Fish Contribute More Nutrients to Ecosystem Than Any Other Source

Written by on December 13, 2012 in Marine Life, Physical Oceanography
Reef fish.

Reef fish. Photo credit: Louiz Rocha, NOAA.

A new study shows that fish play a much more important role in the nutrient cycles of marine ecosystems than previously thought.

Researchers from University of Georgia (UGA) and Florida International University (FIU) have shown that fish are the biggest nutrient contributors in their local ecosystems. Their contribution is so great that they can cause changes in growth rates of organisms at the bottom of the food web.

The study took place in the tropical waters of a large bay on Abaco Island in the Bahamas. Most tropical ecosystems are nutrient limited, which means that the local primary producers (seagrass or algae) require the proper proportions of nitrogen and phosphorous to grow.

But, Jacob Allgeier, a doctoral student in the UGA Odum School of Ecology, explained that he the other researchers have “been thinking about the role of fish and the nutrients they’re excreting in these ecosystems for a while now.” He explained that fish are often overlooked, but that they actually provide fertilizer directly to seagrass as they recycle nutrients through excretion.

They found that seagrass grew faster and held more nutrients at sites where there were more fish than at sites that were home to fewer fish.

“Fish are putting an enormous amount of nutrients into this system-it appears to be even more than all other sources, including runoff from golf courses and all other human caused impacts, combined,” explained Allgeier.

The results highlight the importance of maintaining healthy and diverse fish populations. Different fish provide different nutrients, so “even if you have large numbers of fish, if they’re dominated by one species, they’re filling just one nutrient cycling niche in that ecosystem,” Allgeier continued. “That’s not how these systems are used to being fed nutrients.”

Abaco Island, Bahamas.

Abaco Island, Bahamas. Photo credit: Jacrews7 via photopin cc

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Copyright © 2012 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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