Certain fish may play an important role in controlling cyanobacterial mat growth on reefs, according to a study by researchers at Florida State University.

What are Cyanobacterial Mats?

Cyanobacteria are aquatic, photosynthetic bacteria. The blue-green algae we are familiar with in Florida is one example of cyanobacteria.

These bacteria have been reef builders on Earth for more than 3 million years and play an important role in reef ecosystems by producing nitrogen that is useful to photosynthetic organisms, like the zooxanthellae that live inside coral polyps. But as reefs degrade, these bacteria can form dense agglomerations, which are referred to as benthic cyanobacterial mats.

Research shows that too much mat cover on reefs can inhibit coral larvae settlement, lead to disease and suffocate the corals.

It was previously thought that fish do not eat the bacteria in these mats, but this study notes that certain fish might play a part in controlling mat growth on reefs by doing just that.

How we know this.

The researchers observed fish eating the bacterial mats in reefs in the Caribbean, with the French angelfish and striped parrotfish being the biggest feasters.

Why it matters.

Recently, cyanobacterial mats have gone from covering around .01% to over 20% in some reefs. Scientists predict this number will continue to increase due to human impacts and climate change. The resulting uptick in nitrogen produced by the bacteria can throw the biogeochemistry of the ecosystem out of balance, suffocating the coral according to Ethan Cissell, one of the paper’s lead authors.

What’s next?

The authors emphasize the need for future research to learn whether the fish behavior is new, or simply more noticeable as a result of the increase in bacterial mat coverage and whether the fish could help control the growth of these mats.

Learn More

• Read more details of the study at FSU News.
• Read the full study.
• Learn more about what you can do to save coral reefs.