Biology ETDs

Publication Date



In river systems, there are many factors that impede or facilitate algal standing stock and therefore impact primary production in these environments. I am particularly interested in the influence of edges in riverine systems and how these geomorphic features affect the available surface area for algal production. This study investigates the middle Rio Grande system near Albuquerque, New Mexico, USA. The middle Rio Grande is a turbid, partially braided lotic ecosystem. Although edge characteristics can vary widely, especially between errosional and depositional banks, I hypothesize that edges become important zones of primary production, due in part to decreased water depth, providing increased light availability. Further, edges may provide regions of lower flow velocity, resulting in reduced substrate turnover and increased nutrient retention, facilitating algal attachment and growth. This study aims to elucidate the relationships among position within a transect (i.e. distance from edge), substrate type (i.e. sand, mud, cobble), water chemistry, turbidity, depth, flow velocity, and algal biomass. I use the analysis of chlorophyll a (chl a) concentrations as a proxy for algal biomass in samples taken across lateral transects, each with a different predominant benthic substrate. This work develops the understanding of key contributing abiotic factors that influence primary production in the middle Rio Grande and similar ecosystems by providing insight into the effects of these factors on chl a concentrations. Surprisingly, only transects with the sand substrate exhibited my hypothesized pattern of greater primary production near river edges. In contrast, the transects with cobble and mud substrates show the opposite pattern, in which locations far from the rivers edge contained the highest algal concentrations. These results highlight the complex interactions of abiotic influences on benthic primary production in these systems.

Project Sponsors

National Science Foundation




Rio Grande, algae, edges, primary production, fluvial geomorphology, lotic ecosystem

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Bixby, Rebecca

Second Committee Member

Sinsabaugh, Robert

Third Committee Member

Meyer, Grant