by Alexander Malahoff

Loihi submarine volcano is the most recent expression of the hotspot that produces the Hawaiian Island chain (Fig. 1). Loihi arises from the submarine slopes of Mauna Loa and is growing along its active SE-rift zone by the extrusion of pillow lava and tubular basalts. Located 34 km SE of the Island of Hawaii, the summit of Loihi is 1000 m below the ocean surface. This location makes Loihi an ideal site for submarine neovolcanic exploration since it is a short 24-hour cruise, by ship, from NOAA's Undersea Research Program's (NURP) Center Hawaii Undersea Research Laboratory (HURL) located at the University of Hawaii, Honolulu.

Three pit craters occupy the summit of Loihi. The southernmost crater, Pele's Pit, formed during a two-week seismic swarm in 1996 that collapsed the hydrothermally active cone Pele's Vents. The new pit has steep walls with the floor located 200 meters below the rim of the crater. The crater floor and north slope are sites of spectacular and extensive hydrothermal venting with water temperatures ranging from 30°C to nearly 200°C. Diverse microbial mats surround the vents and cover the near vertical slopes of Pele's Pit. HURL, NURP's Center for Hawaii and the Western Pacific, conducts regular monitoring and supports research projects that study the Loihi hydrothermal systems and its biological communities.

Figure 2. Ocean bottom Observatory at Pele's Vents

The evolution of the Loihi edifice has been the focus of study over the last 13 years. From 1987-1993 an autonomous ocean bottom observatory (OBO) (Fig. 2) recorded time-lapse video, seismicity and individual vent temperatures at Pele's Vents. Repeated multibeam bathymetric mapping of Loihi revealed the exact changes in the summit, which resulted from the 1996 collapse. Hydrothermal plume surveys have also shown radical changes in the flux of energy and dissolved minerals emanating from Loihi. HURL's 2000m capable submersible Pisces V (Fig. 3) allows scientists to conduct detailed sampling of the vent waters, microorganisms and hydrothermal mineral deposits of the Loihi summit.

The National Science Foundation (NSF) supported an extremophile sampling expedition to Loihi in 1999. Microbial mats, including a never before seen jelly-like organism surrounding the 160°C vents were collected for incubation and study at the Marine Bioproducts Engineering Center (MarBEC) (Fig 4). These collections have laid the foundation for a unique experiment planned for 2001. The experiment will use Pisces V to collect the organisms and bring them to the surface in a newly designed extremophile sampler that will maintain the pressure and temperature of their natural environment until they are transferred to a shore based extremophile bioreactor.

Loihi's mid-Pacific location and its sustained hydrothermal system have created a rich oasis for a microbial ecosystem unlike any other in the world. NOAA's National Undersea Research Center (HURL) and NSF's Marine Bioproducts Engineering Center (MarBEC) are cooperating to sample and cultivate the bacteria and archea extremophiles and explore their unique biochemistries in an effort to discover new products to help mankind.

[12/18/00]