A large bloom of Salpa spp. in the northeastern Pacific during the spring of 2012 resulted in a major deposition of tunics and fecal pellets on the seafloor at , 4000 m depth (Sta. M) over a period of 6 months. Continuous monitoring of this food pulse was recorded using autonomous instruments: sequencing sediment traps, a timelapse camera on the seafloor, and a bottom-transiting vehicle measuring sediment community oxygen consumption (SCOC). These deep-sea measurements were complemented by sampling of salps in the epipelagic zone by California Cooperative Ocean Fisheries Investigations. The particulate organic carbon (POC) flux increased sharply beginning in early March, reaching a peak of 38 mg C m 22 d 21 in mid-April at 3400 m depth. Salp detritus started appearing in images of the seafloor taken in March and covered a daily maximum of 98% of the seafloor from late June to early July. Concurrently, the SCOC rose with increased salp deposition, reaching a high of 31 mg C m 22 d 21 in late June. A dominant megafauna species, Peniagone sp. A, increased 7-fold in density beginning 7 weeks after the peak in salp deposition. Estimated food supply from salp detritus was 97-327% of the SCOC demand integrated over the 6-month period starting in March 2012. Such large episodic pulses of food sustain abyssal communities over extended periods of time.

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The Monterey Bay Aquarium Research Institute (MBARI) has developed an autonomous seafloor mapping capability for high resolution mapping of the deep ocean seafloor. The D. Allan B. is a 0.53 m diameter, Dorado class autonomous underwater vehicle equipped with a 200 kHz multibeam sonar, 110 kHz and 410 kHz sidescan sonars, and a 2-16 kHz subbottom profiler. All components of the vehicle are rated to 6,000 m depth. Using precise navigation and attitude data from a laser-ring-gyro-based inertial navigation system integrated with a Doppler velocity log sonar, the D. Allan B. can image the deep-ocean seafloor and shallow subsurface structure with much greater resolution than is possible with sonars operated from surface vessels. Typical survey operations use a vehicle speed of 1.5 m per second (3 knots) and an altitude of 40 m to 100 m. The D. Allan B. has now been operated in a variety of settings, including submarine canyons (Monterey Canyon, Barkley Canyon), submarine fan systems (Redondo Channel, Lucia Chica, San Clemente), seamounts (Axial Seamount), methane hydrate outcrops and gas seeps (Santa Monica Basin, Barkley Canyon), and cable route surveys across continental margin slopes (Monterey Bay). The bathymetry surveys achieve a vertical precision of 0.1 m; surveys from a 50 m altitude achieve 1 m lateral resolution and surveys from up to 100 m altitudes achieve lateral resolutions less than 2 m. The subbottom profile data provides resolution of ~0.1 m with penetrations up to 50 m in soft sediments. These survey data are sufficient in quality and resolution to use in conjunction with visual observations and sampling for mapping benthic habitats in the deep ocean.

The fie ld of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, d iff iculty ex ists in u sin g deep sub mergence vehicle man ipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates.We have developed, tested, and successfully deployed by remotely operated vehicle (RO V) a precision underwater positioner (P UP ) which provides the stability and precision movement required to perform spectroscopic measurements usin g the Deep Ocean In Situ Spectrometer (DORISS) instru ment on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positionin g on the seafloor. P UP is capable of translating the DORI SS optical head with a precision of 0.1 mm in three dimension s over a range of at least 15 cm, at depths up to 4000 m, and under the nor mal range of oceanic conditions (T, P , current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. Th is capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, includ in g the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral gra ins. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.

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