Zooplankton biomass estimation from digitized images: a comparison between subtropical and Antarctic organisms

Abstract

The measurement of mesozooplankton biomass in the ocean requires the use of analytical procedures that\ndestroy the samples. Alternatively, the development of methods to estimate biomass from optical systems and\nappropriate conversion factors could be a compromise between the accuracy of analytical methods and the need\nto preserve the samples for further taxonomic studies. The conversion of the body area recorded by an optical\ncounter or a camera, by converting the digitized area of an organism into individual biomass, was suggested as\na suitable method to estimate total biomass. In this study, crustacean mesozooplankton from subtropical waters\nwere analyzed, and individual dry weight and body area were compared. The obtained relationships agreed with\nother measurements of biomass obtained from a previous study in Antarctic waters. Gelatinous mesozooplankton\nfrom subtropical and Antarctic waters were also sampled and processed for body area and biomass. As\nexpected, differences between crustacean and gelatinous plankton were highly significant. Transparent gelatinous\norganisms have a lower dry weight per unit area. Therefore, to estimate biomass from digitized images,\npattern recognition discerning, at least, between crustaceans and gelatinous forms is required.