I cannot believe how extremely fast this summer has passed by and I am so incredibly thankful that I was able to spend it doing something I really enjoyed. I had no idea going into this program if I would enjoy being in Texas, living in a dorm with roommates, or spending my entire summer doing research. Texas was a lot of fun this the summer and I got to have a lot of cool, new experiences. My REU family and I became extremely close over the course of 10 weeks and I found that I really enjoyed my project this summer. This program helped me gain the confidence to apply for graduate school, fellowships, and many other opportunities in the field of environmental science that I didn’t know about until I joined this program. I am extremely thankful to Dr. Erdner and Dr. McClelland for accepting me into the program this summer and allowing me to work with them at UTMSI. I am also thankful for the graduate students that helped me on my project: Hengchen Wei, Xin Xu, and Yida Gao. Here is my abstract from my project this summer:
TFZs are found at the lower reaches of coastal rivers, where tides influence flow characteristics but there is no mixing with saltwater. The tidal energy slows down the river flow and increases water residence times. Long water residence times allow phytoplankton populations to bloom within TFZs, but spatial variations in ambient nutrient concentrations and physical parameters may affect phytoplankton community characteristics within TFZs. We sampled the Aransas River TFZ in June and July at six sites and investigated the size composition of the phytoplankton community via size-fractionated Chl-a analysis (0.7-5, 5-20, and >20 μm) and flow cytometry (to enumerate pico-, nano-phytoplankton, and cyanobacteria). The ambient nutrient concentrations were measured as well.
The Chl a data show that total phytoplankton abundance is higher in the TFZ than inflowing water during both months. Within the TFZ, total abundance showed no systematic change from upstream to downstream in June but increased consistently in July. The phytoplankton communities were dominated by the 0.7-5 μm fraction in June and the 5.0-20.0 μm size fraction in July. The flow cytometry data showed more consistent spatial patterns for June and July. In both months, the proportion of cyanobacteria increased along the non-tidal/TFZ gradient. Despite the similar spatial patterns, the total counts were higher in June than July. These changes were accompanied by rapid depletion of water column DIN between the non-tidal site and the first TFZ site, which remained low within in the TFZ. N appears to be the limiting nutrient in this system when comparing the inorganic N/P ratio and the particulate organic C/N ratio. Overall, this project showed that the TFZ supports substantial phytoplankton communities. Cyanobacteria become increasingly important from upstream to downstream of the TFZ. TFZs have the potential to export substantial amounts of labile organic matter as phytoplankton biomass to the estuary. Finally, this system is also a N limited system, therefore sensitive to increasing N loadings from the watershed.