Super-urinators among the mangroves: Excretory gifts from estuary’s busiest fish promote ecosystem health
A new University of Michigan-led study of individually radio-tracked tropical fish in a Bahamian mangrove estuary highlights the importance of highly active individuals in maintaining ecosystem health.
The study found that the individual gray and cubera snappers that spent the most time swimming and foraging for food also spread the highest levels of the essential nutrient nitrogen throughout the estuary in their urine.
The excretory contributions of the most active individuals nearly doubled the total amount of nitrogen that would otherwise be present in the ecosystem. That extra fertilizer means more plant growth and more food at the base of the food web.
“In any population, the behavior of key individuals can have outsized impacts on their ecosystem—think Steve Jobs,” said U-M marine ecologist Jacob Allgeier, assistant professor in the Department of Ecology and Evolutionary Biology. “Quantifying the behavior of key individuals in wild populations is an emerging frontier in ecology, with the potential to upend how we define biodiversity and our attempts to conserve it.”
Allgeier is the lead author of a paper published Feb. 26, 2020 in the journal Science Advances. The paper reports the findings of a study that radio-tracked 33 gray snappers and 25 cuberas in a mangrove-lined estuary on Abaco Island in the Bahamas in 2006 and 2007.
In October 2019, Allgeier was awarded an $875,000, five-year grant from the Packard Foundation. Much of that funding will be used for a larger study to radio-track about 500 Abaco Island fish to learn more about their feeding behavior.
The big-picture goal of that research is to understand how an unlikely but renewable source of fertilizer—fish excretion—can be used to stimulate fish production and improve food security for people living in tropical ecosystems.
In Science Advances, Allgeier and his colleagues report that while the most active snappers had an outsized impact on ecosystem health, they were also the most likely to be caught by anglers, who prize their bold behavior and fight.
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