Researcher Spotlight on Dr. Thad Scott
Associate Professor, Department of Crop, Soil and Environmental Sciences
Scott received a base grant from the Arkansas Water Resources Center through the US Geological Survey 104B program to fund a research project titled “The Effect of Global Climate Change on Algal Biomass and Total Organic Carbon Concentrations in Beaver Lake”.
Organic carbon concentrations are increasing in Beaver Lake reservoir in northwest Arkansas. At the same time, atmospheric CO2
levels continue to increase as a result of human activity. Increases in organic carbon can often be attributed to increases in algal biomass, and increases in algal biomass can often be attributed to increases in phosphorus availability. But, in Beaver Lake, phosphorus concentrations have decreased in recent decades because of successes in watershed management activities. So why are we seeing an increase in organic carbon?
Over 400,000 people in Arkansas rely on water from Beaver Lake for drinking, bathing, cooking and many other activities. During the water treatment process, organic carbon can react with disinfectants to form byproducts that might be harmful if consumed in large doses.
The Research Question:
Scott wanted to know, do elevated levels of atmospheric CO2
concentrations, coupled with changes in phosphorus availability in the water, cause increases in algal biomass as measured by chlorophyll a?
Scott and his team collected water from Beaver Lake near the intake for Beaver Water District. Back at the lab, the collected water was used to fill several containers. Different amounts of dissolved phosphorus were added to each container and final concentrations ranged from 0 to 100 µg/L. For each phosphorus concentration, algae were also grown at 3 different CO2
levels representing different atmospheric concentrations: 250 ppm (pre-industrial), 400 ppm (current) and 550 ppm (estimated for the year 2050). The algae were grown for 13 days and then water samples were collected from each container. The water was filtered and the filters were analyzed for chlorophyll a.
As expected, when more phosphorus was available in the water, chlorophyll a increased. Chlorophyll a ranged from less than 10 µg/L at low phosphorus concentrations to about 60 µg/L at high phosphorus concentrations. To put these concentrations into perspective, chlorophyll a (growing season geometric means) in Beaver Lake ranged from almost 1 µg/L near the dam to almost 19 µg/L at Highway 412 east of Springdale (AWRC MSC Publication 372
). On the other hand, surprisingly, elevated levels of CO2
didn’t have an effect on algal production.
This is one of few studies that have looked at how increasing atmospheric CO2
concentrations might affect algal production in reservoirs. The lack of an effect of CO2
levels in this study demonstrates the complexity of the problem and the lake environment, and possibly the limitations of the experimental design. Continued investigation can help inform water resource managers of potential changes in source water quality in response to elevated atmospheric CO2
This research has led to a publication that is currently in review:
Winston, B., E. Pollock, and J.T. Scott. The Effect of Elevated CO2
Caused by Global Climate Change on Reservoir Eutrophication. Lake and Reservoir Management.