A test model for optical plankton counter (OPC) coincidence and a comparison of OPC-derived and conventional measures of plankton abundance

The use of the optical plankton counter (OPC) for processing zooplankton net samples is explored. A comparison of OPC counts and microscope counts from net samples was reasonable. Similarly, OPC biovolume and carbon had a ratio of 23:1 (biovolume;carbon). Coincidence was modelled using the Poisson distribution, and tested with a large diatom Coscinodiscus wailesii. Agreement appeared to he good up to 60 s 1 ; above this, the maximum response rate of the system became limiting.