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Underwater videos could help explain why thousands of starfish are stranded on Welsh beaches

Writer : Emma Sheehan, Affiliate Professor of Marine Ecology, College of Plymouth

Storms this winter have left 1000’s of starfish mendacity stranded alongside the Welsh coast. Many starfish are nonetheless alive once they get washed ashore however many will die as they can’t survive being uncovered within the air for too lengthy.

Till not too long ago why plenty of starfish had been abruptly washed ashore was a thriller, however a latest discovery of a starfish behaviour would possibly assist clarify this phenomena. College of Plymouth scientists devised a novel methodology of “flying” an underwater video digicam to document seabed creatures throughout large sea swells and powerful tidal currents.

The flying video array floats simply above the seabed and is towed behind a ship the place scientists can watch the video feed dwell from the boat wheelhouse. Whereas testing the video off Shoreham-by-Sea, West Sussex, throughout sturdy tidal currents, the group seen lots of of starfish curled up like parachutes, bouncing alongside the seabed.

Starfish had been beforehand believed to be slow-moving creatures that solely crawled over the seabed sticking quick utilizing lots of of tube toes. Seeing them fly previous the display screen was an uncommon expertise however this “starballing” behaviour might clarify why the general public are abruptly seeing plenty of starfish being swept ashore. As they’re flying alongside in large teams, these teams might get swept collectively on to seashores by storms.

An animation of starfish as they transfer alongside the seabed.

What’s starballing?

Little or no is understood about this “starballing” behaviour of the UK frequent starfish Asterias rubens, the place they roll alongside the seabed. Nonetheless, because the discovery talked about above, US scientists have discovered that sea cucumbers – an in depth relative of starfish – additionally exhibit this behaviour throughout sturdy tidal currents.

The mechanism is named “lively buoyancy adjustment” and is a behavioural response to environmental modifications reminiscent of growing water currents which prompts the animal to extend its physique quantity turning into bloated, retracting its tentacles and detaching from the seabed.

This permits starfish to be effectively swept away to new feeding grounds or relocate to breed. It’s prone to be a dangerous methodology of transport if the sturdy currents co-occur with sturdy onshore winds and waves that would take them ashore. This new behaviour might clarify starfish mass strandings.

How starfish “fly” alongside the seabed.

There may be nonetheless a lot nonetheless to study concerning the behaviour of marine creatures. This specific behaviour solely happens throughout sturdy water currents when, usually, nobody can observe it. Vigorous sea situations scale back water visibility and make situations extra harmful and difficult for scuba diving and underwater video surveys, making it more durable for scientists to analysis. This behaviour was solely recorded as researchers had been working throughout sturdy spring tides to check new tools. Nonetheless, business scuba divers have since reported additionally seeing starfish tumbling alongside the seabed in each Wales and Scotland throughout sturdy tidal currents in 2017.

Studies of mass strandings do appear to be growing every year and analysis is required to see if that could be linked to local weather change affecting the climate. UK storms are predicted to extend in frequency and magnitude and that would trigger extra of this to occur sooner or later.

Learn extra:
Local weather change is making ocean waves extra highly effective, threatening to erode many coastlines

Excessive storms within the Lyme Bay Marine Protected Space, on the south coast of England, had a devastating impression on the seabed throughout the winter of 2014. Previous to the storms the realm was thriving having been protected for 5 years from bottom-towed fishing, a practise that makes use of heavy internet or chains to tug the ocean flooring. Reef species reminiscent of pink sea followers, scallops, sponges and corals had been flourishing. Sadly, the storms introduced big quantities of sand that devastated this recovering neighborhood, wiping out many marine animals. One of many few species to deal with the storms had been starfish, presumably through the use of the starballing approach. They had been one of many few creatures to extend in abundance following the storms. The starfish, carnivores who voraciously feed on clams and different sluggish transferring seabed creatures, might also have taken the chance to eat the animals that didn’t rise up so nicely to the storms.

As extra starfish are reported coming ashore in giant numbers within the UK every year it turns into more and more vital to grasp additional what’s driving these occasions and why.


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