Key Findings
A new meta-analysis by UNH researchers indicates that fertilizer pollution in streams and rivers can have ripple effects in the food webs, resulting in harmful algal blooms and fish kills. The study's findings could affect environmental policy nationally and locally by helping regulators reduce nutrient runoff into streams effectively.
About the CO-Author
Bill McDowell, Professor of Natural Resources and the Environment
Contact information: Bill.McDowell@UNH.edu, 603-862-2249, McDowell Lab website
This research first published in Biological Reviews.
Researchers: M. Ardon, L. Zeglin, R. Utz, S. Cooper, W. Dodds, R. Bixby, A. Burdett, J. Shah, N. Griffiths, T. Harms, S. Johnson, J. Jones, J. Kominoski, W. Mcdowell, A. Rosemond, M. Trentman, D. Van Horn and A. Ward.
UNH scientists published research on a meta-analysis analyzing the impact of fertiilzer runoff in river ecosystems. The analysis was based on the results of 184 studies covering 885 experiments run across the world. Co-authored by Bill McDowell, a natural resources professor at the University of New Hampshire, the analysis indicates that fertilizer pollution in streams and rivers can have ripple effects in the food webs when nitrogen and phosphorus, the main components of fertilizer, are added to streams and rivers. The addition of these nutrients in high levels can result in harmful algal blooms and fish kills.
“This study provides a detailed and statistically rigorous assessment of whether, when one adds nutrients — nitrogen and phosphorus — to an aquatic system, the effects go beyond algae growing too fast,” says McDowell. “We found that yes, they do: This increase in algal production translates to higher organisms” like insects and fish. The researchers observed increases in the abundance and biomass of organisms living in streams, as well as the speeding up of processes such as leaf decomposition and the growth of organisms that feed on them.
“Both nutrients affect — typically negatively — the health of aquatic ecosystems and alter food webs. Reducing nutrient inputs of both nitrogen and phosphorus is almost always a good strategy."
The study's lead author, Marcelo Ard?n, explains that the addition of nitrogen and phosphorus can also affect shaded streams where algae does not grow. “Wherever we looked, we saw increases in the abundance and biomass of organisms that live in streams, and also the speeding up of processes that happen in streams – how fast algae grow, how fast leaves decompose and how fast organisms grow that feed on them,” says Ard?n. In these areas, nitrogen and phosphorus can accelerate leaf decomposition and boost the growth of organisms that feed on them. The study discovered an average 48% increase in biomass abundance and activity across all levels of the food web. The responses were most robust when both nitrogen and phosphorus were added together.
The paper addresses a fundamental challenge in environmental science: drawing general conclusions from individual studies. McDowell believes that this study could affect environmental policy both nationally and locally in Great Bay by aiding regulators in reducing nutrient runoff into streams effectively. “Both nutrients affect — typically negatively — the health of aquatic ecosystems and alter food webs. Reducing nutrient inputs of both nitrogen and phosphorus is almost always a good strategy,” says McDowell.
This research was funded by the National Science Foundation under grant DEB-0832653 through the Long Term Ecological Research Network Office. Individual authors were funded by the National Science Foundation under grant DEB-1713502, and the Department of Energy’s Office of Science, Biological and Environmental Research.
