Groupe Interuniversitaire de Researches Océanographiques du Québec
OPC
CHASE 96
The Optical Plankton Counter is an in-situ probe designed to count and size zooplankton and other marine organisms from 250 µm to 2 cm in size. It is a reduced labour alternative to traditional sampling methods and allows a tremendous volume of continuous data to be collected on very fine-scale distribution. During the summers of 1995 and 1996 the OPC was mounted on top of a Conductivity Temperature Depth probe (CTD) with an in-situ fluorometer so that data could be gathered concurrently on both zooplankton and phytoplankton distribution.
The OPC consists of a flow-through tunnel and two underwater pressure cases that house the optics (see above). Plankton passing through the machine interupts the light beams, enabling the profile area of each organism to be generated. On our behalf, Focal Technologies Inc. modified the controller of the OPC to add a time stamp for each organism to the existing OPC data file. For a more detailed introduction to the OPC try the Focal site.
Information is collected real time for each of the instruments and stored on lap-top computers located inside the boat's cabin (at left). One extra for the CHASE 96 field season was the addition of a side mounted ADCP (right) which also collected high resolution data on zooplankton abundance using backscatter intensity. The resulting time-series are now being analyzed using various methods including the use of power spectra, multifractal (in preparation) and neighbour analysis .
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