CO2 is released by the tidal creeks and why they behave differently than the rest of the ocean. One explanation is that the intense decomposition and respiration activities from the small organisms living on the marsh sediment release a large amount of CO2 to the water, resulting in a source of CO2 to the atmosphere. These marsh organisms may also explain why the dolphins like to hang out here in the creek - they are delicious food!
For more details on this study, please see: http://onlinelibrary.wiley.com/doi/10.1002/lno.10614/pdf