Estimating zooplankton biomass through image analysis

Zooplankton biomass can be reliably estimated by a non-destructive method based on the statistical relationship between biovolume and the contents of carbon and nitrogen. Integrated zooplankton biovolume and the corresponding organic C and N contents were analysed in paired fresh and fixed (hexamine-buffered formalin) samples. Sample biovolume was estimated through the integration of individual volumes obtained by semi-automatic image analysis on fixed zooplankton samples. The corresponding C and N contents of paired fresh and preserved zooplankton were analysed with a Carlo-Erba C-H-N Analyser. The method allows simultaneous measurement of integrated and individual numbers and biomass (biovolume, C and N) spectrum. It is non-destructive and allows the minimization of errors and variability attributable to differences in the handling processes of samples and to the presence of particles other than zooplankton, like phytoplankton or detritus particulate matter.