Increases in both phosphorus (P) and nitrogen (N) loading to aquatic ecosystems in the United States have been linked to habitat changes, decreases in biodiversity, increases in hypoxia and harmful algal blooms which are all symptoms of eutrophication. Until recently, freshwater ecosystems were not considered to be impacted by increases in N loading because these waters are considered to be P limited and because there is a prevalence of N2-fixing cyanobacteria that supply N. However, increasing anthropogenic N loading is causing changes in the expression of eutrophication, one of which may be an increase in the proliferation of toxic cyanobacterial blooms. Yet, there have been relatively few studies that have directly addressed the physiology of N quantity and form on growth and toxicity of these organisms. The prevalence of Microcystis aeruginosa, in particular, is increasing. Unlike many cynaobacteria, it does not fix N, and thus may be uniquely poised to proliferate with high N loading into freshwater ecosystems and to take advantage of the altered biogeochemical availability of N. This project will use laboratory continuous culture systems to study the growth and N physiology of Microcystis aeruginosa by (1) comparing differences in rates of growth, N assimilation, and toxin (microcystin) production when grown on inorganic N (NO3- and NH4+) or organic N (urea) sources over an increasing gradient of N:P ratios, and (2) investigating competitive ability for different N sources by examining kinetics of N uptake and two N assimilation enzymes (NO3- reductase and urease).
This project is designed to engage and excite students who are deaf or hard-of-hearing who have traditionally had few opportunities for meaningful research experiences at the undergraduate level. The principal investigator, a beginning deaf female scientist, and her deaf and hard-of-hearing undergraduate students, will examine differences in rates of growth, N assimilation, and toxin production in several strains of the cyanobacterial species, Microcystis aeruginosa. Some experiments will be conducted at Horn Point Laboratory, University of Maryland Center for Environmental Science, where these students will have opportunities to interact with faculty and graduate students working on other aspects of nutrient cycling and algal dynamics. An integral part of the project will be an environmental science lecture series at Gallaudet University, educating this under-represented group, the deaf and hard-of-hearing, about environmental issues including nutrient pollution, eutrophication and climate change. This study will provide deaf and hard-of-hearing undergraduate students with a hands-on project that will serve to lead to larger field studies focusing on the impact of increased N loading on the frequency and magnitude of toxic cyanobacterial blooms. These opportunities should provide them the foundation for graduate school in the environmental sciences.
