Evaluation of the Relationship between Dissolved Organic Material, Nutrients, and Algal Species in Colorado Lakes and Reservoirs
Poster Number:
107
Presenter/Primary Author:
Alia Khan Previous research has suggested that production of non-humic dissolved organic matter (DOM) can be directly related to chlorophyll-a concentrations in surface waters. In recent years, increases in dissolved organic carbon (DOC) concentrations in surface waters have been documented in many northern temperate regions. The underlying processes and the effects of increasing DOC on aquatic ecosystems and drinking water quality are not fully understood. The aim of this study was to expand upon the findings of the interactions between DOM and chlorophyll a concentrations in a lake in the Green Lakes Valley of the Colorado Rocky Mountains to over 30 lakes and drinking water reservoirs across the State of Colorado. Another goal was to gain insight into seasonal trends which could give be expanded to potential impacts of climate change. One reason these relationships are important is that algal derived DOM has been documented as a precursor material to the formation of disinfection byproducts.
Chlorophyll-a, an indicator of algal biomass, and algal species were identified using a Fluid Imaging Technologies FlowCam. Two sampling strategies were used including a one-time sampling event of approximately 30 lakes/reservoirs during the month of July and August, at the height of the expected seasonal algal bloom, in order to increase the ability to characterize a relationship between DOC, chlorophyll-a, and algal speciation. The second sampling effort targeted 10 lakes/reservoirs where municipalities have located intakes, of which two are focused on in this study. These lakes/reservoirs were sampled biweekly from May through September 2010. Samples were collected near the surface (within the epilimnion) and were analyzed for chlorophyll-a, DOC, and algal speciation. Results show that diatoms and cyanobacteria are the most abundant algal groups present. The DOC and chlorophyll-a levels in the drinking water utilities were positively correlated. DOC levels ranged from 2 to 4 mg/L and chlorophyll-a levels ranged from non-detectable to 5 ug/L. For the 30 lakes, the DOC levels ranged from 2 to 8mg/L and chlorophyll a levels ranged from less than 1 to 43 ug/L. The relationship between DOC and chlorophyll-a levels in the 30 lakes were also positively correlated, as well as chlorophyll-a and TN. Furthermore, the abundance of cyanobacteria, was also positively correlated to DOC levels. The quality of the DOC was further studied through fluorescence indices. The data obtained in this study could be used to help the Water Quality Control division (WQCD) of the Colorado Department of Public Health and Environment (CDPHE) develop nutrient criteria for the State’s reservoirs and lakes.
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Student Poster:
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