Horn, Anna, Ecology, Susquehanna University, 1858 Weber Way, Selinsgrove, PA, 17870, horna@susqu.edu; Holt, Jack, R, Ecology, Susquehanna University, 514 University Ave, Selinsgrove, PA, 17870, holt@susqu.edu.
The Upper Middle Creek Drainage in Central Pennsylvania encompasses two recreational reservoirs, Walker and Faylor Lakes, which vary greatly in size and thermal history. Faylor Lake, only a maximum of 4.5 meters deep, holds a volume of .7 x 10^6m^3, as opposed to Walker Lake, which is 9 meters deep, and holds a volume of 4.1×10^6 m^3. Temperature and oxygen measurements reveal that Walker Lake stratifies in June until October, while Faylor Lake weakly stratifies. This past summer, the phytoplankton communities of these two reservoirs were studied, alongside water quality, precipitation, and nutrient concentration primarily during the month of July. The dominant taxa of each reservoir differed, with Walker Lake consistently dominated by Cyanophyta, and Faylor initially being dominated by Bacillariophyta, then Cryptomonas, and finally Chlorophyta. Walker Lake had a maximum of 23 taxa, while Faylor had a maximum of 40 taxa. The Shannon Diversity Index (SDI) of Faylor Lake was also greater than Walker Lake from June to August, with the SDI of Faylor Lake increasing gradually from 1.4 to 2.4, whereas Walker Lake decreased from 1.4 to 0.9. Nutrient concentrations of nitrate, nitrite, ammonia, and phosphate were also measured both within each reservoir at multiple depths, and at the streams above and below. Our data show that concentrations of both phosphate and ammonia decreased from July to October at all depths in both reservoirs. In July, there was a noticeable difference in the highest nutrient, with phosphate being much higher in Faylor, and ammonia being much higher in Walker. While nitrite initially decreased across all depths in Walker Lake, it greatly increased in early October. Nitrate concentrations initially peaked in both Faylor Lake and at the surface of Walker but returned to similar concentrations in October. Comparing the nutrient data and phytoplankton compositions between both reservoirs suggests that nutrient concentrations play a role in shaping phytoplankton communities, and vice versa.
Phytoplankton , Reservoir Ecology , Nutrients