Fish fertilize corals and seagrass, but not the way you think | News from the FIU



Fish are like underwater gardeners, fertilizing the coral reefs, kelp forests and seagrass beds where they reside. Their favorite fertilizer – their own pee.

But, fish communities are facing many changes. Warming oceans mean tropical fish can venture into areas they previously couldn’t when the waters were cooler. And then there are the human impacts, including fishing and habitat destruction.

Will Wied, PhD. student in Justin Campbell’s lab in the CRF Environment Institute, wants to get to the bottom of how these different factors alter the very important nutrient balance. And it goes straight to the # 1 source of those nutrients: fish waste.

“I’m not just looking at how the fish can eat a lot more, but also how their excretion is then recycled. Do they no longer hang out in seagrass beds, so now seagrass beds no longer have a source of nutrients? Said Wied. “It’s about picking out different elements of this overall question of how the community structure dictates the quality and quantity of nutrients.”

Fish waste – excreted through the gills, in addition to the most obvious source – contains many nutrients that are beneficial and essential for life, including nitrogen and phosphorus. If the number of fish decreases and the regular supply of urine slows down, these ecosystems suffer.

The vast majority of Wied’s research takes place in South Florida. Currently, a normal day of fieldwork means he’s out on Biscayne Bay catching fish and putting them in containers filled with filtered water. Then it’s a wait and see if they pee. And they usually do. As Wied points out, if someone caught you in your house, it would definitely scare you.

Wied keeps fish for up to 12 hours, frequently monitoring their health before releasing them. Then it looks at the water to calculate the rate of excretion to show the potential for the amount and type of nutrients they could contribute to a certain location.


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