A beam trawl consists of a cone-shaped body ending in a bag or codend, which retains the catch. In these trawls the horizontal opening of the net is provided by a beam, made of wood or metal, which is up to 12 m long. The vertical opening is provided by two hoop-like trawl shoes mostly made from steel. No hydrodynamic forces are needed to keep a beam trawl open. The beam trawl is normally towed on outriggers, one trawl on each side.

While fishing for flatfish the beam trawl is often equipped with tickler chains to disturb the fish from the seabed. For operations on very rough fishing grounds they can be equipped with chain matrices. Chain matrices are rigged between the beam and the groundrope and prevent boulders/stones from being caught by the trawl. Shrimp beam trawls are not so heavy and have smaller mesh sizes. A bobbin of groundrope with rubber bobbins keeps the shrimp beam trawl in contact with the bottom and gives flatfish the opportunity to escape.

Close bottom contact is necessary for successful operation. To avoid bycatch of most juvenile fishes selectivity devices are assembled (sieve nets, sorting grids, escape holes). While targeting flatfish the beam trawls are towed up to seven knots, therefore the gear is very heavy; the largest gears weighs up to 10 ton. The towing speed for shrimp is between 2.5 and 3 knots.

Raymond C. Smith, Charles R. Booth, and Jeffrey L. Star, "Oceanographic biooptical profiling system," Appl. Opt. 23, 2791-2797 (1984).

"Clarke and Bumpus designed a small two-messenger zooplankton collection system that could be deployed as multiple units on the wire and had a positive means of opening and closing the mouth of the net. A frame attached at the top and bottom to the towing wire supported a cylindrical tube 12.7 cm in diameter and 16 cm long, to which a net was attached. In the mouth of the tube was a flat plate (like a stove pipe damper plate),which closed off the cylinder when the net was deployed. When the first messenger released a spring-loaded latch, the plate was rotated 90°, opening the net; a second messenger rotated it another 90° to close the net. A flowmeter at the back of the cylinder recorded flow through the net." (Wiebe and Benfield, 2003) The instruments were equipped with No. 2 silk nets (22 strands/cm.) and "oblique" hauls were made at a speed of about 2 knots for periods of 25 to 40 minutes.

References:
CLARKE, G. L., AND D. F. BUMPUS, 1940. The Plankton Sampler-an instrument for quantitative plankton investigations. Linnological Society of America, Special Pub., (No. 5): 1-8.

Wiebe, Peter H. and Mark C. Benfield, 2003. From the Hensen net toward four-dimensional biological oceanography. Progress in Oceanography, 56, pp. 7-136.

The Sea-Bird MicroCAT CTD unit is a high-accuracy conductivity and temperature recorder based on the Sea-Bird SBE 37 MicroCAT series of products. It can be configured with optional pressure sensor, internal batteries, memory, built-in Inductive Modem, integral Pump, and/or SBE-43 Integrated Dissolved Oxygen sensor. Constructed of titanium and other non-corroding materials for long life with minimal maintenance, the MicroCAT is designed for long duration on moorings.

In a typical mooring, a modem module housed in the buoy communicates with underwater instruments and is interfaced to a computer or data logger via serial port. The computer or data logger is programmed to poll each instrument on the mooring for its data, and send the data to a telemetry transmitter (satellite link, cell phone, RF modem, etc.). The MicroCAT saves data in memory for upload after recovery, providing a data backup if real-time telemetry is interrupted.

A CTD-fluorometer is an instrument package designed to measure hydrographic information (pressure, temperature and conductivity) and chlorophyll fluorescence.

A CTD-FRRf fluorometer is an instrument package designed to measure hydrographic information (pressure, temperature and conductivity) and chlorophyll fluorescence.

For example, a Chelsea FASTtracka CTD (conductivity, temperature, and depth) device ... (needs updating) can be configured with additional sensors to measure fluorescence and photosynthetically active radiation (PAR) in the water column. Fluorescence data collected by the CTD are subsequently calibrated and corrected to give the average concentration of chlorophyll a in the water column. The Chelsea system can be configured as part of a towed package or in a shipboard pumping system.

