SCUBA News 287
(ISSN 1476-8011)
June 2024

Welcome to SCUBA News. I hope you find it useful. Any questions or comments to news@scubatravel.co.uk.

What's New at SCUBA Travel?

	Unforgettable underwater encounters in Tanzania The archipelagos of Zanzibar and Mafia Island offer beautiful diving with stunning corals, drift dives, little critters plus the chance to see humpback whales, turtles and whale sharks. FIND OUT MORE…
	Is Iceland on your dive destination list? Maybe it should be. It has dive sites that are unlike any others in the world, including in the crack between the American and European continental shelves. LEARN MORE…

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Creature of the Month: the beautiful soft coral, Dendronephthya hemprichi

"Like rich rosettes of royal velvet, they decorate the rusting iron, transforming the unromantic metal stanchions into pillars that would grace a palace"
wrote Robert Gibbings on observing soft corals for the first time on his visit to Hurghada in 1938.

Soft coral. Tim Nichosoln

This beautiful soft coral is on the wreck of the Carnatic in the Red Sea.

The coral is Dendronephthya hemprichi. This species is a pioneer settler. It can clone small fragments of itself with root-like processes that quickly attach to artificial structures like wrecks. Especially vertical structures.

D. hemprichi on the Numidia wreck, The Brothers, Red Sea. Tim Nicholson

As well as cloning itself, this soft coral reproduces sexually year round. They don't have synchronised broadcast spawning episodes though, as many other corals do. They also reproduce at a younger age than other corals. Spawning occurs after sunset and continues until 2 am.

Feeding

The soft coral takes in sea water to expand its body before feeding. This builds up a positive pressure inside the coral that supports the branches and trunk.

D. hemprichi at Fury Shoals. Jill Studholme

Another difference between D. hemprichi and other corals, is that they don't depend on symbiotic algae: they are azooxanthellate (asymbiotic). Instead they feed almost exclusively on phytoplankton. Eight feathery tentacles surround the coral's mouth and whip food into it. They feed on very small plankton such as single-celled algae, rather than larger particles as had previously been thought.

D. hemprichi on Dungus reef. Tim Nicholson

Do they build coral reefs?

At first soft corals were not thought to be reef-building, although they do secrete limestone. In their case this is as internal crystals called sclerites or spicules.

D. hemprichi, with yellow spicules, at Fury Shoals. Jill Studholme

Research though has revealed that some parts of coral reefs are actually made from cemented sclerites of a soft coral.

Because soft corals do not have large skeletons, they grow faster than hard corals

Plant or Animal?

The soft coral is actually a colony of animals, each connected to its neighbour by living tissues. A single coral animal is a polyp - the attractive "flowery" projection.

Soft coral in Malapascua, Philippines. Toby Gibson/DepositPhotos

Where to see this beauty?

You find Dendronephthya hemprichi from around 10 to over 50 m, standing out from walls and wrecks in currents, in the tropical waters of the Red Sea and Indo-Pacific.

In May 2023 divers observed it for the first time in the Mediterranean. Because it can settle quickly on surfaces and reproduce rapidly by cloning, and as the sea is warming, it may soon be common in the Mediterranean as well. This is worrying because as an invasive species here, it may disrupt the native ecosystems. Animals from the highly biodiverse Red Sea are often more competitive than native Mediterranena species. It probably arrived in the Mediterranean through the Suez Canal, like so many other species.

Israeli scientists writing in the journal Biology in 2023 point out:

"Amidst the doomsday predictions of a collapsing ecosystem, bio-invasions in the Mediterranean Sea can also be observed through rose-colored glasses. As the Mediterranean Sea is a remnant of the Tethys Ocean, from a historical perspective, the changes observed can also be viewed as a return to the sea's tropical origins"

Soft corals in Red Sea. Garry Frazer

Phylum: Cnidaria > Class: Anthozoa > Subclass: Octocorallia > Order: Alcyonacea > Family: Nephtheidae > Genus: Dendronephthya > Species: Dendronephthya hemprichi

References and Further Reading
Soft coral is reef building, SCUBA News
Blue Angels and Whales, by Robert Gibbings 1938
K Fabricus, Y Benayahu, A Genin, Herbivory in Asymbiotic Soft Corals. Science, April 1995, Volume 268
M Dahan, Y Benayahu. Clonal propagation by azooxanthellate octocoral Dendronephthya hemprichi. Coral Reefs (1997) 16:5-12
U. Oren, Y. Benayahu, Transplantation of juvenile corals: a new approach for enhancing colonization of artificial reefs. Marine Biology, February 1997, Volume 127, Issue 3, pp 499-505
Nativ H et al. New Record of Dendronephthya sp. (Family: Nephtheidae) from Mediterranean Israel: Evidence for Tropicalization? Biology. 2023 Sep 8;12(9):1220.

Diving news from around the World

	Fishy parenting? Punishing offspring encourages cooperation Punishment is not exclusive to human societies but is also present in how fish enforce cooperation and maintain social relationships.
	From battlefield to reef: Oman creates underwater military museum Oman is repurposing out-of-service military equipment into an underwater museum within the Daymaniyat marine reserve
	The secret sex life of coral revealed Key factors that orchestrate mysterious synchronized coral spawning
	Marine Protected Areas don't line up with core habitats of rare migratory fish 62% of Marine Protected Areas designated to protect rare migratory fish species are outside of their core habitats, according to a new study.
	North pacific grey whales are shrinking and scientists aren't sure why Data reveals a shocking trend: beginning with whales born around 2000, the length of animals has been shrinking by more than three inches per year from a baseline of about 40 feet.
	Sea turtle experts provide best practices during nesting season Researchers provide best practices and answer some of the most frequently asked questions to help protect nesting sea turtles and their hatchlings.
	Marine heatwaves devastate beautiful red gorgonia in the Medes Islands The unprecedentedly high mortality, together with the predicted climate change scenarios, means that these populations are probably at a point of no return
	Great Barrier Reef bleaching crisis like a bushfire underwater It's too soon to tell if the heat-stressed corals of Australia's Great Barrier Reef will survive their fifth mass bleaching in eight years, but the marine scientists who monitor the reef's health are already despairing.

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Photo credits: Diego Grandi, Tatiana Ivkovich, Steven Redmond, Andrea Izzotti/DepositPhotos, Tim Nicholson, Jill Studholme, Garry Frazer, Albrecht Fischer

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CONTACTING THE EDITOR
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Jill Studholme
SCUBA News
The Cliff

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SCUBA News (ISSN 1476-8011)

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