Witnessing the birth of an undersea mountain… and other exciting discoveries!

NOAA's Undersea Research Program supports successful submersible expedition to the American Flagged Pacific Islands

By John Wiltshire, edited by Felipe Arzayus

Much of the South Pacific oceans remains scientifically unexplored. Even less is known about the undersea landscape of this tectonically active zone, and very few deep submergence research missions have occurred due to the limitations imposed by distance from land, water depth and availability of resources. The Hawai‘i Undersea Research Laboratory (HURL) greatly improved this situation last summer, conducting the most extensive diving expedition ever undertaken in the area, on a voyage lasting from March until August 2005. This pioneering undertaking looked at some of the greatest undersea volcanoes and associated ecosystems between Hawai‘i and New Zealand. NOAA's Undersea Research Program (NURP), in collaboration with NOAA's Ocean Exploration focused their work on the 2000-mile stretch from Hawai'i to Samoa that contains a series of American Flagged protectorates. Six NURP-supported projects were undertaken in American Samoa and the U.S. Line Islands. This work followed a highly successful international diving expedition in the Kermadec Arc, north of New Zealand, with strong New Zealand and German participation.

HURL operates two of only nine currently available deep diving research submersibles in the world: the submersibles Pisces IV and Pisces V. During the five-month expedition, the submersibles dove to depths of 2000 meters carrying a pilot and two science observers; the submersibles spent six to eight hours on the bottom photographing areas of high scientific interest and taking samples and key in situ measurements. Submersibles offer scientists the unique advantage of being in the environment they are studying and actually taking benthic measurements and habitat observations right in front of where they are sitting.

Nafanua: birth of a new island

NURP's first project concentrated on American Samoa. Work here consisted of nine dives led by Dr. Hubert Staudigel of the Scripps Institution of Oceanography and Dr. Craig Young of the University of Oregon, focusing on the Samoan volcanic hot spot at Vailulu‘u seamount and a later series of dives by led Dr. Dawn Wright of Oregon State University mapping the deepwater habitats around the eastern Samoan island of Tutuila.

The Samoan chain forms the northern end of the Kermadec Arc, which volcanically expresses itself in the hot spot seamount of Vailulu‘u. This is a very active hot spot with no previous submersible investigations. Vailulu‘u had been bathymetrically mapped but a great surprise was in store for the research team. In the six years since the most recent mapping a 300-meter tall volcanic cone, known as Nafanua, had grown in the summit crater. This incredible level of growth could mean that Vailulu‘u Seamount will breach the sea surface within decades forming a new island in the Samoan group. Culturally, the birth of such an island is a very revered event in Polynesian society. Nafanua's cone area proved to be very active with several distinct types of hydrothermal venting which, in turn produces a range of unique biological habitats. Low temperature hydrothermal vents produced iron oxide chimneys and one-meter thick microbial mats. There were also a series of higher temperature vents that were much less benign. These vents spewed toxic acid waters of low salinity that had temperatures of about 85°C and contained oily looking droplets of immiscible carbon dioxide. These venting areas and the 'moat' at the base of the new cone were almost devoid of macroscopic life. The fluids in the deepest parts of the caldera are evidently so toxic that the base of the new cone is scattered with the carcasses of fish and mollusks that apparently died from the exposure. There is, however, one species of bright red hesionid polychaete that feeds on or near the carcasses. This is an interesting adaptation and a clear indication that Vailulu‘u has much to offer as a natural laboratory to study a complex benthic habitat. The inner wall of the volcano is dominated by sponges of several sorts that feed on microbes of vent origin. The outer volcano walls have octocorals, sponges and occasional asteroids, ophiuorids and crinoids; unlike the inner wall organismas described earlier, analysis of food sources revealed that these are fed from oceanic plankton. It appears from isotopic analysis the experimental determination of the proportion of a given isotope(s) or atoms with the same number of protons, but a different number of neutrons in a sample, that these are fed from oceanic plankton.

At the summit of Nafanua, there is a thriving population of eels (Dysommina rugosa ), each about a foot in length. In fact, there were so many eels congregated at a single vent location that the area was referred to as 'eel city' by the submersible pilots. Interestingly, habitat analysis by Dr. Craig Young showed that this large eel community survived not on the bacteria mats but on crustaceans imported into the system from the water column above. Apart from the abundant eels, only two other metazoans were found near the summit vents. These were a copepod and a scale worm, which were shown to rely on the microbial mats as their dietary source of carbon.

