F. Shane

A Device for Protecting Moored Spectroradiometers from Biofouling

A shutter mechanism for reducing the effects of biofouling on bio-optical instruments deployed on oceanographic moorings has been designed, built, and tested. The initial development was carried out on a spectroradiometer. The optics of the spectroradiometer are protected by copper shutters that rotate out of the field of view prior to a measurement and rotate back after the measurement is completed. The shutter system can sense an obstruction and, if one is detected, attempt to rotate in the opposite direction. The controlling software stores the home position in the memory so the shutter can return to cover the optics, irrespective of direction of rotation. The system has been tested in the equatorial Pacific, where it has provided five months of data that are unaffected by biofouling.

The Development and Ocean Testing of an AUV Docking Station for a 21" AUV

The Monterey Bay Aquarium Research Institute (MBARI) has developed an AUV docking station for a 21-inch (54 cm) diameter AUV. The system was designed for operation with cabled undersea observatories in water depths up to 4 km deep and has been demonstrated in the open ocean, though at much shallower depths. The program demonstrated successful autonomous homing and docking, data downloads, uploading of new mission plans, battery recharging, and complete power cycling of the AUV. We describe the design, and at-sea tests.

Mapping payload development for MBARI's Dorado-class AUVs

The Monterey Bay Aquarium Research Institute (MBARI) is developing an autonomous seafloor mapping capability for deep ocean science applications. The MBARI Mapping AUV is a 0.53 m (21 in) diameter, 5.1 m (16.7 ft) long, Dorado-class vehicle designed to carry four mapping sonars. The primary sensor is a 200 kHz multibeam sonar producing swath bathymetry and sidescan. In addition, the vehicle carries 100 kHz and 410 kHz chirp sidescan sonars, and a 2-16 kHz sweep chirp subbottom profiler. Navigation and attitude data are obtained from an inertial navigation system (INS) incorporating a ring laser gyro and a 300 kHz Doppler velocity log (DVL). The vehicle also includes acoustic modem, ultra-short baseline navigation, and long-baseline navigation systems. A single cylindrical pressure housing contains all of the mapping sonar electronics, and the main vehicle control and acoustic communications electronics are housed in a separate glass ball. The Mapping AUV is powered by three 2 kWhr Li-polymer batteries, providing an expected mission duration of 12 hours at a typical speed of 1.5 m/s. The assembled package is rated to 6000 m depth, allowing MBARI to conduct high-resolution mapping of the deep-ocean seafloor. Initial at-sea testing commenced in May 2004 using the subbottom profiler and 100 kHz sidescan. The sonar package will also be mountable on ROV Ventana, allowing surveys at altitudes < 10 m at topographically challenging sites. The MBARI Seafloor Mapping team is now working towards integration of the multibeam sonar and towards achieving regular operations during 2005.

Cabled instrument technologies for ocean acidification research — FOCE (free ocean CO 2 enrichment)

With rising concern over the impacts of ocean acidification on marine life there is a need for greatly improved techniques for carrying out in situ experiments. These must be able to create a ΔpH of 0.3 to 0.5 by addition of CO<inf>2</inf> for studies of natural ecosystems such as coral reefs, cold water corals, and other sensitive benthic habitats. Thus controlled CO<inf>2</inf> perturbation experiments in the field rather than in aquaria are quickly becoming an essential ocean science tool. Free Air CO<inf>2</inf> Enrichment (FACE) experiments have long been carried out on land to investigate the effects of elevated atmospheric CO<inf>2</inf> levels on vegetation. However, only limited work on CO<inf>2</inf> enrichment using quasi-open systems has yet been carried out in the ocean. Seawater CO<inf>2</inf> has complex chemistry with significantly slow reaction kinetics, unlike land-air experiments where simple mixing is the major concern. Ocean experimental designs must to take these reaction rates into account. The net result of adding a small quantity of CO<inf>2</inf> to seawater is to reduce the concentration of dissolved carbonate ion, and increase bicarbonate ion through the reaction: CO<inf>2</inf> + H<inf>2</inf>O + CO<inf>3</inf>²⁻ → 2HCO<inf>3</inf>⁻ The reaction between CO<inf>2</inf> and H<inf>2</inf>O is slow and is a complex function of temperature, pH, and TCO<inf>2</inf>. The reaction proceeds more rapidly at lower pH and higher temperatures. Marine animals in the natural ocean will typically experience only small and temporary shifts from environmental CO<inf>2</inf> equilibrium. Valid perturbation experiments must try to expose an experimental region to a near stable lower pH condition, and avoid large and rapid pH variability to the extent possible. This paper describes the design, development and testing of an in situ pH perturbation experiment deployed on a subsea cable for control. The paper addresses the differences between the deep-sea and shallow water versions of the experiments and addresses the pH sensor developments that enable long deployments.

Design and development of the CO 2 enriched Seawater Distribution System

The kinetics of the reaction that occurs when CO2 and seawater are in contact is a complex function of temperature, alkalinity, final pH and TCO2 which taken together determine the time required for complete equilibrium. This reaction is extremely important to the study of Ocean Acidification (OA) and is the critical technical driver in the Monterey Bay Aquarium Research Institutes (MBARI) Free Ocean CO2 Enrichment (FOCE) experiments. The deep water FOCE science experiments are conducted at depths beyond scuba diver reach and demand that a valid perturbation experiment operate at a stable yet naturally fluctuating lower pH condition and avoid large or rapid pH variation as well as incomplete reactions, when we expose an experimental region or sample. Therefore, the technical requirement is to create a CO2 source in situ that is stable and well controlled. After extensive research and experimentation MBARI has developed the ability to create an in situ source of CO2 enriched seawater (ESW) for distribution and subsequent use in an ocean acidification experiment. The system mates with FOCE, but can be used in conjunction with other CO2 experimental applications in deep water. The ESW system is completely standalone from FOCE.