The Hensen Net was invented by Christian Andreas Victor Hensen (February 10, 1835 – April 5, 1924) who was a German researcher considered by many to be the 'father' of Biological Oceanography. Hensen is credited with first using the term 'plankton', and the Hensen Net is one of several sampling devices he invented to help with sample collection. The Hensen Net has a 'reducing cone' forward of the net mouth, a simple closure system and a cod end collection device.

References:
Hensen, V., 1887. Über die Bestimmung des Planktons oder des im Meere treibenden Materials an Pflanzen und Thieren. Berichte der Kommssion wissenschaftlichen Untersuchung der deutschen Meere in Kiel 5, pp. 1–107.

Hensen, V., 1895. Methodik der untersuchungen. Ergebnisse der Plankton-Expedition der Humbolt-Stiftung, Lipsius and Tischer, Kiel.

Kemmerer Sample Bottles are used for collecting water and plankton at specified depths. Kemmerer bottle samplers are made from a variety of materials (stainless steel, acrylic, PVC or Teflon). The bottle type is chosen by researchers based on the research focus and sampling requirements of the field program. Lightweight, relatively small Kemmerer bottles are convenient for near surface water sampling.

The U.S. GLOBEC Georges's Bank project used Kemmerer (Kimmerer) bottles to sample nutrients in the surface (2m) waters.

Note: A LIDAR system was used during US JGOFS Arabian Sea cruises to acquire SST, DOM and fluorometric pigment data, but there are also bathymetric LIDAR systems.

The light/dark bottle is a way of measuring primary production by comparing before and after concentrations of dissolved oxygen.

Bottles containing seawater samples with phytoplankton are incubated for a predetermined period of time under light and dark conditions. Incubation is preferably carried out in situ, at the depth from which the samples were collected. Alternatively, the light and dark bottles are incubated in a water trough on deck, and neutral density filters are used to approximate the light conditions at the collection depth.

Rates of net and gross photosynthesis and respiration can be determined from measurements of dissolved oxygen concentration in the sample bottles.

The the Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) is a Fourier Transform Infrared (FTIR) sprectoradiometer with calibrations traceable to NIST standards. The M-AERI measures spectra in the infrared (about 3 to 18 micrometers) range with a resolution of about 0.5 cm-1. It uses two infrared detectors cooled to 78 K by a Stirling cycle cooler to reduce the noise equivalent temperature difference to levels well below 0.1 K.

The radiometric calibration of the M-AERI is done continuously using two internal black-body cavities, each with an effective emissivity of greater than 0.998. The mirror scan sequence includes measurements of the reference cavities before and after each set of spectra from the ocean and atmosphere. The absolute accuracy of the M-AERI calibration is monitored by episodic use in the laboratory of a NIST-certified water-bath black-body calibration target and residual errors in the M-AERI spectral brightness temperature measurements at temperatures typical of the ocean surface and lower troposphere are typically less than 0.03K.

The interferometer integrates measurements over a pre-selected time interval, usually a few tens of seconds, to obtain a satisfactory signal to noise ratio, and a typical cycle of measurements including two view angles to the atmosphere, one to the ocean, and calibration measurements, takes about ten minutes. The absolute accuracy of the spectral measurements (when expressed as a brightness temperature) is 20-30 mK. The measured spectra are processed in real-time to generate measurements of the skin SST and air temperature at the height of the instrument to accuracies much better than 0.1K.

Reference:
Minnett, P. J., R. O. Knuteson, F. A. Best, B. J. Osborne, J. A. Hanafin and O. B. Brown, 2001. The Marine-Atmospheric Emitted Radiance Interferometer (M-AERI), a high-accuracy, sea-going infrared spectroradiometer. Journal of Atmospheric and Oceanic Technology, 18: 994-1013.

The Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) is based on the Tucker Trawl principle (Tucker, 1951). The MOCNESS-10 (with 10 m² nets) carries 6 nets of 3.0-mm circular mesh which are opened and closed sequentially by commands through conducting cable from the surface (Wiebe et al., 1976).

In this system, "the underwater unit sends a data frame, comprising temperature, depth, conductivity, net-frame angle, flow count, time, number of open net, and net opening/closing, to the deck unit in a compressed hexadecimal format every 2 seconds and from the deck unit to a microcomputer every 4 seconds" (Wiebe et al., 1985).

