Dive 10: South Palmyra Slope
May 11, 2017
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Dive 10: Coffinfish

Just before beginning the return to the sea surface, after exploring the seafloor of South Palmyra Slope at a depth of ~500 meters, we saw this chaunax, sometimes called a coffinfish or toadfish, on the wall. Video courtesy of the NOAA Office of Ocean Exploration and Research, Mountains in the Deep: Exploring the Central Pacific Basin. Download (mp4, 22.2 MB)

The midwater fauna today was very different from the other areas we have explored on this expedition. The acoustically detected layer of animals in the water column was closer to the surface and did not extend to the seafloor, but was thick with animals. The near-surface layer was filled with salps – colonial gelatinous tunicates that can form very long chains. On the descent, we saw a lot of fish from 200-250 meters (655-820 feet). Below that, we saw a mix of chaetognaths (arrow worms), fishes, various crustaceans, ctenophores (comb jellies), and a lot of siphonophores (colonial jellyfish) before we made our way to the seafloor.

Remotely operated vehicle Deep Discoverer (D2) began the dive on a steep, carbonate slope at approximately 500 meters (~1,640 feet). Initial observations in this area included a shrimp, a glass sponge with a brittle star hiding in it, a primnoid coral with hermit crabs and a squat lobster, and a brief visit from a bristlemouth fish. As we continued upslope, D2 encountered a snake eel; a corallamorph; and a host of echinoderms – sea stars, urchins, and holothurians (sea cucumbers). As we moved along the track, a rattail came over and we noticed ripples in the sediment before sighting black coral. Other highlights in this area were brightly colored anemones, a scorpionfish, a spikefish, an oreo dory, and a zoanthid-covered bubblegum coral that was host to brittle stars and a squat lobster.

Getting a closer look at the sand, there appeared to be the remnants of a calcareous algae (Halimeda sp.) common in the Pacific at shallower depths. Further upslope, we saw more primnoid corals, bubblegum corals, glass sponges, anemones, and echinoderms. We also found a benthic ctenophore (comb jelly) clinging to a dead coral. We encountered a gold-spotted duckbill fish, a common Pacific fish, as well as a type of flatfish, probably a Samaridae. Another eel swam cautiously by D2’s bright lights. We found several urchins clustered together near a small splendid perch while a brittle star meandered towards a bright blue octocoral. Just before we started our return to the surface, we saw a chaunax (sometimes called a coffinfish or toadfish) on the wall. During the transit back up from the seafloor we again saw a lot of fish, but they seemed to be a different species than those we saw on the way down. The high abundance of salps and fishes here is indicative of high productivity in the area, because both need a significant amount of food to thrive in high numbers.