Coral Reefs Could Benefit from 'Fish Poo' Containing Friendly Microbes

Coral reefs are known to be some of the world's most significant marine ecosystems serving as shelter and source of food for fish and other marine animals, as well as for microorganisms.

These underwater natural habitats are created by reed-building corals, which are designated by scientists to belong in the Animal Kingdom rather than plants.

Reefs do not produce their own food but rely on others.

Being animals and living organisms, corals are also vulnerable to damage and even death.

Aside from other sea creatures eating them, coral reefs can also die from environment-damaging events, including oil spills, ocean warming, pollution, and physical impacts from people and ships.

Amid the threat, conservationists have also considered reefs in recent years of needing protection.

Now, a new study led by researchers in the United States has found that fish poo may serve as probiotics to coral reefs due to the presence of beneficial microbes like bacteria in the feces.

The study found that while corallivores, fish that prey on corals, can damage reefs, their excrement can be beneficial if it does not contain deadly coral pathogens.

Coral Reefs Health

(Photo : Photo by KHALED DESOUKI/AFP via Getty Images)
Orange-spine unicornfish (Naso lituratus), also known as barcheek unicornfish or naso tang, swim by a coral reef off the dive spot of Abu Dabbab along Egypt's southern Red Sea coast north of Marsa Alam on September 17, 2022. - Beneath the waters off Egypt's Red Sea coast a kaleidoscopic ecosystem teems with life, that could become the world's "last coral refuge" as global heating eradicates reefs elsewhere, researchers say. Most shallow water corals, battered and bleached white by repeated marine heatwaves, are "unlikely to last the century," the Intergovernmental Panel on Climate Change said this year. That threatens a devastating loss for the hundreds of millions of people worldwide who depend on the fish stocks that live and breed in these fragile ecosystems.

In the said paper published in the journal Frontiers in Marine Science on Thursday, April 13, researchers from Rice University and their collaborators acknowledged the importance of animal waste products in nutrient cycles and transmission of diverse microorganisms.

The research team attempted to further explore the growing notion that the feces of consumers like predators could impact resource species, which is their prey, through physical and/or microbial activity, according to the study.

In short, the team debunked the long-held notion that corallivores were thought to weaken reef structures, while grazers (fish that consume algae and detritus) were believed to keep coral reefs healthy.

Nevertheless, the scientists involved in the study found the feces of grazers leave big cuts on corals, hypothesizing this occurs since they may contain coral pathogens.

Meanwhile, feces from corallivores contain beneficial microbes that can help the corals thrive.

Also Read: How Will Coral Reefs Survive a Warming Planet?

Corallivores and Grazers

To arrive at their conclusion, the scientists studied the effects of fish feces from both corallivores and grazers on a living coral.

This was made possible by putting pieces of coral in jars with sterile seawater and applied the different types of fish poo with the corals to different jars, as summarized by the AAAS.

The team found that the corallivores' excrement contains bacteria that acts like probiotics, which are live microorganisms recognized by health authorities of bringing health benefits.

Are Corals Plants or Animals?

Contrary to popular belief, corals are animals despite being often mistaken to plants or inanimate rocks, according to the Florida Keys National Marine Sanctuary, which explained that a coral consists of tiny animals called polyps.

A coral polyp is an invertebrate animal that has a size not large than a pinhead of up to a foot in diameter.

The importance of coral reefs to the marine world is recognized by scientists.

However, reefs are damaged due to changing water temperatures, invasive species, ocean acidification, and among others, according to the National Oceanic and Atmospheric Administration Fisheries (NOAA Fisheries).

As of early 2023, Earth has already lost 30% to 50% of its coral reefs already, the NOAA Fisheries added.