Date of Graduation

12-2013

Document Type

Thesis

Degree Name

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

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Scott, J. Thad

Committee Member

Evans-White, Michelle A.

Second Committee Member

Brye, Kristofor R.

Third Committee Member

Haggard, Brian E.

Fourth Committee Member

Bowman, Darrell

Keywords

Biological sciences; Fisheries; Mesotrophy; Multi-use; Nutrients; Phytoplankton

Abstract

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.

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