Cliffhanging corals avoid trawler damage

Jan 20, 2012
Cliffhanging corals avoid trawler damage
Cold water corals in the Bay of Biscay.

Bottom trawling fishing boats have devastated many cold water coral reefs along the margin of the North East Atlantic Ocean. Now, researchers have found large cold water coral colonies clinging to the vertical and overhanging sides of submarine canyons 1350 metres below the surface of the Bay of Biscay.

The overhanging canyon walls protect the coral from bottom trawling, providing a safe haven where it can flourish.

The study, reported in the journal , is the first time such a large number of have been found clinging to canyon walls. The densely-packed coral colonies covered several hundred square metres of cliff face, comparable in size to some of the richest cold water coral mounds found elsewhere along the margin of the North East Atlantic.

"We expected to find something, but we had no idea it would be that much," says Dr. Veerle Huvenne, a marine geoscientist at the National Oceanography Centre and lead author of the paper.

Cold water corals are widespread along the of the North East Atlantic. Large cold water coral reefs exist off the coasts of the UK, Ireland and Norway and support thriving . "Because they create structure on the they provide a habitat for lots of sea life. They're real biodiversity hot spots," says Huvenne.

However, , which drag heavily-weighted nets along the seabed, have damaged or destroyed many cold water .

The newly-discovered cliff-dwelling corals could help repair those damaged areas. Corals need to reach a certain level of maturity before they can reproduce sexually. When they do, they produce free-swimming larvae which can repopulate damaged or destroyed reefs. The shelter afforded by the overhanging cliffs gives the coral the opportunity to develop undisturbed.

To make their discovery, the researchers modified the deep-water remotely operated vehicle (ROV) ISIS. They repositioned its multi-beam echosounder, which is typically used to study the seabed, to point forwards. In this position it could map the canyon walls ahead of the ROV.

Yet the work was not without hazards. "It was very complicated terrain," says Huvenne. "So there was a danger of getting the equipment stuck."

An ROV like ISIS usually finds its route using bathymetry (depth) data from the research ship on the surface but, because of the overhanging cliffs, this wasn't always accurate in the canyon. Instead, the skilled pilots had to rely on the ROV's own instruments to feel their way along. ISIS also had to avoid discarded fishing gear in which it could have become tangled as it approached the cliff face.

Cold water corals are found in large reefs or mounds at depths from just a few metres to more than five kilometres. Most coral species need a solid substrate, such as rock, to grow on, and a regular supply of organic particles on which to feed.

The canyon habitat provides both. The rocky wall offers secure anchor points and the shape of the canyons means they funnel a steady stream of food past the corals.

Explore further: US delays decision on Keystone pipeline project

More information: Huvenne VAI, et al. (2011). A Picture on the Wall: Innovative Mapping Reveals Cold-Water Coral Refuge in Submarine Canyon. PLoS ONE. 6(12): e28755. doi:10.1371/journal.pone.0028755

Journal reference: PLoS ONE search and more info website

Provided by PlanetEarth Online search and more info website

4.8 /5 (4 votes)

Related Stories

Ocean acidification threatens cold-water coral ecosystems

Apr 03, 2006

Corals don't only occur in warm, sun-drenched, tropical seas; some species are found at depths of three miles or more in cold, dark waters throughout the world's oceans. Some cold-water coral reefs are home to more than 1,300 ...

Recommended for you

US delays decision on Keystone pipeline project

Apr 18, 2014

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

Apr 18, 2014

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.