Effect of Increased Temperature and Nitrogen on the Non-N-fixing vs. N-fixing Cyanobacteria in Western Lake Erie: Implications for Competition and Climate Change

Harmful algal blooms (HABs) in freshwater ecosystems, especially of cyanobacterial species (cyanoHABs), are becoming more frequent and expanding geographically, threatening some of the world's largest and most-important water bodies, including Lake Erie in North America. HABs are the result of complex and synergistic environmental factors, though N (nitrogen) or P eutrophication is a leading cause of HABs. With global mean temperatures expected to increase an 2–5¿¿C by 2100, cyanoHABs are predicted to increase even more, given their typically high temperature optimum. We investigated how increases in temperature and N, singly or in combination, affect the growth, food quality, and herbivory of cyanobacteria. Both algal community samples collected from Lake Erie, and isolated N-fixing and non-N-fixing cyanobacterial species, were cultured at 20, 25, or 30¿¿C and 5, 50, 150, or 250 ¿¿M added N (as NO3), and then analyzed for content of photosynthetic pigments. Both temperature and N affected algae, there were temperature x N interactions, and the effect of N and temperature depended on sampling date and the presence/absence of herbivores. In general, increases in N or temperature favored growth of cyanobacteria over green algae and diatoms, especially when both N and temperature were increased and herbivores were present, and, surprisingly, both N-fixing and non-N-fixing cyanobacterial species responded strongly to N at high temperatures. Cyanobacteria (but not green algae and diatom) growth increased with temperature, especially from 25-to-30¿¿C, but N increased cyanobacterial growth primarily only at 30¿¿C and only on the early sampling dates (Aug & Sept, but not Oct). Herbivores often increased cyanobacterial, but decreased green algal and diatom, growth. These results indicate that global warming and N eutrophication will increase cyanoHABs in the future in western Lake Erie, and surprisingly, both N-fixing and non-N-fixing cyanobacteria may increase. Thus, in the face of global warming, it will be important to minimize N inputs into Lake Erie to help prevent cyanoHABs.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biology (Ecology)

Grantor dc:publisher

University of Toledo

Year dc:date

2012

Author dc:creator

• Bista, Deepesh R.

Contributors dc:contributor

• Heckathorn, Scott
• Bridgeman, Thomas

• Ecology
• Environmental Studies
• Climate Change
• Eutrophication
• Temperature
• Herbivore
• Harmful blooms
• Cyanobacteria

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=toledo1345064844

OAI identifier oai:identifier

oai:etd.ohiolink.edu:toledo1345064844