Seafloor life on the Louisville seamounts

The NIWA Deep Towed Imaging System (DTIS) enables us to capture video and still images of sea life on the ocean floor.

Revealed along the transect lines are a diverse array of deep-sea species. Sandy sediment supports various marine worms, molluscs, asteroids, and urchins. On hard substrate and bedrock the animals are even more impressive and colourful such as deepsea corals, glass sponges, brisingid seastars, and the crinoid (feather star). Close associations among the species are observed in their natural environment. A representative collection of the various species brought on board using the epibenthic sled enables sample identification, collection of tissue for molecular analyses, and specimen imaging.

Diverse deepsea corals: Clumps of live scleractinian coral Goniocorella dumosa form a branching matrix that is an important habitat for many deepsea organisms and provides a platform or refuge for several invertebrate groups including yellow crinoids, orange brisingids, small cup corals, purple soft corals, and white lacey glass sponges. Stony coral skeletons are comprised of calcium carbonate and we sample the ocean chemistry close to these structures to measure the carbon, oxygen, and alkalinity to help understand their environment.

Lacey honeycomb glass sponges (Farreidae/ Euretidae): Sponges such as the Farrea glass sponge species are dramatic in their natural habitat.

Sea urchins: Masses of the brown deepsea urchin or pedinid (Caenopedina porphyrogigas) have been seen on the hard rock faces and in association with reef-forming scleractinian corals. Previously known on the Louisville Ridge from a trawl catch, we now know that this urchin is highly abundant on some seamounts and probably widespread along the seamount chain.

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Left image of the seafloor at 1200 m with the scleractinian stony coral Goniocorella dumosa and feathery crinoids attached. On the right a specimen image shows the complex 3-D matrix and distinct orange-pink cups with live polyps.
Small brittlestars are often attached and entwined throughout their honeycomb-like structure (left image). On the right, images of specimens caught in the epibenthic sled show brittle stars, cup, and branching stony corals using the dead framework of Farrea similaris as substrate to settle and grow on.
The black coral Bathypathes occurs sentinel-like in deeper regions, here at 1200 m, on very old, hard, lava flow.
Sea fan (or primnoid) corals are seen attached to hard substrate and bedrock (left image). Species associated with these corals include galatheid squat lobsters, scaleworms, and brittlestars, seen attached to the right angle branches.
Caenopedina specimen image (left) and high densities of the species ‘on the march’ on the hard bedrock flanks of the seamount (right).