Estuarine Transect

August 8, 2009
Written by Kelli L. Edwards

We began our afternoon setting sail from the Savannah State University dock, located at Country Club creek with the bright hopes and aspirations of completing one successful estuarine transect. After much confusion with boating troubles, we launched out into the water on the Pontoon. Although much older than the Tiger II and the Sea Otter, the Pontoon, playfully re-named the Pelican, the Pontoon made for a rather pleasant ride. The purpose of this sail was to combine the useful knowledge we just obtained about changing salinity with hands-on-experience using the CTD.

This handy gadget is approximately 40lbs according to estimation and is deployed off the deck of any seaworthy vessel. Most CTD's record salinity, water temperature, dissolved oxygen concentration, and depth. Each student was given their own specific detailed activity. CJ recorded location using the GPS and kept track of depth, Amber helped Dr. Ogburn with deployement and retreival, Dana helped with GPS monitoring along with CJ, and Donna was our personal photographer and navigator. With myself, "Captain Kelli" guiding us along the waterway, our class successfully reached 4 stations, with the farthest located in the Wilmington River.

Dr. Ogburn carefully instructed each student on the launching of the CTD. This device must be regarded with much care because of its sensitive nature.



For my portion of our study, I looked at the changees in salinity with depth and location as we moved along our transect.
Salinity ranged from 29.2-31.3. According to the data collected, there is not much change in salinity with respect to depth. For our first location in the Wilmington river, the greatest depth (10.356m) and the lowest depth (0.824) varied little when it came to salinity(31.3 and 31.1 respectively). Salinity typically changes in response to depth when the water column is well stratified. With our waterways being both partially mixed and well mixed because of our tidal system, the water column is pretty universal with respect to salinity. One of the most interesting points of this lesson is that salinity changes dramatically in response to freshwater runoff. According to Blanton et al., there can be rapid changes in salinity in response to freshwater input. Even more fascinating is the effect of climate on salinity. In months of dryer almost drought-like conditions, salinity is much higher than in times of heavy seasonal rains. Over the course of time there have been dramatic changes in salinity of coastal Georgia Waters. Considering our season of tropical storms and high freshwater discharge, one can expect continual lower salinity as compared to those years of drought.
Even vegetation changes in response to environmental fluctuation. In 2004, Higinbotham et al. found that vegetation is characteristically distributed along estuaries in response to the salinity gradient in the Altamaha and Satillia estuaries. Juncus (Juncus roemerianus and Spartina cynosuriodes) was found in salinities ranging from 21-1, brackish marsh vegetation (S. cynosuroides and S. alterniflora) was found in salinities ranging fom 15-1, and vegetation catagorized as freshmarsh was found upstream at salinitieis less than or equal to 1.

Overall, this day was extremely successful in understanding the various changes that waterways undergo in response to environmental fluctuation.