The Role of Nitrogen and Phosphorus in the Growth, Toxicity, and Distribution of the Toxic Cyanobacteria, Microcystis aeruginosa

<p><em>Microcystis aeruginosa</em> is among the most common harmful algal-blooming species in the world. Potent microcystins released by <em>M. aeruginosa </em> have been linked to liver failure and death in aquatic mammals, like the endangered California sea otter, and provide a serious public health risk to humans. Once characterized as a freshwater problem, <em>M. aeruginosa</em> is expanding on a global scale, making persistent returns in freshwater, brackish, and coastal marine ecosystems. Though commonly observed dominating aquatic ecosystems in low N:P atomic ratios less than 44:1, the reliability of N:P ratios as a tool for managing and predicting <em>M. aeruginosa </em>blooms is explored through analyzing the specific roles of N and P in influencing its growth, toxicity, and distribution. N is far more influential than P in regulating growth, toxicity, and distribution of <em>M. aeruginosa</em>, and ammonium (NH₄+) is the most bioavailable form of N to <em>M. aeruginosa</em>. Thus, as the proportion of NH₄+ increases in total N concentrations, phytoplankton communities shift towards <em>M. aeruginosa </em>dominance. Changing concentrations of N and P have been observed to influence the N:P ratio values that provide optimal growth, with higher N and P concentrations providing a higher range of N:P ratios in which optimal growth can occur. Furthermore, local environmental factors can influence <em>M. aeruginosa </em>presence more than nutrient availability, with <em>M. aeruginosa </em>favoring extended dry seasons and warmer surface water temperatures between 25-30°C. Management of <em>M. aeruginosa </em>should focus on regulating concentrations of N and P, including NH₄+, instead of using N:P ratios as a management tool. Furthermore, management decisions may be unique depending on local environmental factors.</p>

Name thesis:degree_name

Master of Science in Environmental Management (MSEM)

Level thesis:degree_level

Project/Capstone - Global access

Discipline thesis:degree_discipline

Environmental Management

Year dc:date.available

2014

Author dc:creator

• Parrish, James

Contributors dc:contributor

• Kathleen Jennings, Ph.D.

• cyanobacteria
• Microcystis
• microcystins
• algae
• algal blooms
• phytoplankton
• nitrogen
• phosphorus
• N:P ratios
• aquatic ecosystems
• Environmental Health
• Environmental Microbiology and Microbial Ecology
• Terrestrial and Aquatic Ecology

Repository record dc:identifier

https://repository.usfca.edu/capstone/8

OAI identifier oai:identifier

oai:repository.usfca.edu:capstone-1007