Truck-sized jellyfish and submarine dives

by Kirk Sato

August 17, 2012

Kirk Sato of the USA, biologist from the Scripps Institution of Oceanography and John Hocevar from Greenpeace US return from their dive in a two-seater submersible craft on loan from the Waitt Institute.The Greenpeace ship Esperanza is on an Arctic expedition to study unexplored ocean habitats threatened by offshore oil drilling, as well as industrial fishing fleets.

© Jiri Rezac / Greenpeace

Biologist Kirk Sato embarks on submarine dives in the Arctic

Watching the Esperanza move across the horizon of the Bering Sea, I realized I was about to embark on an experience of a lifetime. However, my training at the Scripps Institution of Oceanography and more recently the research cruise, San Diego Coastal Expedition, prepared me for the field research I was about to conduct with Greenpeace in Pribilof Canyon.

In 2007, a research team led by John Hocevar (Greenpeace) set out to explore Zemchungand Pribilof Canyons for the first time with submersible technology. During these scientific dives, video recordings and collected samples were analyzed by expert biologists around the world. This process was repeated at 36 sites, a new species of sponge was discovered, and new ecological associations were found. Video footage of habitats rich with biodiversity and of unremarkable complexity were documented. We are now exploring the sites missed in 2007 to get a more complete picture of the canyons gems.

Sato examining samples from the sea floor of Pribilof Canyon in the Bering Sea

Being a witness to the scientific operation and underwater world has been a thrilling andeye-opening experience. In the few days onboard the Esperanza, Ive seen the 2-personsubmarine Deep Worker record footage of incredibly dense schools of rockfish, swimming halibut and cod, jellyfish the size of trucks, and rocks covered with dozens of animals. Here in Pribilof Canyon, the 4th largest submarine canyon in the world, weve been able to document some of the activity and biodiversity of the seafloor. We conducted video transects at a depth of about 250-400 meters because destructive trawling activity by commercial fisherman primarily occurs in this range.

Every dive brings up something new and unexpected. One rock has 10 species of invertebrates ranging from sponges and anemones to various polychaete worms and sea cucumbers. Another rock, collected only meters away from the first, contains 5 species of hydroids, 3 species of bryozoans, brittle stars and brachiopods all living in harmony. It seems as though the entire tree of life is more or less represented by the samples retrieved by pilot John Hocevar and his rotating passengers.

Coral pink brittle star

As I break apart a sponge, I cannot help but feel as though Im discovering a specialist amphipod or a fish egg living inside of the sponges pores. And, when I chip away at a volcanic rock using a hammer borrowed from the crew, I cannot contain my excitement when I find 4 polychaete worms and 2 rock-burrowing clams living inside. How are these animals capable of living within this rock, without a constant source of food like those living outside? Are they also chemosynthetic, like many of their hydrothermal vent or methane seep cousins?

It is obvious to me, and to the Esperanza crew and campaign team who witness the sampling process, that the physical structure created by sponges, gorgonian corals, and other animals creates a habitat and a refuge from predators for many other species. Like a tropical coral reef, the organisms living on the cold, dark bottom of the Bering Sea live in close association with other animals. It is obvious that the pink brittle stars gripped to the pink sea fan coral have adapted to look like the coral, possibly to avoid predators, or perhaps as a result of a common diet.

The samples Im preserving in the rubbing alcohol I bought at the St. George store will be identified, documented, and kept in the museum at the Scripps Collections in La Jolla. I will work with experts in taxonomy, including Scripps professor, Dr. Greg Rouse, and Harim Cha of the Benthic Invertebrates Collections to determine the evolutionary relationships of the organisms weve collected. Hopefully on future research expeditions, we will be able to address some of the ecological mysteries of this fascinating canyon. So far, weve only begun to scratch the surfaceof the deep ocean here on the Bering Seaslope.

-Kirk Sato, PhD student at the Scripps Institution of Oceanography. Join us and Kirk in our fight to save the Arctic.

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