Motoda Net (Motoda, 1971). XX13 indicates a mesh size of 100 microns. This is a "messenger based net system which utilized a framework attached to the towing wire. The circular net (56 cm diameter) was a cylinder (80 cm length)/cone (110 cm length) and was mounted on a wire with a triangular framework so that up to 10 could be towed simultaneously."(P.H. Wiebe and M.C. Benfield, 2003. Progress in Oceanography 56: p.25)

Motoda, S. (1971). Devices of simple plankton apparatus V. Bulletin of the Faculty of Fisheries Hokkaido University, 22, 101-106.

The Multi-Variate Moored Systems deployed during the US JGOFS EqPac Process Study was a package of integrated meteorological instruments. The Multi-Variate Moored System included instruments for measuring bio-optical and physical variables including water temperature, current direction and velocity, PAR, Lu683 (upwelling radiance, chlorophyll a fluorescence), and salinity. Instrumentation included: (1) a vector measuring current meter (VMCM; EG&G; Weller and Davis, 1980); (2) a fluorometer measuring strobe-stimulated fluorescence (Sea Tech; Bartz et al., 1988); (3) a transmissometer measuring beam transmission at 660 nm (Sea Tech; Bartz et al., 1978); (4) a sensor measuring scalar irradiance or photosynthetic available radiation, PAR, (E-PAR) in the visible waveband (400

References:
Bartz, R., Zaneveld, J. R.V. and Pak, H. (1978) A transmissometer for profiling and moored observations in water. SPIE, Ocean Optics V, 160, 102-107.

Booth, C. R. (1976) The design and evaluation of a measurement system for photosynthetically active quantum scalar irradiance. Limnology and Oceanography, 19, 326-335.

Dickey, TD, Granata, T., Marra, J., Langdon, G, Wiggert, J., Chai-Jochner, Z., Hamilton, M., Vazquez, J.,. Stramska, M., Bidigare, R., Siegel, D. 1993. Seasonal Variability of Bio-Optical and Physical Properties in the Sargasso Sea, J. Geophys. Res., 98(C1), 865–898, doi:10.1029/92JC01830.

Foley, D.G., T.D. Dickey, M.J. McPhaden, R.R. Bidigare, M.R. Lewis, R.T. Barber, S.T. Lindley, C. Garside, D.V. Manov and J.D. McNeil (1997). Longwaves and Primary Productivity Variations in the Equatorial Pacific at 0°, 140°W. Deep Sea Research II, 44(9-10): 1801-1826.

Weller, R. A. and Davis, R. E. (1980) A vector measuring current meter. Deep-Sea Research, 27A, 565-582.

The MultiNet® Multiple Plankton Sampler is designed as a sampling system for horizontal and vertical collections in successive water layers. Equipped with 5 or 9 net bags, the MultiNet® can be delivered in 3 sizes (apertures) : Mini (0.125 m2), Midi (0.25 m2) and Maxi (0.5 m2). The system consists of a shipboard Deck Command Unit and a stainless steel frame to which 5 (or 9) net bags are attached by means of zippers to canvas. The net bags are opened and closed by means of an arrangement of levers that are triggered by a battery powered Motor Unit. The commands for actuation of the net bags are given via single or multi-conductor cable between the Underwater Unit and the Deck Command Unit. Although horizontal collections typically use a mesh size of 300 microns, mesh sizes from 100 to 500 may also be used. Vertical collections are also common. The shipboard Deck Command Unit displays all relevant system data, including the actual operating depth of the net system.

The HOBO Water Temp Pro v2 temperature logger, manufactured by Onset Computer Corporation, has 12-bit resolution and a precision sensor for ±0.2°C accuracy over a wide temperature range. It is designed for extended deployment in fresh or salt water.
Operation range: -40° to 70°C (-40° to 158°F) in air; maximum sustained temperature of 50°C (122°F) in water
Accuracy: 0.2°C over 0° to 50°C (0.36°F over 32° to 122°F)
Resolution: 0.02°C at 25°C (0.04°F at 77°F)
Response time: (90%) 5 minutes in water; 12 minutes in air moving 2 m/sec (typical)
Stability (drift): 0.1°C (0.18°F) per year
Real-time clock: ± 1 minute per month 0° to 50°C (32° to 122°F)

