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Enlarge ImageBIOMAPER-II: Bio-Optical Multi-frequency Acoustical and Physical Environmental Recorder
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Enlarge ImageMOCNESS: Multiple Opening/Closing Net and Environmental Sampling System (P. Wiebe)
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| BIOMAPER-IIThe BIo-Optical Multi-frequency Acoustical and Physical Environmental
Recorder or BIOMAPER-II is a towed system capable of
conducting quantitative surveys of the spatial distribution of coastal
and oceanic plankton/nekton, near surface bubble fields, and
turbulence, as well as field verification studies of theoretical
plankton reverberation models. The system consists of a multi-frequency
sonar (up-looking and down-looking pairs of transducers operating at
five frequencies: 43, 120, 200, 420, and 1000 kHz), a video plankton
recorder system (VPR), an environmental sensor system (CTD,
fluorometer, transmissometer), and several other bio-optical sensors
(down-and upwelling spectral radiometers, spectral attenuation, and
backscattering, and absorption meters). The lower four acoustical
frequencies utilize split beam technology and are able to make target
strength and echo integration measurements. Also included are an
electro-optic tow cable, a winch with slip rings, and a van which holds
the electronic equipment for real-time data processing and analysis.
The vehicle is capable of operating to a depth of 300 m at 4-6 kn,
while near the surface it may be towed at speeds up to 10 kn. The
system can be operated in a surface-towed down-looking mode, in a
vertical oscillatory "tow-yo" mode, or in a subsurface up/down-looking
horizontal mode. To enhance the performance and utility of BIOMAPER-II
in high sea states, a winch, slack tensioner, and over-boarding J-frame
assembly are integrated with the system for deployment and handling.
Wire tension records and the power spectra demonstrated the substantial
protection that the slack tensioner system provided against excessive
shock loading of the cable and the vehicle in sea states that would
otherwise prevent work. The scientific capability of the vehicle is
illustrated with acoustic, environmental, and bio-optical data sets
collected from the Gulf of Maine on cruises in 1997 and 1999 and in the
Southern Ocean west of the Antarctic Peninsula in 2001 and 2002.
MOCNESSThe Multiple Opening/Closing Net and Environmental Sensing System
(MOCNESS) is a modified Tucker trawl system with a rigid mouth opening
originally built by Wiebe et al. (1976, 1985). The original version had a
100 cm x 141 cm mouth opening with nine 0.333 mm nylon mesh nets each 6 m long.
Instead of a cable connecting the top and bottom of the framework, stainless
steel rods were used on each side of the mouth opening along which the bars
supporting the net dropped. This
provided a fixed area mouth opening that facilitated calculations of water
volume filtered. The system was powered
electrically on conducting wire and originally was controlled from a surface
deck unit. The current version of the
MOCNESS is computer controlled. Sensors
include pressure, temperature, conductivity, fluorometer, transmissometer,
oxygen, and light. Systems may be built
with 1/4, 1, 2, 4, 10, and 20 m2 mouth openings, all with rigid
mouths and using the same release mechanisms, sensors, and computer logging and
controls.
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