Dives on the highly active hot spot volcano were followed by a series of dives in the Eastern Samoan islands, mapping pristine benthic habitats. This work was undertaken once again by Dr. Dawn Wright on Taema Bank and at Fagatele Bay off the island of Tutuila. This project carried out the highly important task of ground-truthing previously-made bathymetric maps of very sensitive biological areas. This supports a major American Samoa government initiative to designate 'no take' zones within pilot marine protected areas. Areas of 20% or greater coral cover are mandated for special protection. Fagatele Bay is an especially sensitive National Marine Sanctuary. This small bay and adjacent canyon were subject to a devastating infestation of Crown of Thorns starfish in the late 1970's, as well as several hurricanes and a severe coral bleaching event in 1994. The Sanctuary is now well on the way to recovery but requires stringent management protocols. The NURP submersible work was able to identify biological 'hot spots', verify key benthic habitats from previous terrain maps and photograph and video a far wider range of deep marine life than previous SCUBA studies had been able to ascertain. At least nine of the species identified in the dive work were new records for Samoa. A very important part of this project was that two secondary school teachers were brought on the cruise as observers. They will be using the photos, videos and maps provided by the science team directly in their classrooms to educate and inspire students who otherwise would never have access to the deeper marine world right off their coast.

A day's sail east of the main Samoan Islands is the Rose Atoll National Wildlife Refuge, which was established in the 1970's. Rose Atoll is a pristine reef that will hopefully be nominated as a world heritage site, a UNESCO driven process that links the concepts of nature conservation and the preservation of cultural properties. Unfortunately, this pristine reef was the site of an October 1993 grounding and following breakup of the Taiwanese fishing vessel Jin Shiang Fa. Initially, the shallow reef was examined for the effect of this ship grounding. After some early salvage attempt the ship's bow section, which was separated from the rest of the vessel, was towed off the reef and dumped into deeper water shortly after the grounding incident. There has been concern that the bow section was stuck on the reef at a depth of less than 300 meters and would continue to negatively impact the reef with iron dissolution and other pollution from continued breakup. The work with HURL was done by Drs. Michael Graves and Suzanne Finney of the University of Hawai'i and Dr. James Maragos of the U.S. Fish and Wildlife Service. The Pisces submersibles surveyed the reef to a depth of 941 meters finding no evidence of the bow and very few cultural artifacts. It appears the atoll may not require additional cleanup efforts offshore and that these efforts can be redirected to monitoring the lagoon and marine facing reefs. This was a significant outcome of the dive program. High levels of biodiversity were found at depth. As many as 60 new or rare species of marine life were identified during the dives. The excellent dive photographs and video documentation of life on this unique atoll will greatly facilitate the process of nomination and successful designation of Rose Atoll as a World Heritage Site.

(Left) Gold coral colonized by two red crinoids at Kingman Reef ( Line Islands ) PI: Robert Dunbar (Middle) Pisces IV collects a coral sample at Palmyra Atoll (PI: Robert Dunbar). (Right) Pisces V with a basket full of coral samples at Kingman Reef as viewed from the Pisces IV (PI: Frank Parrish)

Finding their correct place on the map!

Two additional NURP projects examined the benthic habitats of three of the lesser-known American Flag reefs and islets of the U.S. Line Islands. This work took place at Jarvis Island near the equator, along with Kingman Reef and Palmyra Atoll in the central Pacific within the Intertropical Convergence Zone. The diving work revealed some interesting and unexpected results. Jarvis Island and Kingman Reef, which are primarily sediment scoured carbonate cliffs and escarpments incised with box canyons and deeper chasms, were incorrectly located on the navigational charts; there was a position error with respect to a global reference of about 1.5 nautical miles. This has been brought to the attention of the National Ocean Service and new charts have been updated with correct information. The first group of dives, under the direction of Dr. Robert Dunbar of Stanford University examined deep-sea corals and collected them as accurate recorders of past climate change. Dunbar and his group were able to collect abundant coral samples, particularly at Jarvis Island . However, at Kingman Reef and Palmyra Atoll there was a considerable dearth of the much anticipated Gold corals, highlighting the variable patchiness of coral ecosystems.

A significant NOAA Fisheries program under the direction of Frank Parrish and Bruce Mundy, investigated the biogeography of the deepwater fish and corals in the Line Islands, Barbara Moore, NURP's director also participated as crew in one of the submersible dives, receiving a first hand account on the importance of their research. Preliminary observations found that productivity and organism density varied unexpectedly between sites and was lower than had been expected on the basis of what is observed in Hawaiian waters. Although new species were discovered and records set for existing species, the overall impression was one of an unexpectedly less rich environment than had been proposed.

The five-month South Pacific expedition represents HURL's longest and most successful cruise in its 25-year history. A deeper understanding was gained for many of the processes that form islands and change their benthic habitats – especially given that none of these areas had ever had any systematic deep diving or submersible investigations. This information is directly available to NOAA managers to maximize efforts at protecting many of these threatened and pristine environments in the South Pacific. A follow-up submersible expedition to revisit some of these critical sites is already in planning for 2008-9.