Whole-Reservoir Manipulation and Management Techniques to Enhance Biological Productivity and Protect Water Quality

Three reservoirs of similar size, watershed land use, and qualitative characteristics in northwest Arkansas were selected to compare the effects of chemical fertilization and artificially-induced upwelling on whole-lake productivity (gross primary production and net ecosystem production) as well as algal and zooplankton biomass. These parameters were quantified over a two year period (2011-12) with the goal of understanding how each management technique would stimulate productivity and ultimately enhance sport fish production. The first year of monitoring occurred in 2011 and served as a control for the three lakes. The treatments were initiated in two of the lakes in the second year, with one lake remaining as a control in the second year. Due to difficulty in scaling and manipulation cost,  phytoplankton response ratios from microcosm experiments conducted in 2012 were used to maximize the efficiency of whole-lake fertilization by relating in-lake measurements of secchi disk transparency to microcosm measurements of chlorophyll-a. This allowed us to derive appropriate whole-lake fertilization rates and make predictions for whole-lake responses. Both microcosm and whole-lake phytoplankton response ratios varied seasonally with water temperature and initial dissolved nutrient concentrations.