The Sea-Bird Electronics SBE 26 SEAGAUGE is a wave level and tide recorder with a pressure sensor, accurate clock, precision thermometer and optional SBE 4M conductivity sensor. Pressure data are integrated to give sea level or are burst recorded at rates up to 4 Hz to characterize waves. The standard pressure sensor is a 20 meter (45 psia) Quartzonix, with a temperature-compensated quartz element. Optionally, the SBE 26 can be configured with a Paroscientific Digiquartz pressure sensor with a temperature-compensated quartz element in 13 ranges, from 1 to 6800 meters (15 to 10,000 psia). more information from Sea-Bird Electronics »

The SLOWDROP Optical Profiler is a free-falling instrument package that "has a Sea-Bird 911+ CTD, two multiwavelength absorption meters (WetLabs ac-9), and a multiexcitation spectrofluorometer (WetLabs SAFIRE) as its basic configuration. The package is deployed on a loose data tether, with sufficient buoyancy on the package to obtain descent rates of 15-20 cm/s. These slow descent rates allow data acquisition on centimeter spatial scales and result in multiparameter characterization of small-scale features." (Cowles, et al.,1998)

References: Cowles, T.J., et al., 1998. Small-scale Planktonic Structure: Persistence and Trophic Consequences. Oceanography, Vol. 11(1), pp. 4-9.

The 'Slurper' is a custom designed in situ pumping system that pumps seawater in a way that allows large-volume sampling of pre-determined depth intervals. The 'Slurper' was used during US JGOFS cruises to acquire samples for 234-Thorium and POC/PON analysis (Buesseler et al., 1988). The 'Slurper' sampling system comprised a positive displacement pump coupled to a DC motor. Pump speed and sample volume were controlled via shipboard laptop computer.

A Stramin net is specifically designed to sample plankton near the bottom and one such, designed by F.S. Russell in 1928, the 'stramin' net (Diameter: 1.5 m., Mesh: 6 strands/cm.) was equipped with rollers at the lower edge of its frame in order that it could be safely lowered until it touched the bottom. One "oblique" haul was made from the bottom (or from a depth of 200 m.) to the surface at each station. "It was mounted in an Agassiz trawl frame so that it was centered inside the trawl net, which was also fixed to the frame and cleared the bottom by approximately 17.8 cm. No provisions were made to prevent contamination of the collection during the lowering of the net to the sea floor or the hauling back to the surface."(Wiebe and Benfield, 2003)

References:
Wiebe, Peter H. and Mark C. Benfield, 2003. From the Hensen net toward four-dimensional biological oceanography. Progress in Oceanography, 56, pp. 7-136.

The Submersible Autonomous Moored Instrument (SAMI) measures and logs levels of dissolved chemicals in sea and fresh water. It is a plastic cylinder about 6 inches wide and 2 feet long that is self-powered and capable of hourly measurements for up to one year. All data collected are logged to an internal memory chip to be downloaded later. SAMI sensors usually are placed a few feet underwater on permanent moorings, while others on floating drifters sample the water wherever the wind and currents carry them. The instruments have been used by researchers around the globe in a variety of studies since 1999. Dr. Mike DeGrandpre, University of Montana, developed the SAMI between 1990 and 1993 during his postdoctoral work at the Woods Hole Oceanographic Institution (Woods Hole, MA, USA).

General specifications: (http://www.sunburstsensors.com)
Sunburst Sensors, LLC, 1226 West Broadway, Missoula, MT 59802

 Sensor type: reagent based colorimetry
 Thermistor: accuracy 0.1 degC, precision ± 0.01 deg
 Operating range: -2o– 30 degC, 0-500 m depth
 
SAMI² - CO2
 Measures: partial pressure of CO2 in water (pCO2)
 pCO² range: 150 – 700 ppm (other ranges avail.)
 Precision: < 1 ppm
 Accuracy: ± 3 ppm based on lab calibration*
 Long-term drift: < 1 ppm over 6 months
   *Based on NIST-traceable calibrated NDIR 

