Robotic Fish could Monitor Corals

Researchers at Northwestern University have created a robotic fish that can move from swimming forward and backward to swimming vertically almost instantaneously by using a sophisticated, ribbon-like fin.

The robot, created after observing and creating computer simulations of the black ghost knifefish, could pave the way for nimble robots that could perform underwater recovery operations or long-term monitoring of coral reefs.

The black ghost knifefish, which works at night in rivers of the Amazon basin, hunts for prey using a weak electric field around its entire body and moves both forward and backward using a ribbon-like fin on the underside of its body.

The robot is fitted with a electrosensory system that works in a similar way to the knifefish’s, and the team hope to next improve the robot so it can autonomously use its sensor signals to detect an object and then use its mechanical system to position itself near the object.

Potential applications for such a low-speed, highly maneouverable robot include underwater recovery operations, such as plugging a leaking oil pipe, or long-term monitoring of oceanic environments, such as coral reefs.

Further Reading: Northwestern University

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Climate Change Remains a Threat to Corals

Hopes that coral reefs might be able to survive, and recover from, bleaching caused by climate change are fading for certain coral species, according to new research published by the University of Buffalo this week.

It shows, for the first time, that while hard corals can take up from the environment new stress-tolerant algae that provide critical nutrients, the coral may not be able to sustain the relationship with these algae over a long period. The findings may mean that certain types of coral will not be able to adapt rapidly enough to survive global warming, says the study’s lead author, Mary Alice Coffroth.

“Our findings suggest that not all corals can maintain a long-term symbiosis with these stress-tolerant strains of algae,” she says.

“That’s the problem,” Coffroth continues, “if they can’t take up the stress-tolerant symbionts, or if they take them up but can’t maintain the symbiosis with them, as we found, then they likely won’t be able to adapt rapidly enough to survive global warming.”

During the past two decades, Coffroth explains, coral reefs, known as the rain forests of the sea for their incredible biological diversity, have suffered bleaching events due to high water temperatures and light levels that cause them to literally “spit out” their algal symbionts, which provide their sustenance. Severe bleaching can lead to coral death.

In recent years, though, it has been reported that some corals appear to respond to rising sea temperatures by acquiring new stress-tolerant symbionts from the environment, which could allow them to survive the warmer oceans caused by climate change.

Coffroth says that the UB research shows that while the corals they studied were able to acquire new stress-tolerant symbiont strains from the water, they were unable to maintain that symbiosis for very long.

After about five weeks, the proportion of new symbionts within the coral had declined dramatically and after 14 weeks was no longer detectable in the corals.

SCUBA News is published by Scuba Travel Ltd, the independent guide to diving around the world. We also publish a newsletter - SCUBA News (ISSN 1476-8011) - with destination reviews, ocean facts, marine creature of the month and underwater news.

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