The 100 or so seamounts, which lie between 700m and 1600m deep, host the world’s only known aggregation of deepwater eels. The researchers brought two egg-laden females up from a depth of 1100m for examination, which they believe to be a first.
Deep-sea corals live without sunlight or symbiotic algae, filter-feeding on passing organisms and protecting other animals within their structures, says CSIRO. Fragile and slow-growing, they are vulnerable to fishing and mining activities as well as climate-related changes.
Trawl-fishing was banned in the area in the 1990s, but the team reported that there was no evidence that the coral had recovered from the damage done then. There were however signs that some individual species of coral, featherstar and urchin had re-established a foothold.
One significant finding was said to be that reefs of the main reef-building stony coral Solenosmilia variabilis extended between the seamounts on raised ridges down to about 1450m – indicating that there was far more of the coral than had previously been realised.
A CSIRO-designed deep-tow camera and light system was used to carry out 147 transects over a distance of some 125 miles, collecting more than 60,000 stereo images and 300 hours of video for analysis.
Unfamiliar animals recorded included feathery solitary soft corals, tulip-shaped glass sponges and crinoids. A small net was also used to sample some of the seabed creatures.
Describing operating the 350kg camera rig, CSIRO said it was “an often challenging job, as obstacles like large boulders or sheer rock walls loom out of the darkness with little warning.
“The greatest rapid ascent, a near-vertical cliff 45m in height, resulted in highly elevated blood pressure and one broken camera light!”