A video plankton recorder (VPR) is towed underwater video

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisibl ...

system, which photographs small to fine-scale structure of

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

, from 50 micrometers and up to a few centimeters in size. A VPR consists of five general components: cameras (with magnifying optics), strobe, additive sensor and flight control, underwater platform and interface software for plankton identification.

Technical aspects

In order to obtain high-quality and low-noise images,

charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...

(CCD) sensors are used in the

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

system. In the early design system, the CCD cameras were mounted in one of the arm of the platform. The developments in the recent years made the cameras system possible to be mounted in the platform body along with other sensors and flight control. The magnification power on the cameras should be vary, with high

magnification Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in siz ...

power on the camera, we can obtain detail observation result on the plankton sample, such as

protozoan Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

that has <1 µm resolution . In other hand, the high magnification is able to identify plankton into

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

level while low magnification of the camera will provide the rare and larger taxa. The xenon strobe (red-filtered 80 W) provides the VPR systems with the

Lighting Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylig ...

to support the work of the video camera. It is placed in the other side of the platform arm. This design is intended to provide the area between camera and strobe as undisturbed water volume for continuous observation in the VPR system. As a complex system, VPR can also carry several oceanographic sensors in the same time such as, CTD, transmissometer, fluorometer and flowmeter. These sensors enable the system to measure temperature, conductivity, depth,

flow measurement Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. The common types of flowmeters with industrial applications are listed below: * a) Obstruction type (differential pressure or variable area ...

, fraction of light in the water and the

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

. The housing or platforms for this instrument is varying depend on the purpose of the survey. These are the particular platform that has been tested and used to mount the VPR: # Towed device #

Remotely operated underwater vehicle A remotely operated underwater vehicle (technically ROUV or just ROV) is a tethered underwater mobile device, commonly called ''underwater robot''. Definition This meaning is different from remote control vehicles operating on land or in the ai ...

(ROV) #

Autonomous underwater vehicle An autonomous underwater vehicle (AUV) is a robot that travels underwater without requiring input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes ...

(AUV) # Autonomous profiling mooring The improvements of imaging system to observe, calculate and measure

in the ocean enable the detail observation on the specific plankton community. This early development was conducted by enumerating and counting the

silhouette A silhouette ( , ) is the image of a person, animal, object or scene represented as a solid shape of a single colour, usually black, with its edges matching the outline of the subject. The interior of a silhouette is featureless, and the silhou ...

photography of plankton, the result then is processed with software package such as

Matlab MATLAB (an abbreviation of "MATrix LABoratory") is a proprietary multi-paradigm programming language and numeric computing environment developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementation ...

.Benfield, M.C., et al., RAPID Research on Automated Plankton Identification. Oceanography, 2007. 20(2): p. 172-187.

Imaging software

The most important part in VPR is the plankton identification software. Any developments of the software should improve the required task performed by VPR. In a nutshell, the software should have the ability of: #Importing the plankton images

database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...

in to the system. #Validate the object and evaluate from the background of the sample. This qualification should include the capability of the software to discriminate unknown object from plankton. #Identify and classify the samples therefore plankton can be distinguished from each other. #Presenting the result in the form of; abundance, size of distribution and biomass.

Observation result

The study conducted by Benfield, M.C., et al. has discovered that VPR provided comparable data on the taxonomic composition of the plankton compared to physical plankton survey taken by

MOCNESS MOCNESS is the acronym for ''Multiple Opening/Closing Net and Environmental Sensing System'' and is a net system for plankton in the ocean. The system is towed behind a research vessel with a speed of up to 2.5 knots and consists of five to twenty n ...

. The figure in the right side shows us the general trends in abundance and detail scale patchiness along the observation area.

Advantage and Disadvantages

Although a VPR has a drawback for not being able to identify plankton into species level, the advantages to use this instrument has gone beyond its limitation to provide us with convenient and accurate result. The high resolution result on plankton taxa observation along with synchronized measurement environmental variables from another oceanographic sensor attached in VPR body can be considered as the milestone of this device. In addition, since the observation is conducted visually by photographing the sample, the observation of delicate plankton and gelatinous species can be done accurately without having them destroyed in the net.

References

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Gallery

Source of Picture Gallery
Planktology