Date of Graduation


Document Type


Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level



Crop, Soil & Environmental Sciences


J. Thad Scott

Committee Member

Michelle Evans-White

Second Committee Member

Kristofor R. Brye

Third Committee Member

Brian E. Haggard

Fourth Committee Member

Darrell Bowman


Three reservoirs of similar size, watershed land use, and qualitative characteristics in northwest Arkansas, USA were selected to compare the effects of chemical fertilization and pulsed artificial-upwelling on whole-lake productivity, specifically primary production and phytoplankton biomass. Numerous water quality parameters were quantified over a two year period (2011-13) with the goal of understanding how each management technique would stimulate productivity. This experiment was the first step towards a larger goal to ultimately enhance sport fish production. The first year of monitoring occurred in 2011 and served as a control year for the three lakes. Treatments were initiated in two of the lakes (Lakes Rayburn and Norwood) in the second year, as one lake (Lake Brittany) remained a control. Due to difficulty in scaling and manipulation cost, small-scale microcosms experiments were used in 2012 directly prior to each whole-lake experiment. Microcosm experiments were used to derive appropriate whole-lake fertilization rates and make predictions for whole-lake responses to nutrient additions. Both microcosm and whole-lake phytoplankton responses varied seasonally with water temperature and initial dissolved nutrient concentrations. Few interannual effects from whole-lake manipulation were observed in the treatment lakes due to the `pulse' nature of nutrient additions. However, the short-term data revealed increased concentrations of total phosphorus (TP), total dissolved P (TDP), chlorophyll a (chl a), and <80 µm chl a in Lake Rayburn and, in Lake Norwood, total dissolved nitrogen (TDN), TP, TDP, chl a, and < 80 µm chl a concentrations were elevated. Few whole-ecosystem aquatic studies have been conducted in the manner of this experiment. Preliminary results from these data suggest that periodically pulsed nutrient additions can result in short-term increases in biological productivity without affecting interannual water quality patterns.