Study Shows Tiny Short-Lived Fish Bolster Reef Ecosystems


Scientists might have found the answer to a long-standing puzzle that baffled even the great mind of naturalist Charles Darwin, the father of evolution.

In a study, a team proposed that the small, bottom-dwelling cryptobenthic fishes are the cornerstone of coral reefs, providing food to bigger creatures that thrive in the otherwise nutrient-poor waters.

"Scientists have puzzled over coral reefs for centuries, wondering how such productive, diverse ecosystems survive in what is essentially a marine desert," stated Simon Brandl, a postdoctoral fellow at Simon Fraser University and one of the authors of the study published in the journal Science. "It's remarkable to find that these tiny, almost universally overlooked fishes actually serve as the cornerstone of coral-reef fish communities."

Darwin's Paradox

A coral reef is an underwater ecosystem that supports a diversity of marine creatures, including fishes, crabs, sponges, and a lot of others. However, in 1842, Darwin noted that the clear blue waters surrounding coral reefs mean that there are very little amounts of microscopic plankton.

Researchers have suggested that coral reefs might have a system in place that efficiently recycles nutrients. Others claimed that nutrients washed in from the open ocean might be supporting the thriving life in the coral reefs.

Cryptobenthic Fishes Feed Reef Inhabitants

However, Brandl wondered whether the cryptobenthics such as gobies, blennies, and cardinalfishes were the key. He and his team first investigated how abundant the small creatures are in coral reefs by setting up 58 bell-shaped nets in Belize, French Polynesia, and Australia. They counted up to 100 cryptobenthic fishes per square meter.

They also looked at previous studies and found that the estimated lifespans and death rates of reef species. According to their calculations, cryptobenthic fishes account for almost 60 percent of the fish biomass consumed on the reefs.

"Cryptobenthics do one thing particularly well: getting eaten," commented Brandl.

The cryptobenthic larvae also tend to stay in their natal reefs, providing a continuous stream of new generations of tiny fishes for larger reef fishes to eat.

The researchers hope that the cryptobenthic fishes can provide a resilient foundation for coral reefs, especially now that they undergo a significant and rapid decline due to climate change.

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