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

Tuesday, September 10, 2013: 1:00 PM
Manning (The Marriott Little Rock)
Ben Thompson , Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR
Thad Scott , University of Arkansas
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.