SAMI² - pH
 Measures: Seawater pHT (pH - total hydrogen ion scale)
 pH range: 7-9
 Salinity range: 30 - 36
 Precision: < 0.001 pH units
 Accuracy: ± 0.003 pH units (CRM* intercomparison)
 Long-term drift: < 0.001pH units over 6 months
   *Certified pH reference material from Andrew Dickson (UCSD)

The Vector-Averaging Wind Recorder (VAWR) is a system designed by researchers at Woods Hole Oceanographic Institution (WHOI) to make surface meteorological measurements. The standard WHOI Vector Averaging Wind Recorder (VAWR) of the late 1980s through early 1990s was mounted on a toroid buoy (Dean and Beardsley, 1988). In addition to wind speed and direction, the VAWR could also be configured to record water temperature and conductivity data from sensors mounted at 1 meter depth on the mooring bridle of the buoy (Trask et al., 1995).

The Vertical Multiple Plankton Sampler (VMPS), a variation of the multiple plankton sampler (MPS), is a specially designed opening–closing, multi-layer net system used for collecting zooplankton (Terazaki and Tomatsu, 1997). The mesh size and mouth opening can vary depending on research focus. The VMPS is towed through depth ranges with nets closed at known intervals to yield estimations of standing stock, vertical distribution and diel vertical migration.

The VMPS as described by Wiebe and Benfield (2003) is named the Ocean Research Institute Vertical Multiple Plankton Sampler (ORI-VMPS) with specifications: 100 cm x 100 cm rectangular mouth opening multiple net system that can be equipped with 4 to 10 nets, 510 cm long with 0.33 mm nylon mesh. Nets are opened/closed by surface commands down transmitted via conduction cable to an underwater unit (see Plate 31 C (Wiebe and Benfield, 2003)).

The Video Plankton Recorder (VPR) is a video-microscope system used for imaging plankton and other particulate matter in the size range from a few micrometers to several centimeters. The VPR is essentially an underwater microscope. It consists of four video cameras (with magnifying optics) synchronized at 60 fields per second (fps) to a red-filtered 80 W xenon strobe (pulse duration = 1 microsecond). The current lens on each camera can be adjusted to provide a field of view between 5 mm and 10 cm. Use of higher magnification lenses is currently being explored for viewing protozoans (<1 µm resolution). The four cameras are set for concentric viewing fields so that a range of up to four magnifications can be viewed simultaneously, allowing a wide size range of plankton to be sampled. Depth of field is adjusted by the lens aperture setting, and the volume sampled in each video field ranges from about 1 ml to 1 liter, depending on lens settings. The cameras have been configured for stereoscopic viewing as well.A strobe on the other arm illuminates the imaged volume and flashes 60 times per second, producing 60 images per second of the particles and plankton in the water. The images are then saved internally on a computer hard disk and later plotted.

Deployment: Most commonly, the VPR is mounted in a frame and lowered into the water from the stern of the ship. Sometimes, a CTD also is mounted next to the VPR to collect depth, temperature, and salinity information at the same time as each video image. The instrument is lowered down through the water to a maximum depth of 350 meters to generate a profile of plankton/particle abundance and taxon group along with temperature and salinity. In addition to the towed configuration for mapping plankton distributions, it is possible to deploy the VPR in a fixed position (on a mooring) for viewing plankton swimming behaviors in two or three dimensions. The VPR instrument system has been used in both configurations, and deployment on ROVs has been proposed.

This definition was taken from the WHOI Ocean Instruments Web site and from a US GLOBEC Newsletter.

The Woods Hole Interstitial Marine Probe (WHIMP; Martin and Sayles, 1996) was specially designed for in situ porewater sampling. The WHIMP is equipped with an in situ whole-core squeezer (Bender et al., 1987; Sayles and Dickinson, 1991) for high resolution sampling near the sediment-water interface. It is a 'lander' system of the 'Smith type' that differs from its predecessors primarily in that it incorporates a number of different sampling and analysis strategies onto a single platform. The designers of the WHIMP sampling system wanted to be able to carry out sediment and pore water studies, direct flux measurements with chambers, and conduct in-situ experiments at the same place and time. It includes a syringe to extract water samples at various depths, ranging from less than an inch to two feet.