Sea sawdust: Unexpected diet of crown-of-thorns starfish

New insights from marine scientists are shedding light on an unexpected underwater phenomenon. It involves coral-destroying crown-of-thorns starfish (COTS), their larvae, and their unexpected diet of “sea sawdust.”

Underwater feast: Sea sawdust

The story starts with Dr. Benjamin Mos, a renowned researcher in the School of Environment at The University of Queensland.

Dr. Mos found himself working alongside a team of experts from Southern Cross University. The scientists made an unexpected discovery, observing how this notorious reef pest feeds on a peculiar item.

Scientifically known as Trichodesmium, sea sawdust is a type of blue-green algae bacteria. It often forms large slicks, floating on the ocean’s surface, hardly touched due to its toxicity and poor nutritional value. So how does this come into play with the crown-of-thorns starfish (COTS)?

“Until now, not much has been known about sea sawdust as a food source,” said Dr. Mos. “So we were certainly surprised to say the least.” It turns out, COTS larvae thrive on a diet exclusively made up of this bacteria.

Sea sawdust and coral predation

Sea sawdust, which is named after the way it floats in large rafts on the water’s surface, is a critical player within marine ecosystems. Besides its newfound status as a meal for starfish larvae, it also makes nitrogen from the atmosphere available to other sea life.

“Our findings suggest this could help explain the increase in COTS populations, which have devastated our coral reefs for decades,” explained Dr. Mos.

The nitrogen in sea sawdust moves into the tissues of COTS larvae, acting as a sustenance source. With the recent rise in sea sawdust blooms, this could fuel the growth of COTS populations.

The role of human activities

Investigations into this underwater diet unravel further implications. Previous research has linked human activities to the proliferation of blue-green algae blooms, which create sea sawdust.

Fertilizer usage, sewage treatment, and stormwater runoff have been implicated in the surge of these blooms.

There’s a ripple effect here that we cannot ignore. “It’s important we understand the flow-on effect of how human impacts in one ecosystem might flow on to other seemingly unrelated ecosystems,” noted Dr. Mos.

Curbing the spread of COTS

Addressing the growing issue of COTS populations and their destructive impact on coral reefs requires a multifaceted approach.

Scientists and environmentalists suggest that mitigating human-induced causes of sea sawdust blooms, such as reducing agricultural runoff and improving sewage treatment processes, could be a key step.

Additionally, initiatives like manual removal of COTS, breeding natural predators like the giant triton snail, and implementing marine protected areas are being considered to combat the coral crisis.

Dr. Mos and his team are hopeful that with increased awareness and coordinated efforts, it might be possible to curb the spread of COTS and safeguard the delicate balance of our marine ecosystems for future generations.

The next steps: A puzzle to crack

Are sea sawdust blooms leading to more adult crown-of-thorns starfish on coral reefs? For now, the matter remains unresolved.

Professor Symon Dworjanyn from Southern Cross University’s National Marine Science Centre acknowledges the need for more research. “Our findings could be an important part of cracking that puzzle,” he added.

The goal now is to identify how to tone down the impact of COTS. After all, any measure that gives coral reefs a little more time is worth exploring.

The relationship of COTS larvae and sea sawdust has become an intriguing piece of the bigger puzzle that is our complex marine ecosystem.

A sea of possibilities

When crown-of-thorns starfish larvae feast on sea sawdust, they’re doing much more than grabbing a quick snack. They are tapping into a food source with deep implications for the future of our oceans and esteemed marine life.

As marine scientists continue to unravel these unexpected mysteries of the deep, their finds remind us all of the interconnectedness of life on our planet. From the smallest algae to the most massive coral reef, every little piece matters.

This study is published in the journal Science Advances.

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