Monterey Bay Aquarium Research Institute

Seamounts 2007
June 17 - June 24, 2007

June 19th, 2007

Kristina and Laura R write:
Today was our second day on Pioneer Seamount, the northernmost station during our expedition. We deployed the ROV Tiburon on time at approximately 6:30 am, hitting bottom at about 8 am.  Our transect began at a depth of 1032 m and ran northwestward to shallows at 850 m.  The peak of Pioneer Seamount is located in the oxygen minimum zone of the Pacific, and hosts a colorful variety of species of marine life.

Today we observed more about the ecology of the corals.  In contrast to yesterday, where corals dominated the deeper regions of Pioneer, the shallower depths visited today contained dense aggregations of sponges, such as this enormous goiter sponge (approximately one meter across) at 900m. 


Isidella coral at 1100m depth with a large urchin and sponges covered with crinoids (feather stars).

Additionally, corals today appeared stunted in size, possibly related to the fragile volcanic sandstone substrate, such as pictured below, graced by an octopus and a rare snailfish.  Of the corals seen, the bamboo coral species Keratoisis was less dominant than the species Isidella.  The highlight of the day occurred when one of our biologists discovered in the ship’s lab that Isidella and Keratoisis bioluminesce! We collected two sets of pushcores to analyze the upper sediment layers for assessment of environmental conditions.  The cores originated from two sediment ponds between cones on the seamount. During one core's collection, we captured a small gastropod of the genus Neptunea at the top of the core.


Site markers were left beside groves of corals to mark the beginnings of video transects. We hope to return in the future to document the growth of the corals and changes in the communities along the transects.

Rock samples were also collected throughout the dive to provide insight on the type of volcanism occurring at Pioneer Seamount. The highlights of the rock samples collected included vesicular basalt that we thought during collection was volcanic sandstone, and a basalt with geochronological potential.

Overall, these dives were a great success.  We have now finished our objectives at this site: exploring the volcanic cones on the shallowest part of the seamount and collecting coral samples from a range of depths to anchor the northernmost climate signal we have from the California Current. We observed deep-sea corals at depths ranging from 1490 m to 830 m. We also observed sponge meadows and fields of corals.  The materials collected and animals observed here will provide the scientists on board the Western Flyer with a plethora of new information with which to study the deep sea. We are now steaming south toward Davidson Seamount.


A large, pink nudibranch is perched and feasting on the fine branches of a coral. Crinoids wait below for crumbs.

This new species of urchin is being nudged by the suction sampler nozzle into the biobox, which is 21 cm (8.2") across.


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