Fish Pee; Secret Ingredient to Healthy Coral Reef?

Fish pee seems like it should be a minor player in ocean health -- not so!

It's been long known that big fish are integral to the health of coral reefs, but scientists are still learning exactly what these fish provide to the reef ecosystem. A key piece of information was revealed Tuesday when a new study was published outlining the importance of nutrients distributed through fish urine.

Phosphorus excreted from fish urine combines with nitrogen recycled by fish gills to provide nutrients much needed by the coral reef. These nutrients help coral reefs survive and grow.

"Part of the reason coral reefs work is because animals play a big role in moving nutrients around," lead author of the study and postdoctoral researcher at the University of Washington's School of Aquatic and Fishery Sciences Jacob Allgeier said in a news release.

"Fish hold a large proportion, if not most of the nutrients in a coral reef in their tissue, and they're also in charge of recycling them. If you take the big fish out, you're removing all of those nutrients from the ecosystem."

More than 140 fish species at 110 coral reef sites were studied, with a range of fishing activity from extreme fishing to almost no fishing. A decrease in the numbers of large fish resulting from fishing activity negatively affected nutrient levels.

Coral reefs are delicate ecosystems that rely on a tight recycling of nutrients. A depletion in large fish and key nutrients precede decreased marine biodiversity.

Continued demand for sustainable fishing practices will help to return populations of large fish to normal in overfished areas. Reef recovery is still possible with the return of large fish and their urine.

In the ongoing coral bleaching disaster, the importance of knowledge and conservation of the world's reefs is growing exponentially. Allgeier will continue studying fish urine and reefs to build on his previous work.