PARCA

ParCa was designed in consideration of systems used by e.g. Honjo et al. (1984). The system consists of a modified NIKON Coolpix digital still camera with a 3.34 megapixel resolution. A strobe, mounted perpendicular to the camera, fires a collimated light beam illuminating a known sample volume for statistical analysis of the images. The camera is lowered at a winch speed of 0.3 m s-1, acquiring images in 10m intervals. The system can operate in depths down to 6000m and power supply is provided by a 24V/38h rechargeable DSPL battery. Communication with the ship is provided by a microcontroller and adapted software. A telemetry unit allows full control over the system via the ships coaxial wire. The camera is triggered by the pressure sensor of a CTD probe for accuarte trigger depths.

System components

Image analysis

ParCa images can be analysed immediately after the recovery of the system. An automated macro file within the Optimas software is used for a time-saving evaluation of particle concentrations, to localise interesting areas in the water column, such as particle maxima. A comprehensive image analysis for the extraction of particle specific parameters like size or orientation, can be provided on board as well.

Comprehensive analysis of a ParCa profile
a) particle abundance
b) large, amorphous aggregate abundance (Stringers)
c) turbidity (acquired by the "mean grey value")
d) size distribution
e+f) particle volume

Images

Plate 1: possibly larvacean house (a), eggs (b,d), Acantharia or radiolaria (c)
Plate 2: eggs (a), possibly radiolarian colony (c), pteropod (d), gastropod (e)
Plate 3: pellets or mineral grains
Plate 4: pellets or mineral grains
Plate 5: physonect siphonore (a), radiolarian colony (b,c)
Plate 6: marine snow strings, maybe from diatoms or dinoflagellates
Special thanks to A. Alldredge for identification

References

Honjo, S., Doherty, K.W., Agrawal, Y.C., and Asper, V.L., 1984, Direct optical assessment of large amorphous aggregates (marine snow) in the deep ocean: deep Sea Research i, v. 31, p. 67-76.

Ratmeyer, V., and Wefer, G., 1996, A high resolution camera system (ParCa) for imaging particles in the ocean: System design and results from profiles and a three-month deployment: Journal of Marine Research, v. 54, p. 589-603.

Contact

Name	Phone	Fax	e-mail
Nowald, Nicolas	+49  421 218 - 65612	+49  421 218 - 65605
Ratmeyer, Volker	+49  421 218 - 65604	+49  421 218 - 9865604